Vr __ 011111110@1111@ Compiled by G3HZM Issue number 28 June 1994 -I- Postage stamps It is obvious that the stamps this time are to commemorate the opening of the Channel Tunnel by H.M. The Queen and President Mitterrand on the 6th May. Publicity My article submitted to Practical Wireless has been rejected as too technical. In my early days in radio there was a series of magazines all with the word "Practical" in the title which were known as Camm's Comics after the editor - it looks as though this still applies! However, I have another article with the R.S.G.B. which is being considered. Commercial transceivers It appears that some members are having thoughts on the suitability of their transceivers for use with COHERENT. The old hardware filter required high stability oscillators for both the transceiver and the filter. DDS was not known then but suff icientiy stable transceivers were built. So I think it is worthwhile trying all reasonably modern transceivers even if a long warm-up time is needed. They should at least be much more stable than the commercial models we had available in 1975. The ICOM 728 DL1BEY has written saying that he has an ICOM 728 but it only tunes in 10 Hz steps and there is no provision for the up/down frequency corrections available in COHERENT. As there are, no doubt, other transceivers in use which only tune in 10 Hz steps it would appear to be a good idea if all transmissions are on an exact 10 Hz step and frequencies such as 7040.007 are avoided. All this, of course, assumes sufficient stability and accuracy of frequency. It may then be possible for two stations to maintain contact if only one of them is able to make use of the autotune feature in COHERENT - if neither can use autotune it may still be possible to have a contact if both stations are suff iciently stable. Everything is worth trying. The Kenwood TS450 and TS850 Some time ago Bill de Cade drew my attention to the fact that setting the frequency with the tuning knob does not guarantee that the frequency is what the dial says. The actual frequency may be a few hertz above or below the stated frequency. The way to avoid this inaccuracy is to enter the frequency into a memory and then transfer the frequency to the v.f.o. with the M/V button. Under no circumstances use a memory channel with the autotune feature. If you do the tuning pulses will change channels! There have been four methods suggested for connectingthe up/down linesfrom COHERENT into the TS450. If the microphone connector is opened extra wires can be soldered to the pins. This is not very neat. The second method if you don't use the microphone much is to get another connector and just use the two wires needed. I made the connections to the up/down buttons on an MC-80 microphone. By far the neatest method comes from Henry ZS1AAZ. If you remove the top and bottom covers of the TS450, you will see that the front panel can tilt forward a little. There are four screws to be loosened but not removed. The two lines from the microphone socket go to connector 3 on the digital board which is directly behind the front panel. It is easy to attach two wires to the wires going to this connector and to lead them to the ACC2 socket where pins 1 and 6 are unused and easy to get to. This brings all the connections needed for COHERENT out to the ACC2 socket. Operating frequencies I have mentioned this subject before and a recent letter from Theo DL1 EBE has prompted me to raise the question again. We must decide which band/s and which frequencies are to be used otherwise no- one will get anywhere just calling CO CCW. For some time now I have been using 10 Mhz and it looks to me to be one of the best bands for our purpose. The DX News Sheet lists stations every week which have been contacted on various bands and most continents are represented on 10 MHz. It looks to be a cross between forty and twenty which is what one would expect and it is fairly quiet apart from a few digital stations. The bottom few Khz are most popular for DX contacts but there are spaces further up the band. I would think that somewhere in the bottom 30 Khz would be very suitable for our purpose. One of the quietest frequencies at my location seems to be 10. 1 15 Mhz. Alternatively could I have other suggestions and I will pick the most popular suggestion and we can then make this the main CCW frequency. Please let me have your comments and, if you can operate, let me have the times which you would find most suitable. I will include these times in future Newsletters. This seems to me to be the only way to get some activity. There are quite a few COHERENT boards and programs around so some attempt at contacts must be made. COHERENT stations The following is the latest list I have of licensed amateurs who have the progam and/or sigma-delta board: DF1AE DF2KB DJ2ZV DJ7HS DJ7PO DK3BU DK4BY DKSOK DL1BEY DL2AD DL1BT DL2FI DL6KL EA2SN G3CCH G31RM G3XHQ H69DDO lK2HKS KOLR KC7WW K041DY KE6SO OE6WTD VE21Q VE3GF VE30XX W1AEL W2RV W6HDO WA4TNV ZS 1 AAZ Hans Knebel and Max Carter also have the program. COHERENT V2.4 The latest version of the program is 2.4 which is being tested by Max Carter (of Lowdown fame) and KE6SO. This new version can use BPSK in addition to CCW. This has an advantage over CCW for the same power - more details when available. Bill intends to put a BPSK medfer beacon on the air soon around 1695 Khz running 100 milliwatts. Dave W2RV Dave has recently obtains the board and program and has joined us. In a letter dated the 27th May he tells me that he tuned his TS850S to 18.101 (the frequency of the VE30XX beacon) and could hear it. The s-d board was connected in the approved way to the ACC2 connector on the transceiver. Using the sidetone oscillator to zero-beat failed to receive the beacon coherently. On the 26th May he finally managed to copy for about ten seconds at a time before the signal faded below the noise level. The following is a copy of part of the letter: I have used COHERENT to verify the frequency of the sidetone oscillator. I first used the TS85OS's TUNE mode to zero-beat WWV on 15 Mhz, then changed to CW mode. This generated an Boo Hz audio tone. Pressing the CW key found the carrier to be zero-beat with the CW sidetone signal. I then ran COHERENT. The carrier beat frequency displayed as 800.x Hz. Tuning the TS850S in 1 Hz steps using the UP/DWN microphone buttons produced 1 Hz step changes in COHERENT's frequency display. When I stepped to 795 or 805 Hz COHERENT lost lock; as it should. I plan on using the 800 Hz sidetone to zero-beat CCW signals that I can hear. Then I should be able to run COHERENT and be within a cycle or two. Another possible way, that I have not explored, is to use FFT first. By taking 4096 samples and using a band of 795 to 805 Hz you should be able to pick out the CCW signal. Then tune your receiver until the signal is close to 800 Hz. Computer oscillators Dave has also checked his computer oscillator over a period of 24 hours as mentioned in the COHERENT data sheets and found that it gained 23 seconds! This indicates that the 1.193180 Mhz oscillator is about 320 Hz too high. As I understand it (and Bill will correct me if I am wrong) this does not matter too much as long as only the COHERENT program is used - it becomes significant if attempts are made to contact stations using the hardware filter. Kenwood up/down buttons I do not like having to pick up the microphone every time I want go use these buttons and, what is more, I hardly ever use the microphone anyway. So I decided it would be an idea to make something with just the two buttons which would sit on the table. The ideal answer seemed to be a computer mouse with everything removed but the two micro switches. However, this didn't work as the micro switches have contact bounce which the Kenwood buttons don't. The Kenwood buttons seem to be very spongy so I suspect they may be some form of membrane switch. Adding a couple of S-R flip-flops (CD401 1) driving two igfets solved the problem. There is a convenient source of d.c. on the microphone connector at pin 5 which can be used to power the CD401 1. I found it much easier to remove all components from the mouse circuit board and make a duplicate from a piece of Veroboard using the original board as a template for drilling the holes for mounting and for the micro switches. 73 de G31RM 2 Briarwood Avenue, Bury St. Edmunds, Suffolk IP33 3QF, England