Coherent CW NEWSLETTER Compiled by G3IRM Issue number 16 February 1992 First test transmissions On the 14th December Kurt OE1KYB made some test transmissions after making arrangements with John G3FMW to listen. John telephoned me and we both heard Kurt - he was 599 + with me. He was also heard by Bert G3RHI at the same strength. Bernhard DF3CT also heard the signals at 599 and was able to resolve them on the CCW filter. He tried to contact Kurt butwith only 300mw X0-TX was not heard. First contacts I have had a letter from Bernhard DF3CT to say that he has had a contact on the 27th December with Kurt OEIKYB. Two more were scheduled for the 30th and 31st. Unfortunately these two contacts failed because Bernhard's XO-TX was not working property. Kurt's signals were reported to be good. Bernhard was using a hand key and has now decided that something better (such as a keyboard) must be substituted. Simple CCW transceiver for 7030 KHz I have been trying to find a suitable design for the simplest possible CCW transceiver and think that I may have something which will prove to be satisfactory. The obvious way to start is to took for a reasonably priced CW transceiver kit and then think how to modify it. I looked through all the kits I could find Including those in Sprat for which boards are available and came to the conclusion that the boards which would suit us best were those from C.M. Howes Communications. The kits are not expensive and Howes are prepared to send them anywhere. The main advantage I could see in the Howes kits is that they are available as separate units which can be linked together from the instructions provided. The three kits needed are: CTX40 QRP CW transmitter CVF40 VFO DcRx SSB/CW communications receiver. Other kits which may be useful are: DCS2 S meter DFD5 digital frequency display CBA2 buffer/counter pre-amp ST2 CW side-tone oscillator ASI-2 external dual bandwidth filter. Of these I have the ST2 and ASI-2 which I thought may prove useful though I have not assembled them. I have not yet assembled the transmitter. I see no reason why the receiver and transmitter should not be used exactly as intended except that the crystal in the transmitter and the vfo in the receiver are omitted as described in the notes which come with the kits. The vfo kit is the oscillator on both transmit and receive. So the only item which needs modifying is the vfo and all that needs to be done is to stabilize ft. There is no reason why the circuit I have used to do this should not be used with other oscillators. The modifications to the vfo kit are simple and are as follows: Omit the whole of the lower half of the diagram which provides switching for the rit. It may be possible to use this to switch the low-pass filter Input from the stabilizer to the tuning diode but there seems to be an easier way of doing this as will be described later. Replace R7 and R10 with small rf chokes 0 used 1 mH), substitute a 1 0 pf capacitor for C3 and connect in C4. Short out the connections for C 1 3. Connect the link between C3 and CV1 b. I don't like using power diodes as tuning diodes so I replaced D1 with a B13809. Pin F is now the voltage control terminal. A trimmer capacitor can be added as ft is easier to adjust than the coil slug. The circuit for the stabilizer was taken from an early issue of Woodson's CCW Newsletters which described the station used by Andrew MacCaskey WA7ZVC/WA4MTP for the first recorded CCW contact with Ray Petit in January 1975. The version I have built seems to work satisfactorily but I would like someone ease to have a go and see If they can improve ft. That is why I am giving the circuit I have used in this issue of the Newsletter. If you would like a full circuit diagram please ask for one. The output from the Howes vfo is insufficient to drive the stabilizer so a small amplifier has been added. It is quite likely that the CBA2 pre-amplifier would be suitable but I haven't tried it. A Schmidtt trigger Is used to square up the vfo signal. A D flip-flop acts as a digital mixer to produce output 200 KHz ñ drift. The output goes to a phase detector (the other input is 10 KHz) and low-pa filter. The third harmonic is used to produce transmit frequency of 7030 KHz. The vfo can tuned to 7010 and 7050 without any other changes but I have found that I have to monitor the output on both transmit and receive frequencies on another receiver to be sure the frequencies are correct for the time being I have only 7030 KHz. I have been unable to use 7020 or 7040 presently because the 10 KHz square wave does not have even harmonics. Whatever frequencies you chose to use for the phase detectors ensure that they are square waves with a 50:50 mark/ space ratio. The 10 KHz also goes to a second D type flip-flop and a second phase detector with an input of 500 Hz to provide an offset for the receiver. If your CCW requires I KHz the input to the phase detector have to be I KHz. A second low-pass fitter follow The outputs of the two filters go to digital switch for transmit and receive and then to terminal F o the Howes vfo board. The switches are contrail by a couple of Schmitt triggers from t send/receive line. The devices used are 74HC13 74HC74, 74HC86 and CD4066. The transistor is 2N2222 but many others can be substituted. The divider chain I have uses a 74HC390 followed by 74HC1 93 and a second 74HC390. I hope that some of you will attempt something on these lines a that you may be able to suggest some simple wa that other frequencies can be obtained preferably without the need to monitor the oscillator output. Change of address - G3S81 Colin who supplies our EPLIDs is now at: 17 Denbury Avenue Stockton Heath Warrington WA4 2BL Elektor standard - Deutschlandfunk 153 KHz Ernst DJ7HS has obtained a kit for this standard and has built ft satisfactorily. He can supply the address If anyone is interested. Audio spectrum analyzer Bill's article has now appeared in QST and he has boards and program disc available. Some of the devices used are hard to find in U.K. catalogues but all can be found in the ITT catalogue. Only this week Bill has suggested alternative circuits but these will not fit the board and will look a little untidy so ft's better to get the correct ones If possible. Clover I have received a four page update from Bill Henry on the progress being made with the Clover project. The version to fit inside a PC is called PC-CLOVER and was to have a $995-00 introductory price, I can make copies of the update for anyone who may be interested. C.M. Howes Communications Here are the details of the kits I mentioned above; DcRx receiver 215.90 CTX40 transmitter El 4.80 CVF40 E10.90.These are kit prices, assembled boards are more expensive. Postage and packing Is E1.20 per order.Overseas prices are the same but, if you require airmail you must add E2.50 per kit. The address Is- C.M. Howes Communications Eydon Daventry Northants. NN11 6FT England