The drawing below represents a 3 port node, with 3 sets of TNC + radio + feedline + antenna. A TARPN node could be built from a variety of radios and TNCs, though the Raspberry PI is a required component. The most common new TNCs are TNC-PI and are available from Coastal Chipworks for $45 each. The Raspberry PI and memory card cost about $45 from Amazon or other vendors.The radios are usually old ham monoband mobiles, or surplus commercial radios. TARPN participants can help you find and configure 25watt 6m, 2m, 70cm commercial land-mobile tranceivers for your TARPN project, at under $60 each. See Node Shopping List.
See Networking on Purpose for the why of dedicated links.
Each link runs asynchronous to each other link and so you could have inbound traffic on one link while transmitting a message on another. While it is possible to receive on a radio while transmitting on another on the same band without blocking the receiving radio, it is much easier to do that when on different bands. It may seem difficult or complex to do multiple bands. However, it is easier to do multiple bands than to do two radios on the same band.
The antennas shown include a separate antenna for each radio. You could use a multi-band vertical. Some stations are close enough together that very trivial antennas will perform. However, the hardest part of building a TARPN, so far, has been distance and antennas.
The only required part of the node is that it uses a Raspberry PI. We actually have a well described and specific set of rules for participation. (see Rules for TARPNS) Everything else is dependent on the situation the node/switch is being built for.
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