Compiled by G31RM Issue number 22 June 1993 There have been one or two developments during the past three months which I hope you will find interesting. So let me deal with these first. Cassette tapes I had a letter from Ray Petit about a month ago saying that he had been asked if he had any tape recordings of Coherent CW. After much searching he found four tapes which I now have. I have condensed these so they fit on to two tapes - nothing has been omitted. The first of these is a lecture by W6NEY and plays for about one hour. It was recorded with an audience so there is some background noise but the tape is well worth while. It also includes some recordings of a 100 milliwatt transmission between JA and W6. The second tape has two sets of notes by W3QVC and some recordings of CCW received from VE3DPB. On the second side of this tape are some laboratory tests and alignment notes by Ray Petit. As I rather expect there to be a demand for these tapes I am not sure how to go about distributing them. I will keep one set from which I can make copies so these can be made available on two C90 tapes. There is no need to send blank tapes as I can supply these. The second set I will reserve for borrowers on a first come first served basis. If you ask to borrow the tapes please be prepared to wait for your turn to come around. Tests I had arranged to try some tests with DF3CT at the end of April but there was so much interference that I could not receive his low power signals. I could just hear him as CW but was unable to resolve very much of his CCW. During the tests another station DL1 EBE was calling me and adding CCW to his call. Now I had never heard of DL1 EBE and ignored him for a while as I was trying to receive Bernhard. However, I decided that there may be something in it and asked him to standby. His transmissions were CCW and we had quite a long contact. Theo was using a Kenwood TS830 with no special attempts at additional stabilization though he had allowed a long warm-up period. He will now be trying to add additional stabilization and we hope for further contacts in the future Expedition to the Arctic Circle Paul GOBHA wrote early in April to say that he had applied to be a member of a Combined Services (RAF, RN and Army) expedition to Ellesmere Island on the edge of the Arctic Circle and to say that he had been selected for the short list. The expedition will take place next year and will last for three months. As yet Paul has not heard whether or not he has been selected. The post he applied for was as communications adviser and part of the duties of the selected applicant will be to carry out experiments in some form connected with the duties. Paul has suggested that he would like to try emergency communication under poor conditions and thought of CCW. Until something more definite is known there is very little we can do but, if Paul is selected, there will be a lot we can do to help. What is obvious is that if Paul is successful he would like to have as many stations listening for him as possible. The ideal way is, of course, CCW but listening on a CW receiver would be better than nothing. As there is still some time available I hope to be able to be more definite in the next Newsletter. Information sheets I have collected one or two more articles which may be of interest. The Shrike crystal oven by G4YNM in the April 1993 issue of QEX is another fairly simple oven using a TTL oscillator and a power transistor as heater with a thermistor as heat sensor. (3 pages) There was another article about the synchronous oscillator by the inventor Vasil Uzunoglu in the May 1993 issue of Electronic Engineering. The oscillator is a competitor to the PILL in frequency tracking applications and is much easier to build and use. (4 pages) Copies of these articles are available if you want them - the local library still charges five pence a page though there are rumours that the price is due to increase in the near future. Change of callsign Bernard Greenall G7CBX is now GOPMN New members DK80K DL1 ESE G71VIBN GM3YCG HB9KAT VK6GRQ The Yaesu 990 Bryan Wells tells me he has one of these and that there is an optional high stability oscillator available so it could be suitable for CCW without much modification. This is the sort of information that we need. If many of these transceivers can be used with little or no modification we should be able to get more people interested. With a determined effort it should be possible for the average constructor to built all equipment needed well within a month. As an example of what can be done I recently put a complete Petit filter together in three days! Commercial transceivers - the beat frequency Some of the newer Kenwood transceivers have a beat frequency oscillator which is programmed when the set is switched on and this frequency is retained in the internal memory. I had problems switching between CW and CCW with mine as the beat frequency range is from 400 to 800 Hz in steps of 50 Hz. I imagine Yaesu are also doing things this way now and the same problems could arise. The W6NEY design used 750 Hz for the input frequency and the original Petit design used, I think, 1000 Hz. The 750 frequency can be used if a suitable frequency is available from the standard - 3000 Hz but 1000 Hz cannot be used as it is outside the range of the transceiver tuning. Kenwood supply the transceiver set for 800 Hz and this is a convenient frequency to use for CW so I decided to try and use the same frequency for CCW so there would be no need to go through the somewhat complicated procedure of switching off and reprogamming the memory every time I wanted to change from CW to CCW - changing from a beat note of 800 to 500 Hz. For a beat note of 800 Hz the frequency to the first mixer of the Petit filter must be 3200 Hz. This is quite easy to produce by using four divide by five stages after the first divide stage of two from an oscillator on 4 Mhz. On the way down the divide chain there is an output of 16 Khz which can have a string of divide by two stages to produce frequencies needed for the keyer and the filter. It only takes three 74HC390 devices to do it all. I am at present modifying my filter to do this which will make changing over from CW to CCW very much easier. Correspondence Together with the tapes from Ray Petit was a letter which included the following remark - "Some of the things I have learned in connection with Clover have good application to CCW as well: I want to try them." Whatever these ideas are they should prove to be very interesting though I do not anticipate anything in the near future as Ray is still making improvements to Clover including a super-robust bad conditions modulation format. Danny Higgins has suggested that DSP could be applied to CCW something I had wondered about myself. Perhaps this is what Ray Petit was hinting at in his letter after aH Clover uses DSP! HB9DDO has got HB9BTL interested in CCW. DL1 ESE says that the 5B4CY beacon on 28 219 is useful for testing a CCW receiver. The Petit filter - phasing It seems to me that the phasing control on the filter is the only awkward part of the design. A mechanical switch is not ideal and I often begin to wonder if I have it set correctly. So why not try and use automatic phasing? As a step in this direction I am replacing the mechanical switch (S1 in the OST articles) with an electronic version. One device (CD4067) can have its common pin taken to U9 and ten of its inputs can be connected to U5. The switching inputs can go to the outputs of a counter so that, as the clock is pulsed, the switch will cycle. Using an up/down counter I think this is an improvement in itself. It will then be necessary to find a way of checking the phase of the incoming signal - some sort of phase detector. I will then have to find a way to make the output of this control the clock of the counter. Anyone got any clever ideas? Clover ,Just a mention to say that contacts are still few and far between mainly due to the fact that there are not a lot of stations active in Europe and, no doubt, we are all listening and calling at different times and on different frequencies. I can however get into the TY1 PS mailbox almost at will so it does prove that contacts should be easy. The Elektor Magazine 8032 computer The May 1991 issue of the magazine included this design and there have been follow-up articles ever since. Has anyone built one of these (apart from me) and, if so, would they like to swap notes? 73 for now 2 Briarwood Avenue, Bury St. Edmunds Suffolk IP33 3QF, England