COHERENT C.W. NEWSLETTE-R:@@ W_ - - 0@ Compiled by G31RM Issue number 21 March 1993 Publicity The notes I wrote for the DataComrns column in RadCom appeared in the January issue and resulted in seven enquiries. I send a copy of the CST articles, the list of data sheets we have available'and copies of the last two issues of the Newsletter to all who enquire. So far I have had two acknowidscigments which, to say the least, is a little disappointing. Both of these have asked to be kept on the list of interested amateurs. In the past I have continued to send Newsletters to all who enquire but have now decided not to do so. Each set of sheets I send costs about 21 to copy and post. Those enquirers who send contributions do, of course, continue to receive the Newsletters. Nils Schiffhauer DKBOK publishes an amateur radio handbook in German each year and has asked me to write an article on Coherent CW for the next issue. Unfortunately he did not say how long he would like the article to be. I have written one which will run to a couple of pages and have sent it to him. If he wants it to be longer or shorter he will have to say so. Tests There has not been much response to my thursday evening transmissions. There doesn't seem to be much point in continuing for the time being so long as all members know that I have CCW up and running on all the h.f. bands and can arrange to be active at all reasonable times should anyone want to try for a contact. I have worked Peter SM6FPC on several occasions on both forty and twenty metres with very good copy Information sheets The local library has now installed two new photocopiers using the new style ten pence pieces. One of the machines is a full colour copier but is somewhat expensive to use, the other is very much like the old machine I used and still does A3 copies at ten pence a time. All this means that I do not have to increase the charge for photocopies of data sheets. Fortunately it also means that I can still print the Newsletters in the way I have always done and at the same cost. Commercial transceivers The idea of compiling a list of fully synthesized transceivers seems to have fallen through with the A.R.R.L. failing to do anything. All we can do now is to try and compile our own list. I have proved that the Kenwood TS450 may be suitable for CCW as it stands, it almost certainly will be if the optional TCXO is used and is very easy to modify to stabilize with an external standard. Although I feel sure other Kenwood products will be the same I have no details I believe that SM6FPC was using a transceiver during our contacts which was not fully synthesized and which I think drifted very slightly, a matter of a few hertz. One contact was well over half-an-hour with very little retuning. It therefore looks as though many more commercial transceivers can be used without extra stabilization if a long warm-up period is allowed and the possible inconvenience of a little retuning is accepted. So do not be deterred from trying anything you may have which appears to be stable. I know a lot of emphasis was laid on stability when Ray Petit wrote his original articles but modern transceivers are far more stable than those that were then available and the need for extreme measures may not now be quite as necessary as it was. Clover This could be the last time that I have much to say about CLOVER as, apart from that fact that it was invented by Ray Petit and follows his work on Coherent CW, it has little to do with Coherent CW, A few remarks may follow in future issues but now that PC-Clover is here and working there is really no justification for me to continue. I received my board in December and was very disappointed to find that it did not work - not I hasten to say had this anything to do with the board or the software. The software refused to load correctly except on one or two very rare occasions and there was no response when I connected the TS450. As everything I was using complied with the requirements laid down for CLOVER I was somewhat baffled. I followed the instructions and wrote to Bill Henry for guidance. His reply was more that helpful but, by the time it arrived, I had decided on an alternative course of action. The machine I had used for some time was an Epson PCAX2 and it had functioned (with the odd problem now and again) with all software and hardware I had tried. Surely it could not be the computer at fault, or could it? I have a very friendly local dealer who makes computers to specification and I asked him to try the board in one of his machines - a 386SX. It worked perfectly so it must be the Epson which was causing the problems. The dealer made me a new machine to specification overnight and I had CLOVER installed and working the next day. So what was the problem with the Epson? The only solution I can think of is that perhaps all the lines to the expansion slots are not connected and CLOVER uses one of the unconnected ones or there is a faulty expansion connector. CLOVER really does all that is claimed for it, the only real problem now is finding stations to work. This situation will improve as more stations realize how good the system is. At present there are well over one hundred stations in the States and several others around the world. The list I have at the moment has at least twelve stations outside the States listed but there will be more. The ZS5S API-ink station has a file of active stations but I have been unable to connect to this recently to obtain an up-to-date listing. I have a note on some of the European bulletin boards asking CLOVER operators to contact me. My own tally so far is four stations worked in three countries with all three countries confirmed - not a lot but it is a start. CLOVER is without doubt the best data svstem on the market and the speed at which it transfers data in the block mode has to be seen to be believed. Stabilized oscillators There was an article in the BARTG Datacom Summer 1992 issue dealing with the LM3911 temperature control i.c. which makes interesting reading if you are thinking of making a crystal oven. Correspondence Brian G3MBN has made a standard using Drortwich and reports the same strange variations in frequency that I discovered and mentioned in the last two issues. He is also making up a circuit board for a keyboard. Ernst DJ7HS tried a direct conversion receiver on forty metres but was disappointed with the results and now has an old SB100 which has all the oscillators easily accessible which he hopes to stabilize. I have an article available describing a very simple inductance meter called "All about Henry" which Ernst has now improved and published in the magazine CC-DL no. 11/92. Stewart GM3YCG is one of the new members who has joined us following the RadCom note and hopes to make a start by building the Bill de Cade oscillator. Kurt OEIKYB was one of the earlier members to join us but had to undergo a serious operation a couple of years ago and is still having treatment. His activities are therefore somewhat restricted but he continues to try to improve his CCW equipment. I am sure we all wish him the very best for the future. Bernhard DF3CT is bu 'ilding another frequency standard using the 12.8 MHz TCXO from a mobile telephone and wants to compare this with the VE30BE circuit. I have one or two similar oscillators and have wondered how they work and am therefore waiting to hear the results of Bernhard's efforts. Cliff W6HDO has drawn my attention to an article in the January issue of QST dealing with high performance direct conversion receivers. I have read the article and it proved to be very interesting even though I am no longer trying to build these circuits. The TS450 does all that I need and, no doubt, does it better than anything I am likely to build. Future projects I have been wondering what to do now that my building season is approaching. During the summer months the conservatory (a corner of which I use as a workshop) becomes more habitable. The Petit filter has remaincled very much the same ever since the original articles were published though I did build a circuit which reduced the number of devices quite considerably. I wonder if I can make it even simpler. For example, there are now ready made sample and hold devices which may possibly be used. There really is no reason why the standard, filter and keyer should not all be on one board is another suggestion. 2 Briarwood Avenue Bury St. Edmunds Suffolk IP33 3QF England 73 for now