OnAirDecode LTR trunking (WIP) with an SDR
LTR trunking: the subaudible control words of an analog trunked system (work in progress).
- Group
- Two-way radio
- In the mode list
- 300 bit/s subaudible
What LTR trunking (WIP) is
LTR (Logic Trunked Radio) control data: the 300 bit/s subaudible words on a repeater channel (area, go-to, home, ID, free repeater). Work in progress: control data only, no voice; the check bits are shown but not verified (receive only).
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 300 bit/s subaudible.
What OnAir shows
LTR (Logic Trunked Radio) control data: the 300 bit/s subaudible words on a repeater channel (area, go-to, home, ID, free repeater). Work in progress: control data only, no voice; the check bits are shown but not verified (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 LTR trunking (WIP)
Can I decode LTR 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 LTR 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 LTR 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.