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[RFI] AM radio RFI from 2010 Ford Escape

To: rfi@contesting.com
Subject: [RFI] AM radio RFI from 2010 Ford Escape
From: John Brosnahan -- W0UN <shr@swtexas.net>
Date: Thu, 28 Oct 2010 18:39:41 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
SORRY.  APPARENTLY THE REFLECTOR CHOPS OUT QUOTED TEXT EVEN WHEN IT 
IS CRITICAL TO THE DISCUSSION -- SO HERE IT IS AGAIN WITHOUT THE 
QUOTES.  HOPEFULLY IT WILL GET THROUGH THIS TIME.


Realizing this is not the same model and older than my Escape, I 
think the comment below is worth checking into.  So when I get a 
chance I will try to measure the resistance from the radio case to 
the battery (or frame near the battery).

But based on additional (direct?) comments I am going to look at the 
ignitors and spark plug wires using a separate radio to see if, in 
fact, that is the problem.  At least the symptoms better match this 
source than some of the other suggested sources.

Thanks  --  John  W0UN




=======================================================
Vehicle: 2003 Ford Explorer Sport with stock radio/tape/cd player. 
Went to Mossey Ford and they said radio was working within specs. 
(Yeah right). On weaker am stations found radio almost unusable 
because of ignition noise that followed the engine rpm but almost 
went away at idle. Pulled antenna mast and cleaned with steel wool. 
Did not help. Pulled radio and put a 1 microfarad cap across 12 volt 
to ground leads into radio. Also pulled all connectors and reseated. 
Also tried a filter cap across the 12 volt to ground on the 
alternator. Nothing helped.

=======================================================
I am not sure of how this factory radio was originally installed 
since I bought the car used but I noticed there were two places on 
the back of the radio's steel case where a grounding wire could be 
attached and neither were used. The case was secured by the the 4, 
Ford style side clips which only touched the plasic portion of the 
dash. I measured the resistance between the case and a steel interior 
frame support and found several ohms. Between that support and the 
negative post of the battery had 2 tenths of an ohm. So I attached a 
heavy gauge grounding wire from the frame point, which is above the 
gas pedal and already had a nut and washer, to the grounding terminal 
on the back of the radio. The static on even distant am stations is 
90% reduced.



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