[Elecraft] CW Listening Tones

[James R. Duffey]

Mike - Interesting question.

There is some very nice data in a psychological (physiological?) study that
shows the ear's ability to distinguish between tones is a function of the
frequency of the tones.

There is a broad minimum from about 400 Hz to 600 Hz. Interestingly, there
are slightly different curves for the use of two ears and the use of one
ear.I have a copy of the data somewhere and can dig up the reference for you
if you like.

Having said that, another consideration in receiver design is the steepness
of the crystal filter slopes. As one reduces the center frequency of the
bandpass, the requirements for opposite sideband rejection become more and
more stringent. The use of a 700 Hz side tone in a rig with simple filtering
improves the opposite sideband rejection immensely. It probably has less
effect on a rig with a good filter like the K-2.

Before it was easy to vary the side tone, 700 Hz was the de facto Ham
standard, although the side tones varied all over the map. I think that the
Heath SB/HW-10X series had a 1000 Hz side tone. At least the one on my
SB-110A is quite high.

A too high frequency is tiring in the long run, particularly with narrow
filters. 

Someone at an RSGB convention a number of years ago took data on the tone
that CW operators liked to listen to. The ops could set the tone at their
choosing. They were asked to write down what tone they normally used to
listen to CW first. Almost all used a tone between 400 and 600 Hz, all used
a tone lower than they wrote down (except a professional musician with
perfect pitch), and most used a lower tone when the signal to noise ratio
was low.  

I hope that you found this rambling interesting and useful - Dr. Megacycle
KK6MC/5
______________________
James R. Duffey KK6MC/5
Cedar Crest NM 87009 DM65