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Re: Drake 2880 Problem with AO-40 ???



Hi Jeff,
I have not heard you on the birds lately, but hope you are well.  I believe your setup may be quite common and is leading to a lot of frustration for a lot of people, so I will comment here on the BB for general information.

It looks like AO-40 is not quite as easy to hear as we all had hoped--at least not yet in it's current configuration.  A combination of low NF in the first active device, plenty of gain in both the downconverter and the antenna, and a low squint angle on the bird are all required for solid copy.

The most succesful setups are the ones with high gain antennas (dishes and bar-b-que grills) and/or high performance downconverters like the Mutek and DB6NT.  Your system has a low gain antenna and a d/c with comparatively low gain and high NF.  I know, as mine is much the same (right now).  Your 13-turn helix has anywhere from 10 to 13 dBi gain, depending on the design, and your Drake has (if it is like mine) a NF of about 5 to 6 with only 22 dB of gain.  I have a Conifer preamp ahead of my Drake, adding 6-10 dB of gain and improving the NF to 1.0.  That helps a lot, but it is still a marginal downlink with a small helix.  I plan to install a bigger/better helix and then wait for the orientation changes on Ao-40 before doing anything more drastic.

Also of note is the satellite's squint.  Just because it is close, does not mean it will be easy to hear.  I find I can hear it better at 60,000 km with a squint under 5 than I can at 20,000 km when the squint is over 20.

Hope all this helps....
73,
Jerry, K5OE

In a message dated Wed, 16 May 2001  3:00:24 AM Eastern Daylight Time, K7xq@aol.com writes:

<< Hello All,
 In the wake of hearing about the AO-40 S-Band Transponder Output turned on 
and having successfully received a few minutes of telemetry on a very low 
perigee pass a few months ago, I decided to listen for signals from AO-40 
recently. Unfortuneltly, the Drake 2880 does not appear to have sufficient 
Noise Figure by itself and an external preamp looks like its required. 

Is any one experiencing their Drake 2880 to be deaf ???
Is a external preamp required ???
If so, where can I get one with use with the Drake ???

I do know about a modification / Gaasfet device that can be installed in the 
RF section of the Drake but did not consider installing it due to the fact 
that there are reports that many are using the converter as is with no 
problems.

The antenna is a 13 turn RHCP Helix. I understand many are using this same 
converter and antenna and hearing/working the satellite just fine.

Jeff K7XQ

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