OP25 OP25: CQPSK Or C4FM?

[CanesFan95]

How do we know which setting to use in the .tsv file for the Modulation? Are CQPSK & C4FM the only 2 options? And, is there an option to not have to enter a NAC code and just leave it open?

 

[boatbod]

The modulation in trunk.tsv is ignored for all practical purposes. If you need to change modulation, do it on the command line with -D fsk4 otherwise cqpsk is assumed.

 

[CanesFan95]

Thanks. So the only 2 choices are -D fsk4 or -D cqpsk? Is there a way to know which one to use, depening on what system we're monitoring?

 

[boatbod]

Thanks. So the only 2 choices are -D fsk4 or -D cqpsk? Is there a way to know which one to use, depening on what system we're monitoring?

Start with the default (cqosk) and if that doesn't work try fsk4. You can look at the datascope plot too, but that requires more experience to understand the subtle differences in characteristics between the two modulation techniques. (Size/number of eyes)

 

[CanesFan95]

Understood. So is "fsk4" the same thing as "C4FM"?

 

[redbeard]

Thanks. So the only 2 choices are -D fsk4 or -D cqpsk? Is there a way to know which one to use, depening on what system we're monitoring?

You know what to use based on whether or not the system is simulcast. Regular sites use C4FM, simul sites are CQPSK.

 

[boatbod]

You know what to use based on whether or not the system is simulcast. Regular sites use C4FM, simul sites are CQPSK.

P25 Conventional is almost certainly going to be C4FM. P25 Trunked can be a crap shoot and I'd recommend starting with CQPSK because that should work with either modulation scheme.