Long Range AIS messages

AIS-catcher has the option to listen at frequency 156.8 Mhz to receive Channel 3/C and 4/D (vs the default A and B around 162 MHz) with the switch -c CD. This follows ideas from a post on the Shipplotter forum. The default decoder is available with the switch -c AB. Note that gpsdecode cannot handle channel designations C and D in NMEA lines. You can provide an optional argument to use channel designations A and B in the NMEA line with the command -c CD AB.

In a similar fashion -c X will decode one channel. This is only useful in some instances, see the ZMQ example below.