GB2406971A - Yagi antenna design - Google Patents

Abstract

Constructional and dimensional details and properties of Yagi-Uda antenna designs are described and claimed in which the designs are suitable for receiving digital signal transmissions within a 400 - 900 Megahertz frequency range. The antenna comprises a dipole element 2503, which may be 400 - 420 mm wide, an elongate boom 2501, plural director elements and reflector members 2502, 2504. The director elements may have varied spacing arrangements and may comprise groups of elements of different dimensions which may also have varied spacing arrangements. The director elements proximal to the dipole 2503 may have a spacing of 62mm which may gradually increase to 122 mm between director elements located distal to the dipole. The reflector comprises a corner reflector assembly with first and second intersecting planar members 2502, 2504 which are transverse to the antenna boom 2501. The reflector planar members 2502, 2504 may have a specific spacing from the dipole 2503 and may each comprise a plurality of spaced elements arranged along a reflector boom. The reflector elements may be 470 - 600 mm wide and the spacing between said reflector elements may be arranged within particular size ranges. The antenna is intended to provide stable Digital Terrestrial Transmission (DTT) reception characteristics.

Description

IMPROVED PERFORMANCE ANTENNA

Field of the Invention

The present invention relates to antenna devices.

Background to the Invention

In the United Kingdom, terrestrial broadcast television signals occupy a number of 8 MHz wide channels in the UHF frequency range 470-854 MHz. The channels are numbered contiguously from 21 to 68, the band from channel 21 to To channel 35 being referred to as Band IV, and that from channel 37 to channel 68 as Band V. Channels 36 and 38 are allocated to other services and are not used for broadcasting.

In the United Kingdom, terrestrial digital audio broadcast radio signals (T- DAB) are transmitted in Band lil (217.5 - 230.0 MHz). This band may be extended in the future.

Known antenna devices for reception of television signals are numerous.

Typically, for outdoor domestic use for reception of television signals, an antenna comprises an elongate boom, having a plurality of antenna elements positioned transversely to a main length of the boom, the individual elements being spaced apart from each other along the length of the boom. The individual elements may extend either side of the boom.

A single boom Yagi - Uda dipole array UHF television antenna comprises a dipole element, a back reflector to provide suppression of signals from behind the antenna; and a plurality of antenna elements to provide a directional reception beam. The individual elements may become shorter towards a front end of the antenna which is directed towards a transmitter, in order to provide an increase in 3 o bandwidth.

The great majority of TV antennas in use are of Yagi - Uda derived types.

For most main TV transmitter sites in the UK, all four main program channels occupy a relatively narrow cluster of frequency channels, keeping all the signals within an 8 MHz wide frequency block. Some transmitter sites do fall outside this frequency range.

In the UK, conventionally, TV antennas have been made in three main frequency band variations known as groups. These groups are as follows: To Group A - Channels 21 to 37 Group B - Channels 35 to 53 Group C/D Channels 48 to 68.

Coverage of the whole UHF TV band is designated 'group W' (channels 21 to 68).

The relatively narrow frequency groups facilitate design of Yagi antennas with reasonable performance and acceptable size. In the majority of cases where wider bandwidth has been necessary, either wide band Yagi antennas or o log-periodic antennas have been used.

Referring to Fig. 1 herein, there is illustrated a known single boom Yagi antenna 101. The antenna 101 comprises a director, a reflector and a dipole.

The director comprises a director boom 102 and a plurality of director elements 106 extending laterally either side of the boom 102.

The reflector comprises a pair of reflector assemblies 103. Each reflector assembly 103 comprises a reflector boom 107 and a series of reflector elements 108 extending laterally either side of the reflector boom 107. Each reflector o assembly 103 is located either side of the boom 102 substantially in opposition to the other reflector assembly.

The director boom 102 is supported by an antenna mast 105.

Yagi director and reflector elements (except for the driven element) are parasitic' and do not require electrical connection to the boom. The terminals of the driven element are usually connected to the antenna's terminal box, rather than to the boom.

A typical known television antenna has a series of elements cut to specific lengths which are related to the frequency of the signal which the antenna is To designed to receive. Each element comprises a pair of metal (usually aluminium alloy) rods, sticking out from a boom. Yagi director elements are usually single rods or strips with a centre mechanical attachment to the boom. Alternatively, each director elements may comprise more than one rod or strip.

Referring to Fig. 2 herein, there is illustrated a known antenna 201 comprising X-type director elements. An X-type director element comprises a first pair of rods 202 extending laterally from a side of the boom 102 and a second pair of rods 204 extending laterally from an opposite side of the boom 102. The rods are affixed to the boom 102 by an insulating housing 203. Each pair of rods 202, 204 may be formed of 2 conducting rods of metal, or may be formed of the two arms of a single rod of metal bent substantially into a u-shape with the bend portion of the u-shape being located in the housing 203.

The Yagi reflector element may be a more complex structure such as multiple rods or strips, a metal plate, a wire grid, of some combination of these.

Known television antennas connect a plurality of antenna elements to a boom using a set of plastic clips, each of which provides a seating for an antenna element to hold the antenna element in place relative to the boom. Typically, a bolt or screw is inserted through an aperture in an antenna element, which seats onto a plastics moulding which is formed to secure the antenna element to the antenna boom. For the Yagi antenna, the primary purpose is mechanical connection.

In general, the bigger the antenna and the more elements, the higher the gain and the higher the front to back ratio of the antenna. With increasing number of elements, this increases the number of element to boom connections.

The adoption of DVB-T services in the UK has added 6 digital multiplexes to the previous 4 or 5 analogue services. Due to the need for both types of service to co-exist for the time being, it is frequently the case that DVB-T multiplexes occupy channels far removed in frequency from the analogue services at the same transmitter site. This greatly increases the need for wide band (Group W) antennas for consumers. Moreover the UK Government wishes to see the widespread adoption of wide band antennas for reasons of 'future proofing' i.e. for allowing future reallocation of channel assignments in connection with reallocation of radio spectrum to other non-broadcast uses.

In addition, DVB-T transmitter power levels are frequency lower than for the same analogue services after allowing for a difference of about 20 dB in the go required carrier to noise ratios of the two systems. This is to prevent excessive interference being caused by the DVB-T to existing analogue transmissions, and means that receiving antenna gain performance may be more critical than for equivalent analogue systems.

Also, DVB-T services are currently only radiated from about 80 transmitter sites, compared to over 1000 main transmitter and relay transmitter sites for analogue signals. With DVB-T signals the same channel may be used for transmissions from two transmitters at closer geographical spacing than would be the case for analogue signals. This can make the receiving antenna directional o and cross-polar discrimination performance more critical than for analogue applications.

Additionally, DVB-T is sensitive to impulsive electrical interference, that is, interference caused by sparking contacts in switches, thermostats and the like.

This causes corruption of digital data and consequent disturbances to the continuity of TV pictures, and/or sound. One coupling mechanism by which impulse interference can enter a signal path is by pick up on the outer surface of an antenna feeder, which may pass close to a domestic mains wiring, and which transfers interference to the signal path due to imbalance in the antenna's termination arrangements. RF current flowing on the outside of a coaxial feeder is a common mode signal. If a symmetrical antenna with centre feed dipoles is o connected to a co-axial feeder with a perfect balance to unbalance transformer (balun), then no common mode signal is transferred to the desired differential mode signal path. In practice, imperfections in the balun may allow some coupling, and increase the susceptibility to impulse interference.

:5 Traditionally, many Yagi antennas have had poor baluns, or even no balun at all. This is another area receiving more attention for DVB-T, and good immunity to feeder pick up is a desirable characteristic.

Consequently, since DVB-T is significantly more demanding of antenna o performance than analogue TV, it is creating a demand for wide band antennas of good well defined performance. Yagi derived products that can meet these demands tend to be quite large, which is perceived as a negative aspect by consumers who prefer not to have large antennas.

For the reception of Digital Terrestrial Television (DTT) signals in the UK, there is a requirement that the receiving antennas are designed and manufactured to a minimum industry standard.

It is felt that due to high level of analogue signals in comparison to the lower o digital signals, that the correct antenna has not always been fitted. This has been mainly prevalent in fringe reception areas where OTT reception issues have invariably been improved with the installation of a correct antenna.

The Confederation of Aerial Industries and the Digital Television Group have published an approval process that is required to ensure that antennas conform to a minimum standard. A benchmark specification is to determine that characteristics of an antenna required to obtain stable DTT reception. The benchmark specification does not alter the basic requirements of antenna design but highlights important parameters so that satisfactory DTT reception may be achieved.

o The benchmark is not a legal requirement but a recommendation.

Experience in the industry has indicated that it will be to the industry's advantage to supply equipment to this recommendation.

Summarv of the Invention The inventors have realised a need for an antenna that meets the characteristics of an antenna required to obtain stable DTT reception.

According to a first aspect there is provided an antenna device comprising: o a dipole; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; said first reflector assembly comprising a first reflector boom and a plurality of first reflector elements; said second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; wherein said reflector assemblies have a width in a direction transverse to a length of said boom, in the range 440 to 490 millimetres and/or 550 to 630 millimetres.

Preferably, the plurality of director elements are arranged in a plurality of groups, each said group comprising a pair of said elements placed opposite each other and either side of said boom, wherein a maximum distance between tips of said elements in a group are as follows: for a first group of said elements a distance in the range 245 millimetres to 255 millimetres; for a second group of said elements, a distance in the range 225 millimetres 2 0 to 235 millimetres; and for a third group of said elements, a distance in the range 205 millimetres to 215 millimetres.

Preferably, each director element of said plurality of director elements comprises an x-type element, an x-type element comprising; a first pair of elements extending from a first side of said boom; and o a second pair of elements extending from a second side of said boom, said second side of said boom being an opposite side to said first side of said boom.

According to a second aspect there is provided an antenna device comprising: a dipole; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; wherein along a length of said boom, said director elements are spaced at intervals as follows: a distance between a first set of director elements and said dipole, in the range 62 mm to 82 mm; a distance between a second set of director elements and said dipole in the range 147 mm to 167 mm; a distance between a third set of director elements and said dipole in the range 253 mm to 273 mm; a distance between a fourth set of director elements and said dipole in the 3 o range 368 mm to 388 mm; a distance between a fifth set of director elements and said dipole in the range 462 to 482 mm.

Preferably, the director elements are arranged into groups, each said group comprising a pair of said elements placed opposite each other and either side of said boom, wherein a distance between tips of said director elements in a group are as follows: for a first group of said director elements a distance in the range 240 millimetres to 260 millimetres; and for a second group of said director elements, a distance in the range 220 millimetres to 240 millimetres.

: Preferably, each director element of said plurality of director elements comprises an x-type element, an x-type element comprising; a first pair of elements extending from a first side of said boom; and To a second pair of elements extending from a second side of said boom, said second side of said boom being an opposite side to said first side of said boom.

According to a third aspect there is provided an antenna device comprising: a dipole; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in 3 o a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; wherein along a length of said boom, said director elements are spaced at intervals as follows: a distance between a first set of director elements and said dipole, in the range102mmto122 mm; a distance between a second set of director elements and said dipole, in the range163mmto183 mm; a distance between a third set of director elements and said dipole, in the range 249 mm to 269 mm; a distance between a fourth set of director elements and said dipole in the o range 349 mm to 369 mm; a distance between a fifth set of director elements and said dipole in the range 439 mm to 459 mm; a distance between a sixth set of director elements and said dipole in the range 553 mm to 573 mm; a distance between a seventh set of director elements and said dipole in the range 688 mm to 708 mm; a distance between an eighth set of director elements and said dipole in the range 833 mm to 853 mm; a distance between a ninth set of director elements and said dipole in the range 965 mm to 985 mm; a distance between a tenth set of director elements and said dipole in the range 1107 mm to 1127 mm.

Preferably, the director elements are arranged into groups, each said group comprising a pair of said elements placed opposite each other and at either side of said boom, wherein a distance between tips of said director elements in a group are as follows: for a first group of said director elements a distance in the range 240 mm to 260 mm; and for a second group of said director elements, a distance in the range 220 mm to 240 mm; for a third group of said director elements, a distance in the range 200 mm to220 mm.

According to a fourth aspect, there is provided an antenna device compnslng: s a dipole; an elongate boom; a plurality of antenna elements mounted to said elongate boom and extending in a direction transverse to a main length of said elongate boom; and a reflector, said reflector comprising an upper reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; wherein said dipole comprises has a width in a direction transverse to a length of said boom in the range 400 mm to 420 mm.

Preferably, the dipole has a length in the range 405 mm to 415 mm.

Preferably, the dipole comprises a pair of substantially "U" shaped loops extending either side of said boom, each said substantially "U" shaped loop having a length in the range 200 mm to 210 mm.

According to a fifth aspect there is provided an antenna device comprising: a dipole element; 2 o an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; said first reflector assembly comprising a first reflector boom and a plurality of first reflector elements; said second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; wherein each reflector boom has a first end, and said reflector elements are spaced at intervals along a length of said reflector boom as follows: a distance between a first reflector element and a second reflector element in the range 145 mm to 155 mm; a distance between a third reflector element and said second reflector element the range 90 mm to 110 mm; a distance between a fourth reflector element and said third reflector s element in the range 45 mm to 55 mm.

Preferably. each said reflector element comprises an elongate element having an annular cross-section, and is disposed in a direction transverse to said reflector boom.

Alternatively, each said reflector element comprises an elongate element having a substantially U-shaped cross-section, and is disposed in a direction transverse to said reflector boom.

According to a sixth aspect there is provided an antenna device comprising: a dipole element; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; said first reflector assembly comprising a first reflector boom and a plurality of first reflector elements; said second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; wherein each said reflector boom has a first end, and said reflector elements are spaced at intervals along a length of said reflector boom as follows: a distance between a first reflector element and a second reflector element in the range 90 to 110 mm; 2 0 a distance between said second reflector element and a third reflector in the range 40 mm to 60 mm; Preferably, each said reflector element comprises an elongate element having an annular cross-section, and is disposed in a direction transverse to said 2 5 reflector boom.

Alternatively, each said reflector element comprises an elongate element having a substantially U-shaped cross-section, and is disposed in a direction transverse to said reflector boom.

According to a seventh aspect there is provided an antenna device comprising: a dipole element; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; :5 wherein said director elements are arranged into groups, each said group comprising at least one director element located on said boom and extending transverse to a length of said boom on either side of said boom, wherein a distance between tips of said director elements in a group are as follows: o for a first group of said elements a width in the range 163 mm to 167 mm; for a second group of said elements, a width in the range 158 mm to 162 mm; for a third group of said elements, a width in the range 150 mm to 156 mm; for a fourth group of said elements, a width in the range 143 mm to 149 mm; so for a fifth group of said elements, a width in the range 138 mm to 142 mm.

Preferably, each director element of said plurality of director elements comprises a conducting element conducting integrally of a single shape of material, said element having a substantially u-shaped cross section area.

5Preferably, said director elements are spaced along a length of said boom at intervals as follows: a distance between a first director element and said dipole in the range 28 mm to 48 mm; a distance between a second director element and said dipole in the range 36 mm to 106 mm; a distance between a third director element and said dipole in the range 159 15mm to 179 mm; a distance between a fourth director element and said dipole in the range 237 mm to 257 mm; 2 0a distance between a fifth director element and said dipole in the range 324 mm to 344 mm; a distance between a sixth director element and said dipole in the range 420 mm to 440 mm; a distance between a seventh director element and said dipole in the range 516 mm to 536 mm; a distance between an eighth director element and said dipole in the range 30608 mm to 628 mm; a distance between a ninth director element and said dipole in the range 701 mm to 721 mm; a distance between a tenth director element and said dipole in the range 779 mm to 799 mm; a distance between an eleventh director element and said dipole in the range 859 mm to 879 mm.

Alternatively, said director elements are spaced at intervals as follows: a distance between a first director element and said dipole in the range 28 mm to 48 mm; a distance between a second director element and said dipole in the range 84 mm to 104 mm; a distance between a first director element and said dipole in the range 164 mm to 184 mm; a distance between a fourth director element and said dipole in the range 249 mm to 269 mm; a distance between a fifth director element and said dipole in the range 360 2 5 mm to 380 mm; a distance between a sixth director element and said dipole in the range 476 mm to 496 mm; o a distance between a seventh director element and said dipole in the range 603 mm to 623 mm; a distance between an eighth director element of said dipole in the range 701 mm to 721 mm.

Alternatively, said director elements are spaced at intervals as follows: a distance between a first director element and said dipole in the range 28 mm to 48 mm; a distance between a second director element and said dipole in the range To 89 mm to 109 mm; a distance between a third director element and said dipole in the range 169 mm to 189 mm; a distance between a fourth director element and said dipole in the range 251 mm to 271 mm; a distance between a fifth director element and said dipole in the range 335 mm to 355 mm; a distance between a sixth director element and said dipole in the range 432 mm to 452 mm; a distance between a seventh director element and said dipole in the range s 535 mm to 555 mm; a distance between an eighth director element and said dipole in the range 619 mm to 639 mm; So a distance between a ninth director element and said dipole in the range 714 mm to 734 mm; a distance between a tenth director element and said dipole in the range 794 mm to 814 mm; a distance between an eleventh director element and said dipole in the range 879 mm to 899 mm.

Alternatively, said director elements are spaced at intervals as follows: a distance between a first director element and said dipole in the range 30 mmto50 mm; a distance between a second director element and said dipole in the range 83 mm to 103 mm; Is a distance between a third director element and said dipole in the range 139 mm to 159 mm; a distance between a fourth director element and said dipole in the range 213 mm to 233 mm; a distance between a fifth director element and said dipole in the range 321 mm to 341 mm; a distance between a sixth director element and said dipole in the range 406 mm to 426 mm; a distance between a seventh director element and said dipole in the range 496 mmto516 mm; a distance between an eighth director element and said dipole in the range 602 mm to 622 mm; a distance between a ninth director element and said dipole in the range 790 mm to 739 mm; a distance between a tenth director element and said dipole in the range 831 mm to 851 mm; a distance between an eleventh director element and said dipole in the range 933 mm to 953 mm; a distance between a twelfth director element and said dipole in the range 1037 mm to 1057 mm; a distance between a thirteenth director element and said dipole in the range1149mmto1169mm; a distance between a fourteenth director element and said dipole in the range 1242 mm to 1062 mm; a distance between a fifteenth director element and said dipole in the range 2 o 1369 mm to 1389 mm; a distance between a sixteenth director element and said dipole in the range 1476 mm to 1496 mm.

2 5 According to an eighth aspect there is provided an antenna device comprising: a dipole element; So an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; said first reflector assembly comprising a first reflector boom and a plurality of first reflector elements; said second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; wherein each said reflector boom has a first end and a length, and said reflector elements are spaced at intervals as follows: a distance between a first reflector element and a second reflector element 2 o in the range 83 mm to 103 mm; a distance between said second reflector element and a third reflector element in the range 68 mm to 88 mm; Preferably, each said reflector element comprises an elongate element having a substantially U-shaped cross-section, and is disposed in a direction transverse to said reflector boom, and has a length in a direction transverse to said reflector boom in a range of 447 mm to 467 mm.

3 o According to a ninth aspect, there is provided an antenna device comprising: a dipole element; an elongate boom; 5mounted to said elongate boom, a plurality of director elements extending in a direction transversed to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a range transverse to a main length of said elongate boom and a second reflector Toassembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy claims which intersect each other; said first reflector assembly comprising a first reflector boom and a plurality 5of first reflectorelements; said second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; 20wherein each reflector boom has a first end, and said reflector elements are spaced at intervals along a length of said reflector boom as follows: a distance between a first reflector element and a second reflector element in the range 135 mm to 145 mm; a distance between said second reflector element and a third reflector element in the range 60 mm to 70 mm.

Preferably, a distance between tips of said first reflector element is in a 3 orange of 485 mm to 505 mm; a distance between tips of said second reflector element is in a range of 358 mm to 378 mm; a distance between tips of said third reflector element is in a range of 485 mm to 505 mm.

Preferably, each said reflector element comprises an elongate element having a substantially U-shaped cross-section, and is disposed in a direction transverse to said reflector boom.

Preferably, the antenna device has the following properties: a forward gain of at least 6 decibels for a group A antenna, or a forward gain of at least 7 decibels for a group B antenna, or a forward gain of at least 8 : decibels for a group CD antenna, or a forward gain of at least 7 decibels for a group E antenna, or a forward gain of at least 6 decibels for a group K antenna, or a forward gain of at least 5 decibels for a group W antenna; a return loss ratio of at least 8 decibels for a group A antenna, a return loss o ratio of at least 8 decibels for a group B antenna, a return loss ratio of at least 8 decibels for a group CD antenna, a return loss ratio of at least 7 decibels for a group E antenna, a return loss ratio of at least 7 decibels for a group K antenna, or a return loss ratio of at least 6 decibels for a group W antenna; a cross- polar protection of at least 15 decibels; a directivity of at least -16 decibels at an angle of at least 60 relative to a direction of a main response for a group A, B or CD antenna, or a directivity of at least -16 decibels at an angle of at least 75 relative to said direction of said main 3 o response for a group E, K or W antenna; a feeder pickup of at least 10 decibels for a group A antenna, a feeder pickup of at least 10 decibels for a group B antenna, a feeder pickup of at least 12 decibels for a group CD antenna, a feeder pickup of at least 8 decibels for a group E antenna, a feeder pickup of at least 8 decibels for a group K antenna, a feeder pickup of at least 7 decibels for a group W antenna; where a group A antenna operates in a frequency range of 470 to 606 Megahertz, a group B antenna operates in a frequency range of 582 to 734 Megahertz, a group CD antenna operates in a frequency range of 686 to 584 Megahertz, a group E antenna operates in a frequency range of 582 to 854 Megahertz, a group K antenna operates in a frequency range of 470 to 694 Megahertz, a group W antenna operates in a frequency range of 470 to 854 Megahertz.

According to a tenth aspect there is provided an antenna having the following properties: a forward gain of at least 6 decibels for a group A antenna, or a forward gain of at least 7 decibels for a group B antenna, or a forward gain of at least 8 decibels for a group CD antenna, or a forward gain of at least 7 decibels for a group E antenna, or a forward gain of at least 6 decibels for a group K antenna, or a forward gain of at least 5 decibels for a group W antenna; a return loss ratio of at least 8 decibels for a group A antenna, a return loss ratio of at least 8 decibels for a group B antenna, a return loss ratio of at least 8 decibels for a group CD antenna, a return loss ratio of at least 7 decibels for a group E antenna, a return loss ratio of at least 7 decibels for a group K antenna, or a return loss ratio of at least 6 decibels for a group W antenna; a cross-polar protection of at least 15 decibels; a directivity of at least -16 decibels at an angle of at least 60 relative to a direction of a main response for a group A, B or CD antenna, or a directivity of at least -16 decibels at an angle of at least 75 relative to said direction of said main response for a group E, K or W antenna; a feeder pickup of at least 10 decibels for a group A antenna, a feeder pickup of at least 10 decibels for a group B antenna, a feeder pickup of at least 12 decibels for a group CD antenna, a feeder pickup of at least 8 decibels for a group E antenna, a feeder pickup of at least 8 decibels for a group K antenna, a To feeder pickup of at least 7 decibels for a group W antenna; where a group A antenna operates in a frequency range of 470 to 606 Megahertz, a group B antenna operates in a frequency range of 582 to 734 Megahertz, a group CD antenna operates in a frequency range of 686 to 584 Megahertz, a group E antenna operates in a frequency range of 582 to 854 Megahertz, a group K antenna operates in a frequency range of 470 to 694 Megahertz, a group W antenna operates in a frequency range of 470 to 854 Megahertz.

To According to an eleventh aspect there is provided an antenna having the following properties: a forward gain of at least 7.5 decibels for a group A antenna, or a forward gain of at least 8.5 decibels for a group B antenna, or a forward gain of at least decibels for a group CD antenna, or a forward gain of at least 8.5 decibels for a group E antenna, or a forward gain of at least 7.5 decibels for a group K antenna, or a forward gain of at least 8.5 decibels for a group W antenna; a return loss ratio of at least 8 decibels for a group A antenna, a return loss ratio of at least 8 decibels for a group B antenna, a return loss ratio of at least 8 decibels for a group CD antenna, a return loss ratio of at least 7 decibels for a group E antenna, a return loss ratio of at least 7 decibels for a group K antenna, or a return loss ratio of at least 6 decibels for a group W antenna; a cross-polar protection of at least 15 decibels; a directivity of at least -16 decibels at an angle of at least 60 relative to a direction of a main response for a group A, B or CD antenna, or a directivity of at least -16 decibels at an angle of at least 75 relative to said direction of said main response for a group E, K or W antenna; a feeder pickup of at least 12 decibels for a group A antenna, a feeder pickup of at least 12 decibels for a group B antenna, a feeder pickup of at least decibels for a group CD antenna, a feeder pickup of at least 10 decibels for a group E antenna, a feeder pickup of at least 10 decibels for a group K antenna, a : feeder pickup of at least 9 decibels for a group W antenna; where a group A antenna operates in a frequency range of 470 to 606 Megahertz, a group B antenna operates in a frequency range of 582 to 734 Megahertz, a group CD antenna operates in a frequency range of 686 to 584 To Megahertz, a group E antenna operates in a frequency range of 582 to 854 Megahertz, a group K antenna operates in a frequency range of 470 to 694 Megahertz, a group W antenna operates in a frequency range of 470 to 854 Megahertz.

s According to a twelfth aspect there is provided an antenna having the following properties: a forward gain of at least 10 decibels for a group A antenna, or a forward gain of at least 11 decibels for a group B antenna, or a forward gain of at least 12 so decibels for a group CD antenna, or a forward gain of at least 10 decibels for a group E antenna, or a forward gain of at least 10 decibels for a group K antenna, or a forward gain of at least 10 decibels for a group W antenna; a return loss ratio of at least 8 decibels for a group A antenna, a return loss ratio of at least 8 decibels for a group B antenna, a return loss ratio of at least 8 decibels for a group CD antenna, a return loss ratio of at least 7 decibels for a group E antenna, a return loss ratio of at least 7 decibels for a group K antenna, or a return loss ratio of at least 6 decibels for a group W antenna; a cross-polar protection of at least 15 decibels; To a directivity of at least -16 decibels at an angle of at least 60 relative to a direction of a main response; a feeder pickup of at least 15 decibels for a group A antenna, a feeder pickup of at least 15 decibels for a group B antenna, a feeder pickup of at least 18 decibels for a group CD antenna, a feeder pickup of at least 12 decibels for a group E antenna, a feeder pickup of at least 12 decibels for a group K antenna, a feeder pickup of at least 12 decibels for a group W antenna; where a group A antenna operates in a frequency range of 470 to 606 To Megahertz, a group B antenna operates in a frequency range of 582 to 734 Megahertz, a group CD antenna operates in a frequency range of 686 to 584 Megahertz, a group E antenna operates in a frequency range of 582 to 854 Megahertz, a group K antenna operates in a frequency range of 470 to 694 Megahertz, a group W antenna operates in a frequency range of 470 to 854 Megahertz.

Brief Descrintion of the Drawinas For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which: Figure 1 illustrates a known single boom Yagi antenna.

Figure 2 illustrates a known antenna comprising X-type director elements.

Figure 3 illustrate schematically a plan view of a director according to a first embodiment of the invention Figure 4 illustrates schematically a first assembly of a reflector according to the first specific embodiment.

Figure 5 illustrates schematically two reflector assemblies connected together Figure 6 illustrates schematically a section of a dipole for use with the antenna.

Figure 7 illustrates schematically a perspective view of a dipole.

Figure 8 illustrates a graph showing a forward gain of the antenna as a 2 0 function of the frequency.

Figure 9 illustrates a graph of a directivity of the antenna.

Figure 10 illustrates a graph of a feeder pickup of the antenna.

Figure 11 illustrates a graph of a return ratio of the antenna.

Figure 12 illustrates a graph of a cross-polar protection of the antenna.

Figure 13 illustrates schematically a plan view of a first boom section according to a second specific embodiment.

Figure 14 illustrates schematically a plan view of a second boom section according to the second specific.

Figure 15 illustrates a graph showing the forward gain of the antenna as a function of the frequency.

Figure 16 illustrates a graph of the directivity of the antenna.

Figure 17 illustrates a graph of the feeder pickup of the antenna.

Figure 18 illustrates a graph of the return ratio of the antenna.

Figure 19 illustrates a graph of the cross-polar protection of the antenna.

Figure 20 illustrates schematically a plan view of the director boom and director elements of the antenna according to the third specific embodiment.

Figure 21 illustrates schematically a plan view of a first reflector assembly according to the third specific embodiment.

Figure 22 illustrates schematically an elevation view of a reflector comprising two reflector assemblies.

Figure 23 illustrates a dipole element 2301 according to the third specific 2 5 embodiment.

Figure 24 illustrates schematically a perspective view of a dipole.

Figure 25 illustrates schematically a perspective view of an assembled 3 o antenna according to the third specific embodiment.

Figure 26 illustrates a graph showing the forward gain of the antenna as a function of the frequency.

Figure 27 illustrates a graph of the directivity of the antenna.

Figure 28 illustrates a graph of the feeder pickup of the antenna.

Figure 29 illustrates a graph of the return ratio of the antenna.

o Figure 30 illustrates a graph of the cross-polar protection of the antenna.

Figure 31 illustrates schematically a plan view of a director boom according to the fourth specific embodiment.

Figure 32 illustrates schematically a plan view of a reflector assembly according to a fourth specific embodiment.

Figure 33 illustrates schematically a reflector comprising two reflector assemblies.

Figure 34 illustrates schematically a first reflector assembly according to the fifth specific embodiment.

Figure 35 illustrates schematically a dipole mounted on a director boom.

Figure 36 illustrates schematically a plan view of a director according to an eleventh specific embodiment of the invention.

Figure 37 illustrates schematically a dipole element according to the o eleventh specific embodiment.

Figure 38 illustrates schematically a plan view of a first reflector assembly according to the eleventh specific embodiment.

Figure 39 illustrates schematically a dipole element according to a twelfth specific embodiment.

Figure 40 illustrates schematically a plan view of a director according to a thirteenth specific embodiment.

Figure 41 illustrates schematically a plane view of a director according to a fifteenth specific embodiment.

Figure 42 illustrates the requirements for a coaxial cable connections pass for each antenna standard.

Figure 43 illustrates the requirements showing which antenna standard requires the tilting mechanism test to be carried out.

Figure 44 illustrates the requirements of the minimum value of forward gain 2 o within the designated operating frequency range of the specified antenna standard.

Figure 45 illustrates a chart showing the minimum acceptable values of return loss ratio within the designated operating frequency range of the specified 2 antenna type i.e. 1, 2 or 3.

Figure 46 illustrates the frequencies at which return loss ratio is measured for each antenna standard.

Figure 47 illustrates a chart showing template conformity requirements for antennas depending on the standard and the operating frequency range.

Figure 48 illustrates a chart showing template A illustrating the directivity (measured in dB) as a function of the angle relative to the direction of the main response (measured in degrees).

Figure 49 illustrates a chart showing template B illustrating the directivity (measured in dB) as a function of the angle relative to the direction of the main response (measured in degrees).

Figure 50 illustrates a chart showing the acceptable requirements for cross polar protection for different antenna standards at different operating frequency ranges.

Figure 51 illustrates a chart showing the requirements for feeder pickup for different antenna standards at different operating frequency ranges.

Figure 52 illustrates schematically the apparatus for measuring feeder pickup.

Detailed Descrintion 2 0 There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to

unnecessarily obscure the description.

Referring to Figure 3 herein, there is illustrated schematically a plan view of a director according to a first embodiment of the invention. The director so comprises a director boom 301. The director boom 301 comprises an elongate support. The elongate support is formed from any suitable material, for example aluminium or aluminium alloy. The director boom 301 further comprises a reflector connection 302 configured to afffix a reflector to the boom 301, a dipole connector 303 configured to affix a dipole to the boom 301, a launch director 304, and a first, second, third, fourth and fifth director element locator (305, 306, 307, 308 and 309 respectively). A first, second, third, fourth and fifth director element (310, 311, 312, 313 and 314 respectively) is affixed to the respective director elements locator (305 to 309). The boom further comprises a rear end 315 and a front end 316. The director elements are X-type elements.

A distance 317 from the rear end 315 to the reflector connector 302 is 100 o mm. A distance 318 from the reflector connector 302 to the dipole connector 303 is 160 mm. A distance 319 from the dipole connector 303 to the launch director 304 is 38 mm. A distance 320 from the launch director 304 to the first director element locator 305 is 72 mm. A distance 321 from the first director element locator 305 to the second director element locator 306 is 85 mm. A distance 322 :5 from the second director element locator 306 to the third director element locator 307 is 106 mm. A distance 323 from the third director element locator 307 to the fourth director element locator 308 is 115 mm. A distance from the fourth director element locator 308 to the fifth director element locator 309 is 94 mm. A distance 325 from the fifth director element locator 309 to the front of the boom 316 is 11 o mm. The total length of the boom is 781 mm.

Each director element 310 to 314 is "parasitic", and does not require electrical connection to the boom. In this embodiment, the director elements 310 to 314 are connected to the boom 301 via plastic connecting elements 326 to 330. The director element locators on the boom 301 comprise holes. Each director element connection element 326 to 330 is affixed to the boom 301 by locating the connecting elements 326 to 330 over the respective hole 305 to 309 and inserting a screw or a bolt to affix each director element 326 to 330 in place.

The director elements are of different lengths. The first director element 310 and the second director element 311 have a length 331 of 250 mm. The third, fourth and fifth director elements 312, 313, 314 have a length 332 of 230 mm.

Referring to Figure 4 herein, there is illustrated schematically a first assembly of a reflector according to the first specific embodiment. The first assembly of the reflector comprises a reflector support 401, and a plurality of reflector elements 402, 403, 404, 405 extending laterally from the reflector support 401. The reflector support 401 has a top end 406 and a bottom end 407.

Each reflector element comprises a cylindrical tube with a length of 590 mm, an outer diameter of 8 mm, and a wall thickness of 0.8 mm. The ends of the reflector element are crimped to prevent ingress of water. Alternatively, a cap such as a plastic end-cap may be placed over each end of each reflector element. The reflector element support comprises a plurality of holes. Each reflector element 402, 403, 404, 405 is affixed to the reflector element support 401 by inserting it through a hole at the required location on the reflector element support 401.

A distance from the top end 406 to the first reflector element 402 is 15 mm.

A distance 409 from the first reflector element 402 to the second reflector element 403 is 150 mm. A distance 410 from the second reflector element 403 to the third reflector element 404 is 100 mm. A distance 411 from the third reflector element 404 to the fourth reflector element 405 is 50 mm. A distance 412 from the fourth reflector element 405 to a mounting hole 414 is 15 mm. A distance from the mounting hole 414 to the end of the reflector element support 407 is 28 mm. The total length of the reflector element support 406 is 358 mm.

The antenna according to the first specific embodiment requires two reflector assemblies as shown in Figure 4. Referring to Figure 5 herein, there is illustrated schematically two reflector assemblies connected together.

Each reflector assembly comprises a reflector element support 401 and a series of reflector elements 402, 403, 404, 405. The first reflector assembly 500 is connected to a second reflector assembly 501 by an arrow plate fixing 502.

The arrow plate fixing 502 ensures that the first reflector assembly 500 is maintained at the required angle of 140 to the second reflector assembly 501.

The arrow plate fixing 502 further comprises means for fixing the first reflector assembly 500 and the second reflector assembly 501 to the boom 301.

Referring to Figure 6 herein, there is illustrated schematically a section of a JO dipole for use with the antenna. The dipole comprises a first and a second section. Each section is formed from a strip of metal 601. The strip of metal 601 has a length 602 of 410 mm, and a width 603 of 10 mm. The strip of metal 601 comprises location holes 604, 605 located at either end of the strip of metal 601.

Each location hole 604, 605 has a diameter of 6 mm. The centre of each location holes 604, 605 is 6 mm from the respective edge of the strip of metal 601. The strip of metal is formed from aluminum to provide the required strength, conductivity and corrosion resistance.

A section of the dipole 606 is formed from the strip of conducting metal 601.

2 o The strip of metal 601 is bent into a loop such that the first location hole 604 is in close proximity to the second location hole 605. A first bend portion 607 is disposed in proximity to the first location hole 604 and bends the strip of metal 601 away from a central axis 612. A second bend portion 608 bends the strip of metal 601 towards the central axis 612. A third bend portion 609 bends the strip of metal 601 such that the third bend portion passes across the central axis 612.

A fourth bend portion 610 bends the strip of metal 601 towards the central axis 612. A fifth bend portion 611, located in close proximity to the second location hole 605, bends the strip of metal away from the central axis 612. The strip of metal 601 is substantially formed into a loop to form the section of the dipole.

Referring to Figure 7 herein, there is illustrated schematically a perspective view of a dipole. The dipole comprises a first dipole section 606 and a second dipole section 705. The second dipole section 705 is substantially the same in form and materials to the first dipole section 606. Each dipole section 606, 705 is affixed to a housing 701. The dipole housing 701 further comprises a balun 702.

A bolt or screw 704 extends through the balun 702 and the dipole housing 701, and through the location holes 604, 605 to ensure firm mechanical and electrical connection between the dipole section 606 and the balun 704. The dipole housing 701 is also used to mechanically affix the dipole to the boom 301.

The dipole is affixed to the boom at the dipole location point 303.

The assembled antenna comprises a director, a dipole, a first reflector assembly, a second reflector assembly, and a support. The director comprises a boom and director elements, and is disposed normal to the support. The first reflector assembly and the second reflector assembly are disposed at opposing sides of the director. Each reflector assembly is disposed at substantially 70 to the director. The dipole is affixed to the director.

Referring to Figure 8 herein, there is illustrated a graph showing a forward gain of the antenna as a function of the frequency. The x-axis 801 illustrates the o frequency in megahertz (MHz), the y-axis 802 illustrates the forward gain measured in decibels (dB) and the line 803 illustrates the forward gain as a function of the frequency.

Referring to Figure 9 herein, there is illustrated a graph of a directivity of the z5 antenna. The x-axis 901 shows the angle of the antenna in degrees, and the y axis 902 shows the gain at that angle measured in decibels. Plots of directivity are shown at different frequencies 903, 904.

Referring to Figure 10 herein, there is illustrated a graph of a feeder pickup of the antenna. The x-axis 1101 shows the frequency measured in megahertz, and the y-axis 1102 shows the feeder pickup measured in decibels. The line 1103 shows the response of the antenna at different frequencies.

Referring to Figure 11 herein, there is illustrated a graph of a return ratio of the antenna. The x-axis 1101 represents the frequency in megahertz, and the y- axis 1102 measures the return ratio in decibels. The line 1103 illustrates the return ratio of the antenna at different frequencies.

Referring to Figure 12 herein, there is illustrated a graph of a crosspolar protection of the antenna. The x-axis 1201 represents the frequency in megahertz, and the y-axis 1202 represents the cross-polar protection measured in decibels. The line 1203 represents the cross-polar protection response of the antenna according to the first specific embodiment of a function of frequency.

According to a second specific embodiment, ten director elements are provided rather than five director elements. This requires a longer boom, which can comprise a boom formed of a single section or a plurality of boom sections that can be affixed together to provide a single boom.

Referring to Figure 13 herein, there is illustrated schematically a plan view of a first boom section according to a second specific embodiment. The first boom section 1301 comprises a first end 1302 and a second end 1303. The first boom section 1301 further comprises a hole 1304 configured to affix a reflector, a hole 1305 configured to affix a dipole onto the first section 1301, a launch director 1306, a series of direction elements locators 1307, 1308, 1309, 1310, a first director element 1311, a second director element 1312, a third director element 1313 and a fourth director element 1314.

A distance 1315 between the first end 1302 and the hole for affixing the reflector 1304 is 115 mm. A distance 1316 between the hole for affixing thee reflector 1304 to the hole for affixing the dipole 1305 is 170 mm. A distance 1317 between the hole for affixing the dipole 1305 to the launch director 1306 is 38 mm. A distance 1318 between the launch director 1306 and the hole for affixing the first director element 1307 is 74 mm. A distance between the hole for affixing the first element 1307 and the hole for affixing the second element 1308 is 61 mm. A distance 1320 between the hole for affixing the second element 1308 and the hole 1309 for affixing the third element is 86 mm. A distance 1321 between the hole 1309 for affixing the third element and the hole 1310 for affixing the fourth element is 100 mm. A distance 1322 between the hole 1310 for affixing the fourth element to the second end of the first boom section 1303 is 41 mm.

The total length of the first boom section is 685 mm.

The first director element 1311 has a length 1323 of 250 mm. The second, third and fourth director elements 1312, 1313, 1314 have a length 1324 of 230 So mm. The director elements 1311, 1312, 1313, 1314 are all affixed to the first boom section 1301 such that they are electrically isolated, and extend laterally either side of the first boom section 1301.

Referring to Figure 14 herein, there is illustrates schematically a plan view z of a second boom section according to the second specific. The second boom section 1401 comprises a first end 1402 and a second end 1416. A connector 1402 is provided for affixing the first end 1403 of the second boom section 1401 to the second end 1303 of the first boom section 1301. A series of location holes 1404, 1405, 1406, 1407, 1408, 1409 are provided in the second boom section 1401 for locating the fifth, sixth, seventh, eighth, ninth and tenth director elements 1410,1411,1412,1413,1414,1415 respectively.

A distance 1417 from the first end 1403 to the location hole 1404 for the sixth director element 1410 is 49 mm. A distance 1418 from the location hole 1404 for the fifth director element 1410 to the location hole 1405 for the sixth director element 1411 is 114 mm. A distance 1419 between the location hole 1405 for the sixth director element 1411 to the location hole 1406 for the seventh director element 1412 is 135 mm. A distance 1420 from the location hole 1406 for the seventh director element 1402 to the location hole 1407 to the eighth director element 1413 is 145 mm. A distance 1421 from the location hole 1407 for the eighth director element1413 to the location hole 1408 for the ninth director element 1414 is 132 mm. A distance 1422 from the location hole 1408 for the ninth director element 1412 to the location hole 1409 to the tenth director element 1415 is 142 mm. A distance 1423 from the location hole 1409 for the tenth director element 1415 to the second end 1416 of the boom 1401 is 33 mm.

The total length of the second section of the boom is 750 mm.

The director elements 1410, 1411 1412, 1413, 1414, 1415 extend laterally from the boom 1401. A length of the fifth, sixth and seventh director elements (1410, 1411, 1412 respectively) is 213 mm. A length of the eighth, ninth and tenth director elements (1413,1414, 1415 respectively) is 210 mm. The reflector and the dipole according to the second specific embodiment are identical to those described in the first specific embodiment.

The first and second reflector assemblies, and the dipole are substantially the same as those disclosed in the first specific embodiment.

The assembled antenna comprises a director, a dipole, a first reflector assembly, a second reflector assembly, and a support. The director comprises a boom and director elements, and is disposed normal to the support. The first reflector assembly and the second reflector assembly are disposed at opposing sides of the director. Each reflector assembly is disposed at substantially 70 to the director. The dipole is affixed to the director.

Referring to Figure 15 herein, there is illustrated a graph showing the forward gain of the antenna as a function of the frequency. The x-axis 1501 JO illustrates the frequency in megahertz (MHz), the y-axis 1502 illustrates the forward gain measured in decibels (dB) and the line 1503 illustrates the forward gain as a function of the frequency.

Referring to Figure 16 herein, there is illustrated a graph of the directivity of :5 the antenna. The x-axis 1601 shows the angle of the antenna in degrees, and the y-axis 1602 shows the gain at that angle measured in decibels. Plots of directivity are shown at different frequencies 1603, 1604.

Referring to Figure 17 herein, there is illustrated a graph of the feeder pickup of the antenna. The x-axis 1701 shows the frequency measured in megahertz, and the y-axis 1702 shows the feeder pickup measured in decibels.

The line 1703 shows the response of the antenna at different frequencies.

Referring to Figure 18 herein, there is illustrated a graph of the return ratio 2 5 of the antenna. The x-axis 1801 represents the frequency in megahertz, and the y-axis 1802 represents the return ratio measured in decibels. The line 1803 illustrates the return ratio of the antenna at different frequencies.

Referring to Figure 19 herein, there is illustrated a graph of the crosspolar protection of the antenna. The x-axis 1901 represents the frequency in megahertz, and the y-axis 1902 represents the cross-polar protection measured in decibels. The line 1903 represents the cross-polar protection response of the antenna according to the first specific embodiment of a function of frequency.

According to a third specific embodiment, the director elements of the antenna have a substantially u-shaped cross-section, and are not X-type Jo elements. Other cross-section shapes, such as v-section can also be used.

Furthermore, the reflector elements also have a substantially u-shaped cross- section, rather than a tubular cross-section. This makes the antenna easier to package when it is stored as separate components.

:5 Referring to Figure 20 herein, there is illustrated schematically a plan view of the director boom and director elements of the antenna according to the third specific embodiment. The director boom 2001 comprises an elongate member formed of box-section conductive metal such as aluminium or aluminium alloy.

The director boom 2001 comprises a first end 2002, a second end 2003, a hole 2004 configured to locate a reflector, a hole 2005 configured to locate a dipole, and eleven director elements (the first to eleventh director elements are numbered 2006 to 2016 consecutively). Each director element 2006 to 2016 extends laterally from either side of the director boom 2001, and is affixed to the boom 2001 such that the director elements are electrically isolated from the 2 5 boom.

A distance 2017 from the first end 2002 of the boom 2001 to the hole 2004 for locating the reflector is 120 mm. A distance from the hole 2004 for locating the reflector to the hole 2005 for locating the dipole is 132 mm. A distance 2019 - 2 from the hole 2005 for locating the dipole to the first director element 2006 is 38 mm. A distance 2020 from the first director element 2006 to the second director element 2007 is 58 mm. A distance 2021 from the second director element 2007 to the third director element 2008 is 73 mm. A distance 2022 from the third director element 2008 to the fourth director element 2009 is 78 mm. A distance 2023 from the fourth director element 2009 to the fifth director element 2010 is 87 mm. A distance 2024 from the fifth director element 2010 to the sixth director element 2011 is 96 mm. A distance 2025 from the sixth director element 2011 to the seventh director element 2012 is 96 mm. A distance 2026 from the seventh JO director element 2012 to the eighth director element 2013 is 92 mm. A distance 2027 from the eighth director element 2013 to the ninth director element 2014 is 93 mm. A distance 2028 from the ninth director element 2014 to the tenth director element 2015 is 78 mm. A distance 2029 from the tenth director element 2015 to the eleventh director element 2016 is 80 mm. A distance from the eleventh director element 2016 to the second end 2003 of the director boom 2001 is 19 mm. The total director boom length is 1,140 mm.

A length of the first director element 2006 is 165 mm. A length of the second director element 2007 is 160 mm. A length of the third, fourth and fifth director elements 2008, 2009, 2010 is 153 mm. A length of the sixth, seventh and eighth director elements 2001, 2012, 2013 is 146 mm. A length of the ninth, tenth and eleventh director elements 2014, 2015, 2016 is 140 mm.

Referring to Figure 21 herein, there is illustrated schematically a plan view of a first reflector assembly according to the third specific embodiment. The reflector comprises two such reflector assemblies.

Each reflector assembly comprises a reflector boom 2101, and three reflector elements 2102, 2103, 2104. The reflector boom 2101 comprises a first end 2105, a second end 2106 and a hole 2107 configured to affix the reflector assembly to a second reflector assembly and also to affix the reflector assembly to the director boom 2001.

Each reflector element 2102, 2103, 2104 extends laterally from each side of the reflector boom 2101 and is affixed to the reflector boom 2101 on an upper surface of the reflector boom 2101 such that each reflector element 2102, 2103, 2104 is electrically isolated from the reflector boom 2101.

Each reflector element 2102, 2103, 2104 is formed from conductive metal such as aluminium or aluminium alloy with a substantially u-shaped cross section.

A distance 2108 from the first end 2105 of the reflector boom 2101 to the first reflector element 2102 is 13 mm. A distance 2109 from the first reflector element 2102 to the second reflector element 2103 is 93 mm. A distance 2110 from the second reflector element 2103 to the third reflector element 2104 is 78 mm. A distance 2111 from the third reflector element 2104 to the hole 2107 is 24 mm. A distance 2112 from the hole 2107 to the second end 2106 is 27 mm. The total length of the reflector boom 2101 is 235 mm.

Referring to Figure 22 herein, there is illustrated schematically an elevation view of a reflector comprising two reflector assemblies. The reflector comprises a first reflector assembly 2201 and a second reflector assembly 2202. The first reflector assembly 2201 is connected to the second reflector assembly 2202 by a mounting plate 2203. The mounting plate 2203 is configured to keep the first reflector assembly 2201 at an angle of 140 2204 relative to the second reflector assembly. The mounting plate 2203 is also configured to affix the reflector to the director boom 2001, such that each reflector assembly is at substantially 70 relative to the director boom 2001.

Referring to Figure 23 herein, there is illustrated a dipole element 2301 according to the third specific embodiment. The dipole element is formed from a tubular section of conductive metal such as aluminium or aluminium alloy having a first end 2302 and a second end 2303.

The dipole element has a first bend portion 2306, and a second bend portion 2307, such that the dipole element forms an incomplete loop and the first end 2301 is disposed in opposition to the second end 2303. The first end 2302 and the second end 2303 are separated by a distance 2308 of 20 mm. The overall length 2309 of the dipole element is 290 mm.

The dipole element 2301 comprises a first edge 2311 and a second edge 2312. A distance 2310 between the first edge 2311 and the second edge 2312 is mm.

A first hole 2304 is located close to the first end 2302, and a second hole 2305 is located close to the second end 2303. Each hole 2304, 2305 has a diameter of 4 mm, and the centre of each hole is 5 mm from the respective end.

The holes 2304, 2305 are used to affix the dipole element 2301 to a housing.

Referring to Figure 24 herein, there is illustrated schematically a perspective view of a dipole. The dipole comprises a dipole element 2301, a housing 2402, a balun 2403, first locating means 2404 and second locating means 2405.

The balun 2403 is affixed to the housing 2402 by the first and second locating means 2404, 2305. The dipole element 2401 is also affixed to the housing 2402 by the first and second locating means 2404, 2405. The first locating means 2404 comprises a screw or a bolt that cooperates with the first hole 2404 of the dipole element 2301 and fixes the first end 2302 of the dipole element to the balun 2403 and the housing 2402. The second locating means 2405 comprises a screw or a bolt that cooperates with the second hole 2305 of the dipole element 2301 and fixes the second end 2303 of the dipole element 2301 to the balun 2403 and the housing 2402.

In addition to securing the balun 2403, the housing 2402 and the dipole element 2301 in the required location, the location means 2404, 2405 also form an electrical connection between the balun 2403 and the dipole element 2301.

Referring to Figure 25 herein, there is illustrated schematically a perspective go view of an assembled antenna according to the third specific embodiment. The antenna comprises a director 2501 with director elements, a first reflector assembly 2502, a second reflector assembly 2504 and a dipole 2503. The first reflector assembly 2502 and the second reflector assembly 2504 are disposed at opposing sides of the director 2501. Each reflector assembly is disposed at s substantially 70 to the director 2501. The dipole 2503 is affixed to the director 1450.

Referring to Figure 26 herein, there is illustrated a graph showing the forward gain of the antenna as a function of the frequency. The x-axis 2601 illustrates the frequency in megahertz (MHz), the y-axis 2602 illustrates the forward gain measured in decibels (dB) and the line 2603 illustrates the forward gain as a function of the frequency.

Referring to Figure 27 herein, there is illustrated a graph of the directivity of the antenna. The x-axis 2701 shows the angle of the antenna in degrees, and the y-axis 2702 shows the gain at that angle measured in decibels. Plots of directivity are shown at different frequencies 2703, 2704.

Referring to Figure 28 herein, there is illustrated a graph of the feeder pickup of the antenna. The x-axis 2801 shows the frequency measured in megahertz, and the y-axis 2802 shows the feeder pickup measured in decibels.

The line 2803 shows the response of the antenna at different frequencies.

Referring to Figure 29 herein, there is illustrated a graph of the return ratio of the antenna. The x-axis 2901 represents the frequency in megahertz, and the y-axis 2902 represents the return ratio measured in decibels. The line 2903 illustrates the return ratio of the antenna at different frequencies.

Referring to Figure 30 herein, there is illustrated a graph of the crosspolar protection of the antenna. The x-axis 3001 represents the frequency in megahertz, and the y-axis 3002 represents the cross-polar protection measured :5 in decibels. The line 3003 represents the cross-polar protection response of the antenna according to the first specific embodiment of a function of frequency.

According to a fourth specific embodiment, an antenna is provided having x- shaped director elements and reflector elements with a substantially ushaped cross-section.

Referring to Figure 31 herein, there is illustrated schematically a plan view of a director boom according to the fourth specific embodiment.

The director boom 3101 comprises an elongate section having a first end 3102 and a second end 3103. A hole 3104 is provided for affixing a reflector to the director boom 3101, and a second hole 3105 is provided for affixing a dipole.

A launch director 3106 is also provided extending laterally either side of the boom 3101. The boom is configured to support five director elements (not shown) and accordingly has five director element fixing locations (3107, 3108, 3109, 3110, 3111).

A distance between the first end 3102 and the hole 3104 for affixing the reflector is 100 mm. A distance 3113 from the hole 3104 for affixing the reflector to the hole 3105 for affixing the dipole is 160 mm. A distance 3114 from the hole 3105 for affixing the dipole to the launch director 3106 is 38 mm. A distance 2 o 3115 from the launch director 3106 to the first director position 3107 is 72 mm. A distance 3116 from the first director position to the second director position 3108 is 85 mm. A distance 3117 from the second director position 3108 to the third director position 3109 is 106 mm. A distance 3118 from the third director element position 3109 to the fourth director element position 3110 is 115 mm. A 2 distance 3119 from the fourth director element position 3110 to the fifth director element position 3111 is 94 mm. A distance 3120 from the fifth director element position 3111 to the second end of 3103 of the boom 3101 is 11 mm. The overall boom length is 781 mm.

Referring to Figure 32 herein, there is illustrated schematically a plan view of a reflector assembly according to a fourth specific embodiment. The reflector assembly 3200 comprises a reflector boom 3201, and four reflector elements 3203, 3204, 3205, 3206. The reflector boom 3201 has a first end 3207 and a second end 3208. Each reflector element 3203, 3204, 3205, 3206 has a substantially u-shaped cross-section and is comprised of a conducting material such as aluminium or aluminium alloy. The reflector elements 3203, 3204, 3205, 3206 are affixed to the reflector boom 3201 by fixing means 3209, 3210, 3211, JO 3212 such that each reflector element extends laterally either side of the boom 3201 and each reflector element is affixed to an upper surface of the boom 3201.

The reflector boom 3201 further comprises a hole 3213 to which a mounting plate can be affixed.

A distance 3214 between the first end 3207 of the reflector boom 3201 and the first reflector element 3203 is 15 mm. A distance 3215 from the first reflector element 3203 to the second reflector element 3204 is 115 mm. A distance 3216 between the second reflector element 3210 and the third reflector element 3211 is 100 mm. A distance 3217 between the third reflector element 3211 and the fourth reflector element 3212 is 50 mm. A distance 3218 between the fourth reflector element 3212 and the hole 3213 configured to affix a mounting plate is mm. A distance 3219 between the hole 3213 configured to affix mounting plate and the second end 3208 of the reflector boom 3201 is 358 mm.

Referring to Figure 33 herein, there is illustrated schematically a reflector comprising two reflector assemblies. A first reflector assembly 3300 is affixed to a second reflector assembly 3301 using a mounting plate 3302. A mounting plate 3302 is configured to maintain the first reflector assembly 3200 at an angle of 140 relative to the second reflector assembly 3301. A mounting plate 3202 is also configured to the reflector to the boom 3101.

The dipole of this antenna is substantially the same as that described in the first embodiment of the invention.

According to a fifth specific embodiment, there is provided an antenna substantially the same as that described in the fourth embodiment, except that JO each reflector assembly comprises only three reflector elements.

Referring to Figure 34 herein there is illustrated schematically a first reflector assembly according to the fifth specific embodiment. The first reflector assembly comprises a reflector boom 3401 having a first end 3402 and a second end 3403, a first reflector element 3404, a second reflector element 3405 and a third reflector element 3406.

The reflector boom 3401 is formed of aluminium or aluminium alloy and has a box-section cross section. The reflector boom 3401 further comprises a go mounting hole 3412 configured to affix the first reflector assembly to a mounting plate.

Each reflector element 3404, 3405, 3406 has a substantially u-shaped cross section and is mounted on an upper surface of the reflector boom 3401 such that they extend laterally either side of the reflector boom 3401, an are electrically isolated from the reflector boom 3401. The reflector elements 3404, 3405, 3406 comprise a conductive material such as aluminium or aluminium alloy.

A distance 3407 between the first end 3402 and the first element 3403 is 17 mm. A distance 3408 between the first element 3404 and the second element 3405 is 100 mm. A distance 3409 between the second element 3405 and the third element 34006 is 50 mm. A distance 3410 between the third element 3406 and the mounting hole 3412 is 15 mm. A distance 3411 between the mounting hoe 3412 and the second end 3403 is 28 mm. The overall length of the reflector JO boom is210 mm.

The reflector comprises 2 reflector units mounted at 140 relative to each other. The director boom and director elements are substantially the same as those described in the fourth embodiment, and the dipole is substantially the same as that described in the first embodiment. The reflector, director and dipole are disposed relative to each other in the same way as described in the first specific embodiment.

According to a sixth specific embodiment, there is provided an antenna substantially the same as that described in the fourth specific embodiment, accept that the director boom comprises ten director elements rather than five director elements.

To accommodate ten director elements the director boom must be longer than that described in the fourth embodiment. In this embodiment, the boom comprises a first boom section and a second boom section, although it will be apparent to one skilled in the art that a boom formed of a single section can also be used.

The director boom and the director elements are substantially the same as those described in the second specific embodiment. The reflector elements and reflector are substantially the same as those described in the fourth specific embodiment. The dipole is substantially the same as that described in the first specific embodiment. The reflector, director and dipole are disposed relative to each other in the same way as described in the first specific embodiment.

According to a seventh specific embodiment, there is provided an antenna having 10 X-type director elements and 3 reflector elements on each reflector unit.

The director is substantially the same as that described in the second specific embodiment. The dipole is substantially the same as that described in the first specific embodiment. The reflector is substantially the same as that described in the fifth specific embodiment. The reflector, director and dipole are disposed relative to each other in the same way as described in the first specific 2 0 embodiment.

According to an eighth specific embodiment, there is provided an antenna having 5 director elements, and each reflector unit having 3 reflector elements.

Each reflector elements is formed of tubular metal rather than u-shaped cross- 2 5 section.

The director and dipole are substantially the same as those described in the first specific embodiment.

Each reflector unit comprises three reflector elements and a reflector boom.

Each reflector element is formed of tubular conductive material such as aluminium or aluminium alloy. The reflector boom comprises a plurality of holes, each of which is configured to locate a reflector element. The reflector elements are located in the required holes such that they extend laterally either side of the reflector boom. The spacings of the reflector elements along the length of the To reflector boom are substantially the same as those described in the eighth specific embodiment. The reflector comprises 2 reflector units mounted at 140 relative to each other.

The reflector, director and dipole are disposed relative to each other in the s same way as described in the first specific embodiment.

In a ninth specific embodiment, there is provided an antenna having 10 director elements, and each reflector unit having 3 reflector elements. Each reflector elements is formed of tubular metal rather than u-shaped cross-section.

The director is substantially the same as that described in the second specific embodiment. The dipole is substantially the same as that described in the first specific embodiment. The reflector is substantially the same as that described in the eighth specific embodiment. The reflector, director and dipole s are disposed relative to each other in the same way as described in the first specific embodiment.

For the above nine specific embodiments, the dipole element is described as being positioned below the director boom for each antenna, extending laterally either side of the boom and disposed at substantially 90 to the boom. However, it is possible for the dipole element to be angled at angles other than 90 to the boom, and indeed to be positioned either above or below the director boom when the antenna is installed.

Furthermore, for all of the above specific embodiments, there are many different ways that the dipole can be mounted to the director boom. The dipole can be fixed to the director boom by attaching the housing using conventional fixing means such as screws, nuts and bolts and so on. Furthermore, the housing my comprise a lug to locate in the hole for locating the dipole in combination with a snap-fitting that snap fits about the director boom. In this way, the dipole housing can be securely fitted to the director boom without the necessity for a separate fixing means such as a bolt or screw..

In a tenth specific embodiment, an antenna is provided having an inclined dipole element.

* So Referring to Fig. 35 herein, there is illustrated schematically a dipole mounted on a director boom. The director boom 2001 and the reflector are the same as those described in the third embodiment. The dipole comprises a housing 3501 mounted on the director boom 2001, and an element 3502. The element 3502 is disposed at an angle 3503 of substantially 120 relative to the :s director boom 2001. The angle of 120 is to increase a transfer of a received signal from the first director element 2006 to the dipole element 3502.

The reflector, director and dipole are disposed relative to each other in the same way as described in the first specific embodiment.

According to an eleventh specific embodiment, there is provided an antenna having eight director elements. The director elements have a substantially U shaped cross-section, although other cross-section shapes such as the-section can also be used. Referring to Figure 36 herein, there is illustrated schematically a planned view of the director of the antenna according to the eleventh specific embodiment. The director boom 3601 comprises an elongate member formed of o box-section conductive metal such as aluminium or aluminium alloy. The director boom 3601 comprises a first end 3602, a second end 3603, an attachment point 3604 configured to locate a reflector assembly, an attachment point 3605 configured to locate a dipole, and eight director elements (the first to eighth director elements are numbered 3606 to 3613 consecutively). Each director element 3606 to 3613 extends laterally from either side of the director boom 3601 and is affixed to the boom 3601 such that the director elements are electrically isolated from the boom.

A distance 3614 from the first end 3602 of the boom 3601 to the attachment 2 o point 3604 for locating the reflector assembly is 110 mm. A distance 3615 from the attachment point 3604 for locating the reflector assembly to the attachment point 3605 for locating the dipole is 152 mm. A distance 3616 from the attachment point 3605 for the dipole to the first director element is 38 mm. A distance 3617 from the first director element 3606 to the second director element 3602 is 56 mm. A distance 3618 from the second director element 3607 to the third director element 3608 is 80 mm. A distance 3619 from the third director element 3608 to the fourth director element 3609 is 85 mm. A distance 3620 from the fourth director element 3609 to the fifth director element 3610 is 111 mm. A distance 3621 from the fifth director element 3610 to the sixth director element 3611 is 116 mm. A distance 3622 from the sixth director element 3611 to the seventh director element is 127 mm. A distance 3623 from the seventh director element 3612 to the eighth director element 3613 is 98 mm. A distance 3624 from the eighth director element 3612 to the second end 3603 of the boom 3601 is 15 mm. The overall director boom 3601 length is 988 mm.

A length of the first director element 3606 is 165 mm. A length of the second, third and fourth director elements 3607, 3608, 3609 is 153 mm. A length of the fifth and sixth director elements 3610, 3611 is 146 mm. A length of the seventh director element 3612 is 134 mm. A length of the eighth director o element 3613 is 126 mm.

Referring to Figure 37 herein, there is illustrated a dipole element according to the eleventh specific embodiment. The dipole element 3701 is formed from a tubular section of conductive metal such as aluminium or aluminium alloy having a first end 3702 and a second end 3703. The dipole element has a first bend portion 3704 and a second bend portion 3705, such that the dipole element forms an incomplete loop and the first end 3702 is disposed opposite the second end 3703. The first end 3702 and the second end 3703 are separated by a distance 3706 of 20 mm. The dipole element 3701 comprises a first substantially linear edge 3707 and a second substantially linear edge 3708. A distance 3709 between the first edge 3707 and the second edge 3708 is 57.5 mm. An overall length 3710 of the dipole element 3701 is 260 mm.

A first hole 3711 is located close to the first end 3702, and a second hole 3712 is located close to the second end 3703. Each hole 3711, 3712 has a diameter of 4 mm, and the centre of each hole is 5 mm from its respective end.

The holes 3711, 3712 are used to affix the dipole element 3701 to a housing.

The dipole element and housing are substantially as illustrated in Figure 24.

Referring to Figure 38 herein, there is illustrated schematically a planned view of a first reflector assembly according to the eleventh specific embodiment.

The reflector comprises two such reflector assemblies mounted in opposition to each other. Each reflector assembly 3801 comprises a reflector boom 3802, and 3 reflector elements 3803, 3804, 3805. The reflector boom 3802 comprises a first end 3806, a second end 3807 and anattachment point 3808 configured to affix the reflector assembly to a second reflector assembly, and also to affix the reflector assembly to the director boom 3601 at the reflector assembly JO attachment point 3604. Each reflector element 3803, 3804, 3805 extends laterally from each side of the reflector boom 3802 and is affixed to the reflector boom 3802 such that each reflector element 3803, 3804, 3805 is electrically isolated from the reflector boom 3802.

Each reflector element 3803, 3804, 3805 is formed from conductive metal such as aluminium or aluminium alloy with a substantially U-shaped cross section.

A distance 3809 from the first end 3806 of the reflector boom 3802 to the first reflector element 3803 is 10 mm. A distance 3810 from the first reflector element 3803 to the second reflector element 3809 is 140 mm. A distance 3811 from the second reflector element 3804 to the third reflector element 3805 is 65 mm. A distance 3812 from the third reflector element 3805 to the reflector element attachment point 3808 is 33 mm. A distance 3813 from the reflector :s element attachment point 3808 to the second end 3807 of the reflector boom 3802 is 27 mm. The total length of the reflector boom 3802 is 275 mm.

The first reflector element 3803, and the third reflector element 3805 have an overall length of 495 mm. The second reflector element 3804 has an overall length of 386 mm.

A reflector comprises two reflector assemblies similar to those illustrated in Figure 22. The director, reflector, and dipole are assembled in the same way as described for the third specific embodiment.

According to a twelfth specific embodiment, there is provided an antenna JO having a longer dipole. Referring to Figure 39 herein, there is illustrated a dipole element according to the twelfth specific embodiment. The dipole element 3901 is formed from a tubular section of conductive metal such as aluminium or aluminium alloy having a first end 3902 and a second end 3903.

The dipole element has a first bend portion 3904, and a second bend portion 3905, such that the dipole element forms an incomplete loop and the first end 3902 is disposed in opposition to the second end 3903. The first end 3902 and the second end 3903 are separated by a distance of 20 mm. The overall length of 3904 of the dipole element is 270 mm. The dipole element 3901 comprises a first substantially straight portion 3907 and a second substantially straight portion 3908. A distance of 3909 between the first edge 3907 and the second edge 3908 is 57.5 mm.

A first hole 3910 is located close to the first end 3902 and a second hole 3908 is located close to the second end 3903. Each hole 3910, 3911 has a diameter of 4 mm and the centre of each hole is 5 mm from its respective end.

The holes 3910, 3911 are used to affix the dipole element 3901 to a housing.

ln all other respects the twelfth specific embodiment is identical to the eleventh specific embodiment.

According to a thirteenth specific embodiment, there is provided an antenna having 11 director elements. Referring to Figure 40 herein, there is illustrated schematically a plan view of a director according to the thirteenth specific embodiment. The director 4001 comprises a director boom 4002. The director boom 4002 comprises an elongate support that is formed from any suitable material for example aluminium or aluminium alloy. The director boom 4002 comprises a first end 4003, a second end 4004, an attachment point 4005 configured to locate a reflector, an attachment point 4006 configured to locate a dipole, and eleven director elements (the first to eleventh director elements are numbered 4007 to 4017 consecutively). Each director element 4007 to 4017 extends laterally from either side of the director boom 4002, and is affixed to the boom 4002 such that each director element is electrically isolated from the boom 4002.

A distance 4018 from the first end 4003 of the boom 4002 to the attachment point 4005 for a reflector is 90 mm. A distance 4019 from the attachment point 4005 for a reflector to the attachment point 4006 for a dipole is 150 mm. A distance 4020 from the attachment point 4006 for a dipole to the first director element 4007 is 38 mm. A distance 4021 from the first director element 4007 to the second director element 4008 is 61 mm. A distance 4022 from the second director element 4008 to the third director element 4009 is 8 mm. A distance 4023 from the third director element 4009 to the fourth director element 4010 is 82 mm. A distance 4024 from the fourth director element 4010 to the fifth director element 4011 is 84 mm. A distance 4025 from the fifth director element 4011 to the sixth director element 4012 is 97 mm. A distance 4026 from the sixth director element 4012 to the seventh director element 4013 is 103 mm. A distance 4027 from the seventh director element 4013 to the eighth director element 4014 is 84 mm. A distance 4028 from the eighth director element 4014 to the ninth director element 4015 is 95 mm. A distance 4029 from the ninth director element 4015 to the tenth director element 4016 is 80 mm. A distance 4030 from the tenth director element 4016 to the eleventh director element 4017 is 85 mm. A distance 4031 from the eleventh director element 4017 to the second end 4004 of the director boom 41002 is 11 mm. The total overall length of the director broom 4002 is 1,140 mm.

A length of the first director element 4007 is 165 mm. A length of the second director element is 160 mm. A length of the third director element 4009 is 153 mm. A length of the fourth, fifth, sixth, seventh and eighth director elements 4010, 4011, 4012, 4013, 4014 is 146 mm. A length of the ninth and tenth s director elements 4015, 4016 is 140 mm. A length of the eleventh director element 4017 is 126 mm. The dipole and reflector are identical to those described in the eleventh specific embodiment, as is the overall construction of the antenna.

o According to a fourteenth specific embodiment, there is provided an antenna having an identical director to that described in the thirteenth specific embodiment, an identical reflector to that described in the eleventh specific embodiment, and an identical dipole to that described in the twelfth specific embodiment. The overall assembly of the antenna is the same as that described for the eleventh specific embodiment.

According to a fifteenth specific embodiment, there is provided an antenna having 16 director elements. Referring to Figure 41 herein, there is illustrated schematically a planned view of boom indirect elements of the antenna according to the fifteenth specific embodiment.

The director comprises a first director boom section 4101 and a second director boom section 4102. The first director boom section 4101 has a first end 4103 and a second end 4104. The first beam section 4101 further comprises an elongate member from the box-section conductive metal such as aluminium or aluminium alloy. The first boom section 4101 further comprises an attachment point 4105 configured to locate a reflector, an attachment point 4106 configured to locate a dipole, and 8 director elements (numbered 4107 to 4114 consecutively). Each director element 4107 to 4114 extends laterally from either side of the first boom section 4101, and is affixed to the first boom section 4101 such that each director element is electrically isolated from the boom section 4101.

The second boom section 4102 comprises a first end 4115 and a second end 4116. When assembled, the second end 4104 of the first boom section 4101 is attached to the first end 4115 of the second boom section 4102 such that the first boom section 4101 and the second boom section 4102 form a single 2 0 director boom.

The second director boom section 4102 comprises the ninth to sixteenth director elements (numbered 4117 to 4124). Each director element 4117 to 4124 is electrically isolated from the second boom section 4102, and extends laterally from either side of the second boom section 4102. The second boom section 4102 comprises an elongate member formed of box-section conductive metal such as aluminium or aluminium alloy.

A distance 4125 from the first end 4103 of the first director boom section 4101 to the attachment point 4105 for locating a reflector is 40 mm. A distance 4126 from the attachment point 4105 for locating a reflector to the attachment point 4106 for locating a dipole is 150 mm. A distance of 4127 from the attachment point 4106 for locating a dipole to the first director element 4107 is 40 mm. A distance 4128 from the first director element to the second director element 4108 is 53 mm. A distance 4129 from the second director element 4108 to the third director element is 56 mm. A distance 4130 from the third director element 4109 to the fourth director element 4110 is 74 mm. A distance 4131 JO from the fourth director element 4110 to the fifth director element 4111 is 108 mm. A distance 4132 from the fifth director element 4111 to the sixth director element 4112 is 85 mm. A distance 4133 from the sixth director element 4112 to the seventh director element 4113 is 90 mm. A distance 4134 from the seventh director element to the eighth director element 4114 is 106 mm. A distance 4135 from the eighth director element 4114 to the second end 4104 of the first boom section 4101 is 48 mm. The overall length of the first boom section 4101 is 850 mm.

A distance 4136 from the first end 4115 of the second boom section 4102 to the ninth director element 4117 is 69 mm. A distance 4137 from the ninth director element 4117 to the tenth director element 4118 is 112 mm. A distance 4138 from the tenth director element 4118 to the eleventh director element 4119 is 102 mm. A distance 4139 from the eleventh director element 4119 to the twelfth director element 4120 is 104 mm. A distance 4140 from the twelfth director element 4120 to the thirteenth director element 4121 is 112 mm. A distance 4141 from the thirteenth director element 4121 to the fourteenth director element 4122 is 93 mm. A distance 4142 from the fourteenth director element 4122 to the fifthteenth director element 4123 is 127 mm. A distance 4143 from the fifteenth director element to the sixteenth director element 4124 is 107 mm.

A distance 4144 from the sixteenth director element 4124 to the second end 4116 of the second boom section 4102 is 24 mm. The total overall length of the second boom section 4102 is 850 mm.

The length of the first director element 4107 is 165 mm. The length of the second director element 4108 is 153 mm. The length of the third, fourth, fifth and sixth director elements 4109, 4110, 4111, 4112 is 146 mm. The length of the seventh. eighth, ninth, tenth, eleventh, twelfth and thirteenth director elements 4113, 4114, 4117, 4118, 4119, 4120, 4121 is 140 mm. The length of the fourteenth director element 4122 is 134 mm. A length of the fifteenth and sixteenth director elements 4123, 4124 is 126 mm.

The reflector and dipole are identical to those described for the eleventh specific embodiment with reference to Figures 37 and 38. The overall assembly of the antenna according to the fifteenth specific embodiment is also the same as that described in the eleventh specific embodiment.

According a sixteenth specific embodiment, there is provided an antenna having the same director as that described for the fifteenth specific embodiment with reference to Figure 41, the same reflector as described for the eleventh specific embodiment with reference to Figure 38, and the same dipole as described for the twelfth specific embodiment with reference to Figure 39. The overall assembly of the director, dipole and reflector are substantially the same as that described for the tenth specific embodiment.

2 5 Testing of antennas The standards BS 5640: 1, 11 1978 and ITU-R. BT. 419-3 are used as a guide in testing antennas.

Definitions Operating Frequency Range: Spectrum between maximum and minimum frequencies of particular antenna group.

Group A: Minimum 470 MHz maximum 606 MHz, centre frequency 538 MHz.

Group B: Minimum 582 MHz maximum 734 MHz, centre frequency 658 To MHz.

Group CD: Minimum 686 MHz maximum 854 MHz, centre frequency 770 MHz.

Group E: Minimum 582 MHz maximum 854 MHz, centre frequency 718 MHz.

i Group K: Minimum 470 MHz maximum 694 MHz, centre frequency 852 MHz.

Group W (Wideband): Minimum 470 MHz maximum 854 MHz, centre frequency 658 MHz.

Standard 1 Antenna: (Highest Standard) Standard 2 Antenna: (Intermediate standard) Standard 3 Antenna: (Minimum Accepted Standard) Standard 4 Antenna: (Log periodic antenna standard) 2 5 Polarisation: Horizontally Mounted Antenna or a Vertically Mounted Antenna.

Forward Gain dBd: Reference to a Half Wave Dipole.

Forward Gain dBi: Reference to an Isotropic Source.

Dimension drawing: Documentary evidence of the "Active" parts of an antenna. Clearly showing construction details of all physical dimensions, spacings and tolerances of the director elements and drive element.

"Active" parts: An active part of an antenna is one, which contributes to the electrical performance of an antenna. E.g. director elements, driven element or balun. Non "active" parts would include plastic parts and clamping arrangements if not used as circuit connections in the antenna design. Active parts typically comprise a conductive material such as aluminium, aluminium alloy or anodized o aluminium.

Tolerance: Maximum tolerance to be +/- 3mm.

Active Dipole: A dipole with a built in amplifier.

"Forward Gain" figures are quoted in dBd i.e. gain versus a half wave dipole as defined in BS5640.

Coaxial Cable Connections This procedure defines the methods adopted for the identification of examination and assessment status of an antenna's cable connection. The procedure is: 1. Ensure that the inner and outer coaxial cable core termination points on the dipole connection, are a minimum of 3mm and no more than 20mm apart. (If the installer prepares the coaxial cable correctly this distance will prevent any short circuits).

2. This section is not applicable to F type terminations.

Figure 36 herein illustrates the requirements for a coaxial cable connections pass for each antenna standard.

Tiltinq Mechanism This procedure defines the method adopted for the identification of examination and assessment status of an antenna's tilting mechanism. Figure 37 herein illustrates the requirements showing which antenna standard requires the tilting mechanism test to be carried out.

The tilting method must incline the antenna from a level plane up to a minimum of 15 degrees. Level of Accuracy is +/- 2 degrees.

An antenna that is designated to have a tilting method, and found not to have one will fail this stage of the benchmark.

Electrical Characteristics: Forward Gain This procedure defines the method adopted for the identification of examination and assessment status of forward gain of the antenna. The procedure is as follows: 1. Uncertainty to be 1dB and within 95% confidence.

2. Forward gain to be measured in line with the Substitution method outlined in BS5640 Page 2, Section 3.2.1 (IEC page 9).

3. Produce a graphical representation, showing full frequency response of the antenna.

4. A graph, showing the response of the antenna when horizontally polarised is to be produced.

so Figure 38 herein illustrates the requirements of the minimum value of forward gain within the designated operating frequency range of the specified antenna standard.

There should not be any variation in forward gain exceeding 2dB per 8 MHz of operating frequency range.

Where antenna groups overlap e.g. (E, K and WB) the required gain is apportioned into groups of channels as indicated in figure 38.

Electrical Characteristics: Return Loss Ratio This procedure defines the methods adopted for the identification of examination and assessment status of return loss. The procedure is as follows: 1. Uncertaintyto be 1dB and within 95% confidence.

2. In line with Return Loss Ratio (RLR) BS 5640:1 Section 3.17.

3. Produce a graphical representation, ensuring that the defined antenna group centre frequencies are shown at all times.

Referring to figure 39 herein, there is illustrated a chart showing the minimum acceptable values of return loss ratio within the designated operating frequency range of the specified antenna type i.e.1, 2 or 3.

Electrical characteristics: Directivity This procedure defines the methods adopted for the identification of examination and assessment status of directivity. The procedure is as follows: 1. Uncertainty to be 2dB and within 95% confidence.

2. The test is BS 5640:1 Section 3.5, BS5640: II 4.1 Page 4 (IEC page 13) and ITU-R. BT.479.3.

3. Produce linear or logarithmic plots, with the antenna horizontally polarised, for each of the frequencies listed Figure 40. Figure 40 herein illustrates the frequencies at which return loss ratio is measured for each antenna standard.

Referring to Figure 41 herein, there is illustrated a chart showing template conformity requirements for antennas depending on the standard and the operating frequency range.

To Referring to figure 42 herein, there is illustrated a chart showing template A illustrating the directivity (measured in dB) as a function of the angle relative to the direction of the main response (measured in degrees).

Referring to figure 43 herein, there is illustrated a chart showing template B illustrating the directivity (measured in dB) as a function of the angle relative to the direction of the main response (measured in degrees).

Electrical Characteristics: Cross-Polar Protection This procedure defines the methods adopted for the identification of examination and assessment of Cross Polar Protection. The procedure is as follows: 1. Uncertainty to be 1dB and within 95% confidence.

2. Produce a graphical representation, showing full frequency response of the antenna.

3. The test is carried out in accordance with BS BS5640 Page 3, Section 3. 5 (IEC page 11).

4. A graph, showing the response of the antenna when horizontally mounted is to be produced.

Referring to figure 44 herein, there is illustrated a chart showing the acceptable requirements for cross polar protection for different antenna standards at different operating frequency ranges.

Electrical Characteristics: Feeder Pickup This procedure defines the methods adopted for the identification of examination and assessment status of Feeder Pickup. The procedure is as follows: 1. Uncertainty to be 2dB and within 95% confidence.

2. Produce a graphical representation, showing full frequency response of the antenna.

3. The test is carried out in accordance with the method of measurement for feeder pickup below (Dated 11 April 2003, Issue 2, Author: A. Wade).

4. A graph, showing the response of the antenna is to be produced.

Referring to figure 45 herein, there is illustrated a chart showing the requirements for feeder pickup for different antenna standards at different operating frequency ranges.

2 5 Method of Measurement for Feeder Pickup The term "Feeder Pickup" refers to the tendency for the feeder cable of a receiving system to act to some extent as an antenna itself. Signals picked up on the feeder can be coupled into the wanted signal path, thereby reaching the receiver. Although significant feeder pickup can result from the use of poorly o screened coaxial cable, the coupling mechanism that we are concerned with here is that in which the connection between the driven element(s) of the antenna and a well-screened allows RF current flowing on the outside of the outer conductor of a coaxial feeder (common-mode current) to enter the wanted signal path.

Where the driven element is a balanced structure, such as a half-wave dipole, some form of a balance-to-unbalance transformer ("balun") is required to suppress this coupling.

Feeder pickup is usually an unwanted characteristic of an antenna system and can introduce a number of undesirable effects, for example unpredictable modification of the antenna's radiation pattern ("polar diagram") and degradation of its cross-polar discrimination.

Feeder pickup can also lead to raised levels of interference. In particular, interference radiated from sources close to the feeder may, if feeder pickup rejection is inadequate, reach the receiver at a much higher level than if it were picked-up by the antenna alone.

In the context of digital terrestrial television (OTT) reception this is of concern because of the susceptibility of DVB-T systems to electrical impulse interference. Feeder pickup on the antenna system provides a route whereby impulse interference from household electrical equipment can reach the receiver o at levels high enough to cause disturbances to viewing and listening. TV antenna feeders ("downloads") often run close to mains wiring, providing a mechanism for close coupling of such conducted interference.

The CAI/DTG antenna benchmarking standard therefore includes requirements for minimum standards of feeder pickup rejection performance in order to reduce the risk of undue impulse interference.

This document specifies the measurement method to be used for determining feeder pickup rejection (FPU rejection) as part of the benchmarking so test suite. The measurement is based on the use of the ferrite absorbing clamp to inject a common mode signal onto the feeder of the antenna under test (AUT).

The absorbing clamp is a standard piece of equipment used for EMC measurements and is described in CISPR publication 16-1.

FPU rejection is defined for a single-frequency signal. The FPU rejection of an antenna will, in general, vary with frequency across the antenna's bandwidth.

Thus the FPU rejection measurement results for an antenna will take the form of set of data representing FPU rejection versus frequency typically in the form of a frequency response plot.

To FPU rejection is defined as the ratio, expressed in decibels, of the signal level injected onto the feeder of an antenna under test (AUT) using the absorbing clamp to the signal level measured at a receiver connected to the AUT via a length of well-screened coaxial cable. The signal levels referred to are determined after allowing for the calibrated coupling loss of the absorbing clamp and the attenuation of the coaxial cable.

Measurement of FPU is carried out on a suitable outdoor test site complying with the following requirements: 2 o The ground shall be substantially level.

There shall be no significantly obstructions within a cylinder of radius 3 m, with its axis vertical and centred on the position of the AUT and extending upwards from ground level to a height of at least 10 m; in particular there must be no overhead metallic wires, cables or pipes, etc. passing within the cylinder at any height above 1.2m above ground level.

The following equipment is required: 30.A table or structure of height 1 m (50 mm) for supporting the absorbing clamp made of non-conductive material, e.g. timber. The length of the support is sufficient to allow the absorbing clamp to be moved along the feeder by at least half a wavelength at the lowest frequency of interest (320 mm at 470 MHz).

Ä support "mast" for the antenna under test made from non-conductive material and supported by the table referred to above. Suitable means shall be devised to attach the AUT at the specified height. The mast is capable of being rotated about its vertical axis.

An absorbing clamp in accordance with CISPR publication 16-1 (BS 727).

Frequency response (insertion loss) measuring equipment covering at least the frequency range 470-854MHz and comprising a suitable source and receiver - e.g. a spectrum analyser with tracking generator, or a network analyser. Owing to the risk of off-air interference being picked-up by the AUT, the :5 measuring receiver must be selective - i.e. the use of equipment which employs wideband diode detectors (as found in some types of scalar network analyser) is not permitted.

75 Q test cable for connecting signal source to absorbing clamp.

50-75 Q matching pads, and other coaxial adapters and sundry items are required.

Referring to figure 46 herein, there is illustrated schematically the apparatus s for measuring feeder pickup. The apparatus comprises the antenna under test 4601, and insulating support 4602 for the antenna 4601, an absorbing clamp 1303, a receiver or spectrum analyser 4604, and a signal source 4605. The absorbing clamp 4603 is located on a surface 1306 that has a height 4607 of 1 m above a ground surface. A distance 4608 from the support 4606 to the reflector of the antenna 4601 is 0.5m.

A 75 n test cable 4609 connected to the antenna 4601 is routed in accordance with the antenna manufacturer's instructions, or may consist of the "tail" supplied with the antenna for the forward gain and other measurements.

Care must be taken to route of the cable vertically down the support mast 4602 and through the absorbing clamp 4603 in a manner which makes the measurements repeatable. Where a connection is required between a tail supplied with the AUT and the test cable to the receiver, this shall be made with a Type-F back-to-back coupler with a return loss of not less than 20 dB at the highest test frequency. Alternatively a 50-75 n matching pad may be inserted at this point, the remainder of the cable run to the receiver then being 50 n.

Note that measurements are normally taken with the E-plane of the antenna 4601 at right-angels to the antenna cable 4609, to minimise any direct pickup of radiation from the cable 4609 by the antenna4601.

The output level from the signal source 4605 should be kept to a minimum, consistent with obtaining sufficient signal-to-noise ratio in the measurement. A level of O dBm (into the 50 n test cable) is generally satisfactory. Where the antenna 4601 is an active antenna, line-power at the appropriate voltage is injected into the antenna cable using a suitable 75 n bias tee. The latter should exhibit return losses of not less than 20 dB at the highest test frequency.

To determine the FPU rejection of the antenna 4601, the losses in the measurement set-up are "calibrated out". This can be done in a number of ways and the best method will depend on the type of test equipment being used and whether the raw measurement data is being automatically postprocessed in software. This procedure, therefore, does not prescribe any specific method of calibration. The following additional notes may be helpful: The losses of the test cables may be measured separately and included in a results calculation; alternatively the loss of the two cables together may be taken out by use of a "response calibration" or "normalization" facility in the test equipment. Care must be taken however to ensure that cable losses are measure under well-matched conditions and that the losses of attenuator and/or matching pads are properly accounted for.

The loss of the absorbing clamp is obtained from its calibration data. N.B.

The value required is the absolute loss and not the correction value which is sometimes given on calibration certificates. The clamp loss may either be included in a results calculation or be entered as a "amplitude correction table" in the test receiver.

A measurement consists of collecting one or more "sweeps" of insertion loss readings, and may be taken as either a number of discrete frequency points, or as sampled data from a continuous sweep. In either case the frequency interval between readings shall not exceed 4MHz. Averaging may be used to :5 reduce the effect of noise. Before taking measurements it shall be verified that the antenna 1301is not directly picking up radiation from a feeder. This is done by rotating the support mast by up to 90 in each direction whilst observing the insertion loss readings. Any significant change indicates the presence of direct pickup and in this case the mast should be rotated to minimise the indicated RF 2 o level,otherwise return it to the orthogonal E-plane position.

The absorbing clamp 4603 is moved along the support table in order to maximise the indicated RF level. Usually this occurs with the clamp close to the antenna mast 4602.

For each recorded frequency point the FPU rejection is calculated as follows: FPU rejection = measured insertion loss - sum of all loses in test set-up.

Measured data points where the results are clearly being affected by offair interference pickup by the antenna 4601 (e.g. from a local TV transmitter) may be ignored and replaced by interpolated data.

The first embodiment described conforms to standard 2 of the tests. The second embodiment described conforms to standard 2 of the tests. The third embodiment described conforms to standard 3 of the tests. The fourth embodiment described conforms to standard 2 of the tests. The fifth embodiment described conforms to standard 3 of the tests. The sixth embodiment described conforms to standard 2 of the tests. The seventh embodiment described conforms to standard 3 of the tests. The eighth embodiment described conforms to standard 3 of the tests. The ninth embodiment described conforms to standard 3 of the tests. The tenth embodiment described conforms to standard 3 of the tests.

Claims (32)

1. Claims: 1. An antenna device comprising: a dipole; an elongate boom;

   mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; said first reflector assembly comprising a first reflector boom and a plurality of first reflector elements; 20said second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; wherein said reflector assemblies have a width in a direction transverse to a length of said boom, in the range 440 to 490 millimetres and/or 550 to 630 2 5millimetres.
2. 2. The antenna as claimed in claim 1 wherein said plurality of director elements are arranged in a plurality of groups, each said group comprising a pair of said elements placed opposite each other and either side of said boom, 30wherein a maximum distance between tips of said elements in a group are as follows: di for a first group of said elements a distance in the range 245 millimetres to 255 millimetres; for a second group of said elements, a distance in the range 225 millimetres to 235 millimetres; and for a third group of said elements, a distance in the range 205 millimetres to 215 millimetres.
3. 3. The antenna as claimed in claim 1 or claim 2 wherein each director element of said plurality of director elements comprises an x-type element, an x type element comprising; a first pair of elements extending from a first side of said boom; and a second pair of elements extending from a second side of said boom, said second side of said boom being an opposite side to said first side of said boom.
4. 4. An antenna device comprising: a dipole; an elongate boom; 2 5 mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; wherein along a length of said boom, said director elements are spaced at intervals as follows: a distance between a first set of director elements and said dipole, in the range 62 mm to 82 mm; a distance between a second set of director elements and said dipole in the range 147 mm to 167 mm; a distance between a third set of director elements and said dipole in the range 253 mm to 273 mm; a distance between a fourth set of director elements and said dipole in the :s range 368 mm to 388 mm; a distance between a fifth set of director elements and said dipole in the range 462 to 482 mm.
5. 5. The antenna device as claimed in claim 4, wherein said director elements are arranged into groups, each said group comprising a pair of said elements placed opposite each other and either side of said boom, wherein a distance between tips of said director elements in a group are as follows: s for a first group of said director elements a distance in the range 240 millimetres to 260 millimetres; and for a second group of said director elements, a distance in the range 220 m ill imetres to 240 m ill i metres.
6. 6. The antenna as claimed in claim 3 or claim 4 wherein each director element of said plurality of director elements comprises an x-type element, an x- type element comprising; a first pair of elements extending from a first side of said boom; and a second pair of elements extending from a second side of said boom, said second side of said boom being an opposite side to said first side of said boom.
7. 107. An antenna device comprising: a dipole; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a go plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; s wherein along a length of said boom, said director elements are spaced at intervals as follows: a distance between a first set of director elements and said dipole, in the range 102 mm to 122 mm; a distance between a second set of director elements and said dipole, in the range 163 mm to 183 mm; a distance between a third set of director elements and said dipole, in the range 249 mm to 269 mm; a distance between a fourth set of director elements and said dipole in the range 349 mm to 369 mm; a distance between a fifth set of director elements and said dipole in the range 439 mm to 459 mm; a distance between a sixth set of director elements and said dipole in the range 553 mm to 573 mm; a distance between a seventh set of director elements and said dipole in the range 688 mm to 708 mm; a distance between an eighth set of director elements and said dipole in the range 833 mm to 853 mm; a distance between a ninth set of director elements and said dipole in the range 965 mm to 985 mm; a distance between a tenth set of director elements and said dipole in the range 1107 mm to 1127 mm.
8. 8. The antenna device as claimed in claim 7 wherein said director elements are arranged into groups, each said group comprising a pair of said elements placed opposite each other and at either side of said boom, wherein a distance between tips of said director elements in a group are as follows: for a first group of said director elements a distance in the range 240 mm to 260 mm; and for a second group of said director elements, a distance in the range 220 mm to 240 mm; for a third group of said director elements, a distance in the range 200 mm to 220 mm.
9. 9. An antenna device comprising: a dipole; an elongate boom; a plurality of antenna elements mounted to said elongate boom and extending in a direction transverse to a main length of said elongate boom; and a reflector, said reflector comprising an upper reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; wherein said dipole comprises has a width in a direction transverse to a length of said boom in the range 400 mm to 420 mm.
10. 10. The antenna as claimed in claim 9, wherein said dipole has a length in the range 405 mm to 415 mm.
11. 11. The antenna as claimed in claim 9 or claim 10, wherein said dipole comprises a pair of substantially "U" shaped loops extending either side of said boom, each said substantially "U" shaped loop having a length in the range 200 mmto210 mm.
12. 12. An antenna device comprising: a dipole element; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; said first reflector assembly comprising a first reflector boom and a plurality of first reflector elements; 20said second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; wherein each reflector boom has a first end, and said reflector elements are spaced at intervals along a length of said reflector boom as follows: a distance between a first reflector element and a second reflector element in the range 145 mm to 155 mm; a distance between a third reflector element and said second reflector 3 oelement the range 90 mm to 110 mm; a distance between a fourth reflector element and said third reflector element in the range 45 mm to 55 mm.
13. 13. The antenna device as claimed in claim 12 wherein each said reflector element comprises an elongate element having an annular cross- section, and is disposed in a direction transverse to said reflector boom.
14. 14. The antenna device as claimed in claim 12 wherein each said reflector element comprises an elongate element having a substantially U-shaped cross-section, and is disposed in a direction transverse to said reflector boom.
15. 15. An antenna device comprising: a dipole element; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which 2 5 intersect each other; said first reflector assembly comprising a first reflector boom and a plurality of first reflector elements; Sosaid second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; wherein each said reflector boom has a first end, and said reflector elements are spaced at intervals along a length of said reflector boom as follows: a distance between a first reflector element and a second reflector element in the range 90 to 110 mm; a distance between said second reflector element and a third reflector in the range 40 mm to 60 mm; To
16. 16. The antenna device as claimed in claim 15 wherein each said reflector element comprises an elongate element having an annular cross section, and is disposed in a direction transverse to said reflector boom.
17. 17. The antenna device as claimed in claim 15 wherein each said reflector element comprises an elongate element having a substantially U-shaped cross-section, and is disposed in a direction transverse to said reflector boom.
18. 18. An antenna device comprising: 2 o a dipole element; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate So boom, wherein said first and second reflector assemblies occupy planes which intersect each other; wherein said director elements are arranged into groups, each said group comprising at least one director element located on said boom and extending transverse to a length of said boom on either side of said boom, wherein a distance between tips of said director elements in a group are as follows: for a first group of said elements a width in the range 163 mm to 167 mm; for a second group of said elements, a width in the range 158 mm to 162 mm; for a third group of said elements, a width in the range 150 mm to 156 mm; for a fourth group of said elements, a width in the range 143 mm to 149 mm; for a fifth group of said elements, a width in the range 138 mm to 142 mm.
19. 19. The antenna as claimed in claim 18 wherein each director element of said plurality of director elements comprises a conducting element conducting go integrally of a single shape of material, said element having a substantially u- shaped cross section area.
20. 20. The antenna device as claimed in claim 18 or claim 19 wherein along a length of said boom, said director elements are spaced at intervals as follows: a distance between a first director element and said dipole in the range 28 mm to 48 mm; a distance between a second director element and said dipole in the range 86 mm to 106 mm; a distance between a third director element and said dipole in the range 159 mm to 179 mm; a distance between a fourth director element and said dipole in the range 237 mm to 257 mm; a distance between a fifth director element and said dipole in the range 324 mm to 344 mm; a distance between a sixth director element and said dipole in the range 420 mm to 440 mm; a distance between a seventh director element and said dipole in the range 516 mm to 536 mm; a distance between an eighth director element and said dipole in the range 608 mm to 628 mm; a distance between a ninth director element and said dipole in the range 701 mmto721 mm; a distance between a tenth director element and said dipole in the range 779 mm to 799 mm; a distance between an eleventh director element and said dipole in the range 859 mm to 879 mm.
21. 21. The antenna device as claimed in claim 18 or claim 19 wherein a length of said boom, said director elements are spaced at intervals as follows: a distance between a first director element and said dipole in the range 28 mm to 48 mm; a distance between a second director element and said dipole in the range 84 mm to 104 mm; a distance between a first director element and said dipole in the range 164 mm to 184 mm; a distance between a fourth director element and said dipole in the range 249 mm to 269 mm; a distance between a fifth director element and said dipole in the range 360 mm to 380 mm; a distance between a sixth director element and said dipole in the range 476 mm to 496 mm; a distance between a seventh director element and said dipole in the range 603 mm to 623 mm; a distance between an eighth director element of said dipole in the range 701 mm to 721 mm.
22. 22. The antenna device as claimed in claim 18 or claim 19 wherein a long length of said boom, said director elements are spaced at intervals as 2 5 follows: a distance between a first director element and said dipole in the range 28 mm to 48 mm; So a distance between a second director element and said dipole in the range 89 mm to 109 mm; a distance between a third director element and said dipole in the range 169 mm to 189 mm; a distance between a fourth director element and said dipole in the range 251 mm to 271 mm; a distance between a fifth director element and said dipole in the range 335 mm to 355 mm; a distance between a sixth director element and said dipole in the range 432 mm to 452 mm; a distance between a seventh director element and said dipole in the range 535 mm to 555 mm; a distance between an eighth director element and said dipole in the range 619 mm to 639 mm; a distance between a ninth director element and said dipole in the range 714 mmto734 mm; a distance between a tenth director element and said dipole in the range 794 mm to 814 mm; a distance between an eleventh director element and said dipole in the range 879 mm to 899 mm.
23. 23. The antenna device as claimed in claim 18 or 19 wherein along a length of said boom, said director elements are spaced at intervals as follows: a distance between a first director element and said dipole in the range 30 mm to 50 mm; a distance between a second director element and said dipole in the range 83 mm to 103 mm; a distance between a third director element and said dipole in the range 139 mm to 159 mm; a distance between a fourth director element and said dipole in the range 213 mm to 233 mm; a distance between a fifth director element and said dipole in the range 321 mm to 341 mm; a distance between a sixth director element and said dipole in the range 406 mm to 426 mm; a distance between a seventh director element and said dipole in the range 496 mm to 516 mm; 2 0 a distance between an eighth director element and said dipole in the range 602 mm to 622 mm; a distance between a ninth director element and said dipole in the range 790 mm to 739 mm; a distance between a tenth director element and said dipole in the range 831 mm to 851 mm; a distance between an eleventh director element and said dipole in the o range 933 mm to 953 mm; a distance between a twelfth director element and said dipole in the range 1037 mm to 1057 mm; a distance between a thirteenth director element and said dipole in the range 1149 mm to 1169 mm; a distance between a fourteenth director element and said dipole in the range 1242 mm to 1062 mm; a distance between a fifteenth director element and said dipole in the range 1369 mm to 1389 mm; a distance between a sixteenth director element and said dipole in the range 1476 mm to 1496 mm.
24. 24. An antenna device comprising: a dipole element; go an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transverse to a main length of said elongate boom; 2s a reflector, said reflector comprising a first reflector assembly extending in a plane transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy planes which intersect each other; said first reflector assembly comprising a first reflector boom and a plurality of first reflector elements; -9o- said second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; wherein each said reflector boom has a first end and a length, and said reflector elements are spaced at intervals as follows: a distance between a first reflector element and a second reflector element in the range 83 mm to 103 mm; a distance between said second reflector element and a third reflector element in the range 68 mm to 88 mm;
25. 25. The antenna device as claimed in claim 24 wherein each said reflector element comprises an elongate element having a substantially U-shaped cross-section, and is disposed in a direction transverse to said reflector boom, and has a length in a direction transverse to said reflector boom in a range of 447 mm to 467 mm.
26. 26. An antenna device comprising: a dipole element; an elongate boom; mounted to said elongate boom, a plurality of director elements extending in a direction transversed to a main length of said elongate boom; a reflector, said reflector comprising a first reflector assembly extending in 3 o a range transverse to a main length of said elongate boom and a second reflector assembly extending in a plane transverse to said main length of said elongate boom, wherein said first and second reflector assemblies occupy claims which intersect each other; said first reflector assembly comprising a first reflector boom and a plurality of first reflector elements; said second reflector assembly comprising a second reflector boom and a plurality of second reflector elements; wherein each reflector boom has a first end, and said reflector elements are spaced at intervals along a length of said reflector boom as follows: a distance between a first reflector element and a second reflector element in the range 135 mm to 145 mm; a distance between said second reflector element and a third reflector element in the range 60 mm to 70 mm.
27. 27. An antenna device as claimed in claim 26 wherein a distance o between tips of said first reflector element is in a range of 485 mm to 505 mm; a distance between tips of said second reflector element is in a range of 358 mm to 378 mm; a distance between tips of said third reflector element is in a range of 485 mm to 505 mm.
28. 28. The antenna device as claimed in claim 26 or claim 27 wherein each said reflector element comprises an elongate element having a substantially o U-shaped cross-section, and is disposed in a direction transverse to said reflector boom.
29. 29. The antenna device as claimed in any one of claims 19 to 25 having the following properties: a forward gain of at least 6 decibels for a group A antenna, or a forward gain of at least 7 decibels for a group B antenna, or a forward gain of at least 8 decibels for a group CD antenna, or a forward gain of at least 7 decibels for a group E antenna, or a forward gain of at least 6 decibels for a group K antenna, or a forward gain of at least 5 decibels for a group W antenna; a return loss ratio of at least 8 decibels for a group A antenna, a return loss ratio of at least 8 decibels for a group B antenna, a return loss ratio of at least 8 decibels for a group CD antenna, a return loss ratio of at least 7 decibels for a group E antenna, a return loss ratio of at least 7 decibels for a group K antenna, is or a return loss ratio of at least 6 decibels for a group W antenna; a cross-polar protection of at least 15 decibels; a directivity of at least -16 decibels at an angle of at least 60 relative to a 2 o direction of a main response for a group A, B or CD antenna, or a directivity of at least -16 decibels at an angle of at least 75 relative to said direction of said main response for a group E, K or W antenna; a feeder pickup of at least 10 decibels for a group A antenna, a feeder pickup of at least 10 decibels for a group B antenna, a feeder pickup of at least 12 decibels for a group CD antenna, a feeder pickup of at least 8 decibels for a group E antenna, a feeder pickup of at least 8 decibels for a group K antenna, a feeder pickup of at least 7 decibels for a group W antenna; So where a group A antenna operates in a frequency range of 470 to 606 Megahertz, a group B antenna operates in a frequency range of 582 to 734 Megahertz, a group CD antenna operates in a frequency range of 686 to 584 Megahertz, a group E antenna operates in a frequency range of 582 to 854 Megahertz, a group K antenna operates in a frequency range of 470 to 694 Megahertz, a group W antenna operates in a frequency range of 470 to 854 Megahertz.
30. 30. An antenna having the following properties: a forward gain of at least 6 decibels for a group A antenna, or a forward gain of at least 7 decibels for a group B antenna, or a forward gain of at least 8 decibels for a group CD antenna, or a forward gain of at least 7 decibels for a group E antenna, or a forward gain of at least 6 decibels for a group K antenna, or a forward gain of at least 5 decibels for a group W antenna; a return loss ratio of at least 8 decibels for a group A antenna, a return loss Is ratio of at least 8 decibels for a group B antenna, a return loss ratio of at least 8 decibels for a group CD antenna, a return loss ratio of at least 7 decibels for a group E antenna, a return loss ratio of at least 7 decibels for a group K antenna, or a return loss ratio of at least 6 decibels for a group W antenna; 2 o a cross-polar protection of at least 15 decibels; a directivity of at least -16 decibels at an angle of at least 60 relative to a direction of a main response for a group A, B or CD antenna, or a directivity of at least -16 decibels at an angle of at least 75 relative to said direction of said main response for a group E, K or W antenna; a feeder pickup of at least 10 decibels for a group A antenna, a feeder pickup of at least 10 decibels for a group B antenna, a feeder pickup of at least 12 decibels for a group CD antenna, a feeder pickup of at least 8 decibels for a 3 o group E antenna, a feeder pickup of at least 8 decibels for a group K antenna, a feeder pickup of at least 7 decibels for a group W antenna; where a group A antenna operates in a frequency range of 470 to 606 Megahertz, a group B antenna operates in a frequency range of 582 to 734 Megahertz, a group CD antenna operates in a frequency range of 686 to 584 Megahertz, a group E antenna operates in a frequency range of 582 to 854 Megahertz, a group K antenna operates in a frequency range of 470 to 694 Megahertz, a group W antenna operates in a frequency range of 470 to 854 Megahertz.
31. 31. An antenna having the following properties: a forward gain of at least 7.5 decibels for a group A antenna, or a forward gain of at least 8. 5 decibels for a group B antenna, or a forward gain of at least decibels for a group CD antenna, or a forward gain of at least 8.5 decibels for a group E antenna, or a forward gain of at least 7.5 decibels for a group K antenna, or a forward gain of at least 8.5 decibels for a group W antenna; a return loss ratio of at least 8 decibels for a group A antenna, a return loss ratio of at least 8 decibels for a group B antenna, a return loss ratio of at least 8 decibels for a group CD antenna, a return loss ratio of at least 7 decibels for a 2 o group E antenna, a return loss ratio of at least 7 decibels for a group K antenna, or a return loss ratio of at least 6 decibels for a group W antenna; a cross-polar protection of at least 15 decibels; a directivity of at least -16 decibels at an angle of at least 60 relative to a direction of a main response for a group A, B or CD antenna, or a directivity of at least -16 decibels at an angle of at least 75 relative to said direction of said main response for a group E, K or W antenna; So a feeder pickup of at least 12 decibels for a group A antenna, a feeder pickup of at least 12 decibels for a group B antenna, a feeder pickup of at least decibels for a group CD antenna, a feeder pickup of at least 10 decibels for a group E antenna, a feeder pickup of at least 10 decibels for a group K antenna, a feeder pickup of at least 9 decibels for a group W antenna; where a group A antenna operates in a frequency range of 470 to 606 Megahertz, a group B antenna operates in a frequency range of 582 to 734 Megahertz, a group CD antenna operates in a frequency range of 686 to 584 Megahertz, a group E antenna operates in a frequency range of 582 to 854 Megahertz, a group K antenna operates in a frequency range of 470 to 694 Megahertz, a group W antenna operates in a frequency range of 470 to 854 o Megahertz.
32. 32. An antenna having the following properties: a forward gain of at least 10 decibels for a group A antenna, or a forward :5 gain of at least 11 decibels for a group B antenna, or a forward gain of at least 12 decibels for a group CD antenna, or a forward gain of at least 10 decibels for a group E antenna, or a forward gain of at least 10 decibels for a group K antenna, or a forward gain of at least 10 decibels for a group W antenna; a return loss ratio of at least 8 decibels for a group A antenna, a return loss ratio of at least 8 decibels for a group B antenna, a return loss ratio of at least 8 decibels for a group CD antenna, a return loss ratio of at least 7 decibels for a group E antenna, a return loss ratio of at least 7 decibels for a group K antenna, or a return loss ratio of at least 6 decibels for a group W antenna; a cross- polar protection of at least 15 decibels; a directivity of at least -16 decibels at an angle of at least 60 relative to a direction of a main response; a feeder pickup of at least 15 decibels for a group A antenna, a feeder pickup of at least 15 decibels for a group B antenna, a feeder pickup of at least 18 decibels for a group CD antenna, a feeder pickup of at least 12 decibels for a group E antenna, a feeder pickup of at least 12 decibels for a group K antenna, a feeder pickup of at least 12 decibels for a group W antenna; where a group A antenna operates in a frequency range of 470 to 606 Megahertz, a group B antenna operates in a frequency range of 582 to 734 Megahertz, a group CD antenna operates in a frequency range of 686 to 584 Megahertz, a group E antenna operates in a frequency range of 582 to 854 Megahertz, a group K antenna operates in a frequency range of 470 to 694 To Megahertz, a group W antenna operates in a frequency range of 470 to 854 Megahertz.