Channel K is a remote base in the making: an ordinary VHF/UHF mobile radio you can operate from anywhere in the world through M17, choosing among twenty preset channels by sending a short text message over the air. No internet is needed at the operating end, and no special hardware — because M17's openness does the heavy lifting.
An AnyTone AT-778UV dual-band mobile, programmed with twenty memory channels — local repeaters and simplex calling frequencies — sits at the M17JET site and stays powered on. A small Raspberry Pi alongside it ties the radio into M17-JET as Channel K. When you link your own M17 radio to Channel K, you are connected to that physical radio: your voice goes out over local VHF/UHF, and whatever the radio hears comes back to you over M17.
A remote base lets you put a signal into a local area from far away, by borrowing a radio that is already there. A traveler can keep a presence on the home repeaters from across the country. An operator stuck with a poor location can reach out through a better-sited antenna somewhere else. The radio does the transmitting; you just supply the voice and the commands from wherever you happen to be.
The interesting part is changing channels from a distance. Channel K is steered by M17 text messages. M17 carries text in packet mode, which is entirely separate from the voice stream — so a command arrives exactly as sent, untouched by the voice codec that audio passes through. To pick a channel, you simply send its number.
Direct channel dialing
Send 7 and the base goes straight to channel 7. Send 3 and it goes to channel 3. There is no stepping up and down hunting for the one you want — you name the channel, and the base works out how to get there on its own.
After every command, the base sends a text back naming the channel it selected — for example, CH 7 — AA6BT — so you always get an acknowledgment that the command was received and acted on. A resync command sends the base home to channel 1 (146.520 simplex) any time you want a guaranteed, known starting point.
Every M17 transmission carries the sender's callsign. Channel K honors commands only from its owner's callsign, so no one else can change the channel or key the radio. The callsign itself is the key — authentication is built into the protocol, with no password to manage.
The base keeps its own running count of which channel it is on, rather than reading the radio directly — this class of radio does not report its channel back over a cable. That count is held in step by the confirmation messages and by the resync-to-home command, which lets the base return to a known channel whenever needed. It is a low-parts-count, low-complexity approach, very much in the spirit of the rest of the projects here.
Channel K turns an everyday dual-band mobile into a globally reachable VHF/UHF presence, steered by nothing more than M17 text messages and protected by your own callsign. It needs no internet at the operating end and no special vocoding hardware, because M17's open codec keeps the whole thing light, open, and inexpensive.
A noncommercial hobby project by N6JET, shared freely for anyone interested in amateur digital voice.