Collins Yellow Book suggests that voice components above 1 kHz
contribute most to intelligibility while the lower frequency components
contribute most of the power. Therefore they suggest that the HF part of
the voice spectrum should be emphasized at the transmitter and
deemphasized. I don't know that this scheme has ever been adopted in the
receiver for SSB. Continuous preemphasis and deemphasis is standard
procedure on FM from communications to wide band broadcast. That's
effective at improving the broadband signal to noise ratio at the
speaker. For sure if different brands and models use different audio
spectrum modifications, they won't work well together. This transmitter
spectrum equalization is what Heil microphones do, but without the
complimentary correction in the receiver.
73, Jerry, K0CQ
--
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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