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Page 2

II

Digital
Communications
with Amateur Radio

The Complete
Packet Radio Book

By: JimGrubbs
K9EI

!ladle IhaeK
A DIVISION OF TANDY CORPOR ATION

FT. WOR TH TEXAS 76 102

Page 80

Figure 5-8. Seven modes of operation are provided by the MFJ-1278
Data Controller .

, YlN,$tfOU) m:! MFJMULTI-MODEDATACONTROLLERCOtltftI'tQIN Tt .....a: !"OW(_
-"" ' U'lt....-

ON ....,. OCI> ,.TT ... - ....• • .....I ..•",.- Of'MOOQ. ..., J. tnc
Courtesyof MFJ Enterpr ises, lnc.

Specia lized Un its
Thereare someadditional variations on the TNC that we will look at in upcoming
chapters. One unit sold by AEA for theCommodore64 and 128 is a cross betweena
stand-alone universal unit and a machine specific unit. with the software resident in
the personalcomputer. There are dual-port TNCs and now Network Node Control-
lers (NNCs). AEA also has recently introduced the first true packet radio- a
transceiverspecifically designedfor high-speeddatatransmissionand reception.

Curre nt Choices
In summary, thehobbyist currently has basically these choices for aTNC:
• A TNC 2 unit built by a licensedmanufacturer.Price and proven reliability are the

reasons for choosing theseunits. For thecomputerhobbyist interested only in
packetoperation,TNC 2 units offer an exceptional value intoday'smarketplace.

• One ofthe units usingproprietaryhardware and software. Initially, the amateur
communitywassomewhatreluctant to invest in a unit supported only by a single
manufacturer.However, the companies have proven that they are responsive to
changing conditions and are having little difficulty in attracting buyers.

• A universal terminal unit. Thecombinationof a universalcomputerconnection
using an RS-232 port and the relatively easyprogrammabilityof an all-modeunit
makes aUTU very attractive for anyone wishing to engage in a wide variety of
datatransmissionand reception modes.

• A specializedunit if the hobbyist'sneeds dictate.
• A used TNC. Most older TNCs are stillcompatiblewith today'sequipment. Find

out which version of software is included in the unit you are buying and check on
theavailability of upgrades direct from the manufacturer. TAPR intended to
release an updated version of software for the TNC 1 that would fully implement
the featuresavailable in the TNC 2. Because a number of problems developed
during the project,it has not been completed. But all is not lost for two reasons.

5-11

Page 81

First, the TNC 1 can still be used quiteeffectively in communicationswith TNC 2
type units, though there have been reports ofincompatibility with some versions of
someproprietarysoftware. Second, Ron Raikes, WA8DED, hascreateda replace-
ment softwareprogramavailablefor use on anon-profitbasis thatimplements
many of the desirable features of the TNC 2 code on a TNC 1.

GETTING CONNECTED
Let'snow tum to the details of actually makingphysicalconnectionsandestablish-
ing softwareinterfaces.

The DTE
The DTE, orcomputerside of theconnection,is just about as simple as it can be.If
your computerhas an RS-232connection,particularlyif it is terminatedin a DB-25
connector,most of your work is done already. To begin, you will need aminimum of
three wires:transmitteddata, received data and signal ground. Refer toFigure 2-15
for the locationof theseconnectionson a DB-25connector.

While using the DB-25connectionfrom an RS-232 port is theeasiestand most
commonlyacceptedway of connectinga TNC to acomputer,there arealternatives
for somemachines.In the case ofCommodorecomputers,you canpurchasea plug-
in RS-232adapterfrom several sources. A number of TNCs include special instruc-
tions for connectionto theCommodoremachineswithout using a special interface.
Usually it isnecessaryto change thepositionof a switch orjumperinside the TNC
to accomplishthis. You'll then wire a special cable with a DB-25 on one end and a
24-pin user portconnectoron the other end to match theconnectionson a Commo-
dorecomputer. At least onemanufacturersells a special cablecompletelywired for
the Commodore. Someamateurshavesuccessfullywritten software for other
machinesthat allows the data to be sent and received through thejoystickconnection
or otherports. Wecan'tpossiblycoverall the methods used, though you may find
some helpful hints in back issues ofamateurmagazinesthat regularly devote their
pages topacketradio activities. In the long run, a true RS-232connectionis the
desired way toconnectyour TNC.

TNC Software
You will also need to load some type of terminalemulationsoftwareinto your
computerjust as you would to use astandardtelephonemodem. You can use the
samesoftwarefor packetradio as fortelephoneline communications.You do not
need a specialcommunicationsprogramfor your computerto operate with packet
radio! That is perhapsone of the most frequentmisunderstandingspeople have about
packetradio.

TNC OPERATION
A terminal nodecontrollerhas several modes ofoperation.When you first power it
up, it will give you a sign-on messagesimilar to the one shown inFigure5-9. It
usually indicates themanufacturerand the version of the internalsoftwarecontained

Page 160

D
Index

A
ACK: 4-5
AmateurTeletypewriterOverRadio (AMTOR):

3-12,3-13,4-10
AmericanRadioRelayLeague: 9-9
AMRAD: 9-9
Analog Signals:2-1
ARQ Mode: 3-14
ASCII: 3-8
AsynchronousCommunications:2-8
ATM: 1-1
AX.25 Protocol:4-7, 8-5, 9-10

B
Baud Rate: 2-8
BaudotCode: 3-1
Beacons: 6-6, 6-7
Bell 103: 5-5
Bell 202: 5-5
Bell 212: 5-5
Bit Stuffmg: 8-4
BKONDEL: 6-4
BREAK: 6-9
Buffering: 4-4
Bulletin BoardOperation:1-6
Bulletin BoardOperation,Packet: 6-11

C
CALmRATE: 6-1
CALSET: 6-1
CanadianActivity: 1-5
CarrierSenseMultiple Access: 4-8
CMDTIME: 6-10
CMD Prompt: 5-13
CompuServe:1-2,5-1
ConnectAlarm: 9-4
CONNECT: 5-18
CONOK: 6-4
CONYERS: 6-2
CQ, How to Call: 6-6
Cyclical RedundancyCheck(CRC): 4-5

D
Datagrams: 7-9
DB-25 Connector: 2-15,2-16,5-5
DCD: 5-16
DCE: 2-12
Differential PhaseShift Keying: 2-15, 3-7
Digipeater:4-13
Digipeating: 5-19
Digital Signals:2-3
DISC: 4-11
DTE: 2-11
Dual Port PacketController: 7-6, 9-6
DWAlT : 6-5

E
EBCDIC: 3-10
ECHO: 6-4
England,Tony: 10-6
Error Correction:3-14, 4-1

F
FAD : 5-4
FCC: 1-2
Fido BBS System:6-13
Flags, Start: 2-10,4-3
ForwardError Correction:3-14
FO-12: 10-7
FRACK: 6-5
FrameCheckSequence(FCS): 4-5, 8-5
Framing:4-4
FrequencyShift Keying: 2-13, 3-6
FRMR: 4-11
Fuji: 10-7
Full-Duplex Communications:2-6

G
Garriott,Owen: 10-5
Gateway: 7-6
GatewayNewsletter:9-11

H
Half-Duplex Communications:2-6
HarnNet: 9-10
HDLC: 5-4, 8-2, 8-7, 8-8
HF Operation:6-15
HiddenTerminals:7-5

I
InformationFrames:4-10
Interfacing: 5-14
Interfacing,Walkie-Talkie: 5-17

J
JAMSAT: 10-8
10-12: 10-8

K
KeyboardCommunications :1-6, 6-1

L
Level ThreeNetworking: 7-8
L icense,Novice: 1-2
Local Area Networks:7-3
Look Up Tables: 3-20, 3-21

M
Master Station: 3-12
Meteor Scatter : 10-12
Mode B: 3-14
Modems: 2-12

1-1

Page 161

Modems, Satellite: 10-8
Modems,Telephone:I-I
MONITOR: 5-15
Moonbounce: 10-11
Morse Code: 3-1
MYCALL: 5-15

N
NAK : 4-5
NAK, Implied : 4-5
Network Addressing:7-11
Network Node Controller: 7-9, 9-5
Networks: 7-1
Node: 5-1
NRZ1 Coding: 8-4

o
OSCAR: 10-1
OS1NetworkingModel: 4-6

p
PacketAnsweringMachine:6-13
Packet Radios: 9-6
Packet StatusRegister: 9-10
PACLEN: 6-5
PACSAT: 10-3
PACTIME: 6-9
PAD: 5-4
Paper Tape: 3-8
Parallel Transmission: 2-3
Parity: 3-11
Phase Shift Keying: 2-15, 3-7
PID: 4-10, 8-5
Polling: 4-8
PortableOperations:9-8
Program Exchange: 1-6
PropagationEffects On Packet: 6-16
Protocol: 3-20

R
Radio Sputnik: 10-3
REDISPLAY: 6-2
REI: 4-11
Repeater, Digital: 4-13
Repeater,Voice: 4-12
RNR: 4-11
Routing Tables: 7-10
RR: 4-11
RS-232: 2-15, 8-10
RUDAK: 10-10

S
SABM: 4-11
SAREX: 10-6
SatelliteCommunications: 1-6
Serial Transmission:2-3
Shuttle,AmateurOperationsfrom: 10-4
Simplex Communications: 2-6
Slave Station: 3-12
Smart Modems: 3-20

D
Split Screen Terminal Program: 6-2, 6-3
SSID: 4-9
Start Rags: 2-10, 4-3
Store and Forward: 4-13, 4-14, 6-13, 7-1
SupervisoryFrames: 4-11
Synchronization: 2-9
Synchronous Communication:2-10

T
TCP/IP: 7-9
TeletypewriterOperation: 3-4, 3-5
TeletypewriterOver Radio (TOR): 3-12
Terminal Emulation Software: 2-17, 9-1
Terminal NodeController(TNC): 5-1
Terminal Unit: 3-7
Terminals, Electronic: 2-12
Throughput:2-8, 7-8
TNC I: 5-7
TNC 2: 5-9
TRANS: 6-2, 6-8
TranslationTables: 3-20,3-21
TransparentMode: 6-2, 6-8
Tucson Amateur Packet Radio (TAPR): 5-7, 9-10
Tuning Indicators: 9-3
Tuning, Packet Signals: 6-15
TXD: 6-4

U
UA: 4-11
UART: 2-5, 8-2
VI : 4-11
Universal Terminal Unit: 5-9
University of Surrey: 10-5
UNPROTO: 6-6
UOSAT: 10-5

V
VE3GYQ BBS System: 6-11
Video Tapes: 9-5
Virtual Circuits: 7-9
VITA : 10-5
VI and V2 Protocol: 4-7

W
WA7MBL BBS System: 6-11, 6-12
Wide AreaNetworks: 7-3
Wormhole: 7-10, 7-11, 7-12
WORL1 BBS System: 6-11, 7-10

X
Xerox 820: 8-7, 9-9
XMODEM Protocol: 5-3, 6-8
X.25 Protocol: 4-7

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