[RFI] Ignition Noise, HF Mobile, FORD

Cliff Bond WA4MWM at triad.rr.com
Mon Jun 16 08:43:32 EDT 2003

I recently installed an Icom 706 in a Ford  (2002) F-150 pickup with a 4.6
L. V-8.  It has the Coil on Plug ignition system.

There is very heavy ignition noise (clearly "classic" ignition noise - NOT
fuel-pump noise).  It is s-9 on 80 and 20 mtrs - less on other frequencies.

This is my first entry into HF mobile since HW-12's in the 60's.  I have
tried wiggling wiring, grounding the hood and other components,
disconnecting some cables, etc. - No luck.

I really don't understand this coil-on-plug technology, but I have been told
there are no resistor-plugs and of course no resistor wires.

Any suggestions as to how to proceed would be most appreciated!  I have
tried unplugging wiring to each plug one-at-a-time with no difference noted
in the interferrence level.  What else could I do to further diagnose the
precise cause/source of the interferrence?

Could I expect to get any help from Ford?

My latest Mobile Handbook is from the 60's - out of date to say the least.
Does the latest Mobile Handbook edition have any information on
modern-technology ignition systems?  My 2003 ARRL Handbook (the "general"
Handbook) has a paragraph - not at all helpful.

All of the RFI is through the antenna - when I disconnect the antenna from
the mount, all RFI disappears.  I can hear it on my fixed station when the
vehicle is in the driveway.

Any and all suggestions would be most-appreciated.  If anyone has a similar
installation (HF) in a similar vehicle without interferrence, please let me


Winston-Salem, NC

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