InterceptRadio.com Forums

Hi, folks --

Over the last couple of years, I've accumulated a list of over 700 talkgroup IDs on the 868.175 MHz control channel that don't correspond to existing entries in the interceptradio.com database.

These are:

Unknown talkgroup log entries sorted by date of first encounter
Unknown talkgroup log entries sorted by talkgroup ID

Quite a few of these entries may be spurious, i.e., due to bad packets that were lucky enough to sneak past the Smartnet checksum algorithm. However, at least some of them represent legitimate, undocumented talkgroup IDs. With this many potential "unknowns" in the database, it seems like a good idea to try to identify (or discard) as many of them as possible, for the benefit of all listeners and users.

What are the odds of obtaining some help -- either official or unofficial -- with this Augean task? I will be glad to share any updated information I can find with the maintainer of the Intercept Northwest database.

Thanks for any suggestions! (And yes, one obvious one would be to modify my logging program to record how often a given unknown talkgroup ID appears on the system, to help rule out bad packets and one-time test transmissions. If it turns out that most of my logged entries are spurious, I'll probably do that. Right now, I don't know how big a problem the spurious entries really are.)

-- john, KE5FX

(Note that this is a follow-up to an earlier thread I started in June of 2004.)

Hi John,

I used to maintain a list of TGID's for this area, but the task seemed near impossible when the trunking system was fully populated -- changes seem to happen every day.

I appreicate your list -- it's interesting to see what others are getting. The Intercept list is a good reference for trying to figure out (generally) who might own the ID.

A question for you -- I'm curious when you started/stopped this list?

The last few days, I've been trying to figure out which PD Dispatch is on 37331. I guess it's Tukwila PD, but I haven't confirmed this. I noticed your list doesn't have this ID...



-Nick

Hi, Nick --

The list is generated by my homebrew receiver's control client application, which runs only when I'm listening to it. So the log date doesn't necessarily have anything to do with when the group was actually added by the system manager.

Basically, the client uses a copy of the interceptradio.com list to populate its real-time display of active talkgroups, and whenever an ID shows up that isn't on the list, it makes a log entry.

Again, I have a feeling that many/most of those entries are spurious. I'll probably create a new logfile soon and let the client run in exclusive mode for a few days, and then filter my master unknown-group list to include only entries that appear in both logs. It's hard to believe that they've added 700+ groups, and I certainly don't see many of the unknown groups in use on a regular basis.

Anyone with a broadband connection can run this app, by the way (see the Equinox receiver page linked from the main page in my profile). Availability is typically very high, but the receiver will be moved to Kirkland sometime in the next week or two, so there will be some downtime associated with that. The IP address will also change at that time, requiring a new client download.

Also, I will most likely switch the default trunk bank from the 868.175 Columbia Tower control channel to the 868.775 EPSCA control channel. This will probably result in even more unknown groups showing up in the log.

I keep hoping that the kind soul (Wiz?) who provided the talkgroup list in the first place will post an updated copy one of these days. If that doesn't happen, I may try hacking the client to record 5 minutes of audio from each unknown group that appears, and post the resulting .MP3s for folks to listen to and try to identify. That might be fun, but it certainly won't be foolproof.

John,

I just read your profile on your web site -- certainly an unexpected pleasure. I can't tell you how many hours I spent playing those damn Ultima games. Ultima and Bard's Tale kept me on the family Apple IIc for many nights! You've had a very interesting career already -- when I was that age, I just got lost inside MS and frankly have been too overworked to get out. :oops:

That homebrew system looks pretty sweet. I haven't thought of it, but I'll likely move my BC780XLT next to my desktop computer and have it track 868.175 for me. I just received my BC396T handheld, so it's my latest toy!

BTW, I'm in the Bellevue area myself, and 868.775 can be pretty boring to monitor. It's pretty much Eastside-specific communications -- but nothing happens over here. Most of the interesting chatter is on the Seattle system. I also listen to Port of Seattle -- it's only received with an outdoor antenna from my location however. The new Everett/Sno County system is interesting, but I'm just a little too far away to pick up a clear enough signal from the control channel.

Good to meet you John --

Feel free to pass any lists along... I'll do the same.


-Nick, n7zya

Heh, if I had gotten hooked up with MS at "that age," I wouldn't be complaining too much. :)

I agree that the EPSCA side of things isn't as interesting to monitor. It will come down to the signal quality I get at the new QTH. I almost always get 100% solid copy on the .175 control channel here in Queen Anne, subject to the usual multipath annoyances. Hopefully I can find a good antenna orientation that will give good copy on both. I have not yet tried the Port system.

Make room for the NON Expert. I am by far -- not up on all of the programming aspects, however the basics help. All talk groups are products of the number 16. The Radio Shack PRO-95 and PRO-96 only receive this basic TG Number. The Bearcat units receive all products of the TG. While 37331 has been located -- the basic TG is 37328. +3 seems to be a patch of two or more TG's. My point is to KISS. Keep it simple in all of the lists -- for everyone -- with any type of scanner to understand and identify a real Talkgroup. Everyone should be on the same page. Maybe marking a TG number with + could indicate that use of one or more of the sub-groups. Just an idea. --- Job well done. MTM

Correct; that's why my hex entries all end in '0' (multiples of 16). I keep track of both the original ID encountered and the rounded group ID, just in case the original ID proves useful for something.