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Re: AO-40 ordering antennas, downconverters



If I may offer my 2 cents. 

I run a UEK3000 downconverter that offers ~30db of gain. That runs into my
Icom 756Pro through a 2 meter to 10 meter downconverter. Any attenuation
issues can be handled in the final receiver, should there be the need (and
if attenuation is available therein).

The patch feed does a wonderful job on the offset dish. I gave up on the
helix feed, bought the G3RUH patch feed, and it's terrific! I use it on my
Primestar offset dish. Not putting down helix feeds - they work well - but
the patch feed works well also, and I have had no problems with "over
illumination".

I use a Yaesu G-5400B AL EL rotator and it handles the load without a
problem. Pointing accuracy is not much of an issue for AO40, since it is
almost stationary most of the time. Slight adjustments are all that is
required to keep up with the bird.

You can check out my installation at:

http://www.xyz.net/~joe

73,
Joe
WL7M
Fritz Creek, Alaska

-------Original Message-------

From: kgshutt
Date: Tuesday, July 23, 2002 17:31:02
To: AA2AE; amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] AO-40 ordering antennas, downconverters

Hi Tony,

A few comments:

1. Gain is not that important. With the AIDC 3731 you will have excessive
gain and will need to use an attenuator to prevent overdriving your receiver
and reducing dynamic range.

2. How are you going to illuminate the dish? Helix feeds seem to be better
for an offset dish. A patch feed is often better for non-offset dishes.
Bob's systems use either a dipole feed or "provide your own". Either a
helix or patch is required to obtain circular polarization. Another
critical decision! I'm not sure what feed system is provided with the N3IYR
dish. Just make sure the feed properly illuminates your dish.

3. I have several TSI systems. All perform very well. Great performance /
price ratio. The only problem I have experienced with the TSI systems is
temperature stability. They drift a lot with ambient temperature. Doppler
is also +/- 20 hrz so this may not be such a big problem.

4. The pointing accuracy of the Yaesu G5400/5500 rotor system should be
adequate for a 3' dish. My CD-45 azimuth rotor is marginal.

Good luck with your project. Let me know what you decide to do.

73 de Ken - K5GUU

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