M/A-COM P25, unable to trunktrack, able to decode P25 audio: Is this ESK?

[Jay911]

Hi all,

Please consult the following threads in Western Canada: RCMP in Regina Area and Can anyone identify this signal?.

These guys are having a brutal time trying to get any scanner to handle this system. As I understand it from the thread, no scanner will decode the control channel (audio sample provided in the 2nd thread, for what it's worth), but the individual audio frequencies can be monitored using any P25 capable scanner, in conventional mode.

Unitrunker also has no luck in decoding this system, although some listeners have successfully read NACs.

If it's not ESK, are there any other suggestions as to what it might be? Someone once mentioned it might be like the VA STARS system, but I don't know anything about that one. (To me, STARS is a helicopter ambulance on a conventional frequency here in Calgary )

Many thanks in advance on behalf of the Saskatchewan folks!

[ElroyJetson]

ESK is not an approved option or feature for a true approved P25 trunking system. But it COULD be a system that adds ESK and thus deviates from the P25 trunking standard.

It would then be a proprietary system.


Elroy

[1268]

Sounds like a 9600 baud control channel not ESK , agree with Elroy that ESK is not part of P25.

Just listened to some files... could be a 4800 baud control which is used for narrow band, at least it sounds very similar. Look in the wiki under EDACS and listen to 9600 and 4800 sounds a lot like the 4800.

[MikeOxlong]

Originally Posted by 1268

Sounds like a 9600 baud control channel not ESK , agree with Elroy that ESK is not part of P25.

Yup, it's not part of the P25 standard but that doesn't mean a manufacturer can't add it on as an extra.

P25 is just a standard. Many manufacturers have their extra features which can be added to the base. Motorola adds in lots of extra features that are not part of the P25 package.

This does limit the use of another manufacturer's radios on the system but if you've just bought a P25 system from MA/COM complete with MA/COM radios that support ESK, it doesn't mean you can't have ESK.

What it does mean is that you can't use another manufacturer's radios on the system.

As Elroy says, it's now a proprietary system.

[Unitrunker]

Jay - it is not ESK. It sounds like a Project 25 Phase I signal. I'm guessing the sound file from the other thread was recorded from speaker or headphone audio. An audio sample taken from discriminator audio would provide more details.

[Jay911]

Thanks - I didn't think it was ESK, because I was pretty sure at the very least UT could handle it, if not the more up-to-date firmware in modern scanners.

I directed the Saskatchewan guys to this thread, so hopefully the guys in range of the system will have the ability to record some discriminator audio. Unfortunately, I'm about 500 miles away, so I have no chance of picking it up myself.

[BaLa]

Sounds very close to a Local P25 System on UHF (380)..

This is for a Brand new M/A COM P25IP System.
Trying to find a way to get a recording of mine.


http://www.megaupload.com/?d=DTMKVMO7


Not the best quality, but this will have to do....
By the way..this system is operational, and linked to 3 other sites.

Pro 96 decodes the CC fine as well.

[wa8pyr]

Originally Posted by Mike_Oxlong

Yup, it's not part of the P25 standard but that doesn't mean a manufacturer can't add it on as an extra.

P25 is just a standard. Many manufacturers have their extra features which can be added to the base. Motorola adds in lots of extra features that are not part of the P25 package.

And when those special "value-added" features are being used, the data stream contains manufacturer codes to indicate same. In theory, all P25-compliant radios should be able to work on the system if it's a P25-compliant system. The only thing they won't do is the special features found on radios from other manufacturers.

If it's a true P25-compliant system, it's possible the control channel is being encrypted (which is a feature allowed under the standard, IIRC); if that's the case, you're OOL no matter what.

[wayne_h]

Bumped over to the Trunking Forum since we don't exactly know what it is yet.

[Jay911]

Fair enough, Wayne, but it's a M/A-COM contract and M/A-COM equpment as confirmed by people in the area the system covers, so I'm pretty sure that it's a M/A-COM system.

[richster]

Originally Posted by Unitrunker

Jay - it is not ESK. It sounds like a Project 25 Phase I signal. I'm guessing the sound file from the other thread was recorded from speaker or headphone audio. An audio sample taken from discriminator audio would provide more details.

Wow lucky I found this. Yes that was me who provided that sample a couple of years back, and it was off the headphone jack.

Here is an 8 second sample fresh and unfiltered right off the tap. Hope that helps!

sample2.zip

Regards,
Richster.

[Unitrunker]

Thanks Richster.

I was able to catch some P25 message fragments from your recording.

-B4 00 05 02 00 78 01 A5 24 80 57 E1 Identifier Update 0 Base 138000000 Spacing 15000 Tx Offset 32000000
-B4 00 15 84 28 78 01 A5 24 80 58 C3 Identifier Update 1 Base 138000000 Spacing 15000 Tx Offset 66500000

It is P25 using C4FM (so it is not simulcast). Due to poor decode rate (not a fault of your recording), I couldn't extract any more details.

Note the two nearly identical frequency maps above (broadcast as "Identifier Updates"). This suggests the system implementers are trying to avoid use of "explicit" channel addressing which is less efficient / reliable as "implicit" channel addressing.

The NAC is likely 005.

[richster]

Well thanks for taking the time to look at it, I definately appreciate it!

Regards,
Richster.