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EI2GYB > PACKET 04.10.25 21:46l 91 Lines 5852 Bytes #56 (0) @ WW
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Subj: INTRODUCTION TO PACKET RADIO - PART 1
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INTRODUCTION TO PACKET RADIO - PART 1
by Larry Kenney, WB9LOZ
WHAT IS PACKET RADIO?
A SHORT HISTORY - HOW IT ALL BEGAN
It was in March, 1980, that the Federal Communications Commission approved
the transmission of ASCII for Amateur Radio in the United States. That was
a year and a half after Canadian hams had been authorized to transmit
digital "packet radio", and the Canadians had already been working on a
protocol for it. Doug Lockhart, VE7APU, of Vancouver, British Columbia,
had developed a device that he called a terminal node controller (TNC).
It worked with a modem to convert ASCII to modulated tones and convert
the demodulated tones back to ASCII. Doug had also formed the Vancouver
Amateur Digital Communications Group (VADCG) and named his TNC the "VADCG
board".
Hams here in the U.S. started experimenting with the VADCG board, but in
December, 1980, a ham from the San Francisco Bay Area, Hank Magnuski, KA6M,
put a digital repeater on 2 meters using a TNC that he had developed. A
group of hams interested in Hank's TNC started working together on further
developments in packet radio and formed the Pacific Packet Radio Society
(PPRS). AMRAD, the Amateur Radio Research and Development Corporation, in
Washington, DC became the center for packet work on the east coast, and in
1981 a group of hams in Tucson, Arizona, founded the Tucson Amateur Packet
Radio Corporation (TAPR).
Working together these groups developed a modified version of the commercial
X.25 protocol called Amateur X.25 (AX.25) and in November, 1983, TAPR
released the first TNC in kit form, the TAPR TNC1. In 1984, a great deal
of packet experimentation was done, software for packet bulletin board
systems was developed, and packet radio started becoming more and more
popular all across the U.S. and Canada.
Packet Radio was one of the major developments to hit the world of Amateur
Radio and thousands of hams soon caught the "packet bug". If you're
wondering what it's all about and why so many people got so excited about
it, continue reading. You're about to find out.
PACKET RADIO - WHAT IT'S ALL ABOUT
Packet seems to offer something different from other facets of Amateur
Radio, yet it can be used for everything from a local QSO to a DX contact
thousands of miles away, for electronic mail, message transmission,
emergency communications, or just plain tinkering in the world of digital
communications. It presents a new challenge for those tired of the QRM
on the low bands, a new mode for those already on FM, and a better, faster
means of message handling for those on RTTY. Packet is for the rag chewer,
the traffic handler, the experimenter, and the casual operator.
A ham can get involved very easily with relatively small out-of-pocket
expenses. All you need is a transceiver, a computer, and a TNC or special
packet modem and software. A two-meter rig is preferred, since that's
where most of the packet activity is located. You probably already have
the rig and the computer, so all you need to buy is the TNC, which costs
just over $100, or the special modem and software, which sell together for
about $50.
The TNC, the Terminal Node Controller, is a "little black box" that's wired
between the computer and the radio. It contains software for controlling
the outgoing and incoming transmissions for your station and a modem that
converts the data from the computer into AFSK tones for transmission and
changes the tones that are received by the radio into data for the computer.
The TNC modem works much like a modem that's used to connect your computer
to the telephone lines. It's a simple matter of wiring up a plug and a
couple of jacks to become fully operational on packet. If you prefer to
use the small modem instead of a TNC, you'll need special software for your
computer to replace the software in the TNC. Either method works equally
well.
Packet is communications between people either direct or indirect. You can
work "keyboard to keyboard" or use electronic mailboxes or bulletin board
systems to leave messages. Due to the error checking by the TNC, all of it
is error free, too. (That is, as error free as the person at the keyboard
types it!) As the data is received it's continuously checked for errors,
and it isn't accepted unless it's correct. You don't miss the information
if it has errors, however, because the information is resent until it is
correctly received.
The data that is to be transmitted is collected in the TNC and sent as
bursts, or packets, of information, hence the name. Each packet has the
callsign or address of who it's going to, who it's coming from and the
route between the two stations included, along with the data and error
checking. Since up to 256 characters can be included in each packet, more
than three lines of text can be sent in a matter of a couple of seconds.
There is also plenty of time between packets for several stations to be
using the same frequency at the same time.
If all of this sounds confusing, don't let it bother you, because the TNC
or special packet software does everything for you automatically. Packet
radio might seem very confusing at first, but in a day or two you'll be in
there with the best of them. In this series I'll be telling you all about
packet radio - how you get on the air and how to use it. We'll talk about
the little black box, the TNC, and tell you about all its inner-most secrets.
We'll discuss mailboxes, bulletin board systems, and the packet networks
that allow you to work stations hundreds, even thousands, of miles away
using just a low powered rig on 2 meters, 220 or 450. The world of packet
radio awaits you! - - - -
Part 1 last revised February 8, 1997.
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