Re: [amsat-bb] Dish depth question - follow up

[Phil <phil@xxxxxxxxxxxxxxxx>]

Hello again,

I received three replies and they all indicate that there is a mismatch 
between the aerial and the deeper dish. I'm not surprised since the patch 
that I built (the same as the one at amsat-zl) went together so easily. Too 
easily, it appears, to be working correctly. Maybe I wasn't accurate enough 
with my construction.

The dimensions of the two dishes are:

Steel dish
diameter 1800 mm
depth 275 mm
focal point 736 mm
beacon S 5 above the noise, at the best

Alloy dish
diameter 1860 mm
depth 375 mm
focal point 577 mm
beacon no better than S 1 above the noise

The down-converter mounting point, with respect to the steel dish, didn't 
appear to be really critical. Anywhere within 200 mm of the calculated focal 
point was OK.

The alloy dish was different. I could move the down-converter anywhere from 
almost touching the dish to a metre or so away from the dish with little 
noticeable difference. It is possible that the alloy dish wasn't accurately 
positioned at the time.

So, now I'm investigating another patch aerial.

By the way, I heard a station from Arizona this morning calling CQ. I answered 
but he apparently didn't hear me. Maybe I can make it to the US after all.

-- 
Regards,
Phil
phil@spiderweb.com.au


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