[op25-dev] Re: rx.py progress [5 Attachments]

John Ackermann N8UR jra@febo.com [op25-dev] op25-dev at yahoogroups.com
Sun Jul 2 17:52:56 UTC 2017

Hi Max --

Attached are several screenshots from a recent run.  The first run used 
"-P constellation" and you can see the gnuplot output, as well as the 
error messages in the console where I'm tailing stderr.2

The second run disabled the gnuplot output and the -T command.  The 
console window remained empty with no output.  Note the sample rate 
error that's partially on the console screen and partially in the 
stderr.2 output.

I suspect that sample rate is the crux of the issue, as KB9MWR also 
noted this morning.  Sometimes, I see the sample rate being set 
correctly but most of the time get the errors shown in the screenshots: 
it appears that the -S parameter is not being caught, the default 320000 
rate is used, and that's failing as invalid.  (I normally use 250000 as 
the rate, but have tried with 1000000 and get the same results).

Hope this helps.


On 07/02/2017 01:30 PM, ikj1234i at yahoo.com [op25-dev] wrote:
> 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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