The best communications phones are those that limit the frequencies to either
those of voice band, (roughly 300-3kHz) or even more limiting to CW tone
frequencies of say 700 to 1.2 kHz.
Modern headphones made for computer sound cards, or stereo use, if of any
quality, will go too low in response to undesirable frequencies like 60 Hz,
which will quickly tire a radio operator. In addition, those low responding
phones will pick up the computer hash of rigs having microcontrollers.
Look at ham swap meets and you will likely find old military phones, or
aviation phones. 600 ohm impedance sets do not take much audio gain from the
radio, and thus also lower the background noises. In addition, they do not
have the undesired low frequency response.
My best phones are some Korean war vintage 15,000 ohm magnetic phones. They
were New Old Stock, in original military packaging, and in new condition. They
need only a whisper of audio to produce good copy, and they do not hear my
Scout's microcontroller at all. The audio pot stays at a low setting even for
weak stations.
These also surface in commercial surplus outlets from time to time.
For ear pads for the hard bakelite cases, you go to a drug store and in the
ladies makeup dept. find soft circular sponge pads made for makeup cases. Cut
a hole in the middle of a couple. (They are sold in pairs!) Attach the
resulting donut to each phone using Scotch double sided tape. They make the
old phones much more comfortable than the old wrap around rubber cushions! I
think the old rubber cushions are no longer made, and never seem to turn up in
surplus. These military modified phones are useful for long stints like Field
Day, or contesting.
--Stuart K5KVH
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