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Re: Using C band polar mounts w/ ao-40



Another fantastic idea!  Sure, STOCK TV dish, Paperclip dipole mounted an
inch or so below the TV feed, and bingo, high gain on AO-40.

In fact, such a scheme gives great credence to our launching a cheap AMSAT
into GTO orbit and being able to close the link to 3m dishes everywhere!
The 5 degree offset dipole feed will have no noticible loss in gain than
if it was at the center...  And the wife can still watch TV (when you are
finished)
de WB4APR, Bob

On Sun, 22 Apr 2001, John Wright wrote:

> Due to a brain malfunction, I sent this direct instead of to the BB, 
> however, as I think this
> may be a viable way for users to employ domestic TV dishes for AO40 as well 
> , I'll put it on the BB
> 
> >During a good portion of the orbit, AO40 will be inclined about 5 degrees 
> >to the standard geostationary arc.
>    So if you've got a dish on a polar mount, you may be able to use it on 
> AO40 without upsetting TV reception.
>   ( unless the other half wants to watch a channel during a good pass!! )
> 
> If you mount a feed 5 degs offset from the focal point, you should generate 
> a beam offset by that amount in the opposite
> direction. So by mounting your S band feed 5 deg below the TV feed  then 
> your pointing angle will be 5 deg ABOVE where the
> dish is really pointing,  a 5 deg squint in feed point will only have 
> minimal loss in overall dish gain, so it should be right for
> both TV and AO40 ?? ... Don't forget that if using circular, the dish will 
> reverse the sense of rotation.
> 
> Just an idea, won't upset the use for TV either!
> 
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> 

de WB4APR@amsat.org, Bob

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