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First, the talkgroups should all end in a hex zero. Those sevens and threes etc are different flavors of the "base" talkgroup ID, like a patch or multiselect. See if you recognize them with a zero at the end.
1FDC is a common nuisance hit, might be a system thing. Other ones could also be just garbled data - it only takes one bit error to create a totally different ID, and sending 3600 baud over RF is prone to errors. See which ones occur often, and listen for a real conversation.
1FDC is a common nuisance hit, might be a system thing. Other ones could also be just garbled data - it only takes one bit error to create a totally different ID, and sending 3600 baud over RF is prone to errors. See which ones occur often, and listen for a real conversation.
Interesting, good point about the zero LSDs. That does seem to be true of all the valid group listings. Thanks!
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A little off the subject, but what kind of rig do you use to capture the talkgroups like that?
I will post more about the hardware later -- it's an interesting project in itself. Essentially it's a port of the moto.cpp module from the Trunker 3.83 source code distribution to an Atmel ATmega128 microcontroller. The Atmel chip runs a dedicated 800-MHz data radio module, which is itself part of a larger "DC-to-daylight" homebrew receiver project.
The whole ball of wax is hosted by a Mini-ITX PC motherboard running Win2K, which coordinates the two receiver microcontrollers via RS-232 and manages the user interface:
The UI application generates a log of any groups it doesn't recognize, which is what I posted above.
I have had the receiver hardware up and running for a year or so now, but am just now getting around to writing the application software for it. It is not only possible, but highly probable, that I still have bugs in the lower-level code. :) FlashP's comment about the lower nibble being 0 is exactly the kind of clue I'm looking for. I am still very wet behind the ears at the trunk-tracking business.
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73A6, 73AA, as well as several others are individual ID's. Not TG's
Beats me how those got in there. They are nowhere near any valid talkgroup IDs, even with the lower nibble masked out. Error-correction loopholes are sounding pretty likely at this point. After I mask off the lower nibble in the next revision, I'll probably try keeping track of how many times a given unknown group becomes active, and discard any that never show up more than once or twice.
Really appreciate the help! More later, hopefully....