COHERENT CW    
NEWSLETTER.

Compiled
by
G3IRM



issue number 13



August 1991



Where are we going?
Perhaps I should start this with 'Where am I going?'
It is now over two years ago that Bert G3RH1
suggested that we should try to give Coherent CW
another go. It has always appealed to me as
something out of the ordinary that should give
considerable benefits over normal CW if only
enough stations could be encouraged to have a try.
We all know the problems that the system has but
with modern devices it should be a lot easier than
it used to be. At least that is what we thought two
years ago. The first thing to do was to try for some
publicity and one or two magazines helped by
printing short notes. The second thing to do was to
collect as much useful information as we could and
make this available to those who were interested.
This I have done and now have about forty
information sheets available, all of which have
something of interest for those hoping to build
equipment. Before including an item in the list I tried
to make sure that it would work and, in many cases
built some or all of the circuit for this reason. This
exercise revealed a few mistakes in some of the
published articles and these were corrected. As a
result I now have a collection of boards for various
sections of a CCW station but I do not have a
complete station! So, a week or two ago I got out
the box of CCW bits and pieces to see what I could
find. There were one or two crystal oven oscillators,
a Droitwich4ocked standard, three different versions
of the CCW filter and a few bits of O. equipment
including the odd synthesizer. There were also a
few other miscellaneous items such as keyers and
test generators. There was no doubt that the
Droitwich standard was the one to use. I put the
power on and there was a stable 4 MHz t.t.l. level
output. Hooking this into the original version (the
W6NEY one) of the filter and feeding in 100 msec.
dots again produced the right output. The G4VSO
O. synthesizer came next and this was altered to
cover from 6 MHz up as far as I could make it go
which proved to be about 6.15 MHz covering a wide
enough range of frequencies for all CW, CCW and



data frequencies normally in use. The problem with
this design is setting the frequency. Bob Carter used
a b.c.d switch but this was not enough to cover the
range I now had available and more than one switch
would be needed. So I decided on a new digital
board. In fact, two boards almost alike are needed
for the r.f. and audio synthesizers. I have a
Kenwood DFC230 and looking at the diagram
revealed that there is a digital encoder which,
together with a few cheap cmos devices, can be
made to pulse up/down counters which will set the
inputs to either synthesizer using binary. I copied
one of these and it tuned the audio synthesizer
using Colin Horrabin's e.p.l.d. over the required
range. In my version this now gives a small but
adequate variation of frequency in 0.5 Hz steps
above and below the center frequency of, in my
case, 500 Hz. The controller for the r.f. synthesizer
is now being built to the same pattern. An extra
device or two will add a digital readout of frequency.
When this is completed I will only have the O.
circuits to think about. In the box I also found the
main board for the White Rose receiver - more
about this in a moment for the benefit of overseas
members. In a recent issue of RadCom is a short
description of the White Rose transmitter - again
more in a moment. These two boards can be
combined into a transceiver for CW (and CCW) and
SSB and includes the various data modes. I have
decided to use this for the r.f. together with another
G4VSO synthesizer adapted to the required
conversion frequencies for 20 and 40 meters as a
start. That's where I am going!
What about everyone else? OEIKYB and G3FIVIW
are both operational in the sense that they have had
contacts transmitting as CCW but receiving as CW.
There is every possibility that they will be writing
and, hopefully, arranging tests. These I assume will
be on 7.030 MHz as we originally suggested though
Kurt is able to use several bands with his converted
Kenwood transceiver, G3RHI has a complete station
but is hoping to try and use an unconverted
Kenwood (after a long warm-up period). It will be


interesting to see if this works satisfactorily.  G3CCH
has, as mentioned last time, carried out some tests.
In the hope that I can get my bits and pieces put
together in the next month or so there will be five
stations who should be able to put out signals and,
we hope, receive some as well. I have been
frantically trying to get on with building which is the
reason that this Newsletter is a little later than usual.
But what do we do when contacts have been
established - we can hardly go on working one
another for ever! At least some contacts should
encourage others who have partly constructed
equipment to get on with the job and add to the
number of CCW stations on the air. Then I really
must try and get some more publicity. I am still
hoping for a transatlantic contact one day.
The While Rose transceiver
I think this deserves a mention if only for the reason
that G3TDZ wh designs it, has sold over 2600
boards for the receiver and over O for the
transmitter. The wide difference in numbers is
accounted for by the fact that the receiver was
described in RadCorn for February 1990 and the
transmitter did not come along until June 1991.
The receiver is a well-designed direct conversion
circuit on 6 MHz with plug-in converters for the
desired bands (remember the HRO and its plug-in
coils?). For home builders this has, of course, the
very considerable advantage of simplifying
construction but it does add expense as all the
circuit for the converters has to be duplicated for
each band. Different converter circuits can,
however, be used as required for the various bands,
which in the original design, cover all bands up to
and including two meters. What is more the boards
are some of the cheapest I have ever seen, the
most expensive being the transmitter board at
E3.60. They are excellent boards but do not have
plated-through holes though components can be
soldered to both top and bottom of the boards as
needed to make the through connections. The
existing oscillator circuits can easily be used as
buffers for the r.f. synthesizers used in CCW by
simply omitting one or two components. More
comprehensive notes are included with the
transmitter boards than were given in RadCorn and
details of a four watt amplifier are included. This
uses similar plug-in boards to the converters.
Having to change two boards every time you want
to change band may be a nuisance but it does help
to make the design simpler and more likely to work
than when complicatcd switching is used. The
transmitter if f the phasing type and uses readily



obtainable 1 % resistors and capacitors for the
phase shift networks and will transmit upper or
lower sidebands as required. There are 19 pages if
copies are required. When I have converted the
design to use the two r.f. synthesizers I intend to
use, details of the conversions will also be available.
One interesting point is that the plug-in converters
have many spare pins-and I think these can be used
to change the programming of the conversion
synthesizer to produce the required output when the
boards are inserted to avoiding switching. One nice
point regarding the notes supplied with the boards
is a list of the more hard to find components and
the catalogue numbers of the various firms who can
supply them.
Clover news
Don Graham has sent me a copy of a short article

which appeared in Monitoring Times and the first
pan of Ray Petit's-three-part article in RTTY Journal
has been reprinted in BARTG's Datacom. As this
only appears every three months it could be that
Clover will be fully operational by the time we in the
is

U.K. get to read the final part! So the word getting
around. I applied to the Radio communications
Agency for permission to use Clover and this, much
to my surprise, was granted without having to
answer a whole list of questions. I did send them
the data sheets so far available from HAL'
Communications and these appear to have satisfied
them. So it looks likely that full permission for the
use of Clover will be granted to all U.K. amateurs
when the units are available. I'll follow this up in due
course. I always thought this was the job of the
RSGB but, when I asked them, they told me to write
to the Licensing Authority myself. Permission has
been given for the Clover tests in the States though
I have not yet heard that authorization in any other
country has been obtained.
Operating frequencies
Kurt sent me a list of the frequencies he has been
trying which included the frequencies proposed for
CCW and Clover and those used in the past for
CCW. I have suggested that he concentrates on the
QRP frequencies of 7.030 and 14.030 which we
decided a long time ago would be most suitable as
contacts with non-CCW QRP stations would also be
possible.



73 de G3IRM



2 Briarwood Avenue
Bury St. Edmunds
Suffolk IP33 3OF
England