GB2211609A - Alignment device - Google Patents

Abstract

An alignment device (16) primarily for use in aligning a signal receiving dish with a source such as a satellite is in the form of a sheet having a first scale (17) disposed about an axis (18), plumb means (23, 24) pivotable about the axis (18) and cooperating with the first scale (17) to enable the inclination of a reference line on the device (16) to be ascertained, and a second scale having an origin (28), and a datum azimuth (20) and a desired azimuth (25 or 26) intersecting at the origin (28). <IMAGE>

Description

ALIGNMENT DEVICE The invention relates to a device for use in the alignment of sky-seeking apparatus such as signal reception dishes, telescopes and the like. The invention will be specifically described in relation to the alignment of a satellite television reception dish. In order that a signal can be received from a satellite in geostationary orbit, it is essential that the axis of a dish be aligned with (ie have its axis pointing at) the satellite. This has to be achieved, on installation of a dish, by adjusting the inclination of the axis to a desired angle (for example 280) above the horizontal and then adjusting the azimuth or heading of the dish axis to be aligned with the heading of a specified satellite.

This can be done on very sophisticated dishes using inbuilt inertial direction indicators and automatic drivers, but is too expensive for the home television dish. In addition, the two operations of adjusting the inclination and adjusting the heading can be effected separately using a conventional bearing compass, and a conventional clinometer, although there can be slight problems as such conventional instruments are not usually suitable to allow a dish to be guided relative to such instruments are expensive, and although they may be worthwhile purchases for an installation engineer, they are not for the individual "D.I.Y." owner who-purchases a dish and effects his own alignment.

It is an object of the invention to provide a cheap and convenient device whereby a dish can be aligned with a geostationary satellite.

Accordingly the invention provides an alignment device which has first scale disposed about an axis, plumb means freely pivotable about the axis and co-operating with the first scale to enable the inclination of a reference line on the device to be ascertained, and a second scale having an origin and a datum azimuth and a desired azimuth intersecting at the origin. The origin of the second scale being spaced from the said axis.

The invention also provides an orientation device including a body in form of a rigid sheet and incorporating both a clinometer and a azimuth scale, the two scales having sepatate origins.

Preferably an edge of the sheet forms a or the reference line pre-positioned relative to the clinometer scale.

A or the plumb means can be a bob hanging by a flexible ligament from the origin of the clinometer scale.

The origin of the azimuth scale is preferably coincident with an edge of the sheet. The azimuth scale can contain one or more desired satellite azimuths in addition to a datum azimuth.

The device can be made very cheaply and simple from a sheet of rigid material, as cardboard or plastics and printed with the two scales. A plumb means can be a simple bob with a line connected to the axis serving as a "pointer" relative to the first scale.

The invention will be described further, by way of example with reference to the accompanying drawings wherein: Fig 1 is a view showing an obverse face of a preferred device of the invention.

Fig 2 is a view showing a reverse face of the device of fig 1; and Fig 3 shows the device in use.

Referring firstly to fig 3, a typical satellite television signal receiving assembly 10 includes a dish 11 mounted on a support 12 having a base 13 which has two marks 14,15 which define a centre line of the assembly 10.

For azimuth variation, the assembly 10 has its dish 11 pivotable about an azimuth axis (not shown) which passes through mark 14. The azimuth axis itself is movable by conventional means (again not shown) to vary the inclination of the dish axis relative to the horizontal.

Referring now to Figs 1 and 2, a preferred alignment device 16 of the invention is in the form of a printed sheet of rigid material such as paper, cardboard or plastics material. On one obverse side (Fig 1) the device 16 has a first scale 17 concentric with a bob axis 18. Scale 17 includes a conventional 3600 scale part 17a and additional lines 17b which indicate important points and desirable azimuths such as 19. The zero-1800 line 20 lies parallel to the reference edges 21, 22 of the sheet.

A plumbbob 23 issupported by a plumb line 24 connected to bob axis 18 and serving as a pointer relative to scale 17. This part of the device can be used to set the inclination of the dish axis as will be later described.

Fig 1 also shows that on the same obverse side of the sheet is a second scale which is composed of a "zero" or N-S line (aligned with line 0-180 on the first scale only for convenience) is identical with line 20, and two satellite direction lines 25, 26 which for use in the U.K. are set to desired angles for the EUTELSAT and INTELAST V satellites. Of course a full scale can be given and the user supplied with a list of available satellite directions. This possibility is shown in fig 2 where there is a full 1800 scale 27 around origin 28.

Use of the device 10 is illustrated in fig 3. The heading or azimuth of the dish 11 is set first. The base 13 rests on the ground (which may or may not be level), and the two marks 14, 15 lined up with true south/north using the shadow of an upright, such as a cane, at noon GMT, or by using a compass. The base 13 of the assembly can now b-e secured to the ground to fix the position of line 14-15. The device 16 now placed with its origin adjacent point 14 (as at 29 in Fig 3) and the dish 11 turned about its azimuth axis until the dish axis is pointing towards the correct satellite as set by line 25 or 26 and the desired azimuth fixed (at least temporarily) The device 16 is now used to set the inclination of the dish axis. As shown at 39, with the inclination 16 generally in a vertical plane, a reference edge (as edge 22) is placed on the rim of the dish 11 to place edge 22 in the plane (BB) of dish 11. The dish axis is now parallel to line AA shown in Fig 1. The inclination of the dish 11 is now adjusted until the plumb line 24 coincides with a desired line on the scale.

As geostationary satellites usually are at 280 elevation (from central UK) this is the line marked at 19 on the scale.

After this procedure, the dish 11 is closely directed towards the relevant satellite. Any necessary "fine tuning" can be effected by using a connected television and varying the two angles slightly to get the best reception.

It will be appreciated that the device 16 of the invention is a cheap and convenient means for alignment of a satellite dish.

Claims (9)

1. An alignment device which has a first scale disposed about an axis, plumb means freely pivotable about the axis and co-operating with the first scale to enable the inclination of a reference line on the device to be ascertained, and a second scale having an origin and a datum azimuth and a desired azimuth intersecting at the origin.

2. A device as claimed in claim 1, wherein the origin of the second scale is spaced from the said axis.

3. An orientation device including a body in the form of a rigid sheet and incorporating both a clinometer and a azimuth scale, the two scales having separate origins.

4. A device as claimed in claim 1, 2 or 3 wherein an edge of the sheet forms a or the reference line pre-positioned relative to the clinometer scale.

5. A device as claimed in any preceding claim, wherein the plumb means is a bob hanging by a flexible ligament from the origin of the clinometer scale.

6. A device as claimed in any of claims 1 to 5 wherein the origin of the azimuth scale is coincident with an edge of the sheet.

7. A device as claimed in any preceding claim, wherein the azimuth scale contains one or more desired satellite azimuths in addition to a datum azimuth.

8. A device as claimed in claim 3, wherein the sheet is printed with the two scales.

9. An alignment device, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.