Introduction to Packet Radio
For the GTA West ARES Packet Users

I.   Packet Introduction

Packet radio is a communications mode that provides computer to computer communications across a radio link. It provides the ability to have accurate error free communications, since it uses a method of acknowledging receipt of each transmitted packet of data. Your transmitted information is always received 100% correctly, which is of great importance to ARES.

In most amateur packet stations, data is sent at 1200 baud. There is also activity using 9600 baud, but this is usually used by "backbone" stations. The radio setup requirements involve advanced capabilities, whereas 1200 baud uses the radio's built-in voice capabilities. (Note: Bandwidth considerations limit 1200 baud or faster packet to the VHF or higher frequencies. There is packet activity on HF using 300 baud rates, but this is outside our discussion.)

TOP

A typical packet station consists of a VHF or UHF FM radio connected to a Terminal Node Controller (TNC), connected to a computer terminal. Information is typed on the computer keyboard, interpreted into data packets by the TNC, and transmitted as tones over the radio. At the receiver end, the radio passes the tones into its TNC, which converts them back to data and passes them to the receiving computer. The TNC also acknowledges receipt back to the transmitting TNC. If data was not received correctly, the TNC automatically asks for a repeat.

Packet QSO's can be between two operators conversing keyboard to keyboard, but often involve sending messages to a Bulletin Board System (BBS) for the other operator to pick up at a later time. This is much like how email works.

In normal usage, a station "connects" to another, sends data or carries out a conversation, then "disconnects". While connected, the two stations only transmit to each other, ignoring any other activity on the frequency. (When a station is not connected, it can monitor all the traffic on the channel.)

TOP

The main job of ARES is to accurately pass messages between incidence sites. Speed and accuracy of message handling is imperative. Over the years, excellent methods have been developed to pass traffic by CW and by voice. The advent of digital communications allows amateurs to harness the built-in speed and accuracy of these new modes to make message handling easier and more reliable. A message that may take several minutes to accurately pass via a voice link can be sent by packet radio in seconds. This frees up the voice net to handle other communications.

In the GTA West, we believe that most of the "formalised" messaging should be conducted by digital means, leaving the voice nets for more immediate conversational messaging.

Note: While methods exist now that allow packet radio to interface into the standard internet email system, at first our emphasis will be on standard packet techniques. Using the more advanced techniques will be explored in the near future.

TOP