Go here: http://tonometric.com/adaptivepitch/
But to the point of reading CW in QRM and noise, it's not pitch discrimination that is tested but our brain's ability to detect a coherent tone (the signal) in random noise. As others noted, one way to produce a pure tone is to filter random noise down to a single frequency. Indeed, that's how almost all of our oscillator circuits work; take noise produced by an amplifier and filter it so only one frequency is present. You can use an amplifier (receiver) and "band noise" (QRN) in the same way. So the better we filter out all but the signal, the harder it is to tell what's signal and what's noise other than by pure amplitude change. I'm not expert on human hearing, but I suspect we can discriminate tones (and hear tones in noise) much better than we can discriminate subtle changes in amplitude, especially when one or both of the signals are varying in strength (QSB). Ron AC7AC -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of w9cf While this seems reasonable, when I took an online frequency discrimination test a year or so ago (unfortunately I haven't been able to find the link), I did not find this to be true for me. This test was, of course, not for separating two cw signals, but instead it sent two tones sequentially, and you had to choose whether the second was higher or lower pitch than the first. It repeated this with smaller and larger intervals until it had a measurement within error bars. Obviously different people have different results or there wouldn't be a need for a test. My results were, for the 3 ranges that the test used: 250Hz tones 3.6Hz difference with standard deviation 2.1Hz 500Hz tones 1.9Hz difference with standard deviation 1.4Hz 1000Hz tones 3.4Hz difference with standard deviation 2.2Hz Taking the fractions I get 1.4 percent at 250 Hz, 0.4 percent at 500 Hz, and 0.3 percent at 1000Hz. Although the standard deviations cloud this a bit. I know some ops like to run at low frequency as Jim says, but I prefer higher frequencies, and this hearing test may help indicate why. 73 Kevin w9cf ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
