[amsat-bb] Flex 5000a FM tone issues

Alan wa4sca at gmail.com
Fri Apr 15 10:28:14 UTC 2016


Some people have no problems with full duplex FM.  However, others have.  There are a couple of
factors to tweak.

First, cut the primary sample rate back to 96k if you are running 192k.

Second, make certain that all the voice buffer sizes are the same.  This means on the primary audio
tab, and also Buffer Size|Phone on the DSP tab.  Try 2048, and if that works, 1024.  Probably 96k/2048
would be the place to start as it is most likely to solve the problem.

This is the result of trial and error by myself and others and not, on my part, a deep understanding
of how PowerSDR works.  Not everybody finds the same combination works, so at least part of it
involves the computer (and OS version??) you are using.  However, it is completely reproducible once
you find the right combination.

Finally, are you using 435.170 Mhz (435.172 MHz has also been recommended) for the uplink computer
tuning?  If you are off frequency, the satellite AFC will help, but you can still get a rough audio.



<-----Original Message-----
<From: Jeff [mailto:jeff_griffin at comcast.net]
<Sent: Thursday, April 14, 2016 6:46 PM
<To: APBIDDLE at mailaps.org
<Subject: Re: [amsat-bb] Flex 5000a FM tone issues
<Yes, I will start F/D then go H/D if there is an issue. I really don't care
<about the FM birds anyway, so it's not a real issue. Tell me about the
<buffer issue work around?
<73 Jeff kb2m
<-----Original Message-----
<From: Alan
<Sent: Thursday, April 14, 2016 7:37 PM
<To: 'Jeff' ; 'Amsat'
<Subject: RE: [amsat-bb] Flex 5000a FM tone issues
<While not normally recommended, as a test try working SO-50 in half duplex
<rather than full duplex and
<see what happens.   There is a very peculiar buffer issue which can cause
<bad audio in full duplex.  If
<that is it, there is a work around.
<Question about your comment about building an FM repeater filter.  Are you
<referring to the Transmit
<tab, Transmit Filter?
<<-----Original Message-----
<<From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Jeff
<<Sent: Thursday, April 14, 2016 5:52 PM
<<To: Amsat <amsat-bb at amsat.org>
<<Subject: [amsat-bb] Flex 5000a FM tone issues
<<I?m working my way through setting up my Flex 5000 for satellites. I?m very
<happy with the
<<performance on the linear bird?s , but having some issues with AO-85, and
<SO-50. After getting some
<<bad audio reports on SO-50 yesterday I tried to work the problem out with
<someone on a local repeater
<<who was familiar with my voice. After a few minutes it became very clear
<that it was a CTCSS tone
<<issue as simplex performance was excellent. I thought about this a minute
<and came to the realization
<<that there might be a TX filter in play, and discovered, yes it was set to
<a default of 150 to 2700.
<<Obliviously not FM values. So just before the last pass of AO-85 I quickly
<built an FM RPTR filter of
<<50 to 4k and saved it. It worked a bit better on the pass but I still had
<obvious issues.  Anyone have
<<ideas what the issue might be? I?m thinking a tone level issue, but after
<goggling I found  issues with
<<CTCSS was too HIGH of a level. Any suggestions welcome...
<<73 Jeff kb2m
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