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Re: !!! KEEP CLEAR !!! Ao40 beacon....Ao10 QRM !



In a message dated 12/19/2000 8:51:25 AM Eastern Standard Time, 
jspiess@dplanet.ch writes:

> PLEASE KEEP THE FREQUENCIES CLEAR
>  AROUND 145.900 +/- 10 Kc !!
>  
>  It is real impossible to analyse something could be 
>  sourced from Ao40.  !!!!!

Hi Jens,

I think we're going to find it quite difficult to have everyone avoid this 
portion of the AO-10 transponder. Operators are so used to working there. I 
also think that quite a few may not be on the BB here, so they don't see our 
messages.

Like you I monitor a lot. Have you tried using an audio Spectrum Analyzer? 
This is how I'm able to monitor even with QRM. I'm using Spectrogram ver 
5.1.6a written by Richard Horne. It's available at:

www.monumental.com/rshorne/gram.html

It's a free download and small ~256K. Works with a soundcard. As well as 
being able to see really weak carriers even in the face of heavy QRM, I also 
use it to check for doppler shift of the signal I'm tracking. Obviously if 
the signal doesn't doppler shift, it's not moving and is not what we're 
looking for.

While I have yet to find AO-40, with all this monitoring I'm doing I have 
been able to find numerous neighborhood scanners (beeps and chirps), lots of 
steady carriers with no doppler (spurs in my rig or signals from the 
100megabit ethernet network in my house!) and finally, pulsing data streams 
that turned out to be new transmitters installed by the local water company 
to monitor their tanks.

These signal were the most interesting to find. I heard them on 145.8575. 
When I would switch in my mast mount preamp they would go away. This was the 
clue I needed in my search! I use SSB preamps with band pass helical front 
end filtering. When the signal disappeared when I switched the preamp in, I 
knew it was outside the 2 meter band. It turned out to be at 173.2375. How 
did I hear it on 145.8575? The FT-736R uses a 13.69 IF. 173.2375 minus 2 
times 13.69 = 145.8575. Problem solved.

Good luck in the search and Happy Holidays.

73,
Mike, N1JEZ
AMSAT #29649
Local Area Coordinator
"A closed mouth gathers no feet."
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