Columbia Gas P25 conventional

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wa8pyr

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Just for grins I configured my BCD996XT with the six local Columbia Gas frequencies (in the Columbus area) set up as a P25 system, with a separate single-channel site for each local frequency. With the radio in search mode and using ARC-XT Pro, since last night I've logged the following Radio IDs, all on Talkgroup 1:

451.025 - IDs 19 (3 hits), 2828 (1 hit), 1075 (1 hit), 2911 (6 hits)
451.050 - IDs 1020 (3 hits), 7 (2 hits), 3 (4 hits)
451.125 - ID 13 (1 hit)
452.750 - ID 1080 (1 hit)

I've also got a bunch of hits logged with no Radios IDs (still on talkgroup 1), as follows:

451.025 - 16 hits
451.050 - 4 hits
451.125 - 2 hits
452.750 - 3 hits

I haven't got it set up to record audio yet, but I'm seriously thinking about it so I can try to match IDs with user function, if possible. They're not terribly chatty, so it might not be worthwhile.

I'm still wondering what possible value P25 conventional talkgroups are, when it seems the same purpose (separation of user groups) could be accomplished with a separate NAC for each function.

Anybody else ever tried this?

UPDATE: Just caught "Integration" (ID #7) talking to one of the field techs (ID # 1020) on 452.750 MHz.
 
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n3obl

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I think they use like the talkgroup to differenate between voice and data traffic.

Frank
 

16b

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I think NACs are intended to distinguish between different systems/repeaters and talkgroups are intended to distinguish between groups of users on the same repeater. Like you said you could certainly accomplish the same thing using multiple NACs through the same repeater, though. When programming my Motorola P25 radios, I have the option to turn talkgroups on or off, but even with talkgroups off it still has to populate the talkgroup ID section of the packet with something, so maybe it uses #1. With talkgroups turned on I have the option of strapping a mode to a certain talkgroup or allowing the user to select a talkgroup via a menu item. I suppose the latter is an interesting feature, but with 1000 channel radios it seems like it would be easier and more intuitive to use the strapping method.

I've listened to Columbia Gas before, but they talk so seldom I got bored pretty fast. If you listen to their frequencies on an analog radio, you hear the repeater transmit a short data burst periodically, which is consistent with the use of the status/message functionality that Motorola radios provide. This may explain, in part, why they don't talk much. Of course the data bursts could be something completely different.
 

wa8pyr

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I think NACs are intended to distinguish between different systems/repeaters and talkgroups are intended to distinguish between groups of users on the same repeater. Like you said you could certainly accomplish the same thing using multiple NACs through the same repeater, though. When programming my Motorola P25 radios, I have the option to turn talkgroups on or off, but even with talkgroups off it still has to populate the talkgroup ID section of the packet with something, so maybe it uses #1. With talkgroups turned on I have the option of strapping a mode to a certain talkgroup or allowing the user to select a talkgroup via a menu item. I suppose the latter is an interesting feature, but with 1000 channel radios it seems like it would be easier and more intuitive to use the strapping method.
I've done this on the radios at work as well as a test; still seems like a lot of effort for little gain when separate NAC would accomplish the same thing with much less effort.

I've listened to Columbia Gas before, but they talk so seldom I got bored pretty fast. If you listen to their frequencies on an analog radio, you hear the repeater transmit a short data burst periodically, which is consistent with the use of the status/message functionality that Motorola radios provide. This may explain, in part, why they don't talk much. Of course the data bursts could be something completely different.
They do most of their dispatching now with CAD over cellular air cards. Voice radio is mostly used for car to car or base to car when they need something that requires explaining, or a specific request. There's also a lot of yakking back and forth when there's a gas leak somewhere. I'm not even sure they use the status/messaging function any longer.

Still, it's an interesting challenge; figuring out these things provides some harmless fun for a little while. Maybe I'll start in on the Columbus Schools LTR system next....
 

16b

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They do most of their dispatching now with CAD over cellular air cards. Voice radio is mostly used for car to car or base to car when they need something that requires explaining, or a specific request. There's also a lot of yakking back and forth when there's a gas leak somewhere. I'm not even sure they use the status/messaging function any longer.
That's interesting information to know; nice to know why there isn't much traffic on UHF. It's a neat system, and it almost seems like it's a bit wasted for how little they use it. I'd be interested to know how the repeaters around the state are networked; that is, if they are all linked full time, selectively linked, or not linked at all.
 

wa8pyr

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That's interesting information to know; nice to know why there isn't much traffic on UHF. It's a neat system, and it almost seems like it's a bit wasted for how little they use it. I'd be interested to know how the repeaters around the state are networked; that is, if they are all linked full time, selectively linked, or not linked at all.
Just found out today that the service dispatch repeaters are multicast. You can hear the dispatcher talking on several bases at once, but will only hear the field unit if you're listening to the repeater they are using, which could be anywhere in the state. I don't know, though, if they are all one network or if there are two or more networks.

So far it looks like 451.125 is the service dispatch repeater for Columbus; from what I've monitored, UID 13 is the service dispatcher, and shows up on that channel all the time.

"Integration" uses ID 3 and ID 7.

The only talkgroups I've logged are 1 and 4095. All voice communications I've heard have been on TG 1. Don't know what TG 4095 is, as it usually pops up in the wee hours.
 

wa8pyr

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Columbia Gas P25 conventional: update

Here's the frequency "Hit Parade" so far....

451.025 - 16 hits
451.050 - 15
451.125 - 21 (from monitoring this appears to be service dispatch)
451.2125 - 0
452.475 - 0
452.750 - 23 (this is apparently a common channel)
 
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