P25 carrier squelch GROUP ID?

[Elroy Jetson]

Here's a challenge: What would be the "carrier squelch" or default group ID in a P25 system?

What I'm doing is kind of nutty: Using a P25-capable M/A-Com Jaguar 7100ip to listen to the Nashville Astro system.

It's not quite working...but it's REALLY close. The P25 system is entered as conventional channels with P25 talkgroups,
and if I had a "carrier squelch" talkgroup ID then I'm SURE I'd be able to monitor but not in trunking mode.

I say this because I can hit the monitor button and SOMETIMES get recognizable, correctly decoded voice. But only
briefly, as the group ID is wrong and the radio realizes that and stops the audio.

It's so close...and if I can make this work, then suddenly the scanning world will change again, ever so slightly.

Any help on finding the "carrier squelch" group IDs will be greatly appreciated.


Elroy

[otter9309]

What about $61f ?

[Elroy Jetson]

In decimal, please? This isn't scanner software and only deals in decimal, not hex.

Yeah, I can convert...but it's a pain.

Elroy

[Wicho]

1567

In decimal, please? This isn't scanner software and only deals in decimal, not hex.

Yeah, I can convert...but it's a pain.

Elroy

[Elroy Jetson]

Nope, didn't work. Must find other options.


Elroy

[Bruce1807]

The calculator in windows does a fine job of conversion
Change the view to scientific.
Hit the hex button.
Enter the hex code and click the decimal button

Voula!

works the other way round as well

[Elroy Jetson]

What I mean is, that ID didn't work. It's not the "csq group" if there even IS one.

In P25 mode, the channel itself has an NAC code which DOES have a "Carrier squelch" value, and I'm using that, but also, in P25 mode, the channel HAS to be assigned to a talkgroup as well. And THAT is where the problem lies. The talkgroup
ID isn't going to be the trunking talkgroup ID, I'm sure. And that wouldn't do me any good anyway as I want to hear ALL
the activity on the channel even though it may make it very hard if not impossible to track a conversation. Right now I'm more interested in just getting a M/A-Com 7100ip functional (listening) to decoded digital audio traffic on an Astro SmartZone system.


Elroy

[tvsjr]

Try 7FEh (by the way, hex is standard for NACs...) or 2046d.

[6V6GT]

According to the P25 standard I thought it was F7E (3966).


Tim

[Elroy Jetson]

I am using 7FE as the NAC and I'm getting occasional BRIEF bursts of decoded audio. I think the vocoder must be compatible but something is keeping it from unmuting on the whole transmission. Maybe it's low speed data on the channel causing interference? Maybe it's jus that it's looking for a P25 group ID and there isn't one...I don't know. I've got some
good test equipment at my disposal but for this I'd need a good data analyzer and a lot of time..or some insane luck.

I think I may place a call to macom some time today. All I really want to find out right now is just what the P25 group ID
should be if you want to hear all traffic. If there is one. If there's not one, how come I'm getting brief bursts of decoded
audio?

Incidentally, does anyone know the current state of the Nashville Metro astro system? Full digital, P25, what? I know that
it's at least mostly digital and it's a smartzone system, but beyond that....not sure.


Elroy

[radioinstl]

NAC Monitor = F7E (Hex)

When this Rx NAC ID (Network Access Code) is set to “7FE”, the radio unmutes to any ASTRO call regardless of the call’s NAC ID or the radio’s ASTRO Rx Unmute Rule set for the current channel.

[515]

I haven't tried listening to P25 trunked voice channels with a P7100 in conventional mode, but have tried it with some other brands...

Do you have your "Squelch Mode" set to MON or NORM in the "P25 Conv Frequency Set" tab? According to the P25 standard, the MON setting should allow the radio to unmute on any P25 voice signal. The NORM setting should require the NAC to match for unmute, but not care about the talkgroup. The SEL setting should require both NAC and TG to match for unmute. There's no guarantee the P7100 actually works this way, though.

Most if not all Motorola trunked systems with P25 voice channels transmit the audio as an alternating string of two types of P25 voice frames. The type of frame is identified by the Link Control Opcode (LCO) value, which can be seen on a P25 service monitor. On a trunking voice channel, the opcode alternates between that of a standard P25 conventional group voice call, and one more specific to trunking. Pretty much any P25 conventional radio knows how to deal with the standard LCO=1 P25 Group Voice frame, but many non-Motorola radios get confused and mute when they encounter the frame more specific to trunking. So, that's probably why you're hearing bursts of audio--the radio is only decoding the standard frames and muting on the trunking specific ones.

I'd definitely try the "hear all" RX NAC of 3966/F7E, in conjunction with the "all call" talkgroup of 65535/FFFF, but really the MON squelch mode setting should take care of it, providing the radio isn't coded to just mute whenever it encounters anything other than the standard P25 conventional voice frames.

[tvsjr]

NAC Monitor = F7E (Hex)

When this Rx NAC ID (Network Access Code) is set to “7FE”, the radio unmutes to any ASTRO call regardless of the call’s NAC ID or the radio’s ASTRO Rx Unmute Rule set for the current channel.

Yeah, that's right... 7FE... F7E... hard to keep track!

Elroy - F7Eh or 3966d.

[Victor Xray]

Elroy's asking about an Astro (conventional) Talkgroup ID while you guys are referring to NAC ID. Those are two separate subjects; unless NAC is ultimately what Elroy is wanting but asking in the wrong way, which I doubt.

[Hightower]

Does this NAC monitor (F7E) work on the Astro Saber 512K vocon with Host/DSP of 05.06.xx / 06.05.xx?

I've tried setting of F7E for RX NAC and transmitted some odd ball NAC - it did not un-mute with the 512K vocon.

I'm assuming with this 512K Astro Saber, NAC monitor was not implemented yet. Correct?

Now would an Astro Saber 1 Meg vocon with new 7.71 firmware support Nac Monitor using F7E?

[mr.syntrx]

Motorola dragged their asses for a very long time in implementing F7E. IIRC a CPS version addressed that issue together with newer firmware.

[MattSR]

It was implemented with HOST 7.25 and CPS 5.02 or there abouts.