6.25 kHz FM Information
6.25kHz channels were split from 12.5 kHz channels by the FCC. Raveon’s RV-M6 data radio modem can operate on 6.25kHz, 12.5kHz, or 25kHz wide channels.
Now the FCC licenses 6.25 kHz channels on “offset” frequencies within the previous 12.5 kHz channel
6.25 kHz channels are “dropped in” between existing 12.5 kHz radio channels. They allow as close as 6.25 kHz from the center of the 12.5 kHz channel.
The FCC created additional narrow-band spectrum by adding hundreds of new licenses with 6.25kHz bandwidth.
If you have a 12.5 or 25kHz channel, you can create two or four offset 6.25kHz channels. This may require you get a waiver from the FCC.
Modulation with 4-level FSK uses 2 bits per symbol. Typical FM deviation for 6.25kHz 4L channels is:
Bits:00 Deviation: -1050Hz
Bits:01 Deviation: -350Hz
Bits:11 Deviation: +350Hz
Bits:10 Deviation: +1050Hz
