II.. - . . ..Co@@.@ NT:C.WV: I------ 1. .. ....... I., I I..I... @ I..... . I - I . . . NEWSLETFER' I....".., - .. ...... . -1-....,.-.-.. I I ...... I Compiled by G31RM Issue number 15 December 1991 New member DJ7PO Joe Ruschmann, Offenburg New callsign VE30BE is now VE21Q Correction Cliff W6HDO has drawn my attention to a mistake in the last issue - Ray's frequency for Clover experiments is 1 0 1 00 1 00 Hz otherwise he would be operating outside the band! Newsletter distribution In the last issue I gave you a list of amateurs who are on the mailing list. It now appears that others not shown on the list are also reading ft. Dick K6ARE passes his copy on to KA6DXY and K6TS, Mike W136ERR gets a copy from W6HDO and W3QVC gets a copy from Bert VE3DPB! I am indeed grateful to those who are passing on copies not only because ft all helps to make our activities better known but it saves me postage. Postage stamps I always try to put a special stamp on letters sent overseas in case -there are any stamp collectors around. Did you look carefully at the last one? I had intended to draw your attention to ft but forgot. However, Cliff spotted that ft was a commemorative for the Ordnance Survey and showed a section of a map in the middle of which was a village called 'Ham Street'. If you missed this and would like another stamp let me know and I'll put one on your next Newsletter. Audio spectrum analyser In an attempt to keep ahead of the professionals I can now tell you that a very simple design for an audio spectrum analyser will probably appear in the January 1992 issue of OST. It was designed by Bill VE210 and consists of a simple board which can be built for about $25. The heart of the system is software which runs on a PC and does not need a maths co-processor. Audio into the interface board is taken from the receiver which digitizes ft to 7,200 a-bit samples per second. These bytes then pass to the PC via the RS232 port at 115.2 kilobaud. The opposite function to generate audio from a program in the PC has aJso been built. Any conceivable waveform can be generated (so long as ft is below 3.6 KHz) which can be fed into the microphone socket of the transceiver As Bill says 'Who needs DSP?'. As long as the bandwidth is not more than a reasonable 3 KHz or so, the PC with the Interface can handle DSP In real time. The only problem I can see is that Bill has a 33 MHz 386 machine which all of us do not have. I'm hoping ft will work on a 286! Another interesting point came from Bill's letter. Amateur radio in Canada has been de-regulated and they can use any mode (even those not yet invented) so long as they don't exceed the licensed power or bandwidth regulations. Computer CCW Following on from the last paragraph, Bill seems to be well on the way to gMng us a computer CCW program so that all you will have to provide will be a stable transmitter and receiver. I quote from a very long and interesting letter I have had from him. 'Actually, even the crude set-up I now have, which costs only a few dollars to build (the DAC circuit is more expensive, as we cannot rely on the PC for accurate timing: dynamic RAM refresh cycles coming along at random, interrupts to be serviced, etc. - so we must use a rather large (I use 8 KB) hardware buffer on the board - but DAC circuit still only costs about $40 to build - could be used to perform the Coherent CW function entirely in software, with the added bonus that we can also 'track out' small differences in frequency between TX and RX. This is important because ft eliminates a whole lot of expensive and hard to calibrate hardware frequency standards. Even cheap crystal oscillators will hold a frequency to within a few parts per billion, If you only need ft for half a second! This software CCW receiver would be very similar to the expensive, complicated gadget I built years ago. The main difference is that I used a dedicated nowadays, we can use a stancaru tJC to ao it. it we are to track out the frequency variations, it would probably need a rather fast PC, though. But these days, all I see are 386's and 486's. hi! OST has asked me to think about a follow-up article (to the one mentioned above), something on DSP. I am still mulling this over. I think I favour the multiple frequency component modem idea, but maybe a coherent CW receiver entirely in software (using the little interface board described in the first article) would be easier to start with.' I know you will all be looking forward to hAure developments of Bill's ideas and I will keep you informed especially when the OST article has been published. Copper clad board Mike WB6EER follows up the notes I gave last time by saying that he has some thin double-sided copper clad board which is so thin that It can be cut with ordinary scissors and he finds It excellent for making screens. I have never seen anything so thin here in the U.K. which Is why I doubted if copper clad board could be cut with tin snips. Kenwood TS940S Kurt has completed his conversion of this transceiver and has sent me a full set of diagrams and plans together with the printed circuit boards needed. If anyone has this Kenwood and would like to convert it for use with CCW please let me know and I will send the diagrams and boards along. It is a tremendous job to undertake but, with the ready made boards, much of the work will have been simplified. Sepac/Inspire Just a further short note to say that I have the November update sheet from Mike WB6ERR for anyone who is interested. Crystal ovens There was a note in RadCom for November which was taken from Electronics Australia regarding the construction of a simple oven. If anyone would like a copy please ask. The crystal is enclosed in a 35mm film canister and attached to it are a BC178 and a 56 ohm 5 watt resistor. The canister has a plastic foam lining. A separate small circuit board is used to detect the temperature of the BC 1 78 and to control the heating of the resistor. Unfortunately there are no details of the performance of the arrangement. I have one or two other circuits for oven control including the excellent one from Bill de Cade. You should all have a list of the various data sheets available but ff I have not sent you one, again please ask. HAPPY CHRISTMAS AND A PEACEFUL 1992 From members There has not been very much correspondence recently. I keep saying that some of us are getting near being able to transmit and receive CM From the way things are going I feel confident I shall be there by the end of the year. G3FMW John built one of the earliest CCW filter designs many years ago and has recently had a look at Bert's OST version which appears to have convinced him that he should build one as well. G31RM I now have only the various stages to join together and the power supply for the transceiver to tidy up. Then the time has come to try It all out. G3RHI Bert has abandoned his idea of trying to use an unmodified Kenwood and will be building a simple one band transceiver. Perhaps I have been guilty of collecting too many more advanced ideas from magazines whereas I should have been pushing forward the idea of using the simplest equipment possible in order to get stations on the air. W7GHM Ray tells me that the software for Clover is almost complete and tests are being carried out. Write If you have anything to say that may prove helpful or interesting to other members. 73 Peter / 5