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EI2GYB > TECH 14.08.24 12:44l 179 Lines 9589 Bytes #999 (0) @ WW
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Subj: INTRODUCTION TO PACKET RADIO - PART 4
Path: IZ3LSV<I0OJJ<UA6ADV<CX2SA<PI8ZTM<EI2GYB
Sent: 240814/1017Z @:EI2GYB.DGL.IRL.EURO #:32431 LinBPQ6.0.24
INTRODUCTION TO PACKET RADIO - PART 4
by Larry Kenney, WB9LOZ
DIGIPEATERS AND NODES - THE BASICS
DIGIPEATERS:
Digipeater is the term used 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 information, temporarily
store it and then turn around and retransmit it. Your TNC can be used by others
as a digipeater if you have the command DIGIPEAT turned ON.
You use a digipeater by entering its callsign after a V or VIA in your connect
sequence. Here are some examples of proper connect sequences:
C W6PW-3 V WB9LOZ-2
C N6ZYX V WA6FSP-1,WD6EOB-3
C W6ABY-4 V K6MYX,N2WLP-2,AB6XO
In the first example, the sequence shown means: Connect to W6PW-3 via the
WB9LOZ-2 digipeater.
Your TNC will allow you to enter up to eight digipeaters in your connect
sequence or in your UNPROTO path, but using more than 3 usually means long
waits, lots of repeated packets and frequent disconnects, due to noise and
other signals encountered 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.
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 (PACLEN set to 40 or less) 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. This is 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 to use the
node network. The difference between a digipeater and a node that you should
note here is that you connect to a node rather than using it in a connect path
as you do with a digipeater. Some packet stations are set up so that they can
be used as a digipeater and as a node.
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. It is most common for a node to 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 BERKLY and the callsign of
WB9LOZ-2, so you could connect to it using:
C BERKLY or
C WB9LOZ-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 connect
to the node and then enter a connect request to the other station. Say you
wanted to connect to K9AT using the WB9LOZ-2 node. You first connect to
WB9LOZ-2:C WB9LOZ-2
and then, while you ARE STILL CONNECTED TO THE NODE, you enter the connect
request to K9AT:
C K9AT
The node will then retransmit your connect request and you'll receive one of
two responses: "Connected to K9AT" or "Failure with K9AT". Once you are
connected you hold your QSO just as if you had connected direct or via a
digipeater. When your QSO is finished, go to command mode on your TNC (Control
C) and enter:
D <CR>
and you will be disconnected from the node and the station you were working.
Some nodes have a BYE command available for disconnecting. You can get a list
of available commands from any node by sending a question mark. All of the node
commands will be covered in detail later in this series.
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 list of the frequency ports available.
NODE NETWORK:
The packet nodes work together to form a packet node network. Once an hour each
node transmits a list of other nodes that it knows about. The neighboring nodes
use this information to keep track of the other nodes in the network. We will
discuss how all of this works later on in the series.
When you're connected to a node you can enter:
NODES <CR> 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 available
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 N6XYZ. He's told you he
uses the W6ABC-3 node, so you check the node list and see that GOLD:W6ABC-3 is
listed. WHILE YOU ARE STILL CONNECTED TO YOUR LOCAL NODE you 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. Remember, with
digipeaters you needed to know the exact sequence of stations. With nodes you
don't. The network does that for you.
You might have to be a little patient here, since it sometimes takes a few
minutes for the connection to be completed. Don't type anything while you're
waiting for a response because any new information received by your local node
will override any previously entered information. When the network has
completed its work you'll receive 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 and got connected to the node.
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 acknowledge 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 acknowledgements 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 than when
using a similar number of digipeaters.
When you're finished with the QSO, you disconnect in the normal manner. Use the
BYE command, if available, or go to Command Mode on your TNC and enter:
D <CR>
Using either method, the entire path will disconnect for you automatically.
Nodes offer a variety of other features besides allowing you to connect to
other stations. We'll look at those and go into much more detail on the packet
network in parts 10 and 11 of this series.
Part 4 last revised February 13, 1997.
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