Hi David
AGC questions.
We had the WIA broadcast running all weekend on 50.25 in 700D and 2020
in 'berra.
I was mobile around canberra for some of the weekend with FreeDV, with
my laptop and the FT857
Something interesting and unexpected experiences..
When I had the AGC set to SLOW, the demod would occassionally throw an
error. I could hear huge deep holes in the received signal. this is expected
Around town, approx 20dB flat fading, Approx 10 to 15 fades per second,
some very deep
FreeDV got through those holes pretty well (L=4)
Thinking that I might get improved performance with AGC on FAST , the
results were unexpected, and the demod was unable to cope. BER was sky
high, clock recovery all over the shop etc.
Back to slow AGC, mostly fine. I have some grabs of this , I see FreeDV
only gets 60 second grabs, - not enough I will need to recompile and
longer periods permitted.
I have not delved into the code on this yet- any skeletons in the
cupboard that need some work? Any internal AGC that may be fighting the
other AGC ?
I appreciate that was flat fading like that on VHF mobile is NOT
generally found on HF, and this OFDM modem was designed for HF.
73
glen
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