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[RFI] Ferrite on Spark Wires

To: <rfi@contesting.com>
Subject: [RFI] Ferrite on Spark Wires
From: EDWARDS, EDDIE J" <eedwards@oppd.com (EDWARDS, EDDIE J)
Date: Thu, 16 Nov 2000 11:24:22 -0600
> -----Original Message-----
> From: David Jordan [SMTP:wa3gin@erols.com]
> Anyone try using clam shell ferrite over spark wires to reduce spark
> plug noise?
        I'm not real versed in auto noise problems, but the ARRL's RFI
Handbook has a whole chapter on it.  It covers ignition, alternator &
generator noise, DC motors, noisey switches, microprocessors, wiring
problems, and how to diagnose auto noise problems; in addition to unintended
consequences experienced with older "fixes" of noise problems that worked
only on older cars but not on today's cars.

        I don't think a single ferrite will give enough impedance on HF to
do any good.  And adding enough of them to have some effect will be a mess
and cause more probelms than they fix.  Think of the stress and vibration on
the poor wire with 12-18 ferrites hanging on it!

        The tried & tested method appears to be resistance/impedance wiring.
This can slow the rise-time of the ignition pulse reducing noise on higher
freqs.  That is if you do have ignition noise and not one of the others
mentioned above.

        de ed -K0iL

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