p-25 cai trunked/conventional mode break down

[Curfew]

I realize that this may be something that's fluid depending on the user and how their stuff is programmed.

Anyone with any sort of scope on transmit/ receive modes with p-25 cai according to what band the radios are being used in. For example 850mhz= NFM, VHF HI band= FM,
UHF= WFM, VHF LO= AM/ FM

Sort of a breakdown or chart in what is the norm with modes in band plans to enhance reception quality, and make sure everything in the scanner is set correct according to whatever system/band is utilized? Thanks.

 

[mancow]

You won't use WFM or AM with P25 CAI.

 

[Curfew]

So we are down to FM and NFM? Which one would be used the most?

 

[mancow]

P25 CAI is a form of modulation that uses QPSK or C4FM. It's not just a digital "sound" that can be carried on any form of moduation.

 

[Curfew]

Thanks mancow, curfew.

 

[mancow]

So, with that I guess you could put it in the list as just another modulation form like, am, fm, etc...

As for what mode the radio has to be in for it to decode that depends on the receiver. Like with the 96, it has to be set to FM before it will catch a digital conversation. It's not really anything to do with the modes but a function of how the radio is designed.

Motorola units don't have WFM or AM to contend with so it's a moot point there.

 

[ctrabs74]

So we are down to FM and NFM? Which one would be used the most?

My local PD (West Chester, Pa.) recently began testing P25 on its conventional channels. I have those freqs (500.4125 and 500.5125) on FM with no PL. I also have Philadelphia PD 800 TRS and Phila. FD/city services 800 TRS - both full-time P25 - set to FM as well.

However, the State of Delaware 800 TRS and Bucks County, Pa. UHF TRS - both of which are full-time P25 - and Montgomery County, Pa. 800 TRS - which is mixed analog (PD/EMS) and P25 (Fire) - come in just fine on NFM. And the few times that I've heard some P25 TRS in New Jersey (Burlington County and Montclair Twp, Essex County), they come in on NFM just fine.

My guess is that it would depend on the system and how it's set up. At least from my personal experiences.