HF Communication

[agustin65-oss]

HF radio support?

Would it be possible to use shortwave radio as another way to send Knit messages?

Maybe an external radio modem could connect to Knit through USB and forward messages over HF to another node, even thousands of kilometers away.

Just throwing this out there. Is this technically feasible?

It would be very strange, it could reach many more places than Lora, for those who have a permit, an antenna or are amateur radio operators it would be good.

[mus2go]

So like a USB output support to connect to different things?
Maybe with some standard configurations (parity bits and different protocols? Idk) built in.
Though I would put those under some advanced section.
This would be perfect for tinkerers who want to test/use their own devices for communication.

[zaventh]

Technically it could be possible, though HF bandwidth would make it a bit limited. The main problem is legality. Laws vary around the world. In the US, you would need an Amateur radio license to transmit on HF. And that same license prohibits encrypted transmissions. So it would be limited to the Nearby chats only.

I have a GMRS license and a BTECH GMRS Pro which can do Part 95 text message tramissions. It implements APRS to do essentially do text messaging over the GMRS bands. I have thought about hooking Knit into that, but they don't have an open API for it so I'd have to reverse engineer it. You are also not allowed to do Part 95 over repeaters in the US, so it would only ever be point-to-point.

The problem I found with APRS over GMRS is that if the receiver is offline when you send the message, they never receive it. And since there is no delivery receipts, you never know if they actually received your message until they reply. A poor signal could easily lose packets and thus the entire message with no recourse. Trying to get this to work in the field is one of the main reasons I wanted to build Knit. It was not very reliable.

This is why LoRa is so popular. It can be used by unlicensed operators. It operates on UHF so bandwidth is much better. And in the US you can run encrypted traffic over the ISM bands. I haven't tried it myself yet but I see people obtain hundreds of kilometer ranges using multi-hop paths with the right LoRa setup.

This is why I built Meshtastic support into Knit. It's cheap, unlicensed, encrypted (with Knit) and works well with the Meshtastic approach to meshing. I was actually out on the beach and got a Meshtastic chat in Knit from someone who was in a plane with a LoRa board at 32,000 ft (~10km) above me. Pretty neat 🙂 .