[op25-dev] Re: rx.py progress

ikj1234i@yahoo.com [op25-dev] op25-dev at yahoogroups.com
Sun Jul 2 17:30:34 UTC 2017


Hi John

we need to do a better job of documenting the process of initial acquisition of the system.  The process itself could be made easier, as could 1,000 other things...

Could you post the command line you're running, and if possible post a screen print of the 'datascope' and 'constellation' plots...

The best approach usually has been to first get the control channel coming in well in manual tuning mode (i.e., no -T parameter), then (and only then) to try to get voice decode working.    In rx.py the way you'll know when the CC is tuned correctly is the number in the upper-right corner of the page (TSBKs) should be increasing steadily.  Assuming you have the correct CC frequency, the most common troubles tuning are: not using the proper PPM correction (-q parameter), failing to add an offset (I usually use -o 50000), incorrect RTL gain setting via the --gains (-N) parameter, incorrect use of FSK4 mode on an LSM P25 system (and vice-versa, using the CQPSK mode on a C4FM P25 system)...  Tuning in the CQPSK mode is fussier than in FSK4 mode, and messages should get written to the stderr file in the event of a slight mistuning... 

Max
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