Madison Trunking - Digitial Signals??

[bc780l]

Anyone know what's up with TGIDs on the City of Madison Motorola trunking system:
51696
55138
55328
55360
55408

Receiving occasional digital signals on my 396, but no P25, ENC, or LNK indicators showing. Playing with P25 level setting, but no difference so far.

 

[UPMan]

P25 will typically sound much like open squelch. Is that what you are hearing, or does it sound more like a control channel or other data burst? It isn't too unusual for some automated (non voice) data systems to be assigned TGIDs on trunked systems, and those would not be P25.

 

[bc780l]

Sounds like P25 motorboating when the signal thresholds are not tuned properly. Duration of signals are similar to what voice transmissions might be, a mix of short and long, and can switch channels in the trunking pool, but only very infrequently.

Just heard TGID 64784 also come up, but was for a very long burst--doesn't seem likely for voice and no reply. I've also noticed some sort of preamble to the data stream (usually indicates some handshake going on--but to what or whom?).

For clarity, this is the specific system I'm referring to: http://www.radioreference.com/modules.php?name=RR&sid=1451

Likely data, but with all the testing going on with the system lately ...