COHERENT C.W. NEWSLETTER:@ X_-V - Compiled by G31RM Issue number 29 September 1994 Postage stamps Stamps this time are from a series illustrating events which take place in the U.K. each year. Publicity My article submitted to the R.S.G.B. is now being considered by the technical committee and, as the editor considers it a "very interesting article", it looks as though it may get published. Sigma-delta interface As I am little short of anything interesting to write this time and as there has been very little correspondence arriving, I am going to include a circuit diagram which may be useful. This is on the reverse and was sent to me by Dave Race W2RV. The circuit is used to integrate the sigma-delta board and a Kenwood TS-850S. It should also work with the TS-450S. Dave says in his letter....... You will note that I used two boxes. One box houses the sigma-delta board and opto-isolators while the other is used as a remote control box. This allows me to place a small control box on my desk just in front of my transceiver while keeping the bulk of the wires out of the way at the other box. I used the +8v d.c. g 10ma transceiver microphone voltage to activate a relay that controls the 9v d.c. battery voltage to the sigma-delta board. In addition to the isolation feature, the relay disconnects sigma-delta power if I forget to turn the power off at the remote control box and then turn off the TS-850S. I placed an audio transformer between the TS-850S ACC2 audio output and sigma-delta audio input. This provides d.c. isolation between the radio and the computer (you'll note that the sigma-delta board is grounded to the computer via the data output connection). I installed reverse voltage diodes across the 4N35 LED's for two reasons. One was to provide a constant load to the RS-232 line and the other was to prevent the LED from breaking down when reverse biased. Since I use the CW sidetone oscillator to zero beat the received signal, I can press the remote control's CW switch to perform that function. The UP/DOWN switches perform the obvious. As the normal operation of the TS-850 in CW mode is LSB, for COHERENT to increase the pitch of the audio tone, the transceiver must be moved down in frequency. When I tried to use microswitches in a defunct computer mouse for the UP/ DOWN controls I was unable to make the transceiver tune in single steps and operation was very erratic as I mentioned last time so that I had to add R-S flip-flops. Dave uses ordinary push switches. W2RV tests Dave started test transmissions on the 9th and 10th July. From 14OOz to 1430z on 10.115 and from 1430z to 15OOz on 14.061. He has tried to repeat this each weekend. Transmissions consist of 30 seconds of framing dots followed by calls to me for 30 seconds for the first minute. Then follows a listening period of 1 minute before the procedure repeats. The calls are addressed to me in the hope of avoiding non-coherent stations calling but any coherent station hearing Dave may, of course, call him. I think I may have heard something once or twice but cannot be sure. The only other report I have received is from DJ7HS who has not heard any signals. If you cannot listen coherently you can always try to receive W2RV as normal c.w. New members Three new members have joined us recently - Ludwig Hallinger DL2MG, Dott. Ing. Franco Schellenbaum 11 -1 0025 and Heinz Schnait OE5EEP. I will include a full mailing list in the next issue. JVFAX Although this is not CCW I am including this note in case anyone has the JVFAX program (freeware) from DK8JV. Ul 1 in the circuit diagram is shown as 74LS157 - it should be 74LS158 - or you will get negative pictures! The latest version is 7.0 and I can let anyone interested have a copy of the disc. 2 Briarwood Avenue, Bury Saint Edmunds, Suffolk IP33 3QF, United Kingdom 73