[Bob F]

I am not sure how I can better describe the noise. The signal has an additional
modulation by the 60 Hz, distorting the AM audio. You can hear the background 60
Hz, and the audio warbles with it.

My previous car had no such response on its AM reception. The Seattle station
that I hear it on (The only AM station I listen to) is not a particularly strong
station, although I have heard it on a cheap portable radio when I was 280 miles
east in Spokane WA.

Bob


GregS wrote:
In article , "Bob F"
wrote:
The noise only occurs when I am driving near power lines. It varies
as the lines
nearby change. When there is no powerline close to the road, there
is no problem. The distortion/modulation is bad enough at its worst
to make to understanding the spoken word difficult. The problem
depends entirely upon my location. Each time I drive by the same bad
spot, the problem recurs.

You failed to fully describe the noise.
Are you listening to weak stations.
Take another portable AM radio and compare.

Surprisingly, my Cavalier Am radio is decent. I was amazed
how many stations came in during the daylight.
Most of my after market radios have miserable AM performance.
Mostly from poor engineering and internal digital trash.
I think the analog tuners were the best.

greg



MOSFET wrote:
First off, Greg knows much more about EE matters than I so I defer
any and all questions of a technical nature to him.

HOWEVER, that being said, I DO know that your car's engine
(alternator, sparg plugs, ect.and other accesories in your car) emit
more EMI (electromagnetic interference) inside your car than your
typical suburban power lines along side every residential rode. In
my 25 years involved in car audio, I have NEVER heard of problems
caused by your ordinary power cable.

True, when I have gone near LARGE CURRENT bearing cable like from a
damm or reactor to a substation I do encounter noise over my AM
band. I really don't think there is anything you can do about that
as the EMI just plain over-powers and distorts all AM signals.
There's no way for your radio to discern what's an AM signal and
what's EMI on the AM band, a little like going through an "EMI"
tunnel. But those type of massive lines tend to be few and far
between

But again, I have NEVER heard of plain old suburban power cable
causing EMI. There just isn't enough juice going through those wires
to create the kind of interference your describing, unless, again,
you live near VERY large current bearing cable.

I'm curious, how did you deduce it was the power cable causing the
interference? Are you sure that's the source?

MOSFET


"GregS" wrote in message
...
In article , "Bob F"
wrote:
I recently acquired a 1994 Dodge Caravan with a pioneer supertuner
AM/FM radio.

It has bad problems on an AM staion I listen to whenever I am near
powerlines. There is a 60 Hz hum that modulates the audio causing
bad distortion. I thought

this would be a grounding problem, and have tried adding an
additional temporary
ground at either end of the antenna cable, with no effect. Can
anyone offer any

help in solving this?



Is it hum or buzz. I'm thinking buzz.
I don't think i ever encountered this, but power lines will emit
noise. Is the noise all across the band ?
A different type of antenna may help. I'm thinking a big loop on
top of the roof.

greg