170.725 - P25 Digital

[bneilson]

Hey guys,

I was in downtown SLC (300 South 200 West) the night before last and was copying P25 Digital traffic on 170.725. Based on the traffic and the un-key I would say they were on a repeater...

Unfortunately I was never able to get a good copy on the audio, just the typical digital static, so I wasn't able to ID them.

Anybody have any more insight on this? I was thinking after the fact that I may have just been off frequency a bit from 170.750 that shootingnews mentioned in this thread. However each time I tuned it came back as 170.725.

 

[gldavis]

I've heard voice inversion encrypted P25 traffic on this freq for some time now. My 500 shows a NAC of N293. Research indicates this could be either FBI or ICE comms. I keep hopeing for some plan voice traffic, but so far nogo.

 

[ecps92]

In Dallas this has been set-up as a Federal Interop Frequency.

Maybe also now in UT ??

Hey guys,

I was in downtown SLC (300 South 200 West) the night before last and was copying P25 Digital traffic on 170.725. Based on the traffic and the un-key I would say they were on a repeater...

Unfortunately I was never able to get a good copy on the audio, just the typical digital static, so I wasn't able to ID them.

Anybody have any more insight on this? I was thinking after the fact that I may have just been off frequency a bit from 170.750 that shootingnews mentioned in this thread. However each time I tuned it came back as 170.725.

 

[bneilson]

@gldavis, you say encrypted and inverted? If it was just inverted we should be able to record it and beat it with a computer. If it is encrypted we are done

@ecps92, I recently moved back to Salt Lake from the Dallas area. I was in Frisco and had a great time listening to the Collin County TRS. When I left the DPS Troopers were just starting to convert to Digital but hadn't on the Tollway yet.

 

[theaton]

170.725

I've picked up a digital signal on 170.725 and had it noted as a "digital pager" in my DB. But that was just a guess. That frequency is not on any of my lists as belonging to a particular agency. I guess it will remain a mystery until we pick up something intelligable.

-Tim

 

[gldavis]

They're using voice inversion encryption. From what I've heard, it sounds like it is the "rolling" type of inversion.

 

[N7YUO]

Folks, you can dowload a voice inversion descrambler, free from Italian Ham IZ8BLY

http://xoomer.alice.it/aporcino/VoiceDescrambler/index.htm

I have used this descrambler and it is good.
Of course it's iilegal to listen to others' encrypted comms. (mandatory disclaimer)

 

[ecps92]

I think we are getting OFF-TOPIC the Original Poster stated "P25" and P25 is not Voice Inversion

They're using voice inversion encryption. From what I've heard, it sounds like it is the "rolling" type of inversion.

 

[gldavis]

I think we are getting OFF-TOPIC the Original Poster stated "P25" and P25 is not Voice Inversion

You are correct. P25 is a standard of digitizing the audio before transitting it. However, you can "encrypt" a P25 transmission in the same manner you can "encrypt" an analog transmission. This encryption can be done by either digitizing the audio and adding a second data stream to the digitized audio (digital encryption), or by inverting the audio before digitizing it (inversion encryption).

You can have analog, encrypted analog, P25, or encrypted P25. I have heard in this area all the above. Once I've ID'ed a freq as being Encryted I still listen to it on the off chance that one of the radios will "loose" its key. This does happen once in a while (but not often).

I hope this helps.