[TVI-RFI-EMI] Re: [Mobile-Portable] Radiated noise-Chrysler Town & Country van

Sat, 17 Aug 2002 11:27:40 -0400

I'd sure appreciate it if you'd keep the Mobile-Portable list informed of
your discoveries.  It will save some of us repeating your efforts.

I copied the TVI-RFI-EMI list since there are frequently real helpful
and experienced folks there.

73, doc kd4e

> 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:[email protected]]
> Reply To: doc
> Sent: Friday, August 16, 2002 21:26
> To: [email protected]
> 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
>
>
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