World of Ham Radio 1997/WOHR97_AmSoft_(1997-02-01).iso/packet/docs/packet04.doc

Text File | 1997-02-01 | 7KB | 131 lines

INTRODUCTION TO PACKET RADIO - PART 4 - by Larry Kenney, WB9LOZ

USING DIGIPEATERS AND NODES:

DIGIPEATERS:
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 W6PW-3 v W6PW-1
C N6ZYX v WA6FSP-1,WB6LPZ-1
C W6ABY-4 v K6MYX,N2WLP-2,AB6XO
The "v" means via.  In the first example the sequence shown means: Connect
to W6PW-3 via W6PW-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 SF and
the callsign of WB9LOZ-2, so you could connect to it using "C SF" 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
enter a connect request as though you were connecting direct from your TNC,
such as "C WB9LOZ".  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 WB9LOZ".  Enter "PORTS" for a port list.)

When you're connected to a node enter "NODES" <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 W6AMT-3 node, so you check the node list and see that
SFO3:W6AMT-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 W6AMT-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 some-
times takes a few minutes for the connection to be completed.  You'll then
see one of two responses: "Connected to W6AMT-3"  OR  "Failure with
W6AMT-3".  If it can't connect for some reason, try again later.  It could
be that W6AMT-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 W6AMT-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 W6AMT-3.  W6AMT-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 W6AMT-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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