[IRCA] Yes, SAH!

[Charles A & Leonor L Taylor <calltaylor@xxxxxxx>]

SAH= subaudible heterodyne= CARRIER BEAT= a frequency way below audible frequencies =0.0 - 15 Hz or so.

The further two r-f frequencies are from each other, the greater the frequency of the heterodyne.

If one station on, say 1000 kHz (1,000,000) is 1 Hz away from another, 999.999 kHz (999,999.0) or 1000.001 kHz (1,000,001) the two make a carrier beat of 1 Hz. If one moves, drifts upwards, somewhere around 20 Hz there will be heard a heterodyne.

The lowest frequency audible by people is 20 Hz, and that's where the FCC set the frequency tolerance. ITU went one better and set it at 10 Hz. But as a percentage, fewer stations outside NA and central Europe hold that tolerance.

Most US & Canadian station run closer than 5 Hz of exact center.

An offset of 10 Hz will cause a "gurgle" in the modulation of the two stations.

Perfesser Chuck

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