Which version of PSDR are you using Brett? Version 2.2.3 fixed a very
big issue with AM reception (AGC tracking the sideband energy rather
than the carrier energy) that was present in all the previous 2.x.x
versions and the later 1.x.x versions. That being said, I do notice what
sounds like peak distortion on some strong signals when using the AM
mode. I do not hear it when listening with other conventional AM
receivers that I use. Adjusting the AGC-T slider in PSDR doesn't seem to
stop it, but I wonder if adjusting the variables in the DSP AGC/ALC
setup tab might address it. The "max gain" and "attack" values might be
a good starting point for experimentation. Curiously, I never hear that
distortion with PSDR when listening to strong signals on the AM
broadcast band, so it may have something to do with selective fading and
the way PSDR deals with it.
As Tim may have been inferring with his question, the "peak distortion"
phenomenon is not present on those signals when listening in SAM mode.
Unfortunately, some of the older AM transmitters being used are not
perfectly stable and tend to move a few Hz when modulated. The SAM
detector warbles now and then with those stations as it tracks them on
peaks. It's most notable on 10 meter AM where there's a multiplication
factor being applied to the VFO in the older transmitters. So, at this
point, I find that I switch back and forth between AM and SAM to see
what seems to work best with different stations I run into. I'd be
curious what others may have noticed when operating AM or when SW
listening in the AM or SAM modes.
73,
Rob W1AEX
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