I must disagree with Ron about the "matching tones". When you "zero beat" the transceiver with a received signals using the sidetone or spot tone, matching the frequencies of those two audio tones is exactly what you are doing. With a tracking sidetone, as in most modern transceivers, those two frequencies are the same when the transmitter is on exactly the same frequency as the received signal. The PROCESS the operator uses to get those two frequencies to be the same can ultimately be to listen for the slow beat between them and to make the beat frequency got to nearly zero. That only works, however, after they are very close, and you have to somehow get them that close. You don't have to have perfect musical pitch to determine whether one is higher or lower in pitch than the other, and that's how most of us get close. Indeed, for even the most demanding CW operating, you don't have to be EXACTLY on the other station's frequency: within 10-20 Hz is just about always close enough. You often want to deliberately be offset slightly to avoid QRM, etc. I think the problem arises when operators are so unaware of the difference between the sidetone and the received signal pitches that they end up calling 400 Hz or more off, perhaps outside the passband of the other station, and/or on top of an adjacent station. Some, it seems, assume that if they can hear the other station at all, they must be on the same frequency. Even with a narrow CW filter, that could be 400 Hz off, and well outside the other station's passband..
I don't mean to disparage those with serious hearing losses, some of which I'm sure can make this tone matching difficult or impossible. (Most of us, after all, are of an age when hearing loss is common. Years of operating without AGC didn't help.) These folks obviously have to use other methods, such as Dual PB, CWT, APF, or just a narrower filter. I doubt, however, that all the operators who call me way, way off frequency have this problem. I still think Wayne and Eric should come up with the "Reverse CWT", which would put the OTHER station's transmitter on frequency. (Tongue firmly in cheek!) 73, Scott K9MA ********* AC7AC wrote: You may be quite right, Tom. Many of us have various levels of hearing loss. However, the "red flag" that causes people to say things like that is the use of the phrase "matching tones". There is *no* "matching tones" in the process of zero beating, which gives the impression the person is trying to do the wrong thing! We don't care what frequency the "tones" we're hearing are. We are listening for the third tone that disappears when "zero beat" is achieved. So it's only a matter of hearing whether a tone is there or not. It WAS easier in the "old days" because there was only one tone and we tuned until it disappeared completely. Nowadays we have three tones, only one of which disappears at 'zero beat'. Having the other two tones, whatever frequency they might be, at the *same* level makes the third tone as loud as possible so it's easier to hear when it disappears. Having followed this thread many times over the past decade, I'm becoming convinced that some people have a very hard time hearing more than one tone at a time. Even minor QRM on a CW signal stops them cold unless they can filter it out in the receiver. For such people hearing the third tone is probably very difficult or impossible. Many of us OTs have for years used very broad receivers on CW and learned long ago to listen to several signals at once, picking out the one we want to copy just as one picks out one conversation out of many in a crowded room. Perhaps what we're seeing today is a side effect of modern receivers where listening through real QRM is almost unknown. 73, Ron AC7AC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
