QRM ocr

1980sDocument1985QRM 1985

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Amateur
Radio
News \ FEBRUARY 1985

Issued by the Tasmanian Division of
the Wireless Institute of Australia

Radiotorial (Comment
Listening to our broadcast on Sunday mornings, your Editor
has been impressed with the gallant efforts of our most recent
announcer, Barry VK7/KAD, to involve us all much more in the W.I.A.
operations. In all three branches in VK7, we continually suffer
from the "dead wood" syndrome experienced in many voluntary
organisations. there are even levels of "deadness": lowest level -
those who don't bother to join W.I.A. at all (either it's too
expensive or, "I might get stuck with some sort of responsibility");
next-lower level: those who join but never come to meetings or
admit to being members("I just pay my sub to get 'A.R.'"); then
there's low level: those who are members and attend meetings but
only to chat with their mateswor criticize those who are trying
to improve the Association and incidentally, the conditions for
our hobby ("Stick-in-the-mud" lot in the W.I.A. - never make much
progress - but I'll stirTom-upil)-The stirring-Up=referred to
almost always consists of a harangue about the inefficiency of
Council or Divisional Officers - never an offer to become part
of the system, to provide experience or expertise.
Your Editor once resigned from a Union because he was
disgusted with the way it was run. It was a salutary experience!
The Union never faltered in its bias towards the red end of the
spectrum, and your Editor was left with no means of publicising
what later proved to be a disastrous situation. Never again! The
motto should be "If you want to improve an organisation, you must
be part of it" - and that doesn't mean just being a non-participating
member.
The setting-up of an "activity group" in the south, similar
to the one already flourishing in the N.W. Division, ought to
lead to the involvement of more and more amateurs as the different
areas of activity come into being. The same principle should apply
to the main Divisional body - there are enough experienced and
well-qualified members to start practical sections on all aspects
of our hobby, from Morse practice to satellite operations, from
soldering to computers. Young members joining W.I.A. must be
bored beyond measure by the stultifying content of our meetings,
oand the "dead wood'" atmosphere created by the very people who
could be broadening their enjoyment and knowledge of amateur radio.
Are YOU going to put in something this year for the benefit
of fellow-members and the W.I.A. in general?? Or are you merely
going to sit back and see what you can get out of it??
Be Warned! If you're in the second category, you may soon find
there is nothing to get out of the W.I.A. (i.e., the same as you
put in) because the "live wires" will leave to form separate
splinter groups where they CAN get interest and action and find
it possible to widen their horizons.

\;(Q WHAl
/‘i‘%AhJ \J}<a{:fgil'

l.\/;

The Editor's deadline for copy for the March issue of QRM
is+ERIDAY
; det+« MAREH: +sDORItsmissndtsdd

A SMALL PROBLEMH(from December issue)
The antenna feed point problem by VK7/CV is solved by using
the reciprocals of the heights shown.

Foed
v
-ALy bt e
ol g e
';?o - 0.0125 Jéo LB - Lo, thsvalieleanis bloe b L e
Add these two figures together, result: 0.0625.

O.%625 = 16.. Height of feed point = 16 metres.

0 i
B
35 _1 '+ 4_
=5
§ 80 |
ThiS X = T 16 metres.

Any questions????

FiQ RW.8 Adk E

One 2m handheld IC2A ... oo 01 0iB200:5091
One Superboard Computer with
gofiercial cGse, sofrtwore, etc., ... 3200.00,
Contact Peter Frith, VK7PF, QTHR or (003) 430182.

ettt e et ettt S
Pidol LI Jd Re Al PDyds O
There have been a number of articles on "Packet Radio" in "A.R."
magazine, and there will be an on-going segment bi-monthly, sourced
from the Sydney Amateur Digital Communications Group (8ADCG) and
the Melbourne Packet Radio Group (MPRG) alternately.
These articles have covered the field fairly extensively and in
some detail, and should be read again by anyone who may be thinking
of "having a go"." This contribution is intended perhaps to answer
some basic questions that may arise. :
As a quick'description - Packet Radio is a system that allows
the transfer of information (QSO's) or data in a digitally encoded
form at high speeds in short bursts (packets). It can be operated
on all bands and modes permitted to the amateur by D.0.C., direct -
i.e. station to station, via repeater or via satellite.
Because the transmission and reception of the signals is
controlled by microprocessors, and each packet is of short real
time duration, it is possible to have as many as 16 users on the
same frequency in individual QSO's, in what appears to them to be
the same time. As an example of speed: RTTY operates at around 50
baud; Packet runs at 1200 baud, some 24 times as fast. Some of the
time saved is used by the "housekeeping" of the system, which
includes checking and verifying the correctness of the transmissions.
Assuming you are considering a move into Packet Radio. What do
you need? Additional to a suitable rig, which you probably already
have in the shack, you will require three items:
1. A Terminal. :
2. A Terminal Node Controller (TNC).
3. A Modulator/Demodulator (MODEM).
With the above, the system operates broadly as follows: Output from
the terminal in binary code is assembled into a packet conf@ining
the address, data, end of message etc., by the TNC which also
handles the baud rate conversion from the terminal speed to the
transmission speed. The TNC passes this to the MODEM where the
packet is converted to AFSK 2 tone modulated form which is then
sent to the Tx. Incoming signals follow the reverse route.
1. The Terminal: May be any Displgy or Typewriter type terminal,
(ex-RTTY, for example) or almost any computer from mainframe to
personal micro. It MUST have RS 232 connection and be able to
generate ASCII character code.
2. Terminal Node Controller: There are two main approaches:
One is to write programmes for all the requirements as sodtware
for a computer that is used as a terminal - a big job and not
for the faintheated. It also ties up the computer completely.
The other is to use a dedicated TNC which will handle all the
programming requirements. This way leaves the computer terminal
available for other duties, and is the way to go if a typewriter
type is used. In this method, the programs are all contained in
ready processed chips.
Ways and means are:
(a) Bage Boards and circuits - Quite practical as the
necessary chips, ready programmed, are available individually
ds are the base boards. 5 ' :
(b) Kits - These are supplied by the various Amateur Groups.
They contain the boards and all vital chips, including the
programmed ones. NOT supplied are the readily available
miscellaneous parts.
(c) Fully Built - I believe a large USA-based electronics
group has plans to market a fully-built TNC/MODEM combination
black box.
3. MODEM: Commercial Modems capable of 1200 baud can be used.
Experience has indicated that add-on timing circuitry is needed.
Circuit boards for dedicated Modems are available and can be
supplied as part of the TNC kit. Components are readily available
commercially.
COSTS: Depend on how you wish to travel.
1. Terminals: If you suitable RTTY gear, it should be
almost nil cost. At the other end, o full-featured keyboard/VDU
intelligent display terminal will cost about $1,000.00 + S.T.!!
If you use a computer, almost anything goes. Vic 20's and converted
TV Monitors are in practical service.
2. “TNC "8 and MODEMS
:
(a) Base boards - approx £40.00 for TNC plus
$20.00 for Modem.
An estimate for all components is $350.00.
(b) Kits - Two are currently immediately available.
One from Vancouver through SADCG and
costing about F190.00 One from TUCSON, USA
direct at about $240.00 - Both include the
Modem Board and software in EPROM.
SADCG estimate of total assempled cost is
$300.00. A combination TNC/Modem kit from MPRG
will be available shortly. Prices not yet known.
(¢) Fully-built - no prices or release dates are
yet available.
Apropos "Vancouver" and "Tucson": These are two control
procedures (protocols) advanced as the best (or at least different).
AX25 developed by the Tucson USA Group, which has recently been
adopted by the ARRL; and V1/V2 originating from the Vancouver
(Canada) Group. After much testing, the SADCG and MPRG have
adopted the V2 for normal operating in their respective areas.
They also advise that V2 fits the requirements of D.0.C. whereas
AX25 does not. However, AX25 is used in satellite and HF into
the USA, and the TNC kits software will run both protocols.
All this sounds vaguely familiar and if you are confused, you are
not alone!!
However. Packet is a whole new area for the amateur and will
appeal to "nuts and bolts" buffs as well as the operator typWes.
Still interested?? I have nine copies of the information release
of the SADCG - approx 10 A4 poges. Also I hope to have a Vancouver
TNC kit here by the time this is printed. Give me a call.
Russ Pitman VK7ZRP.

Phone 278453.
ICOM|

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