This document is designed to provide the ARES operator with enough
information to be able to function adequately as an emergency
communicator. It is not intended to provide a technical foundation
for this portion of the Amateur Radio hobby.
Why Packet Radio ?
Packet Radio provides a somewhat-secure method of
transmitting/receiving data. Somewhat in that not just anyone with a
scanner can listen to the information but NOT secure in that anyone
with a receiver, TNC and computer can read the information being passed.
Packet increases the accuracy of the information by having it
written rather than transmitted by voice and while the transmission
time is a bit long (1200 baud is very common at VHF/UHF) the accuracy
and increased confidentiality make it a good choice for ARES activities.
How does it work ?
Packet radio consists of a computer, Terminal Node Controller (TNC),
a radio and some cables connecting all of the parts. Some of the TNCs
are happy with the full 25 pin cables and some are only happy with
nine pin cables (see the TNC manufacturers instructions). The
connection between TNC and radio will have ground, transmit audio,
receive audio and puch-to-talk (PTT) lines.
The computer will be loaded with one of many flavors or software that
(depending on flavor) will operate as a subtask of the computer, to
some that make the computer function as a dumb terminal. With the
latter, if you try to make the computer do anything else it will lock
up and do nothing. Ask a person with full packet training before you
try to get the computer to multi-task.
The recommended software for ARES/RACES operation is
WinPack. This software allows you to compose a message without
being connected. This is a VERY important function in that you
are not clogging the frequency while you type.
The terms you will need to know and understand are:
- Packet - the name of the piece of data sent from your computer
to another. It has a header with the call of your station and
the call of the station you are talking with (plus a little
other information) followed by what you typed in.
- TNC - Terminal Node Controller. The device that acts as an
interface between the computer and the radio. It normally
includes a MODEM (MOdulator DEModulator) and will have a
micro-processor included. Other things about the TNC are:
- TNC state - Status of the TNC at that instant. Some of the
status names are:
- Disconnected - Idle state where the TNC will monitor
activity on the frequency and display that information
on your computer.
- Connected - The state where the TNC has established
contact with another station and is ready to exchange
information. When you are connected, the channel
activity will no longer be displayed on your computer
(there are ways around this but don't worry about them).
- Converse Mode - once the TNC connects to another TNC it
will normally enter converse mode so that anything you
type in at your computer is transmitted to the other
computer each time you press the Enter key.
- Commands - Instructions to the TNC telling it what you wish it
to do. A small subset of these commands are:
- MYcall - Definition of the call to be used by the TNC.
- Connect - Request to connect to another computer.
- Disconnect - Request to sever connection with another computer
- Send - Request to send a message to another user. This will
be used when you have connected to a BBS (bulletin board) or
cluster (interconnection between multiple users).
- Read - Read a received message from the cluster/BBS.
- CHeck - Normally set to zero for ARES work (keeps the TNC
from automaticly disconnecting if the activity is low).
- Status Lights:
Status lights may vary by manufacturer. The most common are:
- PWR - Power on indicator
- CON - Connect indicator
- STA - Data from the computer is ready to send but has
not been sent yet.
- PTT - On when PTT line is "down" (transmitting).
- DCD - Incoming data indicator. The information available after
this light goes out will only be displayed if the
information was for your station.
- Digi-Peater - a relay station between stations that cannot hear
- Packet Bulletin Board Systems (BBS) - a local collection point
for messages between users. Usually linked to other BBSs to
exchange messages for additional users.
- Cluster - Similar to a BBS but often without the links to
- Keyboard-to-Keyboard - Connection used to talk to other amateurs
directly. Normally you will be talking with a single station or
to a cluster.
What will I do ?
If you are part of the setup team, you will be asked to set up the
station. Each of the districts with district-owned equipment will have
a set of instructions for you to use. Most cables will be labeled
with information telling you where each is to be connected.
You will setup the equipment per district instructions and:
- Power up the computer
- Load the communications program
- Power up the TNC
Note: The software used will determine if the TNC will
need to be powered up before the communications program is loaded
(read the setup instructions).
- Power up the radio
- Connect to the Cluster
This leaves only for you to operate, i.e. send and receive messages
as required by your location.
Note: Most districts will have a set format for their messages.
Contact your team leader to get a copy of the format used by your
Do not adjust, play with or fiddle with any piece of equipment
in use for an event, during that event, unless it is malfunctioning.