COHERENT CW@@
               NEWSLETTER@. @



Compiled

by
G31RM



Issue number 12



June 1991



Publicity
Bert G3RHI had a short article on CCW printed in
the current issue of BARTG's magazine Datacorn
with little success. However, as I write this I have
had a call from GOOKX who read the article.
There were also some very complimentary remarks
about Clover in a letter in the May issue of QEX.
As a result of my remarks last time regarding those
members who have not reported progress recently,
only three replies have been received - all others
have been deleted from the list of members. I
suppose most of them only enquired out of curiosity
and decided n ot to follow up the project.



Clover news
Ray Petit had a great time showing Clover at Dayton
and Stephan HB9DDO met him there. The units will
be made by Bill Henry's HAL Communications and
it was on this stand that Ray was demonstrating.
With an organization as well-known as HAL taking
part in the project there is every prospect of a good
launch for the new system. Ray has now sent me a
copy of the specifications for the t.n.c. If anyone
would like a copy please ask. It is hoped that the
first full scale testing will start towards the end of the
summer. Jack ZF1 HJ and I are on the list for some
of the first units available and will be taking part in
the tests. Ray is looking for volunteers from
Australia/ New Zealand, Hawaii, Europe and Asia to
take part in the tests. It looks as though Clover will
operate in very much the same way as Amtor so far
as the operator is concerned with just an RS232
connection between the computer and the t.n.c. and
the usual connections between the t.n.c. and the
transceiver., I was pleased to see that Ray appears
to have relaxed the stability requirements from what
I originally understood they would be and the
transceiver must now be stable within 10 Hz of the
net frequency. This, I imagine, will make a lot of
commercial transceivers suitable and so avoid what
I thought would be one of the problems, namely,
getting the operators to build stable transceivers. I'll
keep you informed.



More of Bert's comments
With my biblical three score years and ten in sight
and the chance of DXCC on CCW more than
remote I looked at my almost complete CCW station
with some misgivings much as I have enjoyed
building ft and learning from doing so. For some
months I have used my VE30BE keyboard and my
G3SBI keyer to produce CW to CCW standards and
put them on the air usually at faster than 12 wpm. I
think the CW standard attracts attention. My
keyboard and keyer require 5 Khz and 1 Khz inputs
to function on CCW timings. Starting with a 4 MHz
crystal in a homebrewed oven followed by a 5 MHz
commercial unit cheaply acquired I finally plumped
for the Droitwich standard (data sheet 14) and
dividers from sheet 23. The frequency standard
worked and gave me a feeling of achievement in
meeting professional standards. I am now going to
add a 50 Hz output to drive a clock from Droftwich.
This should equal MSF timekeeping standards with
the advantage that, separated from Droftwich, it
could be run from 50 Hz mains albeit with less
accuracy. My CCW project, except for the 10 Hz
filter, is put to good everyday use.



Comments from DJ7HS
Ernst has now completed a 40 metre transceiver, a
frequency standard and the CCW filter but reports
that he could not get-an oven from Fair Radio Sales.
It looks as though they have sold out. He makes a
couple of remarks stating that,-although he is quite
enthusiastic about CCW, it is only an enhanced form
of CW and needs a human operator (which can be
fun).
1.     I do not like the idea of my PC talking to
someone else's PC.
2.     To gain an advantage from CCW almost certainly
indicates low power operation. There are more
sophisticated formats such as spread spectrum and
frequency hopping but these are a little beyond the
capabilities of the average amateur.
He then asks ' How about a form of coherent
RTTY?'

After looking through various circuits I decided to
try the KH6CP (number 25 in my list). I have always
liked the Plessey SL6440 as a mixer and used this
in place of the NE602. As this requires a centre-
tapped output coil to allow the power to be applied
I added a small I - 1: 1 audio transformer to feed
into the differential amplifier. Other than this the
circuit was very much as the original but I used the
G4VSO synthesiser. Everyone says that direct
conversion receivers are microphonic and they are
subject to hum pickup. The whole circuit was very
firmly mounted using my usual method of cabinet
manufacture (built like a battleship) and this cured
the microphony. The hum seemed to be present no
matter what I did until I moved the power supply
well away from the circuit board. When it was over
a metre away the hum went away! The answer
would therefore appear to be to make the power
supply in a separate cabinet and put this at the
other end of the bench. One other problem was
gain. There was far too much of ft and this, no
doubt, contributed to the hum problem. Almost
every station blocked the receiver and produced a
poor note due to the excessive clipping which the
original circuit was using. By reducing the feedback
resistors in the differential amplifier, the audio filter
and the audio amplifier a very good T9 note was
produced from the signal generator and gain was
still more than adequate. To get a better match to
the headphones or loud speaker I added an LM386
with a gain of one. The output from the original
audio amplifier is adequate for driving the Petit filter.
The transmitter is almost the same as the original
but with the tuning components suitably altered and
the r.f. output is about 1.5 watts - not a lot but
enough for a start.



The high precision standard - item 41

John G3CCH together with a friend G4EQD have
adapted the standard for U.K. television frequencies.
I have a block diagram of the divider chain used if
anyone else is interested. The pickup loop used was
about four turns of wire wound on the core of the
line output transformer using p.t.f.e. covered wire as
far away from the e.4'1.,. as possible. Flower for
the divider chain came from the television power
supply and the whole unit is screened in a tobacco
tin on the back of the television. John has also
carried out some interesting experiments by leaving
his 100 mW transmitter running at home sending
dots only. He then went to the local radio club wfth
a receiver and found it extremely difficult to receive



I I-         , , - " , q- - - - -III 10.1 I@j " - - I- 0 V 'Iacl V a @,

most marked. John described it as a "chalk and
cheese" sftutation. Which is just as it should be.



From here and there

G3CCH queries the version of the filter which uses
the e.p.l.d's. from Colin. Most of the op-amps have
been replaced by Texas devices in the TIL series.
John, among others has mentioned that he cannot
find anyone in the U.K. advertising the ones
specified. I see no reason why others such as the
07* and 08* series should not be used in place of
the 09* series which I used. If anyone has problems
with these please let me know. John's 100 mW
transmitter has worked into Dorset and Salop from
South Humberside. Reports were not exactly
wonderful but better reports are expected when
CCW is available at both ends.
G3FMW John keeps in regular touch over the
telephone and is making steady progress though I
still think he is doing ft the hard way having built the
original circuits fifteen years ago and now trying to
adapt them. I know the problem as I have built
things in the past only to find that before I have
completed them there are better ways of going
about ft. It is difficult to abandon things which are
nearly complete and start again.
G3JPP Ted is due to retire in 1992 and hopes to
have more time available for construction. Those of
us who have retired tend to forget that there are
other poor souls who have to go to work and have
only a restricted, amount of time available for their
hobbies. Hopefully by the time Ted can join us we
will have a few stations active.
OE1 KYB Kurt has almost finished his conversion of
the TS940S being held up when I last heard for a
74HC4059. I now have all his diagrams and board
layouts available for anyone else who may like to
attempt such a major conversion.
OK3EW Like some others Juro is turning his
attention to Clover - perhaps he will be the first in
Eastern Europe to join in.
W6HDO Just after I had posted the last issue I
received a note from Cliff to say that his beacon F- --'
been destroyed by             and is now off the air.
He hopes to be able to modify it before putting ft
into use again.
Y23VH Lutz tells me that, following the reunification
of Germany the Y calls will disappear and may be
replaced by DL1.



73 for now de G31RM