In my area there is a tetra system with 3 frequencies, 394.7375 , 395.2375 , 395.7375 . Using Telive monitor, I found that the three frequencies have the same MNC and the same downlink frequency ( 394.7375 ) . which frequency should use to monitor all traffic?. or should use the 3-channel system telive_3ch. If the second option, this work with only 1 USB RTL?
the frequencies are within the range that can be covered with one dongle, so i would use only one dongle (unless you have a reason to use multiple dongles, for example 3 dongles, each with its own directional antenna aimed in a different direction).
also check if this is the same colourcode (but most probably is).
launch in separate windows:
./receiver1 1
./receiver1 2
./receiver1 3
launch the 3 channel grc receiver and set baseband to 395M, and use offsets -262.5k, 237.5k and 737.5k, and this will give you the right frequencies.
launch telive, tetrad etc
this will let you monitor all of the 3 channels, as if it were one system. you might see two of these frequencies being turned off periodically when there is low traffic.