On Thu, 31 Mar 2005 07:05:54 -0600, "hasan schiers"
wrote:

p.s., I might add for learning sake, several of your answers, Richard, beg a
"why not". (As in, why doesn't it matter which end, distributor or plug
would be more effective, Stacking chokes vs. spacing them out along the
wires doesn't matter? Why not?)

Hi Hasan,

Because the placement is along a very short (in terms of wavelength)
current path. A current path snubbed anywhere is snubbed everywhere.

Your observation that most modern cars don't have ignition noise is
borderlline laughable for two reasons:

Those reasons are what we call anecdotal evidence. Anecdotal evidence
may be true to the sufferer, but that does not make it universal.
More the problem, the anecdotal evidence is likely another problem
being described and the evidence misapplied.

The most common source of noise is not the engine electronics
(although this is literally the source); it is in the failure of
grounding and orientation of lead paths. When you look at a car, you
see one huge metal can and think it must be uniformly conducting. The
sad fact is that it is not. Doors and hood and trunk lid are very
common coupling points to the interior as they present very large
capacitive links to the electronics inside. Some manufacturers insure
they are bonded to the frame, others do not. This is all commonplace
"taken for granted" grounding that does not exist and we get
occasional reports of extremely frustrated experimenters who struggle
to only find the hood (the last thing tested) was the culprit.

What keeps automotive electronics (much less their computers and their
own radios) going in the face of this haphazard grounding is that they
have long figured out how to reference all their equipment to the same
potential. This is your problem and you have not found that spot.

That spot appears to be elevated with respect to where you chose to
ground your equipment (or you chose several points and you suffer
ground loops). The noise is being injected by conduction and it is
very hard to snub currents traveling along frame and sheet metal.

If this problem emerged over time, and is found to be ignition wire
specific, then you have also described the same issue. Those wires
were coupling into a path between your ground and the system common.
A simple test:

Does your car's AM/FM radio reveal the same noise on your gear?

Manufacturers make sure this never happens long before they engineer
another tenth gallon per mile savings into your car. The difference
in the sensitivity between your gear and the car's FM is not very
large (if at all).

73's
Richard Clark, KB7QHC