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Re: Ed's startup response



A 60 cm dish on L-band is going to be only slightly better than a bare 
dipole.  More power into the feed will compensate somewhat for the small 
reflector size, but you will still lose a lot of it -- 4kW ERP is not 
much when you're trying to get to an apogee that is near GEO altitude.

I have to ask, why use a dish on L-band?  A Yagi, loop Yagi, or helical 
would give you a much better F/B ratio with a much smaller and more 
manageable antenna, and would give you substantially better gain than 
even a 2-3 meter dish (2 meter dishes aren't really even big enough for 
C-band, let alone L-band) in a much more portable package.  I might 
start thinking in terms of dishes for 2.4+ GHz, but 1.2 is more Yagi  or 
helical territory.  60cm dishes aren't really that great until you get 
up into Ku-band ..

> Graham,
> You are correct, 20 watts into a 60cm dish on L Band will not do well. 
> The
> 60cm dish will develop about 15db gain if the wind is blowing your
> direction. You do one of two things. Diameter or power. I must stick 
> with
> 60cm on my portable so I'll use 80 or 160 watts of TPO. That will yield 
> from
> 2000 to 4000 Watts ERP. That should work fine. You will not burry the S
> Meter, but you should be able to make do.
> -----Original Message-----
> From: graham shirville [mailto:gshirville@btinternet.com]
> Sent: Wednesday, December 12, 200rr1 8:58 PM
> To: gjmouse@neo.rr.com
> Subject: Re: [amsat-bb] Ed's startup response
>
>
>> use as a portable. I have built a 2&1/2 turn L-Band helix feed to mount
>> around the 2.4Ghz patch. Thus, I'll be L-band up link and 2.4Ghz down.
>
> Hi Gunther,
>
> I have been considering using one dish for mode L and S, but really
> concluded from other peoples comments that one needs a bigger than 60cms
> dish for the L band uplink even using say 20 watts at the dish.
>
> What are your thoughts/experiences?
>
> cheers and thanks
>
> Graham G3VZV

"Go ahead and do it, you can apologize later." -- RADM Grace Hopper, 
1906-1992
"The sunset is an illusion, but the beauty is real." -- Richard Bach

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