Details of elevation system

Many thanks to David GM4JJJ and David G4YTL for their help and advice. Many thanks in particular to Henry 9H1CD for taking the trouble to scan photos and diagrams and email them to me.

General view of the system (click to enlarge)	Anyone thinking of building a similar system to mine should bear in mind that my array consists of only 4 * 2.2 wavelength yagis and is therefore pretty modest. Whilst I consider my system to be fairly robust (I hope), it would be advisable to upgrade the hinge mechanism and the tubing generally for a larger system.
	Elevation Hinge This consists of a 1.5" aluminium tube rotating inside a 2" piece of ally tubing. The end stops on the hinge consist simply of U bolts. It would be possible to shim the inside of the hinge to make it a close fit and also to grease it, but I did not bother with my light-weight arrangement. The 1.5" pole I used was not particularly heavy duty. I would certainly recommend that it should be of at least 3mm thickness and I shall replace mine when I next get the mast down. View showing the satellite screwjack attached by angle iron to the static part of the hinge. This was while the system was still being 'mocked up' on the ground.
	View showing the system in the air and showing more clearly the hinge arrangement and geometry of the screwjack.
	View from the front showing the 1/4" steel mounting plate. The small plastic box on the right hand side contains a servo pot. With a small weighted arm attached to the spindle and operating against a simple bridge circuit, this provides the output to the elevation display. Calibration is simple. Two pots provide zero and scale. Whilst resting on a flat surface the readout is zeroed. It is then turned through 90 deg and the scale set to 90. Calibrated!
	Opposite is a copy of G4YTL's circuit diagram for the bridge circuit. The DVM is sold by Maplin Electronics in the UK, but any locally available DVM should be readily adaptable, or of course an analogue meter could be used.