P25 on the bands

Use this section to discuss Digital Amateur Radio operations, such as D-Star and other digitally-encoded traffic
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26mb04
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P25 on the bands

Post by 26mb04 »

Is there any P25 activity on the bands? There are/were some P25 capable repeaters, but info seems to be scarce. What codec is the norm, VSELP, IMBE or AMBE? Is the ID system the same as DMR? What about network access codes? It seems 295 is common for repeater access in USA.
Sent from my GP300 using DTMF

pete_uk
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Re: P25 on the bands

Post by pete_uk »

Its really an American thing, I doubt there are many radios in the hands of amateurs over here.

Phase 1 radio systems operate in 12.5 kHz digital mode using FDMA access method. Phase 1 radios use Continuous 4 level FM (C4FM) modulation—a special type of 4FSK modulation

To improve spectrum use, P25 Phase 2 was developed for trunking systems using a 2-slot TDMA. Phase 2 uses the AMBE+2 voice codec to reduce the needed bitrate so that one voice channel will only require 6,000 bits per second.

26mb04
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Re: P25 on the bands

Post by 26mb04 »

That's fair enough, I knew it was largely a USA thing. I'm going to propose a UK P25-specific schedule for 70cm:

NAC: TX 293 (default), RX either 293 or F7E (all).
Talkgroup: 1 (default) , calling on FFFF (all)

Frequencies: Ideally the UK digital voice allocation for calling etc., but if it's busy with DMR go to 438.0375 and work up from there.
Sent from my GP300 using DTMF

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