[hpsdr] Test Results of Strange AGC Behavior with PowerSDR for HPSDR

[James ( Pete) Gaddie W6XX]

I wrote a PDF format report detailing my test results and conclusions on 
the PowerSDR AGC issues.  The AGC problems are essentially identical for 
both PowerSDR- HPSDR and the current versions for Flex Radio.

  Since attaching a PDF file to a list message is not allowed, I am 
listing just the first three paragraphs of the report below.   To get a 
copy of the entire PDF file send an email request to 
"gaddie at pacbell.net" .  The report is 5 pages and contains plots of the 
measured AGC characteristics for HPSDR-PowerSDR W5WC, PowerSDR-Flex 1500 
and for comparison an Elecraft K3.

First Three Paragraphs:

"I recently installed Power SDR, W5WC Version 1.19.3.2, Date: 12-31-10.  
The setup is an HPSDR 3-board combination of Ozzie, Mercury and 
Penelope. My computer uses an Intel Core 2 Duo, 2.4GHz, 2GB RAM.  The 
firmware versions are Ozy 1.7, Mercury 2.9, Penelope 1.2.

In listening to on the air HF SSB signals I noticed some audio 
distortion and non ideal AGC behavior compared to listening to the same 
signals on an analog receiver.  The AGC performance is better than with 
the previous Power-SDR version but on my system it still leaves a lot to 
be desired. In an effort to see what is happening I ran some test on the 
Mercury board with stepped level and analog variable level CW signals.  
I also did the same tests on a Flex1500 and an Elecraft K3.

The main conclusions are as follows. These apply to the latest PowerSDR 
versions for both HPSDR and the Flex 1500. The AGC slope option is not 
implemented properly.  The Hang-Threshold control does not work 
properly.  If the Hang-Threshold setting is anything greater than zero, 
for falling signals the hang and decay times are not invoked. At 
Hang-Threshold settings greater than zero the AGC provides no gain 
control on falling signals until the signal is interrupted or it reaches 
a very low level. It behaves as if an infinite hang-time were invoked.  
As there are interactions between these various setting there may be 
other undiscovered problems.  The test methodology and results are 
described in detail below."


73,

Pete W6XX

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