APCO25 Mobile Data?

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realgeo

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Good evening, everyone! The "wandering one" has returned! :*)

Here in the Murray area recently, I've been picking up a new channel in the OPPD frequency layout.

The frequency in question is 859.28750 and is up nearly constantly. Most of the time, it sounds as if it's transmitting APCO25 "idle" codes - codes that are sent when no actual data is being sent.

Then, infrequently, you hear bursts of sounds that are irregular and interrupt the rhythmic sound of the "idle" codes. Sometimes, the irregular sounds are quite lengthy, other times, just temporary.

My BCD396T recognizes the signalling as P25, but only displays "LNK", indicating "data on a voice channel". The UniTrunker "knack.exe" program tells me that the NAC is 140, which is what ORIN/OPPD is using.

Other frequencies with this same behavior include 858.2875 and 858.4875, however they are not as strong as the first one I mentioned.

Is it possible that OPPD is using this channel for Mobile Data in the APCO25 format?

I thank you for your observations!

73's
 

realgeo

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Howdy, again, everyone!

Running the UniTrunker "packets.exe" program while listening to the OPPD Murray site's control channel, 866.11250, with my RS Pro97, one finds the following line in the data:

E 16 00 00 C0 05 2D FF FF FF FF BF F3 9DC3 SNDCP Data Channel Announcement Explicit Opt 00 AA=1 RA=1 TX channel 0-52D(859.28750) RX channel F-FFF(876.60000) DAC (data group) FFFF

So, apparently the 859.28750 channel is some sort of Mobile Data channel that OPPD is using. My question is, what does "SNDCP" mean?

Does anyone know what kind of Mobile Data system OPD/DCSO is using??

73's
 

N5PCX

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realgeo said:
Howdy, again, everyone!

Running the UniTrunker "packets.exe" program while listening to the OPPD Murray site's control channel, 866.11250, with my RS Pro97, one finds the following line in the data:

E 16 00 00 C0 05 2D FF FF FF FF BF F3 9DC3 SNDCP Data Channel Announcement Explicit Opt 00 AA=1 RA=1 TX channel 0-52D(859.28750) RX channel F-FFF(876.60000) DAC (data group) FFFF

So, apparently the 859.28750 channel is some sort of Mobile Data channel that OPPD is using. My question is, what does "SNDCP" mean?

Does anyone know what kind of Mobile Data system OPD/DCSO is using??

73's
Just to through you a bone!!!! This will give you a starting point.


SNDCP SNDCP stands for Sub Network Dependent Convergence Protocol. This is part of layer 3 of a GPRS protocol specifications.
http://www.answers.com/topic/sndcp


Good Luck

Wes
 

SCPD

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realgeo said:
Does anyone know what kind of Mobile Data system OPD/DCSO is using??
73's
OPD has their own I don't know what frequencies, they don't you any of the TRSs freqs, and DCSO uses Sarpy's MDT system, but they are currently building their own on 4.9GHz.
 

realgeo

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Hey, Wes!

Very good - I should've Googled it before I asked about it!

So, it looks like they might very be encapsulating IP traffic over the SNDCP data channel, which would be an excellent way to use off-the-shelf mobile computing equipment for Trouble Ticket tracking, or whatever use you could think of!

OPPD could equip their trucks with industrial-strength laptops, giving the line/repair crews access to resources on the OPPD intranet, that would only be available at a Service Center or other fixed location.

As I mentioned, this "data channel" has become active in the last few days, so they must be doing some testing!

Thanks for the link and info!

73's
 

realgeo

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Hey, KG4HWM!

I think that 855.7125 and 855.8375 are two of the MDT frequencies in the Omaha area - I don't remember which is Sarpy's, but one of them is.

By chance - do you know if they're running the MDC4800 protocol?

George B.
 

43g70

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I think OPD uses a cellular provider for their Mobile Data.

They used to be on the Racom System.

43g70
 

realgeo

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Hey, KG4WHM!

Yep - I can hear the 858.48750 signal from Murray, but it was at about the same strength as the Elkhorn control channel, so that makes sense.

I was also hearing this on 858.28750, which exists on the following licenses and their associated sites:
KNER504: Statewide NE and Statewide IA
WPSZ331: Gretna, Omaha, Blair, Telbasta, Julian, and Elkhorn
WPTA210: Murray, Syracuse, Steinhauer, Barada, Cedar Bluffs, Nashville.

73's
 

realgeo

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Good morning, everyone!

On my way into work this morning, I heard several transmissions on 408.0000. Most of them are single-digit unit numbers calling each other - "1 calling 2 - are you in your office?", "No, 2 is away". Another one I heard was "We're currently maintenancing the alarms on 10".

Some of the traffic, although short, sounds like law-enforcement traffic, although I can't confirm that.

Last night, on the way home, I heard a female voice ("3") talking to a male voice ("4"), but I was in the 132nd and Center area, where the signal wasn't as strong, so the voice was somewhat garbled.

The signal, however, is VERY STRONG along I480 and the Leavenworth area, and points to the west. My 396T's signal meter is pegged in this area, as well as downtown.

Just my observations.

73's
 

realgeo

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W0JJK said:
855.7125 is Sarpy MDC Frequency.

W0JJK
Howdy, W0JJK!

Thanks for the info! Yeah, I had found that one in the FCC database after asking the question in this thread! :*)

73's
 
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