[RFI] AM radio RFI from 2010 Ford Escape

John Brosnahan -- W0UN shr at swtexas.net
Thu Oct 28 12:46:25 PDT 2010


Guys,

Thanks for the help so far and here are a few more specifics.

To those who suggested the dealership.  I am sure they will not be 
able to add anything since the noise is not extremely strong and will 
not be detected when listening to AM stations once I am in town.  It 
is only an issue when I am rural with weaker AM signals.

Thanks to Dave Hachadorian, K6LL, for his link to test the fuel 
pump.  This test has confirmed what I believed to be true in the 
first place -- that it is NOT the fuel pump.

I do not see any noise associated with the ABS sensors as some have 
suggested as a possibility.

And there is no specific (varying) frequency associated with the 
noise like the typical "while" of an alternator.

Again, the noise appears when I press the gas pedal and disappears 
(well, drops 10 dB, which is acceptable) when I let up on the gas 
pedal.   So if I am driving at any typical speed (25 mph to 65 mph, 
say) there is a "frying" (broadband) noise that a ham rig with a 
decent noise blanker would probably reduce significantly, but that 
makes it difficult to understand the commentator, and as soon as I 
let up on the gas pedal the noise drops to an acceptable level.

My guess is that it is really an issue with either the fuel injection 
system or the ignition system that shuts down when the engine is 
coasting and needs no fuel -- possibly the fuel is cut entirely off 
or the ignition is turned off during coasting at speed.  This 
reduction in noise is much less when sitting still and letting up on 
the gas pedal, probably due to the need to maintain the engine fuel 
supply and ignition to keep the engine idling.

I again spent a few more hours of google searching to no avail.

Since it is hard to duplicate the coming and going of the noise when 
sitting still it will be hard to use a hand held receiver to locate the noise.

I appreciate the comments so far and especially from hearing from 
some old friends!     ;-)

John  W0UN




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