Westfield State Maintenance

Discussion forum for scanning Western Massachusetts, including the cities of Springfield, Pittsfield, Holyoke,
and all cities and towns within the counties of Berkshire, Hampden, Hampshire, and Franklin.
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xplorer417
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Westfield State Maintenance

#1 Post by xplorer417 » 04 Sep 2019 20:58

hi i tried putting that tg in my scanner it was changing it too 16776415 it won’t take the16777215 so it got to be off i know i’m doing it right.

Frequency: 159.735
Color Code: 1
Slot: 1
Talkgroup ID: 16777215

cdgordon
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Re: Westfield State Maintenance

#2 Post by cdgordon » 05 Sep 2019 09:22

That is most likely the radio ID and not the TGID.
I believe that the limit for talkgroups on a DMR system is the same as a P25 system. 65536 (FFFF) talkgroups and 16777215 (FFFFFF) users. It is actually a few less because the standards have a few TGs and RIDs reserved for special functions.
One of those special radio IDs is 16777215 which is "All Subscribers" or talk to everybody on the system. If a radio is programmed with that ID, it will be heard by everyone regardless of talkgroup.

chris

xplorer417
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Re: Westfield State Maintenance

#3 Post by xplorer417 » 05 Sep 2019 19:11

so ur saying 65536 is the tg id is that correct

cdgordon
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Re: Westfield State Maintenance

#4 Post by cdgordon » 05 Sep 2019 19:50

No, nowhere did I say that was the talkgroup. All I said was that 16777215 is not a valid DMR talkgroup.

chris

xplorer417
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Re: Westfield State Maintenance

#5 Post by xplorer417 » 05 Sep 2019 22:37

hi i’m not the one that initially posted this topic.ok i got what ur saying so 16777215 is also not a valid TG either if so why did they add it to the database if it’s right when’s it not.someone needs to recheck it.

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Re: Westfield State Maintenance

#6 Post by W1KNE » 06 Sep 2019 08:13

So we've had a few people here, and on RR confirm "16777215" as a talkgroup. I have seen it as well when decoding using a 536 decoding DMR systems.

I was always under the impression that this is a TG associated with the "all subscribers" use, but as a TGID, not a RID.

Let me ask around a bit on this, but the 16777215 *does* decode on the Uniden scanner as a valid TGID.
Mike Fitzpatrick
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Owner: Scan New England - NECRAT.US
Issues with Scan New England can be privately addressed to me. W1KNE at scan-ne.com.

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Re: Westfield State Maintenance

#7 Post by W1KNE » 06 Sep 2019 08:20

http://www.systemcom.as/admin/uploads/p ... nologi.pdf

Some light reading. Check out page 27. It refers to it as an "All Call Group", which makes me think when a RID with that comes up, it comes across the system as the all call TGID, which is a reserved TGID.
Hence why the scanner shows it as TGID. My guess is some radio systems are either misconfigured or intentionally configured to have all radios use it, to prevent "channel bumps" by the users.
And based on that, because it is a special reserved TG, that some scanner software or whatever he's using, isn't accepting it.
Mike Fitzpatrick
Broadcast Engineer - RF Enthusiast
Owner: Scan New England - NECRAT.US
Issues with Scan New England can be privately addressed to me. W1KNE at scan-ne.com.

cdgordon
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Re: Westfield State Maintenance

#8 Post by cdgordon » 06 Sep 2019 10:55

OK, sorry, my error, I stand corrected. I thought the DMR addressing was the same as the P25 addressing where there is a limit for TGs that is 65535 (FFFF) talkgroups. I went into the ETSI DMR Standard document and they allow the same number of talkgroups as radios, >16 million. TGID 16777215 is reserved for "All TGs"

ETSI TS 102 361-1 V2.2.1 (2013-02), pg118
"Systems which do not use the partitioned address scheme for "All talkgroup Idn" or "All unit Idn" shall use FFFFFF
to address everybody on the system."

chris

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Re: Westfield State Maintenance

#9 Post by wb1hbu » 06 Sep 2019 11:04

Hello,

Conventional DMR uses 24 bits for talkgroups and radio ids, so 16777215 is valid for a talkgroup. The radio id does not have to be 16777215. Connect Plus has the same limits. Motorola Capacity Plus uses 255 as the all-call talkgroup because Motorola reduced down the range of valid talkgroups and radio ids.

There is a taxi company in Boston where each taxi is on a separate talkgroup and the dispatcher is on the all-call talkgroup. The dispatcher has all the taxi's talkgroups in the RX List. This allows the dispatcher to talk to each taxi, but the taxis can not talk to each other. This emulates the old full duplex taxi setup with the base on one frequency and the mobiles on another frequency.

Regular talkgroups and Radio IDs for conventional DMR have a range from 1 to 16776415. 16776416 to 16777215 consists of reserved and special talkgroups/radio ids. Annex A of the DMR Part 1 Air Interface Protocol (ETSI TS 102 361-1) lists the numbering.

73 Eric

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Re: Westfield State Maintenance

#10 Post by cdgordon » 06 Sep 2019 14:09

I went mobile with DSDPlus and monitored several conversations. I only logged the 16777215 TG. If that is how the system is programmed, you could put any talkgroup into a 2 way radio and it would hear the conversation. The individual mobiles/portables have individual IDs so I can't figure out why they would run that TG. It is possible that they intend to grow the system and utilize the two slots and are simply using the all talkgroup ID until then.

chris

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