CCWN NEWSLETTER Compiled by G3IRM 11 - Issue number II April 1991 The Newsletter I have now been sending the newsletter out for about two years and a number of members have written reporting progress made. There are some who have not written for a long time and if you are one of these there will be an * after your call on the envelope. If you are not in the U.K. please let me know if you are still interested - photocopying and postage costs money. If you can send something of interest to members I will be happy to accept. In future I intend to send copies only to those I know are interested. All members who have sent contributions will, of course, continue to receive copies. There is very little to report this time so I will copy something from the old CCW Newsletters from 1975. 1 am running out of these but will try to continue and send you a Newsletter every two months but cannot promise to do so. Limits of communication due to propagation conditions from CCWN 75:23 It may have occurred to some of you, if we can gain 23.5 db by reducing the bandwidth from 2000 cycles to 9 cycles by a CCW filter, why not reduce ft by another factor of 100 and get another 20 db. There are at least three problems with this. 1.The required frequency stability is beyond our present capabilities. We need about 2X10-7 and can obtain about 10-7 with care. Another factor of 100 would require 2x10-9 which is beyond our present techniques. In my (W6NEY) judgment this could be achieved. 2. Narrower bandwidth will reduce the information rate. Our current CCW signals, using 100 mSec. pulse length give 10 bits of information per second which results in 12 wpm. A decrease in bandwidth by 100 would give only 0.1 bit per second or approximately about O.12 wpm. Several years ago I built a coherent binary code system which worked at 0. 1 bit per second and operators found ft frustratingly slow. 3.Modulation of the signal by the propagation path. Experiments I did with the above system lead me to estimate on the average each skip adds about 0.5 cycle FM modulation at 14 MHz, although there are times when little modulation occurs. Thus a typical signal going from U.S. West Coast to Japan might make 4 skips and therefore have 2 cycles of modulation added. This causes large losses with a 0.1 bit per second filter. It looks like the propagation modulation of skip signals makes the limit of useful filters about the same as the convenient-for-humans CW rate of 10 bits per second. Space communications are another matter as the modulation of space signals is far less. Therefore, it is my estimate that we are near the point where decreasing information rate and increasing propagation loss due to modulation meet for the most efficient communication between points on earth by means of propagation skip. On the other hand, under favorable conditions, I am sure we can get another 20 db if we accept lower information rates. If you stop and think about it, even hams who are sending at 10 bits per second (12 wpm) are actually communicating at only about 1 bit per second when you leave out the information loss from QRM, sending errors, simplex operation, repeated information, receiving errors and preambles. I predict we will see a new type of ham station in the next decade which should be communicating at 1 bit per second in duplex operation. A small computer on each end will receive information from the operator at a rate and by an input method convenient for him, e.g. keyboard or code key. Transmission between the stations will be QRP- One watt will be plenty as with 40 db gain it will be 10 db more effective than a KW with current techniques. Perhaps 10 watts will be customary for hand-held antennas. The computer will automatically switch transmission to the highest information rate which can be handled by the propagation path. It will receive information at the rate sent by the other station, but display it for the operator in a way convenient for him, e.g. by audio CW, CRT character display, typewriter or spoken characters (I will leave spoken words for the next decade although it is now technologically possible). I further predict that one of you reading this will be the first to build such a station That was written in 1975 by Chas. Woodson. It very much looks as though he wasn't too accurate in his predictions but some of the features mentioned will be used in Cloverleaf. I hope those of you who have copies of these old notes will bear with me - by far the majority of members do not have copies and will, I think, find reading them interesting New members G4DWC Denis Cannings, Brackley OK3EW Juro Babel, Bratislava W6HDO cliff Buttscharcit, Morro Bay Appeal for information ' Due to the shortage of new data and information I have had to repeat the above item from an old Newsletter. Anything you may come across or any bright ideas you may have are welcome. Although the old notes are interesting it would be much better if you could supply something new. The 2 MHz crystal ovens Cliff W6HDO has been on a trip to the Persian Gulf and took the opportunity to try out the ovens obtainable from Fair Radio Sales. His intention was to use the time to age the crystals. The units held 0.1 Hz stability for the entire two months in the Saudi Arabia area! He recommends using at least 15 volts in place of the usual 12 volts as this gives an order of magnitude better stability. The units when bought are not aged. After six months they seem to stabilize. Do not move the coarse adjustment but rather change the value of the ten turn resistor. Anything between 5 and 50 K is alright. The idea is that the mechanical coarse adjustment has long ago been frozen in position and is best left alone. News from members DF3CT Bernhard has built the G4VSO synthesizer and is using it with a d.c. receiver. He has also discovered a mistake on the G4VSO r.f. synthesizer. The diodes to the binary switches should be reversed. DJ4SB Gerd has sent me a list of AGCW-DL stations operating QRP giving details of the stations used. There are six pages plus notes. G3CCH John has built the QRP transmitter described in the original CCW articles. G3FMW John is back again making steady progress@ with his receiver after suffering a heart attack. Nice- to hear from you John. G4FKH Gwyn has completed the Theunissen oscillator from Elektor magazine. GW3DEX Norman has started the G3S81 keyer and is collecting parts for the standard oscillator. OEI KYB Kurt is continuing to make progress with his Kenwood conversion but final details are not yet available. OK3EW Juro has asked for details of the Group - our first enquiry from Czechoslovakia. WUOI Jim comments on the extraction of AM broadcast station carriers as a source for frequency standards. This stems from the article in QEX describing the synchronous oscillator. I cannot vouch for broadcast stations in the States or other parts of the world but I do know that the Droitwich transmitter on 198 KHz is locked to an atomic standard and must be good enough for the purposes for which we need a standard. I now have my standard locked to this station and, as is to be expected it is on frequency from the minute it is switched on and stays there indefinitely. Jim has moved address again but is now settled in California and will be modifying his A/D board to use an external clock before starting to write software to emulate the CCW filter. In view of the number of computers in amateur radio use such a program should help enormously in getting CCW going again. There are a lot around who are not such keen constructors as some of us! W6HDO Cliff has a CCW beacon operational on 179 KHz which transmits CCW and BPSK for five minutes each. It runs continuously. The Newsletter is compiled with an Epson PCAX2 computer using WordPerfect 5.1 and the original copy is printed on an HP Deskjet 500 using Elfring Soft Fonts. Peter Lumb G31RM 2 Briarwood Avenue Bury St. Edmunds Suffolk IP33 3QF England 73