Re: Re elevation on a dish
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Hi Dave ,
Had to wait for the frost to lift to take these pics .
My masthead 60cm dish and Elevation system .
18" jack used with base end pivot made from 3" exhaust clamp around the standard Scaf pole mast extension above KR600 inside cage support ( just below bottom of pic).Extra large clamp allows one leg of U bolt to be fitted with a turned alum sleeve spacer to take the eye of the base balljoint of the jack.Also allows positional adjustment to set up desired stroke/maximum dish travel..
Top end of jack fits onto a welded pivot bolt attached to underside of a 2 x 1" steel hollow section , welded or bolted to a steel stand-off plate that has a steel hinge at the mast end .The other end of the hinge is welded to a steel Scaf clamp , which again can be adjusted to setup the final geometry .
The dish is mounted on 1.25" dimeter steel tube that came with it - in this case it is a 90 degree bent item so that is why the 2X1" hollow section is used to offset the dish tube and put the vertical load thrust on the centre line of the vertical mast .Room to add masthead PA/front end housings just behind the dish , without adding much loading to the feed arm etc .
You will notice the system puts the offset dish well forward offset to the mast - this allows the top rim of the dish to travel to an effective 30 degrees of Elevation .
That allows pointing at QO100 and well above ground noise sources for Sun noise measurements and I have decoded DL0SHF several times over last few years .Other antennas on mast above are positioned to offset the dish system , again putting the vertical loading equally about the rotator cage .
The small box on a standoff 1"x1/8" aluminium flat bar just in front and below dish base is housing a G4JNT AZ/EL digital sensor .
Which ever system you build make sure the jack is adjusted so its internal limit switches limit the travel within limits that protect the dish - I managed to fold this dish at the top with 12V supply and the only thing I noticed was a sudden rise in ground noise !
After 30+ years up the mast the only thing that needed replacement was the jack ( running leadscrew nut fractured ) - the light coloured cylinder on the jack is an old aluminium Dow Corning Vacuum oil can - this covers the top end jack seal to prevent rain getting in when/if the seal cracks - smother all surfaces in Waxoil ....