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“By the way, have you ever listened to one of the
jumbly sounding local channels at night on one
of your C-Quam stereo radios?”
Yep. I believe this is caused by all the night time “skip” from stations piled up on top of each other on those frequencies. Since some of them are “beating” with each other, the “jumbly” sound is two or more stations causing the C-QUAM decoder to literally go crazy, thus the jumbly warbble sound.
In mono receivers, usually what is heard is a sort of “scramble” mix of these mixed mashed signals fading in and out of each other. Sometimes when they fade away, there might be one signal that begins to come in clear, then the skip effect happens and its all a scramble again.
“when I hear somebody mention Khan,
I still hear Captain Kirk screaming, “KHAN!!!!!”
in Star Trek 2.”
LOL!! Ya I remember that scene! The Khan-Hazeltine system was a rather weird approach. This one worked by having the lower side bands and upper side bands from center carrier be the L-R platform. This system would allow a listener to use either a single radio for regular mono reception, or two radios tuned slightly off center frequency to get the stereo effect, or a single radio equipped with the Kahn-Hazeltine decoding circuits.
Only problem was that the unwanted effects of whistling, rumbling and incorrect phase correction due to wave propagation would really mess with the audio. It would sound like your speakers were put into a bathtub and listening to sound through the water..”wah-wah” or similar to the very old early stereo audio approach of spinning loud speaker arrays at a certain RPM to get stereo effect..which worked well for a set of speakers, but on a carrier wave subject to skywave and co-channel clutter…it really was problematic.
Today, an off-shoot of that Kahn-Hazeltine system, called “Power Slide” for mono stations. This uses the same approach as the earlier stereo system did by taking advantage of the lower and upper side bands from carrier center. Basically borrowing from one side band to boost the other, thus resulting in increased modulation depth and clarity. This is not to be confused with the NRSC curve as the NRSC is simply applying a band pass filter in the audio chain and does nothing with either lower or upper side bands in a modulated AM signal.
“Sony still markets
the SRF-A300 radio in Japan.”
Yep. A very nice and well designed unit. Does anyone know why Sony primarily sells this unit mostly in Japan??
It is not because of a lack of interest or lack of AM Stereo stations in the US or elsewhere. Japan has a very limited number of FM channels. As anyone knows, Japan is not exactly a gigantic land mass, but heavily populated. To make up for the lack of FM spectrum available, the majority of stations on the MW band transmit in C-QUAM stereo!
AM stereo certainly has it’s history. A history that goes back to the pre WWII era. The earliest known and documented AM Stereo broadcast was in 1924, station WPAJ (now WDRC AM)by using two MW transmitters on two separate frequencies. And trust me…the stereo separation in that approach would seriously give even today’s FM stereo a run for its money! And beat it hands down!!