HP-1: Modulation Question (Sudbury, MA PD)

[BOBRR]

Hello,

I have been listening to our local PD (Sudbury / MA / Middlesex County) on 852.9125
Comes in fine. This is from an old FL I created years ago for the HP-1 which I have gotten working again.
Modulation is shown as NFM.

On looking at RR now for the PD, I see that they list the freq. the same, but the Modulation
is shown as P25e.
I understand that the e means encrypted.

Might someone please explain this for me:
I understand that NFM is, well, FM modulation.

P25 is digital, though. Correct ?

Do they use both simultaneously do you think ?
Or, likely that they switch, sometimes one, and sometimes the other, but use the same freq. ?

*Should I enter the freq in the FL twice, each with a different modulation ?

Thanks,
Bob

 

[jonwienke]

NFM is the basic modulation. P25 is the digital format transmitted with that modulation. You can't select P25 as a modulation type, because it isn't one. Its a digital format.

 

[wscranston]

Are you saying that you are currently listening to Sudbury PD on that frequency? Even though they are ostensibly encrypted?

 

[BOBRR]

Hi,

I guess what confused me is that RR shows the "Mode" for the PD, which I take to be the Modulation, as
the P25e. For the FD, eg. it shows NFM.

Misprint in the RR database ?

I can, now and then, pick up the PD, so my guess is if they are using encryption,
it's "part time" perhaps.

A quick thanks if I may, for all the help and assistance.
Would be lost without all of your help.

Regards,
Bob

 

[jonwienke]

RR combines both modulation and digital format in a single field. P25 and DMR always use NFM 12.5Khz channels, NXDN can use either 12.5 or 6.25KHz FM channels to transmit bits.

 

[ve3ext]

will be in Sudbury for t/giving will listen and advise if anything is different than what we now know
Jerry

 

[IAmSixNine]

The little e indicates part time encryption. So some Enc some in the clear.
Think of the protocols as being run on top of the modulation.
So you have narrow band channels that can run NXDN, P25, DMR or simply analog.
Most digital will be narrowband or ultra narrowband. 12.5khz spacing or 6.25.