DID TEURS

Marc I. Leavey, M.D. WA3AJR
4006 Win/ee Road
Randallstown MO 21133
April may be the month lor
fools, but the biggest fool of all
around here would be me if Ilgnored
your leiters and questions.
So this month let's turn to
the mailbag.
Some lime back, I mentioned
thai Dave l undquist WA2UWK
was in need of Information for
the Lenkurt 25-A demodulator
thai he had acquired. Indications
are that Dave got all the information
that he asked for, and
more. With the help of Sheldon
Dattcn WA 4MZZ and Rich strenlow
KAIICSG , and who knows
how many others, both Dave
and I now have a bit more information
on the Lenkurt.
This unit was (is?) in use by
various wire servic es to distribute
signals on slow-speed
teleprinter channels. It is configured
to allow lone pairs hom
around 300 Hz to 7 kHz, center
frequency, to be used. Thus, several
different signals could
share the same line, using different
audio tone frequencies,
with the differentiation made by
the receive filter in the Lenkurt
unit. Hopefully, Dave will be able
to adapt the thing to amateur
RnY. Good luck, Dave!
There seems to be Quite a bit
of interest In connecting various
teleprinters to low-level TTL circuits.
A1C Randy L Bray, stationed
at Bergstrom AFB, Texas,
writes that he tried to drive a
compact Model 26-KSR retety~
from a demodulator yielding
a TTL-level output. A slight
lack of drive there, no? Well, be­
Ing the industrious serviceman
that he is, Randy went on to devise
the circuit shown in Fig. 1.
Th is uses a matched pair of
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20 73 Magazine· April, 1981
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Fig.f. rrt-toooter conversion.
4N25 cctcrectetcrs to convert
the TTL level to a pl us-minus s !xvolt
swing, suitable for driving
the polar Input of his printer. To
take care of occasional upsidedown
stations, he uses one section
of a 7404 TTL hex inverter,
which may be switched in to up.
side-up the upside-down renegade.
Looks like a nice piece of
work, Randy.
Along the lines of Interfacing,
Reginald Theriault, from Rimouski,
Quebec, is cu rrently using a
Mod el 2&ASR Teletype and a
HAL ST-5 demodulator on 6().
wpm, 5-level RnY. He has recently
come by a video terminal
and wonders how to use it on
RnY. Reg, the terminal you describe
Is set up, as are most termtnets,
to use the eight·bit
ASCII code, described In RnY
Loop a few months back. As a
se rial RS·232 output Is available,
the physical connection of t he
terminal to a demodulator such
as the ST-5 should not be too
hard. However, you will be running
ASCII , not BaudoUMurray
ecce. Although this is legal in
the United States, I am not sure
about Canada's viewpoint. Further,
most RnYers are stili using
Murray/Baudot (try to keep
things fair !). There are two main
ways to co nvert to five-level
code, If you want to: a standalone
hardware conversion or a
computer.
The hardware conversion
would use a UART to input the
serial data and convert It to parallel,
a ROM and associated
chips to look up and change
code groups, and another UART
to ou tput the transformed code,
perhaps at a di fferent speed.
This method is cheap, it works,
and several schemes have been
published in 73 through the
years.
~
A computer may be programmed
to do the same conversion,
from one code to another
and back again, and will do it
just as well asa simple board, at
many times the cost. But what
you gain is some intelligence In
the conversion. The computer
can provide features such as
message buffers, au tomatic
identif iers, and other bells and
whistles which make operating
a real pleasure. Now, I don't
think I would run out and buy a
computer just to run RnY, but
once you have one you won't believe
how many new uses you
can find.
This leads us to another Quest
ion: wh ich computer? Wel l,
from the RnY point 01 view, I
really don't think that matters
much. My biases run toward the
6800 family, but that is because I
have one and have written Quite
a bit of software for it. The
TRS-80, by Radio Shack, is clearly
one of the most popular microcomputers
on the market,
spawning accessory suppliers
and even whole magazines (have
you tried 80 Microcomputing
yet?). A typical Question comes
from John. T. Gubernard K2LSX,
of Bergenfield, New Jersey, who
writes that he has a TRS-80 and
Is looking for ways to get on the
air with it.
Guess what else the mail
brought? One of our 73 aovertteera,
Vic Frump K8EXJ, passes
along information about his Bit·
Byt er RTTY system for th e
TRS-80. This system is designed
for either a Level I or l evel II
computer and has Quite a list of
features, including split-screen
operation, with received intermalion
scrolled in the bottom
two-thirds of the screen and the
transmit buffer in the top third,
automatic AnY and CW identification,
single-key ca, RY, or
QBF, and 60· or t ee-wpm operanon.
The unit keys the loop, so
interfacing to most systems
should be straightforward. lnterested?
Drop Vic a line at UHF
Sales & Service Co., Route 1,
Box 52A, Evans WV 25241 . Be
sure to m'ention RTTY Loop
when you write, OK?
Pic tures on RnY is always a
good topic, but, unfortunately,
one which has caused quita a bit
of co ncern in these pages In
months past. As I write this (in
January), there still is no word
on the ongoing saga of Teleprinter
Art, ltd. There are pictures
out there, however, and
you don't have to pay for them!
Russ Lawson K1MOU drops me
a note that several active hams
have reams of pictures they will
gladly send to anyone, over the
air. Ken WA4MNT, in St. James
City, Florida, says that he has
Quite a few , and W. E. Symons
K41H passes along a similar li st
as long as your arm.
Most letters I get are Questions
or req uests for this and
that bit of information. I would
like to acknowledge one this
month that was just a nice note.
I can remember back a few
years, when I was an intern, how
tight my time was and how precious
every spare moment became.
This sc hedule only gets
worse th e further into the system
you go, t hrough residency
and Fellowship. That is why this
note, from Joseph R. salvatore,
M.D., now a Fellow at Roger Williams
General Hospital in Providence,
Rhode Island, means so
much. Joe was one of my interns
a few years ago, and I lost track
01 him when he left the area to
further his education. I don't
know wh at his callsign is now,
but I am sure that he does not
have much time to operate.
Thanks for reading the maga·
zine , Joe, and best of tuck.
Our sister publication, Kilobaud
Microcomputing, has been
giving Quite a bit of space to
communicating over telephone
lines. These Computer Bulletin
Board Systems (CBBS) now form
a viable means of getting Intermat
lon across the country without
worrying about propagation
conditions. Users 01 6800 svstems
might be interested in an
article in the February, 1981 , tssue
which details the method I
use to hook up to the CBBS locally.
By the way, if you want to
leave me a message, you might
try the Baltimore Micro·Mail Service,
at (301r655-0393, calling
only between the hours of 10 am
and 10 pm, eastern time, or the
Prodigy system, at (301 r337·
8825, available 24 hours a day.
Both of these systems are ring.
back, CP/M·based computers.
To access, call the number, let
the phone ring once, then hang
up and dial again. The computer
will answer when you ca ll back
'0.
Going to look at another piece
of equipment next month. What
Is it? You may not think you
need it, but once you 've bought
one you wouldn't be without
It. Curious? Don't miss next
month's RnY Loop!