Australian
Amateur
Packet
Radio
Association
AN INTRODUCTION
TO
PACKET RADIO
PRODUCED BY
AUSTRALIAN AMATEUR PACKET RADIO ASSOCIATION
(AAPRA)
Copyright (c) 1990
59 Westbrook Avenue
Wahroonga
NSW 2076
AUSTRALIA
First release January 1989
Revised September 1989
Revised October 1990
TOPICS DISCUSSED PAGE
INTRODUCTION 1.
ABOUT AAPRA 1.
WHAT IS PACKET? 3.
WHAT YOU WILL NEED 5.
WHY CALL IT PACKET? 7.
OPERATION OF A PACKET STATION 7.
DIGIPEATING 8.
PROCEDURES 9.
THE ROSE NETWORK 11.
BULLETIN BOARDS 13.
FUTURE DEVELOPMENTS 15.
EQUIPMENT FROM AAPRA 16.
GLOSSARY OF TERMS 17.
Page 1
AUSTRALIAN AMATEUR PACKET RADIO ASSOCIATION
(AAPRA)
INTRODUCTION
The intention of this booklet is to provide in
plain language, a basic understanding of what
Packet is about. At first glance it may appear
complicated and confusing, however, basic
operation is simple, as the default parameters of
the all important `black box' will take care of
most situations. You may of course explore the
possibilities of entering your own parameters as
you become familiar with its operation.
It is proposed to deal here only with the AX.25
protocol as this is now the world-wide standard
and the one supported by this association. There
are other protocols but they are outside the scope
of this booklet.
PACKET RADIO is a means by which error-free
information can be transmitted and received. It
requires a computer for its operation, and
normally the operators communicate by means of
keyboards and monitor screens. Facilities to store
and forward messages are usually available, as is
access to bulletin boards and databases.
The mode of Packet is an ideal marriage for the
radio amateur who dabbles with computers and is an
interesting way to obtain ERROR FREE communication
in either rag chewing, programme or information
transfer and satellite communication.
If however, you are not computer minded but wish
to be involved in Packet, there is really no
problem as the role of the computer can be very
elementary.
ABOUT AAPRA
The Australian Amateur Packet Radio Association
(AAPRA) was formed in April 1985 with an initial
membership of ten. Current membership exceeds 400,
encompassing all Australian states and territories
and several overseas countries, so we are truly
multi-national. The Association was formed for
persons interested in the science and technology
of Packet radio communications and all associated
interests.
AAPRA exists to promote and encourage the use of
Packet radio (AX.25 protocol) by amateur radio
operators. Services offered by this Association
include:-
* informative newsletters
* supply of software and kits (C=64 &
Microbee)
* help with computer terminal software
* information on the supply of TNCs and
modems
* providing a voice in the W.I.A.
* developing a Packet network throughout
Australia
Page 2
The Association (a non profit making group)
produces a newsletter "DIGIPEAT" quarterly
informing members of the latest local and
overseas developments and achievements including
technical articles on equipment modifications and
updates. Current annual membership is $12.00 and
$18.00 for members outside Australia.
AAPRA has supplied equipment and assisted other
radio clubs to set up the digipeaters in
Hornsby VK2RPH, Newcastle [Watagan Mts] VK2RPN,
Mittagong [High Range] VK2RPS, Nowra
[Mt.Camberwarra] VK2RSD Coff's Harbour [Bruxner
Park] VK2RCH, Wollongong [Mt.Murray] VK2RAW, Tumut
[Mt.Tumorroma] VK2RPT, Orange [Mt.Canobolas]
VK2RAO, Townsville [Mt.Stuart] VK4RAT, Burnie
VK7WP, St.George [Mt.Bindo] VK2RDX, Gladstone
[Caliope Range] VK4RCA, Tamworth [Nowendoc] VK2RPW
and [Mt.Kaputar] VK2RAB, Ballarat [Mt.Buninyong]
VK3RPC, Albury-Wodonga [MT.Stanley] VK3RNU,
Griffith [Mt.Bingar] VK2RGF, Lismore [Mt.Nardi]
VK2RLO, Manly [Terry Hills] VK2RMB.
Other applications are currently being considered
to set up digipeaters by providing TNCs, radios
and technical advice. The resulting network is
expanding rapidly particularly in the Eastern
States. The improvement of the network by using
ROSE for linking and directing communications has
been our most recent effort, and it is now
operating well. There is still much to be done to
develop UHF links in that system. ROSE will be
described later. The funds for these operations
have been provided from surplus accumulated from
sales of packet equipment to members.
The Association stocks products from Pac-Comm. If
you require a unit for HF and VHF there is the
PAC-COMM TNC 320 with tuning indicator; there is
also the TINY-2 TNC which is suitable for VHF
only. Both these units will suit any computer with
an RS232 port or TTL connection. New Paccomm
models such as the TINY-2 PLUS with 96K RAM and
75K PMS memory, and an upgrade kit for the TINY-2
to PLUS specifications, can be supplied. We look
forward to the time when locally produced TNCs
become readily available.
AAPRA supplies software to emulate TNCs using
Commodore "C=PAK", ( for C64, 128 and SX64) and
Microbee "BEEPAK". The C=PAK programme is written
by Chris Mills, and our Association has sole
distribution rights. This package comprises a
personally programmed disc or cartridge, a bare
printed circuit board, instructions for assembly
of the simple modem, and operating instructions.
The board is connected directly to the user port
of the Commodore computer without using a
Commodore RS232 interface. The programme provides
all the usual facilities of the TNC (AX25 level
2), digipeating, beacons, file transfers etc, and
the modem has dual ports, supporting HF and
VHF/UHF use, with software control.
Page 3
The software AAPRA supplies for the Microbee
"BEEPAK", is a programme written by Gerard Hill,
and enables Microbee PC's also to utilise Packet
radio. In the case of disc based Microbee fitted
with the SCC option (the 8530 chip) a simple modem
similar to the Commodore modem is all that is
required. Some models require a simple
modification to the core-board. For older
ROM-based models an EPROM containing the software
can be fitted on-board but a more elaborate modem
using the 8530 is required externally. This
version is not provided by AAPRA as it is not
economic compared with a commercial TNC using the
RS232 port and TELCOM.
Parts to complete the boards of both C=PAK and
BEEPAK are readily available. If you prefer
AAPRA is able to supply full modem kits which
include components, edge connector, box, sockets,
LEDs etc. Mike plugs are not provided. Assembled
and tested modems (for AAPRA members only) require
only plugs. A summary is included at the end of
this booklet.
Members of AAPRA are notified of up-dates for
equipment in "DIGIPEAT" our quarterly newsletter
and technical enquiries should be directed to
Barry White VK2AAB (02)-487-1428 or to the
secretary.
WHAT IS PACKET?
Packet is a development of the original modes of
radio communication such as Morse and Teletype.
These modes are essentially digital patterns of
ON-OFF signals and are used to represent items of
information such as letters of the alphabet,
numbers, punctuation etc. The signals are
transmitted between stations by methods such as
radio or cables, and are written down or printed
out.
Morse is a relatively slow but simple mode. The
brain and ears form a sensing device that is
superior to other means of receiving Morse code
patterns, as they are much better at pattern
recognition in the presence of extraneous signals
and noise.
In order better to automate communication,
teletype was developed. It involved more complex
patterns generated by mechanical "computers".
This gave improved speed and good recognition of
patterns. But it is susceptible to production of
false patterns when extraneous signals and noise
are received. Because of the speed involved,
brain and ears no longer help, although there is
still use for the brain in guessing what corrupted
messages were meant to say. The same problems
occur even after electronic devices have
supplanted the mechanical ones.
Page 4
RTTY (Radio TeleTYpe) characters are made up of
groups of five ON-OFF signals - the standard code
now used was devised by a New Zealand sheep farmer
named Murray, though generally it is misnamed
Baudot code which is a less efficient earlier
code.
With the same sort of electronic equipment, ASCII
code which provides up to 255 characters using a
seven or eight unit code, can be employed. It is
subject to the same kind of interference problems
as Baudot when used in radio communications, so it
is rarely used unadorned. Within a computer there
is no interference, so as you probably know, all
computers talk ASCII of some sort.
To improve message transfer, error correction was
incorporated, and AMTOR (Amateur Microprocessor
Teleprinting Over Radio) is one such development.
It uses code in groups of three characters, so
that the value of each group must total a fixed
sum. If it does not, when the receiver adds it
up, it is rejected and retransmission is
requested. When it is correct it accepts it and
asks for the next group. Using this mode, almost
error free messages can be exchanged. When
propagation conditions are bad, the rate of
information transfer will slow down but it will
still be error free. However, the number of
character types is limited by the five unit code,
and there has to be a reactive link between both
ends of the communication path.
Here is where PACKET comes in.
Packet uses ASCII code, so can have 255 symbols.
Messages are sent in groups of up to 255 units as
compared with the three of AMTOR. Complex error
checking is installed, as is information to guide
the Packets through the system. The system is
comprised of Terminal Node Controllers (TNC)
connected to transceivers, each linked with its
own computer that gives commands to the TNC and
writes and displays the messages. The packets are
dispatched entirely automatically. They provide an
error-free means of communication that permits
multiple use of a single frequency. Anything that
can be put into digital form can be sent over
Packet radio; for example, digital sound or
television.
At the present time it is very easily used to
transmit written messages, computer programmes and
files that are written in ASCII or even binary
code, between radio amateurs. And the result is a
screen full of characters in front of your eyes.
Bulletin Board Systems (BBS) form a useful part of
the system, providing the source of lots of
information and can act as "mailboxes". They also
help in the spread of information by communicating
with each other, exchanging files and messages.
Most Packet is best used on VHF, and using the
property of digipeating, VHF links over long
distances form a useful communication network. HF
radio is less efficient with Packet due to
propagation difficulties often giving rise to many
Page 5
errors, hence retries, so that information
transfer is much slower. Packet lengths need to
be reduced. In these conditions AMTOR may be
better, but the restricted number of characters
used by AMTOR creates difficulties in linking
Packet and AMTOR systems. A system to join the
two, called APLINK, is now being used to connect
Packet systems more effectively across long
distances.
This very brief description leaves a lot unsaid,
but it should lift some of the veil of mystery
surrounding Packet. It is just the thing for
people who are interested in both radio and
computers, but it also is a fine means of
communication for people who can remember about
three simple keyboard commands.
WHAT YOU WILL NEED
Although Packet radio involves high technology and
the latest state of the art components, the basic
equipment required is relatively simple to
assemble as many amateurs have found. You can of
course obtain pre-assembled units at a most
reasonable price.
The essential requirements are:-
A. 1. A Personal Computer and a Terminal
programme OR
2. A Personal Computer with TNC-emulating
software, such as C=PAK and BEEPAK
B. 1. A TNC (black box) such as TINY-2. OR
2. A modem for the C=PAK or BEEPAK.
C. A transceiver preferably with a fixed high
impedance audio output, and squelch.
A. COMPUTER
There are of course many breeds and varieties of
computer. Essentially the requirement is that the
computer can run a communications programme. There
are many such programmes, such as YAPP, available
in public domain depending on your machine. The
vital requirements are that its parameters can be
set to:-
baud rate 1200
parity even or Nil
data bits 7 8
stop bits 1 1
It is via this programme that data is sent between
you and the TNC. The commands issued to the TNC
are also via the same programme.
Page 6
B. TNC and MODEM
1. Hardware Type
These two units are sometimes combined into a neat
black box which contains its own microprocessor,
usually a Z80. It will also include memory chips
for holding its programme and the data you will be
transmitting and receiving. Another chip, the
HDLC integrated circuit, does all the checking and
handling of the data as it enters and leaves the
TNC.
2. Software Type
If by chance you are a Commodore or Microbee user
there are programmes available from AAPRA which do
the job of the TNC; this together with a simple
modem (also available from AAPRA) is all you will
require to enjoy the full benefits of Packet.
There are other programmes, such as DIGICOM for
Commodores, Grosvenor for the Spectrum and Tandy
COCO. There are also many other modems available
to buy or build. We are not in a position to give
specific advice on these.
C. TRANSCEIVER
The bulk of operation at this time is on VHF-FM.
The original channel set aside for the mode was
147.575 MHz but usage is now spreading to other
frequencies namely 147.600, 144.800, 144.850,
144.900, & 145.050. This will depend on the area
in which you operate.
HF operation is increasing; this can be helpful to
those living away from repeater-serviced areas.
The BBS service also makes good use of frequencies
within these bands. 10.147 and 14.107MHz are areas
being used.
UHF usage is still in its infancy. It is envisaged
that these frequencies will be used to provide
links between main centres for through traffic
flow, rather than have mail forwarding clutter the
local VHF frequencies. This is most desirable in
the higher density areas.
Ideally a transceiver for Packet should have such
a response as to keep the levels of the Packet
tones equal. Pac-Comm make a radio tailored to the
needs of digital radio only.
The connection of your radio to the TNC is a
simple affair utilizing the microphone socket for
audio input and Push-to-Talk. Audio line output or
an external speaker socket which most radios have
these days provide audio to the TNC/Modem. Full
instructions will be supplied with the device you
choose.
WHY CALL IT PACKET?
Each Packet is a "sandwich" consisting of, in
order of transmission, header information,
followed by the data you typed, (if any - some
packets contain no user data), followed by a very
Page 7
important 16 bit number called Frame Check
Sequence (FCS). It is this packaging of the data
that sets Packet radio apart from all previous
types of Amateur communication, and which gives it
special properties.
OPERATION OF A PACKET RADIO STATION
Packet Radio QSOs are started by a CONNECT
process, which sets up the "handshaking" between
the two stations that ensures error-free
communications. QSOs are terminated by a
DISCONNECT process, which leaves both stations
free to start a new QSO. Packet QSOs can also make
use of digipeaters, other Packet stations which
can automatically relay packets from one station
to the other over a specified route.
A local station to station connection is achieved
by VK2AAA issuing the following command whilst in
COMMAND mode. (When first switched on most TNCs go
into the COMMAND mode, so what you type will be
treated as a command.)
:-
"C VK2BBB" (C is short for CONNECT)
VK2AAA ____________>>>_____________ VK2BBB
VK2BBB will respond and VK2AAA's screen will show:
***CONNECTED TO VK2BBB (for the TNC or BEEPAK)
**SETTING LINK** VK2BBB [DATE] [TIME] (for C=PAK)
*CONNECTED TO* VK2BBB [DATE] [TIME]
Then the QSO follows.... VK2AAA has the 1st over.
To end the connection one station simply issues a
"DISCONNECT" instruction. This is achieved by
sending a "D" whilst in COMMAND mode. The screen
will then display:
*** DISCONNECTED (for the TNC or BEEPAK)
*DISC* VK2BBB [DATE] [TIME] (for C=PAK)
DIGIPEATING
You may wish to have a QSO with another station
that is beyond your direct radio range. If a third
Packet station is in range of both you and the
station you want to talk to, that station can
relay your packets. You set up the Packet routing
when you initiate a connection. Your programme
will then automatically include the routing
information in the Packet it sends.
The diagram below shows an example situation in
which digipeating is useful.
Page 8
VK2AAA _____>>____ VK2RRR _____>>____ VK2BBB
VK2AAA cannot reach VK2BBB directly, but both can
reach VK2RRR.
This connection is achieved by VK2AAA issuing the
following command whilst in COMMAND mode:-
"C VK2BBB V VK2RRR" (for the TNC or BEEPAK)
"C VK2BBB VK2RRR" (for C=PAK)
VK2BBB will respond and VK2AAA's screen will show
***CONNECTED TO VK2BBB VIA VK2RRR (for the TNC
or BEEPAK)
**SETTING LINK** VK2BBB [DATE] [TIME] (for C=PAK)
*CONNECTED TO* VK2BBB [DATE] [TIME]
You can specify a routing list of up to eight
intermediate stations. For example, consider a
modification of the example above :-
VK2AAA _____ VK2CCC _____ VK2DDD _____ VK2BBB
You specify the digipeaters in the order you would
encounter them going from your station to the
station to which you wish to connect.
Unfortunately, long strings are often
impracticable due to the increased probability of
retries being needed. A retry occurs whenever an
error is detected by the receiving station. It
rejects the packet with the error and asks for a
retransmission from the originating station.
Your station can also act as a digipeater for
other stations. This does not require any special
actions on your part, your TNC will do everything
automatically. If your station is digipeating you
may occasionally notice your transmitter keying
during lulls in your own transmissions. Of course,
a station has to be turned on in order to
digipeat, and all need to be on the same
frequency!
Digipeating does not have to be specified if you
are using a ROSE network (see later). There is
also a "conference network" that requires a
specially programmed digipeater, by which it is
possible for several stations to conduct a
round-table net.
UNSUCCESSFUL CONNECTIONS.
Sometimes you will initiate a connect sequence
that cannot be completed. The station may not be
on the air, or it may not be in range of your
station. You may have even mistyped the other
callsign. If the programme does not get a connect
response to its first connect Packet within a
specific time, it will try again. You can control
the number of attempts (or retries). If the
computer does not receive an answer after the set
number of attempts it will stop trying. The retry
count is also activated during a QSO. Each Packet
you send to the other station is "acknowledged",
or ACKed by the other station, and vice versa. The
ACK means that the Packet was received without
Page 9
errors, the FCS (Frame Check Sequence) was
correct.
This is the means by which Packet radio can ensure
error-free communications. Sometimes a Packet will
not be received correctly by the other station,
either because of accidental interference from
another Packet station (a collision), or because
of other channel noise. If your programme does not
get an ACK soon enough, it retransmits the Packet
and starts the retry count, activating it each
time an un-ACKed Packet was transmitted until it
reaches the preset retry count. The connect
attempt or QSO is then automatically disconnected.
This feature prevents tying up the channel under
hopeless conditions.
YOUR FIRST PACKET QSO.
Although there are still many features you should
be familiar with for comfortable Packet operation,
you are probably eager to get on the air and try
out your programme. Arrange to have another Packet
operator on air to help you. Make sure that your
friend will be close enough to ensure solid copy,
with no FM "popcorn" noise.
PROCEDURE.
CONNECTING STATION BEGINS THE QSO.
The calling station (The one using the
"CONNECT"command), is the station which sends the
first Packet. All kinds of confusion will result
if the called station AND the calling station both
begin the QSO. Even though there is no possibility
of "doubling" with Packet (unlike phone), the
resulting confusion of not knowing who's turn it
is, does take some sorting out.
HOWEVER, when connected to a BBS, wait till it
prompts you to give it a command.
EACH TRANSMISSION ENDS WITH "KK"
The normal Packet QSO is similar to that
experienced on RTTY with the letters KK added to
the end of each "over". This is to let the
receiving station know that you have ended your
transmission and now it is the other station's
turn to transmit. Transmission of the packets is
extremely fast and since many of us are poor
typists, there can sometimes be considerable
delays between packets. Delays can lead the
newcomer to think that it is now their turn and
chaos often results. International QSOs sometimes
use ">>" symbol instead of "KK".
COMMENCE EACH TRANSMISSION WITH A CARRIAGE RETURN.
When you begin each over, commence with a carriage
return (C/R). This is to let the other station
know that "you are still alive" and have commenced
typing your reply. Otherwise, if you are really
slow on the keyboard, it could take up to a minute
or so to type your reply and the other station may
think you have gone off the air.
Page 10
CONCLUDE QSO WITH "SK SK"
At the conclusion of the last over, end the
transmission with SK SK. This gives the other
station the opportunity to "tie the ribbons" etc..
EITHER STATION MAY DISCONNECT.
When the QSO has ended and both parties have sent
their last packets (ended with SK SK), either
party may issue a disconnect Packet.
When you are connected to another station you are
in CONVERSE mode. In order to give the DISCONNECT
command you have to change to COMMAND mode. (See
below). Then you can press D, which is the command
to disconnect.
The C=PAK programme gives information in two
status lines at the top of the screen, from which
you can tell if all packets have been sent. Dont
disconnect if a packet is still waiting to be sent
and ACKed, or the other station will not have
received all that you typed in.
TNCs have a status LED to give that indication.
BEACONS.
The TNC is able to send beacons at preset
intervals. This mode can be used to send
announcements or test messages whilst unconnected.
Use this function with caution as too many
beacons, or beacons too frequently, add
unnecessary congestion to a busy frequency.
STATUS.
Your programme may be in COMMAND, UNCONNECTED,
CONNECTED or FILE TRANSFER mode.
COMMAND MODE.
This mode is selected with , or RUN/STOP
on the Commodore, and enables the issue of
commands within the programme. These commands are
not transmitted. Digicom requires a colon at the
first place on the line, to enable the command
mode.
CONNECTED or UNCONNECTED (UNPROTO) MODE.
Text typed on the keyboard is transmitted
regardless of whether you are in connected or
unconnected mode. The information you type is
assembled by the programme into packets and
transmitted over the radio. The send Packet
character (a carriage return [C/R]) causes the
input to be packetised for transmission. If you
type a full Packet length of characters without
typing the send Packet character [C/R], your input
will be packetised and transmitted anyway.
An UNPROTO transmission is one that is not
addressed to another station in particular,
enabling one to call CQ, for example.
The number of characters in a Packet is usually
128 but can be as many as 256. Sometimes when
Page 11
operating on HF the number of characters in a
Packet can be reduced to just a few, e.g. 5 or 10.
FILE TRANSFER MODE.
Packet radio is very well suited to the transfer
of data between computers. In some cases whilst
transferring programme files there will be
conflict between the special characters contained
in the file and the main programme; this will
cause some unusual screen graphics to appear and
sometimes after transfer is complete it is
difficult to work out where the cursor should be.
To overcome this simply go to COMMAND mode with:
1. TNC - send three C's within the time
set by the command CMDTIME. In layman's
terms, quickly. There will be a short delay
and the "cmd:" prompt will appear. To clear
the screen, use the command as set by the
terminal programme (commonly ALT C ). You
should study the manual carefully before
attempting this option as other parameters
may need to be altered.
2. C=PAK - (RUN/STOP), press SHIFT and
CLR/HOME followed by a Carriage Return.
This will clear the screen and allow you to
continue. There are programmes such as YAPP that
have been designed to transfer binary files
without such conflicts, but they are
computer-specific.
THE ROSE NETWORK.
ROSE software and the associated node controllers
and radios are being installed progressively at
appropriate locations. ROSE identifies each
location by an address derived from area and
exchange codes of the existing telephone system.
The user does not need to know how to get to an
address; all that procedure is set up within the
network.
The Rose network software improves the reliability
of the transfer of packets from the originator to
the destination station through the chain of
repeaters. It does this by sending the
acknowledgement ACK between each link in the chain
rather than from the remote end back to the
origin.
As you have seen previously the protocol used in
amateur packet radio is AX25 which is derived from
a commercial landline protocol defined by the
CCITT called X25. In Rose we use X25 between the
repeaters only. In X25 each repeater, known in X25
as a switch, has an address which complies with a
CCITT standard known as X121. This address
comprises 6 figures. It has been decided that the
telephone STD and exchange codes will be used for
this purpose.
As an example, the Hornsby and District Amateur
Radio Club's repeater VK2RPH has an address of
247600. The 2 is the STD code for Sydney and 476
Page 12
is the exchange code for the area in which the
repeater is installed. This repeater acts not only
as a normal digipeater (VK2RPH-1) but also accepts
a connection to its node controller, through which
the software directs the packets via links
(generally on VHF/UHF but eventually there will be
HF links too) to their destinations. The following
is a list of the present Rose repeater numbers:
VK2RPH 247600 Hornsby
VK2RMB 245000 Terrey Hills
VK2RDX 633600 Mt Bindo
VK2RPS 487100 Mittagong
VK2RAW 488500 Wollongong
VK2RPT 694700 Tumut
VK2RSD 442100 Nowra
VK2RAO 636500 Orange
VK2RGF 696200 Griffith
VK2RPN 49.... Newcastle
and so on......
Wollongong, Nowra and Newcastle are
still to be converted. There are ROSE nodes north
of Sydney which will be linked as further nodes
are installed in the gaps. UHF links already exist
from Sydney to Orange, and within the Sydney area.
All these nodes act as ordinary digipeaters using
the sub-station identifier (SSID)"-1" eg VK2RPH-1
At the time of writing quite a few Rose nodes are
operating. Assume that VK2RPH is local for you.
You want to call VK2AAA in the Orange area.
You do not need to know about the Orange
repeater's code. All you need to know is the
telephone number of VK2AAA, or that of his local
post office. Let us assume that his phone number
is (068) 82 4101. Enter the following:
C VK2AAA V VK2RPH,688200 (With C=PAK omit "V" and
",". Use spaces instead.)
The system will reply "Call being Set Up" and then
"Connected to VK2AAA". This does not mean the
connection is made, but is to stop your TNC trying
again to connect while the call is being set up.
On true connection, it will say "Call completed.."
The Orange repeater is set up to accept all calls
for telephone STD exchange codes in its RF
coverage so it will recognise the above number as
being in its coverage area. The node at VK2RPH
will have been told the route to take to reach the
688200 area repeater. Without ROSE, you would have
to know which repeaters to use on the way to
Orange.
For more information on the operation of this
software you should look in the files of the BBSs.
AAPRA members will be kept up to date in the
Associations newsletter DIGIPEAT which is produced
on a quarterly basis.
BULLETIN BOARDS.
The Bulletin Board Service (BBS) has developed
into a worldwide network, providing access to
information by way of message forwarding. Messages
may be lodged with your local BBS for transmission
for all to read or if you wish by private message.
Page 13
There are many options available , for example
messages may be `addressed' to a particular Packet
operator at another BBS where he is located, no
matter where in the world.
The use of a BBS is very easy - you simply
`connect' in the normal fashion, BUT wait for the
BBS to prompt you before typing anything. On your
first connection you will receive a welcome
message and be asked to supply your first name.
ALWAYS wait for a prompt from the BBS before
sending anything; the prompt will be in the form
of a menu. Should response be slow there is a
temptation to hit the carriage return key. This
does not help and in some early versions of the
software caused a problem. Sending indiscriminate
carriage returns merely sends out additional
Packets and helps to slow down the system.
On your first connection with a BBS you should ask
for the `help' file. Open up a file on your
computer to save the incoming packets (or if using
a C-64 the information will go into the receive
buffer and may be saved to disc after logging
off). Send an "h", then log off on completion by
sending a "b" (for goodBye) and study the
information you have just received. You will be
surprised how easy it is to use the system and
just how versatile it can be. The BBS systems can
differ... read the help files carefully.
As a matter of courtesy, if operating a BBS in
peak times when there is a lot of traffic, you
should avoid downloading large files as this will
clutter the frequency and possibly inconvenience
other users who may be enjoying a quiet QSO.
Remember to download large files at a quiet time.
For the benefit of those users of MS-DOS/PC-DOS
and Commodore computers, there is also public
domain software available from some BBS's. Such
files are binary files and the technique of
downloading is a little different, so you should
seek additional information prior to attempting
this procedure depending on the system you are
running.
If you intend to leave a lengthy message on the
BBS it is a good idea first to produce the message
on your word-processor. It must be an ASCII file,
that is an "unformatted" or "non-document" type.
Once you are connected to the BBS it is easy to
send the prepared file rather than try to type
whilst connected, as the BBS usually will only
wait a short time before disconnecting you while
you are typing out the message. Apart from that
you may be tying up the system unnecessarily
whilst others are waiting.
Page 14
A SAMPLE SCREEN
cmd:c vk2xy
*** CONNECTED to VK2XY [06/10/90 17:02:28]
[MSYS-1.08-H$]
Hello John, Welcome to VK2XY's MSYS BBS in Hornsby
Enter Command:
A,B,C,D,G,H,I,J,K,L,M,N,P,R,S,T,U,V,W,X,?,* >
LL 4
Msg# TR SIZE TO FROM @BBS DATE TITLE
4125 B$ 767 MISC VK4XS VKNET 901006 HF FREQ.
4124 B$ 642 MISC VK4ZGJ VKNET 901006 DOS VIRUS
4123 B$ 927 NEWS VK4ZWI SPACE 901006 TOMATO
4111 B$ 406 DX ZL2BLC ARRL 901006 CONTACTS
Enter Command:
A,B,C,D,G,H,I,J,K,L,M,N,P,R,S,T,U,V,W,X,?,* >
b
*** DISCONNECTED [06/10/90 17:04:12]
SOME BASIC BBS COMMANDS
A = Abort current listing (Does not act
immediately)
C = Conference mode
B = Logoff the system (Bye)
D = Download (send me) ASCII file
G = Active gateway
H = BBS Help file
I = Information about the system
J = Lists the calls heard by the BBS
K = Kills or deletes a message
KM= Kill mine
L = Lists messages since last on.
LL 10 =List latest 10 messages only
LM = list messages for me (list mine)
N = Enter your Name
R = Read message #(insert message no. after space)
RM = Read messages for me
S = Send a message to the system
S VK2XYZ = Send message to VK2XYZ
T = Talk to the operator
U = Upload an ASCII file to the BBS
V = Shows Version of the BBS software
W = What the available files are
X = Expert status, changes the menu presentation
Y = Yapp binary file transfer for IBM type users
? = Used together with another letter gives help
on the topic that letter refers to.
N.B. Some BBSs have a file called something like
USER.DOC, which contains detailed information.
Look for it by giving the command "W". Then
download it by keying in "D user.doc", or whatever
filename you find.
Page 15
FUTURE DEVELOPMENTS
Packet radio is a rapidly evolving mode and many
changes can yet be expected. Protocols are still
under review and such areas as high speed modems
and satellite communications are prime targets for
development.
The use of digipeaters has been effective in
enabling amateurs spread over large areas to
partake in the packet activity that has been a
feature of the last few years. However digipeaters
have a major disadvantage in that if a packet is
misread by the addressed station or a repeater
along the way, the packet has to be sent again all
the way from the originating station.
To overcome this problem network software has been
developed that repeats the packet only between the
repeaters concerned with the lost packet. The
systems used for this procedure are known as the
Open Systems Information Protocols. These OSI
standards approved by the CCITT comprise seven
levels of control. With the introduction of
network software we will be implementing level 3.
The software that we are at present installing is
known as ROSE. With this system we are able to
connect to our local repeater and specify the
station that we wish to connect with and the
repeater that is near that station. Our local
repeater will know which other repeaters it must
use to reach the remote repeater.
While the users will connect to the network on the
two metre band the connections between the
repeaters will be on the 70cm band or another band
such as HF, and will enable packets to pass
through busy areas of activity without having any
effect on the local traffic.
Ways and means are being sought to increase the
speed at which information can be sent. Some
equipment just is incapable of coping with this,
which will probably lead to stratification of
amateur packet operators as in other fields where
the super-dooper exists alongside the Heath
Robinson. Some people will devote themselves to
Satellite Communications where packet has come to
the fore, with as many types of modem as there are
satellites!
Packet is an exciting addition to the hobby of
Amateur Radio utilising modern technology.
Good luck and good Packetting!
***
Page 16
EQUIPMENT AVAILABLE FROM AAPRA
PACCOMM PRODUCTS
TINY-2 TNC VHF TNC (boxed and ready to go)
Includes Personal Message System
and KISS
TNC 320 Dual port TNC with tuning
indicator, PMS, KISS.
(VHF and/or HF, complete and
ready to go)
PC 320 TNC 320 on a 3/4 board for
installing inside an IBM clone.
On-screen indicators.
DR 200 Available on request.
AAPRA PRODUCTS
C=PAK or BEEPAK
(Packages for Commodore and Microbee)
Modems are dual port (HF and VHF/UHF) with tuning
indicator. They are powered by the computer power
supply, and port switching is done by software.
The software has the owner's callsign embedded.
This can only be altered by AAPRA, for which there
is a small fee.
1. Disc version (disc & instructions)
2. Eprom version (cartridge & instructions)
3. Modem (built & tested requires only radio
plugs) supplied to AAPRA members only
4. Modem kit (edge connector, box, all
components, etc. requires only mike plug)
5. PCB & Connector only
(Registered s/w owners only)
6. Microbee coreboard mod. kit
SOFTWARE UPDATES
COMMODORE V4.4 (for registered owners
only of earlier versions, available
since September 1987)
Software callsigns can be reprogrammed
Pac-Comm software version 1.1.6
Available for TNC200, TNC220 & TINY-2
* KISS and PMS (Personal Message
System) are standard in new TNCs.
* PMS is an option for 32K RAM versions
of TNC2/200, TNC220 and TINY-2 units,
and KISS comes with it.
*32K RAM chips are available for units
lacking them.
Please note:
* New Eprom can be supplied
* Old Eprom can be reprogrammed
(Eproms cannot be swapped)
Write to AAPRA in copious detail if ordering,
especially regarding Microbees in their many
varieties.
Current price lists are published in DIGIPEAT or
can be obtained from the secretary to whom
applications for membership whould be directed.
SASEs are appreciated.
Page 17
GLOSSARY OF COMMON TERMS
ACK -Acknowledgment, the control signal
sent to indicate correct receipt of
a transmitted packet.
ADDRESS -A character or group of characters
that identifies a source or
destination.
AFSK -Audio frequency-shift keying.
AMICON -AMSAT International Computer
Network-Packet radio operation on
amateur satellite, AMSAT-OSCAR 10
to provide networking of ground
stations acting as gateways to
Packet radio networks.
AMTOR -Amateur microprocessor teleprinting
over radio.
APLINK -Amtor Packet Link
ARQ -Automatic Repeat Request, an error
control technique in which a
sending station, after trasmitting
a data block, awaits a reply (ACK
or NAK)to determine whether to
repeat the last block or proceed to
the next.(Amtor mode A)
ASCII -American National Standard Code for
Information Interchange, a code
consisting of seven information
bits.
AX.25 -Amateur Packet radio link-layer
protocol approved by ARRL Board of
Directors in October 1984.
BAUD -A unit of signaling speed equal to
the number of discrete conditions
or events per second.
BBS -Bulletin Board System
BUFFER -A portion of memory allocated as
work space
CARRIER DETECT-Formerly Received Line Signal
Detector, a physical-level
interface signal that indicates
that the receiver section of the
modem is receiving tones from the
distant modem.
CLEAR TO SEND -A Physical-level interface circuit
generated by the DCE that when ON
indicates the signals presented on
the Transmitted Data circuit can be
transmitted.
COLLISION -A condition that occurs when two or
more transmissions occur at the
same time and cause interference to
the intended receivers.
CONNECTION -A logical communication channel
established between peer levels of
two Packet radio stations.
CRC -Cyclic Redundancy Check, a
mathematical operation in which the
results are sent with a
transmission block to enable the
receiving station to check the
integrity of the data.
DESTINATION -In Packet radio, the station that
is intended receiver of the frame
sent over radio link either
directly or via a repeater.
Page 18
DCE -Data Circuit-Terminating Equipment,
the equipment(for example, a modem)
that provides communication between
the DTE and the line radio
equipment.
DIGIPEATER -A link-level gateway station
capable of repeating frames. The
term "bridge" is used in industry.
DR200 -A TNC device produced by Pac-Comm
to provide two port operation
suitable as a dedicated Digipeater.
DTE -Data Terminal Equipment, for
example a VDU or teleprinter.
DXE -In AX.25, Data Switching Equipment,
a peer (neither master nor slave)
station in balanced mode at the
link layer.
FCS -Frame Check Sequence (see CRC)
FEC -Forward Error Correction, an error
control technique in which the
transmitted data is sufficiently
redundant to permit the receiving
station to correct some errors.
(Amtor mode B)
FIELD -In Packet radio, at the link layer,
a subdivision of a frame,consisting
of one or more octets.
FLAG -In Packet switching, a link layer
octet(01111110) used to initiate
and terminate a frame.
FRAME -In Packet radio, a transmission
block consisting of opening flag,
address, control, information,
frame check sequence and ending
flag fields.
GATEWAY -In Packet radio, an interchange
point.
HDLC -High-level Data Link Control
HOST -As used in Packet radio, a computer
with applications programmes
accessible by remote stations.
JAS-1 -JAMSAT/JARL amateur satellite
having Packet-radio capability.
KISS -Keep It Simple Stupid. Simple TNC
programme for use with TCP/IP. As
most of the work that is done by
the normal TNC programme is done in
the computer only a very small part
of the normal programme is needed
in the TNC to handle the transfer
across the RS232 and taking data
from the SIO chip, also detecting
DCD.
Page 19
LAYER -In communications protocols, one of
the strata or levels in a reference
model.
MODEM -Modulator-Demodulator, a device
that connects between a data
terminal and communication line (or
radio). Also called Data Set.
PAD -Packet Assembler/Disassembler
PMS -Personal Message System available
in Pac-Comm software release 1.1.6
PROTOCOL -A formal set of rules and
procedures for exchange of
information within a network.
RAM -Random Access Memory.
RECEIVED DATA -Physical-level signals generated by
the DCE are sent to the DTE on this
circuit (RxD).
REQUEST TO SEND- Physical-level signal used to
control the direction of data
transmission of the local DCE.(RTS)
ROSE -Radio Amateur Technological Society
Systems Enviroment. It is the
network software AAPRA is hoping to
install throughout the repeater
network system.
RS-232-C -An EIA standard physical-layer
interface between DTE (terminal)
and DCE (modem), using 25-pin
connectors.
SOURCE -In Packet radio, the station
transmitting the frame over a
direct radio link or via a repeater
SSID -Secondary Station Identifier. In
AX.25 link-layer protocol, a
multipurpose octet to identify
several Packet radio stations
operating under the same callsign.
TAPR -Tucson Amateur Packet Radio
Corporation, a non profit
organisation involved in Packet
radio development.
TCP/IP -Transmission Control
Programme/Internetwork Protocol. It
is a widely used system for
connecting different computer
networks.
TNC -Terminal Node Controller, a device
that assembles and disassembles
packets (frames).(used
interchangeably with PAD)
VADCG -Vancouver Amateur Digital
Communications Group
YAPP -Yet Another Packet Programme.
Communication software written for
IBM and compatibles for Packet use.
X.25 -CCIT Packet-switching protocol.
***
Last update to this page: 22/2/00