We all owe John our eternal gratitude for finding serious bugs in the
ALC system that I have fixed (ending overshoot and some internal
ghosts/IMD forever). He put some serious test equipment on the job
(that I did not have at my disposal) and within literally a few hours of
studying his documentation and looking at the code, the problem was
fixed. Much to my chagrin, his first email on the subject wound up in
one of the cascaded bit buckets (spam filters) that protect me from the
world. Gerald then showed me the document while I was in the middle of
doing the first round of the wideband IQ work (also available in the
test branch) and it just slipped my mind until a month ago.
In an attempt to eek out the last measure of good sounding high
performance TX, John suggested this new ordering and did his own
version of the reorder. It does indeed sound great. It his MEASURABLE
lower in band IMD (the transmit filters are so steep it had to be in
band from the DSP).
This is the test branch, svn 3122 and higher.
It has new ALC, wideband image reject, and much more.
WARNING WARNING WARNING, DANGER WILL ROBINSON.
The image reject in the new code requires you to recalibrate your radio
and store values in the EEPROM just like now. There is no easy mapping
between old and new so the old goes away and the new replaces it. Once
you do this, you will be unable to get good image rejection upon
returning to the trunk or 1.18.0 Release without recalibration again.
This can be a really tedious process. The new algorithm is blistering
fast but to go back, you have to do the "old stuff". The wideband image
reject then dynamically tunes to signals on the band from this starting
point. If things go well, this will be in the new release, and it
appears to be a complete winner so far.
So if you do not understand what I am talking about in this just
finished pseudo-English paragraph, DO NOT USE THE TEST BRANCH. We
really cannot be bugging Dudley, et. al. with support issues on this
test code. They do not have sufficient hours in the day.
Bob
N4HY
john_eck...@agilent.com wrote:
As of svn 3122 the phone tx performance of PowerSDR is greatly improved (IMHO).
The tx alc is working like a champ.
You can drive your linear harder without it tripping. The compressor (DX
Button) and compander (CPDR) sound great.
To set up the audio, set the TX Meter to 'ALC Comp' and adjust the mic gain
until you get 2 to 3 db of alc compression
on voice peaks. Then you can run 3 to 5 db of 'DX' for full sounding high
quality rag chew audio. Or run it all the way to
10 to bust through the pile ups.
Let us know what you think.
73,
John
k2ox
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