Originally Posted by woody_46
Hello, I have tried all 3 versions of DSD and only version 1.41 will decode my P25 system. It decodes very well BTW. The only difference I can see is that 1.41 puts the program in QPSK mode while both newer versions put it in C4FM mode. So you ask what's the problem? 1.41 does not ignore the encrypted traffic.
Oh and thanks to everybody working on this project!
I've never had much success with DSD and C4FM demodulation of P25, on any version of DSD.
I actually gave up on DSD completely for many months before I came across this trick..
For best results and minimal packet loss, I run DSD1.60 and edit the batch file and force DSD to run GFSK modulation by inserting the -f1 -mg switch in the command line.
This gives me almost perfect decode on Phase 1 P25 and low signal strength performance as good, if not better than my 996xt.
When running, I get one star (error rate) decode on all most P25 transmissions and only higher error rates when the signal is very weak at ~10dB above the noise floor.
I've tested this on several high and low end PC's and it has been confirmed by others too.
There seems to be some kind of problem with the C4FM demodulation process within DSD.