OnAirDecode MPT1327 trunking (WIP) with an SDR
MPT1327 trunking: the control channel messages of analog trunked radio systems (work in progress).
- Group
- Two-way radio
- In the mode list
- Analog trunking, control channel
What MPT1327 trunking (WIP) is
MPT 1327 analog trunking control channels (UK MPT 1327 / MPT 1343, VHF and UHF): 1200 bit/s FFSK on the FM control channel. Work in progress: lock, the codewords received good and bad, the system identity, a list of the control messages (time, type, caller and called address, channel number) and the channel table. Control channel only: no traffic channel audio is decoded and nothing encrypted is….
Frequencies and settings
OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is Analog trunking, control channel.
What OnAir shows
MPT 1327 analog trunking control channels (UK MPT 1327 / MPT 1343, VHF and UHF): 1200 bit/s FFSK on the FM control channel. Work in progress: lock, the codewords received good and bad, the system identity, a list of the control messages (time, type, caller and called address, channel number) and the channel table. Control channel only: no traffic channel audio is decoded and nothing encrypted is decoded (receive only).
Limits and what it was checked with
Checked with generated signals and impairments; recordings of real signals welcome.
Which radio you need
Any radio that tunes this range works. An RTL-SDR covers roughly 24 MHz to 1.7 GHz, and every other radio in the radio guide reaches it too. Antenna height and a clear view of the transmitter matter most.
Receiving and the law
Questions about MPT1327 trunking (WIP)
Can I decode MPT1327 trunking (WIP) with an RTL-SDR?
Usually yes for narrowband signals, as an RTL-SDR tunes roughly 24 MHz to 1.7 GHz at up to about 2.4 Msps. Wide signals such as TV channels need a faster radio, and OnAir says next to the source what the selected radio can do.
Is it legal to receive MPT1327 trunking (WIP)?
In many countries it is illegal to intercept or disclose private radio communications. OnAir is a receiver: encrypted calls show up only as encrypted and are never decrypted, and voice needs a library you install yourself. Follow the law where you live.
Can I try MPT1327 trunking (WIP) in OnAir without a radio?
Yes. Most modes include a built-in synthetic test signal, so you can open the screen and try the controls before you own a radio.