[Elecraft] K3 Need for compressor

[K8TB]

    If we are talking about modifying the K3 transmit audio, we also 
might want to look at installing a "phase rotator", or "phase scrambler".

Most male voices are very asymmetrical. This presents a real problem 
with broadcast radio, especially AM. With US AM transmission, you are 
allowed 100% negative modulation, and 125% positive modulation. With a 
proper AM transmitter and audio chain, and the 125% positive limiter 
disabled, and the right "type" of a male voice, you can get 175-200% 
positive modulation while never exceeding 100% negative. Flip the 
polarity of the audio driving the transmitter, and you will cause 
carrier clipping on the negative modulation, while never going over 
60-75% positive modulation. The broadcast equipment manufactures will 
many times look at the asymmetrical waveform and flip the polarity of 
the audio signal. Today, most stations depend on the microphone 
processor to balance out the microphone audio, by simple phase 
scrambling of the low end of the audio. This effect smooths out the 
sound of many male voices. I can turn the phase rotator on and off on my 
radio stations microphone processors off (Symetrix 528e's), and my 
announcers will complain that their voices sound a little "brittle".

If you have ever look at your SSB signal on an oscilloscope, you may 
have noticed that the waveform goes higher in one direction than another.

It might be interesting to experiment with external processors on the 
effect, or lack of effect that phase scrambling might do for SSB.

    You can read up on how you can do this at several places:

W3AM does a good job at:
http://www.w3am.com/8poleapf.html

http://www.nu9n.com/am.html

http://www.omniaaudio.com/tech/speech.htm

http://www.euphonicmasters.com/orban_article.php
pdf of above at:
http://www.orban.com/support/orban/techtopics/Appdx_Radio_Ready_The_Truth_1.3.pdf


tom bosscher K8TB