PACKET
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When you have finished your conversation you need to end the connection. To do this, you go into
the Command Mode and type a
d
for Disconnect. Remember to press the return or enter key after
any command to the TNC. Once your station has received the acknowledgment for the the discon-
nect packet the TNC will send this message to your screen:
*** DISCONNECTED
Either station can issue the disconnect command, no matter which station originated the connect.
Digipeating
Everything we have done so far will only be heard by those within range to hear your signal. With
Packet-Radio it is possible to get further than that. The DIGIPEAT parameter in the TNC comes de-
faulted ON. This makes you a possible relay station, or digital repeater – digipeater, or just digi for
short. In many VHF communities one, or more, of these is put up in a good, high location and re-
ferred to as a dedicated digi. The TNC and radio is all that is needed for the digital repeater to do
its job. A computer would be needed if you wanted to change a parameter, but it would not need
to stay there for the digi to work. The higher the antenna, the more effective a digi will be, but re-
member, every TNC has the capability of being a digipeater.
If we turn the MRPT command ON, we will begin to see more than just the "from" and "to" sta-
tions of the monitored packets. We will also see the callsigns of those stations that have been used
as digipeaters. (If you turn HEADERLN ON the headers will end with a return and be on a separate
line from the packet data.) This list of stations is often called a path. Here is an example of what
you might see:
WK5M>KA5ZTX,IAH*,LAG,AUS:
Hi there
In this example WK5M is talking to KA5ZTX using the digipeaters IAH, LAG and AUS. The asterisk
beside IAH tells you that you are hearing that digipeater. You will notice that IAH, LAG and AUS
are not real callsigns. The TNC provides parameters (MYALIAS and ALIAS) to set up an alias,
which is often easier to remember than a callsign. To make this connection WK5M would have
typed the following command to his TNC:
c ka5ztx v iah,lag,aus
v
is short for via and up to 8 digis may be used. You must specify digis in the order they will be
encountered along the path from your station to the station you wish to connect to. A space must
be typed after the
c
and on both sides of the
v
, but digis are separated by commas and no
spaces. A path can also be used with the Unproto command:
u cq v nom,lch,sli,bix
Unproto sets up the path for anything that is subsequently typed in the Convers Mode where no
connect exists. Connect issues a connect request to the specified station, via the specified path.
Then an error-free conversation can take place between them.
When digipeating the packet goes all the way from the first station, through all relay stations, then
to the destination station. Then the response also has to take this same path in reverse. Chances
for collisions, therefore retries, are multiplied with every digi used. This is often called end-to-end
acknowledgment. Another way to get from one place to another is to connect a "node". A node
will take care of the acknowledgment between it and the next node or end user. See the KA-NODE
section for more information. Ask your local packeteers about other kind of nodes which may be in
your area, such as TheNet and NET/ROM.
