[RFI] High local noise level...

[Kenneth G. Gordon]

Today, I connected the audio output of my transceiver, a Yaesu FT-890, 
set to AM-wide, tuned to 3580 KHz, into my computer and fired up 
Spectran.

Spectran is exhibiting a very wide-band series of peaks in the noise 
which appear to be multiples of 60 Hz.

Like 180, 360, 480, etc. Spectran is reporting the main peak to be at 
360.68 Hz. I am assuming that the 0.68 Hz is caused by imperfect 
calibration of something in my system.

These peaks continue up through approximately 4 KHz.

On the "S" meter, my noise level is reading at a constant approximately 
15 dB over S-9.

There are periodic, random, changes in the "sound" of the noise level, 
and although the peaks as shown on Spectran change a bit, they revert 
back to the "normal" sound and apperance within a few seconds.

Furthermore, the noise blanker in the FT-890 appears to have zero effect 
at reducing the noise level.

I have eliminated any source from my home, by operating the receiver and 
the computer from a car battery, and turning off the house main breaker.

No reduction in either appearance in Spectran, or strength of the noise 
level was noted under these circumstances.

Ideas? Suggestions?

Ken W7EKB