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The Packet Radio “2 N 1” Handbook by Buck Rogers K4ABT

Section 1; Packet Radio “The Basics” Section 2; The X1J4 System Node Operator’s (SNO) Handbook

Section 1; Packet Radio “The Basics” A Packet Primer for the new Packeteer __ Page 0

Chapter Two

LEARNING ABOUT PACKET CONTROLLERS

The TERMINAL NODE CONTROLLER (TNC)

By now you have heard the phrase, “terminal node

controller” or “TNC” several times. The terminal node

controller (TNC) performs as an interface between the

computer and the transceiver. The TNC combines a

modem and a packet assembler-disassembler (PAD), that

accepts information from your computer and sends

received data to your computer.

The TNC (prior to 1983 it was called a “PAD” or packet

assembler/disassembler) that breaks data into “packets.”

Since 1983, the “PAD” has become known as the “tink”

or TNC.

Packets are normally 128 letters or characters in length.

In our Packet TNC we have the option to increase this

packet length up to 255 characters in length. The TNC

command that allows us to make this change is called

“PacLen.”

Once the TNC has received the data from your computer,

it then breaks it into packets about 100 characters long

and combines additional (bytes) information to the

outgoing data. The added bytes include the destination

addressing, error-checking, and frame control

information. Address and destination information that is

added in by the TNC includes the callsign of the target

station and the callsign of the station sending the packet

(data).

THE ALL-MODE CONTROLLERS:

These are controllers that transmit and receive PACKET

and other digital modes, such as:

PACKET, PACTOR, AMTOR, RTTY, CW, FAX

(WeFax), Slo-Scan TV (SSTV), and NavTec. They also

offer multiple ports for VHF and HF operations. The

MFJ-1278B is one such "multimode" controller that fits

into this category. The features may differ from one

"all-mode" controller to the next, so it would be in your

best interest to investigate the options which best suit

your needs.

THE PACKET CONTROLLERS:

If you plan to operate packet only, but you wish to use

both HF and VHF packet, you may want to look for a

controller which has a tuning indicator for use on the HF

bands. The MFJ-1274B is one such Packet only

controller that operates HF and VHF Packet.

It has a Packet tuning indicator for use when operating at

HF. Most of these controllers operate both HF and VHF

Packet.

Almost all Terminal Node Controllers (TNC) operate

both HF and VHF, but to try operating HF packet without

a tuning indicator is like fishing without bait, your

chances of catching anything are, little to none.

Now if you just want to operate VHF packet, there are

numerous TNCs to fill your fancy. As of this writing,

just about every TNC now supports the "MAILBOX "

feature. This allows the user to set the MAILBOX or

PBBS command ON while the computer or terminal is

being used for other tasks, such as letter writing, and data

processing. The mailbox will receive and store messages

while you are using the computer off-line or away.

If your desire is to use the ultimate in a digital, all-mode

controller, then check into the MFJ-1278 and the

companion software terminal program, MultiCom for

Windows.

Once you’ve used this combination, the rest are paled by

comparsion.

KEYBOARD-TO-KEYBOARD CONTACTS:

The number one use of Packet radio is probably keyboard

to keyboard contacts through a Packet network. Like

other digital communications modes, Packet radio can

be used to talk to other amateurs. For those who cannot

use HF frequencies, two Packet stations can talk to each

other across long distances using a PACKET radio

network.

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