Project:Packet Radio

Aim

Several of us on the Amateur Radio IRC channel expressed an interest in setting up and managing a packet network for London and a BBS on that network.

Getting involved

• Talk to: Marrold (2E0SIP), MatStace (2E0TPS), Paul (M0OKE), Rawles (2E0RLZ), Samuelkf (M0SKF). Or people from further afield: Baldrick, WSPR.
• We chat a lot on #lhs-radio on Freenode.
• Previous meetings: 2018-03-18T18:30 at Penderel's Oak; 2018-04-24T19:00; 2018-06-19T19:00 and 2018-07-24T19:00 at Greenwich Observatory.

Background

Back in the 80s and 90s, packet radio linked amateur radio stations together. In fact, it goes back even further than this — the use of TCP/IP on amateur radio preceded the appearance of the public Internet. Anyway, whereas at the time most people were getting their data using modems and telephone lines, radio amateurs were experimenting with terminal node controllers (TNCs) and radio waves.

The TNC takes a chunk of data, splits it into packets, and sends it over VHF/UHF, and a TNC on the other end decodes, error-corrects and delivers it. TNCs are also digipeaters, repeating traffic for a further-flung station. An adaptation of the AX.25 protocol is used to handle many TNCs using one frequency. The result is an error-corrected, transparent and automatic network. Such networks are still in use; APRS, a protocol to share tactical information and short messages, is built on top of packet.

Some TNCs had a feature whereby you could leave messages for their owners. Bulletin board software began to develop partly out of this, allowing one-to-one message exchange and posting on forums, real-time chat, distributing news and data, and whatever the operators of the BBS want to offer. The scene may be quieter, but it isn’t dead. Ten or so packet BBSs still exist in the UK.

We might be able to reach quite a lot of people from a central London location. However, we’d need somewhere with decent coverage and we’d also need a full license to run an unattended node. Furthermore, to repeat or rebroadcast other peoples’ messages we’d need a Notice of Variation for each node that is on and unattended.

Getting started

Get a TNC and connect it to your computer and radio.

You may already have a TNC in your radio. APRS-equipped radios like the Kenwood TM-D710, TH-D74A, TH-D72A, TH-D7A and even earlier models have internal KISS TNCs. If you have a Kenwood TM-D710GE or similar, you may be interested in Simon's notebook of how to get connected to packet with it.

The AX.25 support in the Linux kernel via kissattach then enables you to connect to other packet nodes, use BBSs and so on. The PicoAPRS, a 50g dedicated APRS transceiver, also has a KISS TNC mode.

You can also use your sound card as the modem part of the packet radio TNC, with your computer doing all the processing in the CPU. For this you need the soundmodem driver.

A more plug-and-play way to get going is to borrow a TNC from the TNC pool.

You can then hook it up to your computer and radio and run a terminal emulator like minicom to send commands to the TNC.

Connect to GB7CIP

While its likely that there are packet users around repeating packets, GB7CIP is a well-connected packet radio node listening in Caterham, Surrey. Several of us have been connecting to it over RF and its BBS and generally learning stuff. You can also join in by connecting over IP, that is, if you have a UK amateur radio licence. You need to telnet gb7cip.theskywaves.net 6300 to access the BBS. You can register from there. There was a BBS in Amersham, GB7IPF, but that's now IP-only.

Ideas for other next steps

• There's a VHF Tait 8110 in the shack that would make a nice Packet / APRS radio
• Meeting in the hackspace, we can work out what we all know and what we need to know, look that stuff up and generally educate each other in the ways of packet. We could even start to follow the Zork instructions.
• Find ways of encouraging other radio amateurs to connect to packet. When we have a space again, we could get people to bring in their VHF/UHF radios and lend out TNCs where needed.
• Look into getting a small block of addresses on network 44 for our network, ideally under the club call. We need to understand the network layout for this.
• Trying to get packet working over HF.
• Testing out potential links between our home stations.

Bulletin

The project update bulletins for the London Hackspace packet radio network are sent out on the first of every month to inform the packet radio community of our progress. The bulletin is sent to HACKRS@GBR, meaning it is propagated to the other British packet bulletin board systems and will be seen by users logging onto GB7### AX.25 BBSs.

The latest is September 2018, but you can also read the bulletins from April 2018, May 2018, June 2018, July 2018 and August 2018.

Links

• BBS lists here and here.
• The Skywaves, including some stuff on AMPRnet.
• Baldrick introduced us to TARPN, a project to encourage builders to build the largest amateur radio packet network that they can. The TARPN is based on G8BPQ nodes running on a Raspberry Pi computer with outboard TNCs or TNC emulators.
• G1NNA's stuff and G8BPQ's stuff.
• The list of UK AX25/packet repeaters, which includes APRS digipeaters, and the details of the ETCC PACKET/AX25 Manager.
• A great article on Setting Your TNC's Audio Drive Level.
• Frequency Deviation Measurement with an RTL-SDR Dongle, Dr. Carol F. Milazzo KP4MD. Achieves the same as above, but with more modern techniques and cheaper equipment. Again, this article (and accompanying video) will teach you a bit about FM in the process.
• Intro to Packet Radio in the modern age with Direwolf, Technologically Induced Coma
• Direwolf Software TNC - MicroHAMS 2018. Great talk from the author of Direwolf, John Langner WB2OSZ. Covers some TNC/packet history and explains why doing it in software can be advantageous.