In article ,
Ron Hardin wrote:

Ron Hardin wrote:

WOWO 1190 Fort Wayne IN seems to have a low-frequency rumble in the
stereo difference channel, up to about 240 Hz.

It's audible if you listen to either sideband alone (with or
without sync detection) but inaudible if you listen to both
sidebands, say as normal AM or DSB sync detection.

I noticed it a couple weeks ago and it's still there.

They're 160 miles away, so maybe somebody closer can hear it
better.

Here's audio http://rhhardin.home.mindspring.com/wowo2.ram

the sound of a diesel engine idling.

Received sync detected LSB. It's _completely_ gone on AM or sync
detected DSB. Sounds the same on USB as LSB.

So, in other words, it's in the difference channel only.

You are describing a case of power supply switch noise or power line
noise getting into the radio. DSB detection will have greater common
mode rejection than USB or LSB. Try some chokes on the power cord or
change the power supply. Find the thing in your house that is generating
the pulse noise on the AC mains.

--
Telamon
Ventura, California