[Mobile-Portable] Radiated noise-Chrysler Town & Country van

[Rick Markey]

Doc,

It's a mini van and the antenna is a screwdriver mounted on a trailer hitch 
at the rear of the vehicle.  On the Blazer, it was also mounted at the 
rear, on the spare tire carrier.  Both vehicles are the same basic chassis 
and engine, just different body styles.  And there are obviously some 
differences in the vehicle wiring, etc.

It definitely comes in via the antenna.  I can even hear it on my 2M rig. 
 I tried grounding the exhaust system at several points on the Blazer. 
 Have not tried that yet on the van.  I have only one ground on the exhaust 
and that's at the last hangar at the rear of the vehicle.

I have also considered the possiblility that, as you suggest, the DC wiring 
in the vehicle is acting as an antenna, radiating the ignition noise. 
 Prior to getting rid of the Blazer, I was about to add a coil/capacitor 
filter to the DC lead on the coil.  I may try that on the van - I just have 
to get motivated enough to pull the dog house off and start poking around. 
 Vans are nice to drive but a pain to work on!

There was an article in one of the QEX magazines about shielding the 
ignition system.  My attempts at that were not very beneficial.  I even 
went so far as to spray the outside of the distributor cap with an EMI 
shielding material.  That produced results similar to shielding the wires - 
an arc and then a misfire.

I've run mobile for a number of years and have learned to exorcise most of 
the demons that plague mobile installations.  But the ignition noise 
problem has eluded all my attempts at a solution, so far.  Without the 
TS-50 noise blanker, I'd be screwed!!

One thing I haven't tried yet with the van is to circle the van with my 
portable SW receiver and a small loop on a stick.  That might give me a 
clue or help me find a "hot spot."  I just keep looking, hoping to find the 
solution someday.

de Rick, KN3C

----------
From: 	doc[SMTP:e.net@verizon.net]
Reply To: 	doc
Sent: 	Friday, August 16, 2002 21:26
To: 	kn3c@arrl.net
Subject: 	Re: [Mobile-Portable] Radiated noise-Chrysler Town & Country van

How close is your antenna to your engine?

Have you tried an antenna at the rear vs the front of the vehicle?  I am
curious as to the distance the noise is radiated, and if the stereo and
rear light cables may be functioning as antennas.

Varying the angle of a test antenna near the vehicle "may" tell you
something about the source of the radiated noise as well as trying a
directional antenna near the vehicle.

Just speculating, haven't tried all of that yet, still need to treat the
known sources!

73, doc kd4e

> I had a real bad experience trying to shield the ignition wires with
copper
> braid.  I eventually ended up with a misfire and had to remove the
> shielding.  My noise definitely is radiated - ie it comes in via the
> antenna.
>
> I'm not sure there is a solution!
>
> de Rick, KN3C