GB2250136A - Radio signal receiving apparatus and aerial - Google Patents

Abstract

Receiving apparatus, particularly for locating transmitters attached to birds or other animals, comprises an elongate casing (12) and an aerial system (15) comprising arms (30, 40, 50) each rotatable about a vertical axis relative to the casing but mounted in a fixed position relative to the length of the casing, and at least some of the arms being telescopically expandable and contractable. A receiving circuit (23) is located in the casing and is connected to the aerial system by a cable (56). The aerial system has a central dipole (30) rotatable about a vertical axis (31), a rear reflector (50) having two arms rotatable about a vertical axis (51), and a front director (40) having two arms rotatable about vertical axes (41), with the centre of gravity of the apparatus being substantially over the handle (13) both in the folded and expanded conditions of the aerial. <IMAGE>

Description

RADIO SIGNAL RECEIVING APPARATUS This invention relates to radio signal receiving apparatus, particularly for detecting the direction from which a signal is being transmitted. The invention is particularly concerned with such apparatus which is portable and hand held in use and carries a direction responsive aerial mounted thereon so that the apparatus can be swung round to detect in which direction it is pointing to receive a maximum or minimum signal.

Such receiving apparatus is particularly useful for tracking birds or other animals which are carrying transmitters.

Known such receiving apparatus comprises a receiving circuit located within a generally elongate casing,(normally resembling a short gun and referred to as a receiving gun), with a trigger type carrying handle projecting from the lower side of the casing by which the apparatus is held with one hand and pointed in a substantially horizontal direction, and a foldable and expandible aerial system mounted on the top of the casing. The casing is of larger cross section adjacent its rear end where the receiving circuit and control panel are located and narrower adjacent its front end with the handle located nearer the rear end substantially under the centre of gravity in the folded condition of the aerial system.

The aerial system comprises three parts which in the extended condition extend parallel to one another, normal to the length of the casing and spaced apart in the direction of the length of the casing. The aerial system comprises a central dipole arm, a rear reflector and a front director.

In the folded condition, they lie alongside one another extending in the direction parallel to the length of the casing. There may be several reflector arms and several director arms. The dipole must be connected via a cable to the receiving circuit.

Known aerial systems of this kind for use with a receiver gun have the three aerial parts mounted respectively on three telescopically connected tubes extending parallel to the casing length and expandible well beyond the front of the casing. Only when these tubes have been so expanded can the arms of the three aerial parts be rotated about vertical axes to their working positions extending normal to the casing length. Such expansion extends the length of the apparatus in use considerably and completely unbalances the receiving apparatus so that the centre of gravity is well forward of the handle and the apparatus is awkward and tiring to use. The length of this known receiving apparatus when expanded is approximately 85 centimetres.

An object of the present invention is to provide an improved aerial system for a receiving apparatus and a receiving apparatus including an aerial system which apparatus is shorter than existing such apparatus in its working condition and better balanced.

Accordingly, in one aspect, the invention provides an aerial system having mounting means for mounting it directly on the casing of a receiving apparatus, in which the aerial system is movable between an expanded working position and a folded position but in which the centre of gravity of the aerial system is substantially the same in both positions.

This allows the centre of gravity of the receiving apparatus to remain substantially over the handle both in the expanded and folded conditions of the aerial system.

In another aspect, the invention provides a receiving apparatus having an elongate casing with an aerial system mounted thereon, the aerial system comprising a plurality of arms each rotatable about a vertical axis relative to the casing but mounted in a fixed position relative to the length of the casing and at least some of the arms being telescopically expandible and contractable.

In a preferred form, a receiving apparatus comprises a receiving circuit, a substantially elongate casing having a handle and in which the receiving circuit is located, an aerial system mounted thereon, the aerial system comprising a central dipole part rotatable about a vertical axis fixed relative to the length of the casing, a reflector part mounted adjacent the rear of the casing and having two arms rotatable about a vertical axis fixed relative to the length of the casing, and a front director part mounted adjacent the front of the casing and having two arms rotatable about vertical axes fixed relative to the length of the casing.

This receiver apparatus including its expanded aerial, in the preferred embodiment described hereafter, has a length of approximately 55 centimetres and preferably the length of the receiver apparatus is no greater than 65 centimetres.

The receiver apparatus includes a cable member connecting the dipole to the receiving circuit and preferably this cable has a length no more than 5 centimetres. In the preferred form, this cable has a length no more than 2.5 centimetres. Because the central dipole is fixed relative to the length of the casing and is positioned in the central portion of the casing the length of this cable can be kept small. This reduces the signal loss between the dipole and the receiving circuit. In the prior art receiving apparatus, because the dipole mounting moves to a position adjacent the front of the casing in its working position a cable of length greater than 15 centimetres is required.

Some or each of the mountings for mounting the aerial arms for rotation preferably include a biasing means arranged to provide a positive bias to locate that arm in either the extended working position or the folded position. Such a biasing means resists movement of the arms from their required positions so that they do not fold unintentionally from the working position thus distorting the signal nor rotate out of their folded position when being transported which could lead to damage. This mounting may be claimed independently.

One embodiment of receiving apparatus, in accordance with the invention, will now be described, by way of example only, with reference to the accompanying drawings of which: Figure 1 is a side view of a receiving gun with the aerial system in its folded condition, Figure 2 is a plan view of the gun of Figure 1, Figure 3 is a plan view of the gun of Figure 2 but with the aerial system in its expanded working position, Figure 4 is a view on an enlarged scale and partly in section section through a mounting block for mounting the aerial arms, and Figure 5 is a perspective view of the block of Figure 4 showing how the parts fit together.

A receiving gun- for locating the direction of a source of transmitted radio signals, and which is adapted to be portable and hand held in use, comprises a casing 12, a trigger type handle 13 projecting from the casing lower surface 14 and an aerial system 15, of the Yagi type, mounted on its upper surface 17. The casing is wider and deeper at its rear end 18 than at its front end 19, the cross section reducing in steps towards the front and the handle 13 is located substantially below the centre of gravity. The central elongate axis of the casing in the direction of its length is indicated at 22.

A receiving circuit diagrammatically indicated at 23 is located in the casing and powered by a battery located in a battery compartment 24 with a control panel let into the rear casing surface. The receiving circuit may be of any conventional form but is preferably of the form described in our British Patent Application Number 9014937.8.

The aerial system 15 comprises a central dipole 30 fixed to a dipole post 31 rotatably mounted in a mounting block 32 fixed to the casing at a position within the central third of the length of the casing. The dipole arm 30 is rotatable about a vertical axis between the folded condition shown in Figure 2 extending parallel to the length of the casing and co-planar with the axis 22 of the casing and a working position shown in Figure 3 extending normal to the length of the casing. The dipole 30, in known manner, carries a gamma match 33 mounted thereon by a support block 34 and further connected to the dipole by a connection block 35, the spacing between these blocks being determined by the frequency of signals which it is required to pick up.

Extension partss 36 are telescopically slidable within the dipole arm at each end and are movable between the folded position within the dipole arm 30 and the extended position extending outwardly therefrom.

The aerial system further comprises two director arms 40 each mounted on a post 41 rotatably mounted in a bearing block 42 fixed to the casing adjacent its front end. Each director arm can be rotated about a vertical axis 43, spaced to one side of the central axis of the gun, between a folded condition extending parallel to the casing length and a working position extending normal thereto. Each arm 40 includes a telescopically mounted extension part 44 movable between a folded position within the arm 40 and an extended condition extended outwardly therefrom. The aerial system further comprises two reflector arms 50, each mounted on a post 51 rotatably mounted in a bearing block 52 fixed to the casing adjacent its rear end.Each arm 50 is rotatable about a vertical axis 53 spaced slightly to one side of the central axis of the casing and is rotable between a folded position extending parallel to the casing length and a working position extending normal thereto. Each of the arms 50 includes a telescopically extending part 54 movable between a folded position substantially within the arm and an extended position extending outwardly from the arm.

All the extending parts 36,44,54 are guided within their tubular arms for smooth sliding movement with sufficient friction that they remain in the positions to which they are placed and have plastics material guards 55 at their free ends.

The dipole/gamma match 30, 33 is connected by a short cable 56 of 2 centimetres length to the receiver circuit 25.

All of the aerial arms 30, 40, 50 are mounted in a similar manner to their posts 31, 41, 51 and each of these posts is similarly mounted in their respective mounting blocks 32, 42, 52, so that only one mounting will be described with reference to Figures 4 and 5.

The tubular arm 40 has an inner end part 40A connected to an outer end part 40B by a screw thread connection 60. The upper surface of post 41 is formed with a part circular sectioned cylindrical channel 61 to receive the part 40A secured therein by a screw 62 or other fastening means such as a rivet. The post 41 is circular sectioned cylindrical and mounted in a similar shaped socket 63 in the block 42. The post 41 is biased upwardly by a spring 64 located in the socket beneath the post. A generally horizontally extending slot 65 is formed through a corner 66 and adjacent side portions of the block and opens into the socket 63. The slot has grooves 67, 68 at its ends providing upward extensions of the slot extending horizontally at right angles to one another. These grooves are connected by gently curved surfaces with the upper surface defining the slot. A pin 70 extends sidewardly from the post and locates in the slot so that when it is at either end of the slot it is located in one of the grooves 67, 68. In order to move it out of one of these grooves, the post must be slightly depressed against the action of the spring. Such a bias acts to provide a positive location of the aerial arm in the position to which it is moved, either the working position or the folded position, and to resist movement therefrom.

Claims (9)

1. An aerial system having mounting means for mounting it directly on the casing of a receiving apparatus, the aerial system being movable between an expanded working condition and a folded condition, in which the centre of gravity of the aerial system is substantially the same in both positions.

2. A receiving apparatus comprising an elongate casing with an aerial system mounted thereon, the aerial system comprising a plurality of arms each rotatable about a vertical axis relative to the casing but mounted in a fixed position relative to the length of the casing and at least some of the arms being telescopically expandable and contractable.

3. A receiving apparatus comprising a receiving circuit, a substantially elongate casing having a handle, an aerial system mounted on the casing, a receiving circuit located in the casing and connected to the aerial system by a cable means, the aerial system comprising a central dipole part rotatable about a vertical axis fixed relative to the length of the casing, a reflector part mounted adjacent the rear of the casing and having two arms rotatable about a vertical axis fixed relative to the length of the casing, and a front director part mounted adjacent the front of the casing and having two arms rotatable about vertical axes fixed relative to the length of the casing.

4. Receiving apparatus according to Claim 3 in which at least some of the arms are telescopically expandable and contractable.

5. Receiving apparatus according to Claim 3 or Claim 4 in which the receiving apparatus in its expanded condition has a length less than 65 centimetres.

6. Apparatus according to any of Claims 3 to 5 in which the connecting cable means has a length no more than 5 centimetres.

7. Apparatus according to Claim 6 in which the connecting cable means has a length no more than 2.5 centimetres.

8. Apparatus according to any of Claims 2 to 7 in which the mounting means for mounting the aerial arms for rotation relative to the casing include biasing means arranged to provide a positive bias to locate that arm in either the extended working position or the folded position.

9. Receiving apparatus substantially as described herein with reference to or as illustrated in the accompanying drawings.