[BC] AM Stereo and Leonard Kahn

[RichardBJohnson at comcast.net]

I think this is another of your jokes. I wish you wouldn't interrupt a serious discussion in this manner. Some folks might think that you are contributing in a serious technical manner. For the unwashed, the "Powell Crosley" method of stereo was two radios, sometimes in one box. The left channel was on AM and the right channel was on FM. Of course this meant that AM only had half of the performance and FM the other.

And of course the color-wheel was a sequential field system that would make everything stroboscopic even if it had been adapted to a kenescope.

Also, the Kahn system was distortion-less in a strict technical sense. There was no inherent distortion in the system definition itself, only in its implementation.  A properly designed detector, such as available nowadays as a single-chip solution to a radio, would not generate the distortion of a notoriously defective envelope detector designed just after the galena detector. The correct solution would add no (zero) (0) cost to a modern radio receiver design. Kahn was way ahead of his time because he knew what the military was doing because he was doing it for them. Nowadays, we have software-defined radios that use the principles defined and invented by Kahn.

In addition, if you somehow obtained a 23 dB reduction in S/N because of FM Stereo, your mathematics are seriously askew. The pilot is 20 dB down. It consumes ten percent of the available headroom with 90% remaining. That is a 0.9151 dB reduction in headroom. For monophonic operation of the receiver, both left and right channels exist with no S/N ratio difference beyond the 0.9151 dB. With stereo, the sub-channel which contains the  L-R components is shifted up in frequency. With a Gausian noise distribution, the sub-channel will have a 6dB reduction in S/N. I won't bother to sum this into the main with the proper sqrt(L^2.R^2). Instead I'll just kill off an impossible further reduction of the whole 6 dB for a 6.9151 dB reduction in S/N.

My stereo generators, even the first, has such a good S/N ratio that this reduction was inconsequential. 

http://book.abominablefirebug.com/BlogFiles/Wilkinson.jpg

Cheers,
Richard B. Johnson
Book: http://www.AbominableFirebug.com/

----- Original Message -----
From: "Dana Puopolo" <dpuopolo at usa.net>

Kahn stereo had in excess of 10% harmonic distortion at 100 Hz-and more at 50
Hz. I know it, because  I measured it. None of the others had distortion that
low. The FCC didn't just grab Magnavox out of thin air-they had a decision
matrix that was 100% public-EVERYONE could see it, including Leonard Kahn. Let
me ask you a question David-what would have happened to FM had Powell Crosley
been as petulant as Leonard Kahn was? After all, Crosley's FM system only had
a 6 db SNR penalty-compared to the 23 db system we wound up with and was 
technically a much BETTER system then the one adopted in 1961.