[NLRS] Gray 24 G dishes from 2010 Tail Gate Swapfest

[Dr. Gerald N. Johnson]

The Direct TV types offered by N0HZ earlier in the afternoon work OK at 
24GHz but get tedious to aim with less than 2 degree beamwidth. And 
travel for 10 GHz OK. To solve the aiming at 24GHz, design the feed for 
a smaller dish, say 8" at the focal length of the offset dish. E.g. 
underfeed it. The directivity will go down to something reasonable, yet 
you won't have to actually build something. So you will need a larger 
feed horn. If the stamped dish didn't warp, you could cut it down on a 
band saw to be 8" wide and 16" high using the present center for the 
aiming point of the feed, or maybe 8" wide and 10 or 12" high tilting 
the feed to that portion of the remaining dish to include mounts. It 
would be a little pain to set up the feed, but you could at least cut a 
streak 8" wide top to bottom and then cut that in half and use 
individual feeds at 24 GHz for each of those two pieces. And I susppect 
the cut pieces could warp and cost considerable gain at 24GHz from the 
lack of support given by the folded back edge in that stamping.

Using the little mirror dots and the sun like Bill Clark showed at CSVHF 
last summer might be a big benefit at 24GHz to allow correcting the 
focus of the bits of dish. For that matter your 24" dish would cut down 
and provide pieces, maybe as many as 4 pieces each 8" on a side, with 
different aiming points for the feed than it had originally, whether 
offset or prime focus.

73, Jerry, K0CQ

On 4/19/2011 11:24 PM, WBØLJC wrote:
>
>
> I am looking for one of the Gray 24 G dishes that were sold a
> Tail Gate Swapfest last year. Is anyone willing to sell or loan
> to me one for the SBMS contest. A group of us are planning to work
> 24 GHz along paths from Indian Mounds Park down the river
> valley. I need a smaller dish for my second 24 G WBFM loaner
> unit. I have some 24" dishes, but they are to big to carry around
> roving.
>
> Please let me know.  You are all welcome to join us and get in
> on the fun.
>
> Thanks and 73, Gary  WBØLJC
>
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