USING DIGIPEATERS AND NODES

Introduction to Packet Radio Part 4.

Digipeater is the term we use to describe a packet radio digital repeater. Unlike the FM voice repeaters, most digipeaters operate on simplex and do not receive and transmit simultaneously. They receive the digital infor-mation, temporarily store it and then turn around and retransmit it. Your TNC will allow you to enter up to eight digipeaters in your connect sequence, but using more than 3 usually means long waits, lots of repeated packets, and frequent disconnects, due to noise and other signals encount-ered on the frequency.

When entering the list of digipeaters in your connect sequence, you must make sure that you enter them in the exact order that your signal will use them. You must separate the calls by commas, without any spaces, and the EXACT callsigns must be used, including the SSID, if any. That means you need to know what digipeaters are out there before you begin randomly trying to connect to someone. Turn MONITOR ON and watch for the paths that other stations are using.

Here are some examples of proper connect sequences: C N6CKS-3 v N6CKS-1 C N6ZYX v WA6FSP-1,WD6EOB-3 C W6ABY-4 v K6MYX,N2WLP-2,AB6XO The "v" means via. In the first example the sequence shown means: Connect to N6CKS-3 via N6CKS-1.

Something to remember when using digipeaters is the difference between making a connection and sending information packets. If the path isn't all that good, you might be able to get a connect request through, but will have a difficult time with packets after that. The connect request is short so it has much less of a chance of being destroyed by noise or collisions than a packet containing information. Keeping information packets short can help keep retries down when the path is less than ideal.

NODES:
Net/Rom, TheNet, G8BPQ packet switch and KA-Node are names that refer to a device called a packet node, another means of connecting to other packet stations. Later on in this series you'll find a complete review of node operation, but for now we'll cover the basics so that you can begin using the node network. The difference you should note here is that you connect to a node rather than using it in a connect path as you do with a digi-peater.

First, you need to determine what nodes are located close to you. You can do this by monitoring and watching for an ID or by watching to see what other stations in your area are using.

You'll note that most nodes have an alias ID in addition to its callsign. Once you determine the callsign or alias of a local node, you connect to it the same way as you connect to any other packet station. You may use either the callsign or the alias to make the connection. For example, the node I operate has the alias ID of FYF and the callsign of W6FFF-2, so you could connect to it using C FYF or C W6FFF-2. Either one will work.

When you connect to a node, your TNC automatically switches to converse mode, just like when you connect to any packet station. Anything you now type is sent to the node as a packet, and the node acknowledges each packet back to your TNC. For the remainder of your connection your TNC works only with this one node. To use the node network to connect to another local station, you simply enter a connect request as though you were connecting direct from your TNC, such as: C K9AT. You do this, however, while you ARE STILL CONNECTED TO THE NODE. The node will then retransmit your connect request and you'll receive one of two responses: "Connected to (callsign)" or "Failure with (callsign)". Once you're connected you hold your QSO just as if you had connected direct or via a digipeater.

When you're finished, go to command mode on your TNC (Control C) and enter "D" (CR) and you will be discon-nected from the node and the station you were working. (NOTE: If the node you're using is a G8BPQ packet switch, it might have several frequency ports. You'll have to enter a port number between the C and the callsign in your connect request to indicate the frequency you want to use, such as: C 2 K9AT. Enter "PORTS" for a port list.)

When you're connected to a node enter: NODES (or N) CR} and you'll receive a list of other nodes that you can reach on the network from the node you're using. You'll note that the node list will vary in length and in the calls listed as you move from frequency to frequency, since all frequencies are not linked together. The list gives both an alias ID and a callsign for each node. The alias ID often gives you a hint as to where the node is located, but not always. To find out for sure where a node is located you'll need to get a copy of the descriptive node listings that are avail-able on most packet bulletin board systems. These complete lists give the alias, callsign, location, frequency and other information on each node in the network.

To connect to a station in another area using the node network you first must determine which node is closest to the station you want to work. For demonstration purposes, let's say we want to connect to N6ZYX. He's told you he uses the the W6ABC-3 node, so you check the node list and see that GOLD:W6ABC-3 is listed. WHILE STILL CONNECTED TO YOUR LOCAL NODE you first connect to the distant node by sending a normal connect request, in this case C GOLD or C W6ABC-3.

Your TNC will send this as a packet to your local node and your local node will acknowledge it. The network will then go to work for you and find the best path between your local node and the one you're trying to reach. You might have to be a little patient here, as it sometimes takes a few minutes for the connection to be completed. You'll then see one of two responses: "Connected to W6ABC-3" OR "Failure with W6ABC-3". If it can't connect for some reason, try again later. It could be that W6ABC-3 is temporarily off the air or the path has decayed and is no longer available. We're going to be positive here and say we received the first option.

Once you're connected to W6ABC-3, enter "C N6XYZ". Again, your TNC will send this as a packet to your local node and the local node will acknowl-edge it and send it down the path to W6ABC-3. W6ABC-3 will then attempt to connect to N6XYZ. Here again you'll get one of the two responses:

"Connected to N6XYZ" OR "Failure with N6XYZ".

If you get connected, you hold your QSO just as you normally would, but there's one BIG difference-your TNC is receiving acknowledgements from your local node, and N6XYZ is receiving acknowledgements from W6ABC-3. The acknowl-edgements do not have to travel the entire distance between the two end stations. Each node in the path handles the acknowledgement with the next node in line. Because of this, retries are greatly reduced, and your packets get through much faster. When you're finished with the QSO, you disconnect in the normal manner- go to Command Mode on your TNC and enter "D" CR}. The entire path will then disconnect automatically for you. Nodes offer a variety of other features besides allowing you to connect to other stations, and we'll look at those in parts 10 and 11 of this series.

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