That's the most compelling argument I've seen to explain this...when Ron
mentioned that the modulation was in the Q channel, you had to know that
it wasn't coming from conventional amplitude modulation.

Here's my recording of the "WFAN hum", as received today on a
battery-powered Sony SRF-A100 receiver in wideband AM Stereo mode:

ftp://ftp.amstereoradio.com/uploads/wfan-hum.mp3

This was received in C-Quam-compatible mode, but switching to ISB
(Kahn) mode yielded no audible difference. A spectrum analysis of the
L-R component reveals it to be a 120 Hz hum with multiple harmonics
extending well above 1 kHz... so it's more of a "dirty" hum, akin to
that of an audio device with inadequate filtering of its DC power
supply.

Yeah, that's what my ears tell me, too....it's not a ground loop, in my
opinion...sounds just like the buzz I get when I plug a DC-powered radio into a
battery eliminator, before the eliminator's loosely-coupled transformer-powered DC
supply's come up to full filtering. The only other thing I could think it is (which
you've pretty much eliminated when you said you see it even in the midst of a power
failure (I assume that was in August?) is that I've seen it where the AC line can get
intermodulated somehow with a station, which is localized around only one station or
so. Even that, however, is amplitude modulation, so it's doublenixed as a possible
explanation.
--
For direct replies, take out the contents between the hyphens. -Really!-


"WBRW" wrote in message
om...
That's the most compelling argument I've seen to explain this...when Ron
mentioned that the modulation was in the Q channel, you had to know that
it wasn't coming from conventional amplitude modulation.

Here's my recording of the "WFAN hum", as received today on a
battery-powered Sony SRF-A100 receiver in wideband AM Stereo mode:

ftp://ftp.amstereoradio.com/uploads/wfan-hum.mp3

This was received in C-Quam-compatible mode, but switching to ISB
(Kahn) mode yielded no audible difference. A spectrum analysis of the
L-R component reveals it to be a 120 Hz hum with multiple harmonics
extending well above 1 kHz... so it's more of a "dirty" hum, akin to
that of an audio device with inadequate filtering of its DC power
supply.