Re: K3 Filter Ring with Noise?
Posted by w9cf on Aug 09, 2009; 9:34pm
URL: http://elecraft.85.s1.nabble.com/K3-Filter-Ring-with-Noise-tp3410069p3414276.html
Jim Brown wrote:
...
>BUT -- human hearing is logarithmic, both in pitch and amplitude. Our ability
>to separate frequencies is based on proportional differences in frequency, so
>setting the CW pitch to a lower frequency gives the ear greater ability to
>separate signals (or signal and noise) that are close together in frequency.
>That is, if the pitch is set to 500 Hz, 100 Hz bandwidth is 20% of the signal
>frequency, whereas at a pitch of 1 kHz, 100 Hz bandwidth is only 10%. I know
>some really good CW operators (N6RO is one) who regularly work at pitches
>below 500 Hz for this reason.
>
>BTW -- I know exactly what the original poster of this thread is talking
>about -- I really suffered from it when I lived in Chicago.
>
>73,
>
>Jim Brown K9YC
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