January 3rd, 2011
As I have been getting involved with amateur radio this year, I’ve been taking notes on what I’m learning about certain things: tips from people on rigging up a bicycle antenna to achieve a 40-mile range, setting up packet radio in Linux, etc. I have long run a personal, private wiki where I put such things.
But I really wanted a convenient place to put this stuff in public. There was no reason to keep it private. In fact, I wanted to share with others what I’ve learned. And, as I wanted to let others add their tips if they wish, I set up a public MoinMoin instance on . So far, most of my attention has focused on the amateur radio section of it
This has worked out pretty well for me. Sometimes I will cut and paste tips from emails into there, and then after trying them out, edit them into a more coherent summary based on my experiences.
Now then, on to packet radio and Debian. Packet radio is a digital communications mode that runs on the amateur radio bands. It is a routable, networking protocol that typically runs at 300bps, 1200bps, and 9600bps. My packet radio page gives a better background on it, but essentially AX.25 — the packet protocol — is similar to a scaled-down TCP/IP. One interesting thing about packet is that, since it can use the HF bands, can have direct transcontinental wireless links. More common are links spanning 30-50 miles on VHF and UHF, as well as those going across a continent on HF.
Linux is the only operating system I know of that has AX.25 integrated as a first-class protocol in the kernel. You can create AX.25 sockets and use them with the APIs you’re familiar with already. Not only that, but the Linux AX.25 stack is probably the best there is, and it interfaces easily with TCP/IP — there are global standards for encapsulating TCP/IP within AX.25 and AX.25 within UDP, and both are supported on Linux. Yes, I have telnetted to a machine to work on it over VHF. Of Linux distributions, Debian appears to have the best AX.25 stack built-in.
The AX.25 support in Linux is great, but it’s rather under-documented. So I set up a page for packet radio on Linux. I’ve had a great deal of fun with this. It’s amazing what you can do running a real networking protocol at 300bps over long-distance radio. I’ve had real-time conversations with people, connected to their personal BBS and sent them mail, and even use AX.25 “nodes” (think of them as a kind of router or bridge; you can connect in to them and the connect back out on the same or different frequencies to extend your reach) to connect out to systems that I can’t reach directly.
MoinMoin has worked out well for this. It has an inviting theme and newbie-friendly interface (I want to encourage drive-by contributions).