Join an existing network

TNCs and Radios -- Making Links

After installing the OS, utilities, applications and the TARPN scripts on the Raspberry PI, you are ready to start hooking up radios.

Each TNC-PI may be wired to a single radio which can establish a link to some other TARPN node.
When establishing frequencies and bands you must make sure that one of your radios in transmit will not block the reception of a packet by another of your radios.

A suggested TARPN node site would have 3 radios, one each on 51, 145, and 440Mhz. You can acquire an antenna like the Comet GP-15, and three commercial radios, like the Vertex FTL-1011, Kenwood TK760H, and Kenwood TK805D, three TNC-PI daughter cards, and a Diamond MX-2000 Triplexer. With 100' of LMR400 coax cable and several connectors you can build an entire three port node for about $700, not including cabinetry, antenna mounts, lightning protection, power supplies and batteries.

Using the 3 port TARPN node described above you can now make links to neighbor nodes and begin building a network. Your 51Mhz Vertex can talk 15 miles through forest to another same kind of radio but is very sensitive to noise and variable by season and weather. 440Mhz radios have much shorter range, are terribly affected by foliage and hills, but are much less sensitive to noise and rarely are subject to weather enhancements. If you are lucky enough to have a tall structure or view-home to work from, you can get range out of 440Mhz that is nearly up to the useful 6m range. On 440 we have a wide ham-band and can separate the radios by frequency to allow more than one link per site on that band. On 2m, multiple links per site are possible but only by using cavity filters (which can be done for $60 or so) or by having lots of signal available at the receivers.

Continuous Up Operation

Some packet radio users consider that packet is cheap because the only piece of equipment required to make it work is a TNC. Radios are free because the hams already have them and they can serve both voice and data functions interchangeably. A $700 TARPN station will therefore seem to be really expensive. It is hard to argue with that logic. If the stations involved are complacent with having packet radio only intermittently available, and to having inconsistant results when they try to use it, then TARPN may not be for them.
The interesting thing about packet radio networking, as separate from infrequent guest operation, is that each participant's station becomes part of the network and is a service to the other hams. Not only do other stations get enjoyment from using the paths each has created, but each builder becomes part of an emergency system, a step above being merely prepared. They also get to learn how to, and gain experience from, keeping a resource on-line indefinitely, a wholly different regimen from whipping out their HT on the way to work.