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FAQs ➜ FAQ: Node/Switch Diagram

FAQ: Node/Switch Diagram and brief description

Every station in a Terrestrial Amateur Radio Packet Network consists of a Raspberry PI, a TNC, a radio, and an antenna. The Raspberry PI TARPN architecture is expandable. You can start with one TNC, radio and antenna, and add more later if the need arises.
Note: As of Jan 1, 2020 the TNC-PI is discontinued. Our plans now call for the use of the $30 NinoTNC instead of the TNC-PI. The NinoTNC, a product of our TARPN group, is cheaper, but the N9600A NinoTNC uses USB to connect to the Raspberry PI. This change will require respinning quite a bit of application code, scripting, web pages, cabinetry.

Please sign up for the TARPN email reflector for more news about assembling a TARPN node in this changing landscape.

In the meantime, many of the diagrams and web-pages about our preferred TNCs and how they are connected, are out-dated and confusing.

Please contact the group, using our reflector, for help.

I'm sorry for the inconvenience!


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. NinoTNC is available for $30 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 transceivers for your TARPN project, at under $60 each. See Node Shopping List.

Why multiple radios? Why multiple bands?

Each station can have one or more links, with one link per neighbor. TARPN nodes use dedicated point to point links to neighbors to overcome congestion and collision problems.

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.

3-port-node--modified
Here is a block diagram for a typical TARPN node design. Click to see supplemental detail and larger images.

The images appear to specify that we must use NinoTNC to build a TARPN node. We designed NinoTNC ourselves to be the easiest to acquire and support. It's also cheap. There are other solutions and the Raspberry PI with G8BPQ's linbpq program is very versatile. You could build a node which uses TNC+radio combo boxes, or uses TNCs which are stand-alone units using USB to talk to the PI, and the radios could be handie-talkies or on the same band as one another.

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.

Please visit our FAQS page for more background info. If you can't find what you are looking for, we may not have thought of the question you are asking. I would really appreciate an email advising me of the mistake. I'll pass it around to the appropriate party and find out an answer. Send me an email at the address shown on my QRZ.com page. When I get an answer I'll either pass it on to you, or publish it on the web page and tell you about it. Thanks.



See also TARPN features and
Networking On Purpose
© Tadd Torborg, 2014↝2020 -- all rights reserved