APCO 25 control ch

[SteveRoberts]

i have found a system that is P25, some encrypted use and some not (with my 396t) it has about 7 channels in use, I have searched either side of the active channels but cant find a control ch, any ideas?

system is in the UK at 430mhz

Cheers
Steve.R
Very much a P25 virgin

 

[EricCottrell]

Hello,

The P25 could be conventional channels. It can be used for either trunked or conventional. The control channel can be a Motorola control channel or a P25 control channel.

I would set up a search of the whole band (likely 420 to 440?) in one of the search ranges of the 396T. There is an search option named control channel only. If enabled, the radio will search the range, stop on the control channel, and trunktrack the system. The audio is muted until a trunked voice transmission occurs.

The Digital Modes Samples page has a small wav file of what a P25 control channel sounds like. Look for the Motorola ASTRO APCO-25 Trunking Control Channel entry.
http://www.kb9ukd.com/digital/
You could also search with data skip and control channel off and see if any received signal sounds similar to the wav file sample.

73 Eric

 

[SteveRoberts]

APCO25 Control ch

Eric
Thanks for the reply, I have searched the range 408.000 to 440.000 and found no control channel. so i can only assume its a non trunked net. I didnt realise they could be non trunked, so thanks for that, i thought i was going mad..

my only question/problem for this assumtion is, that users will somtimes be using one ch then another time they will be using another ch for the same user same use as they were before, which is why i thought it would be trunked. (does that make scense?)

Its strange how 3 USAF bases within 35miles of each other have 3 different systems, RAF Lakenheath Moto TypeII, RAF Mildenhall APCO25 Trunked (both in the 408/415 range)and the one i am trying to work out RAF Alconbury/Molesworth looks like APCO25 Non trunked (in the 430 range).

Thanks again Eric

Steve.R