Setting the manual gain mode in op25 will take away AGC and more importantly will
remove the false spike in the center of the spectrum. This is quite so that you can
visualize
the "Real" control channel from a figment of the Airspy's imagination.
Note that a full reboot or removal and re-plugging of the SDR into the USB port will be
required to clear the Airspy from previous linearity or sensitivity modes. Changing of
the
rx.py command line arguments and restarting rx.py will not clear the internal registers
of
the device, something that it took me a while to figure out.
I would still recommend starting with (-q 0) while checking for the presence of
TSBK's
coming from the control channel, and/or verification of a legitimate p25 signal by
observing
the constellation or symbols plots. But I think you'll be ok in using FFT once you
have the
AGC gain modes disabled.
Please let us know how you make out. Good luck!
Bill
-----Original Message-----
From: op25-dev <op25-dev-bounces(a)lists.osmocom.org> On Behalf Of op25(a)zellners.com
Sent: Sunday, September 6, 2020 9:29 AM
To: op25-dev(a)lists.osmocom.org
Subject: Re: [op25-dev] rx.py Airspy MASTER GAIN Setting option?????
Quoting wllmbecks(a)gmail.com:
The yellow highlighted text below in my rx.py command
line is an
example of how my R2 device was set to manual gain mode whereby the
device responds to user specified LNA, MIX,
and IF gain settings.
./rx.py --args "airspy=0,sensitivity=0,linearity=0,bias=0" -N
'LNA:15,MIX:15,IF:10' -S 2500000 -T trunk.tsv ………
Thanks... I think that may be the
magic,airspy=0,sensitivity=0,linearity=0,bias=0, as those names are
present in the other program, but hmm... I would expect since I nuked
them in that program it would persist? I guess not..
I will try this during some tests today... have to work on a more
mission critical option at first.
Thanks....