Re: Motorola IIi Hybrid Trunk decoding

Has anyone written a motorola trunk decoder for gnuradio? I’d like to be
able to dump all active audio in a trunk to separate streams by
talkgroup. I’d love to know about any trunk decoders in general.

In addition to Nick’s Moto Smartnet II decoder on CGRAN, the op25-dev
project also has a trunked system receiver for P25 systems.

At this moment the trunk control channel isn’t actively parsed in real
time. Instead all of the channels of the trunked system, including the
control channel, are logged to disk (or routed to asterisk app_rpt).

Generally, all the voice channels are decoded to audio and relayed to
the VOIP world (asterisk app_rpt), whereas the control channel data
would be routed over a UDP “connection” for logging in Wireshark. We
also have a Wireshark parser for P25 frames although it currently
doesn’t delve very deeply into the P25 trunk control protocol message
(TSBK) frames.

Finally would like to mention that our receiver works well with
so-called “CQPSK/LSM” systems from Motorola - the “simulcast” distortion
has caused a lot of trouble for attempts to receive this type of
modulation using other reception methods such as FM-based systems (i.e.,
any radio using demodulated FM - a.k.a. the disc. tap) - this includes
several commercial receivers marketed today…

73

Max

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