Packet

Disclaimer

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:

1. 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.
2. 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:
   1. TNC state - Status of the TNC at that instant. Some of the status names are:
      1. Disconnected - Idle state where the TNC will monitor activity on the frequency and display that information on your computer.
      2. 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).
      3. 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.
   2. Commands - Instructions to the TNC telling it what you wish it to do. A small subset of these commands are:
      1. MYcall - Definition of the call to be used by the TNC.
      2. Connect - Request to connect to another computer.
      3. Disconnect - Request to sever connection with another computer
      4. 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).
      5. Read - Read a received message from the cluster/BBS.
      6. CHeck - Normally set to zero for ARES work (keeps the TNC from automaticly disconnecting if the activity is low).
   3. Status Lights:
      Status lights may vary by manufacturer. The most common are:
      1. PWR - Power on indicator
      2. CON - Connect indicator
      3. STA - Data from the computer is ready to send but has not been sent yet.
      4. PTT - On when PTT line is "down" (transmitting).
      5. DCD - Incoming data indicator. The information available after this light goes out will only be displayed if the information was for your station.

3. Digi-Peater - a relay station between stations that cannot hear each other
4. Packet Bulletin Board Systems (BBS) - a local collection point for messages between users. Usually linked to other BBSs to exchange messages for additional users.
5. Cluster - Similar to a BBS but often without the links to other BBSs/Clusters.
6. 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:

1. Power up the computer
2. Load the communications program
3. 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).
4. Power up the radio
5. 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 district.

Do not adjust, play with or fiddle with any piece of equipment in use for an event, during that event, unless it is malfunctioning.