[hpsdr] Companding in SDR RX Front End

[stoskopf at tri.net]

> National describes a receiver gain control system in their GSM A/D and
> downconverter chip
> 	http://www.national.com/ds/LM/LM97593.pdf

When the original TAPR/AD DSP box came out I thought about a similar process:

picking off a couple of upper output bits from the A/D, when they were
exceeded simply hitting the front-end variable gain stage with a little
pulse to the gain control until the signal fell below threshold.  Simple
RC recovery decay.  Never got around to trying it.  A bit of delay, but at
the sampling rate certainly faster than the audio derived AGC I used with
the Plessey chip set in the 70s!

N0UU

Also, finally took the Atlas/Ozy/Janus stack totally apart, erased the SW
totally and started over.  System back to normal!  Thanks to those who
gave hints.


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