Changing P25 System Modulation

[dtscho]

Is there no way to change P25 site modulation except by using Func + Chan? For Motorola P16 and EDACS systems, changing the modulation is an option under Edit Site, but modulation is not present as an option for P25 sites.

Changing from NFM to FM is important for monitoring Virginia's statewide system, STARS. I made the change using Func + Chan, and then read the scanner back to Sentinel to preserve the change. Otherwise, every time I write from Sentinel to the scanner, the modulation is changed back to NFM, and I have to manually fix it.

Thanks,
Dave

 

[jim202]

Is there no way to change P25 site modulation except by using Func + Chan? For Motorola P16 and EDACS systems, changing the modulation is an option under Edit Site, but modulation is not present as an option for P25 sites.

Changing from NFM to FM is important for monitoring Virginia's statewide system, STARS. I made the change using Func + Chan, and then read the scanner back to Sentinel to preserve the change. Otherwise, every time I write from Sentinel to the scanner, the modulation is changed back to NFM, and I have to manually fix it.

Thanks,
Dave

You have me confused. Why would you set your scanner to wide band to listen to a narrow band signal? Like everyone else under part 90, the state of Virginia has narrow banded all it's VHF channels it uses.

 

[rjdj2000]

See here: BCDx36HP Test for P25 Decode Improvement

 

[dtscho]

I'm aware that STARS should be monitored as NFM, but the scanner does not receive talkgroups with NFM nearly as well as when using FM, for some reason.

As for changing the band defaults, I'd rather not do this, as I only need the modulation changed for STARS.

Dave

 

[JamesO]

STARS is a PITA.

The problem is VHF and the longer wavelength. The peaks and nulls are much greater than with 800 MHz. With STARS you can hold the scanner in your hand and monitor the control channel, move your arm 1 foot left or right and the control channel will disappear.

Changing the modulation type seems to change the gain and/or AGC somehow in these scanners as they do not really have 2 narrower IF FM filters.

Also I think the other problem with STARS is the 2.5 kHz step size. I see most of the software and control is for a minimum of 5 or 7.5 kHz steps, not 2.5 kHz and maybe the tuner is not actually on frequency so going with the wider FM setting may capture more of the signal??