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

Hi Richard and thanks for the definitive comment (short lead issue).

Yes, the problem manifests on the AM radio as well. We are going to do a
ground analysis when we do the new wires...I might note, however, that this
car has been ignition noisy from day 1 (I got it with about 11,000 miles on
it). I was quite disappointed when I first used the AM radio. FM is not as
bad, but it is still discernable. It is VERY obvious on 2m FM, not so much
so on 440 FM. I do believe the problem has gotten worse over time and right
now it is "unacceptable", which I hope will help us isolate it.

I'm familiar with the "ground window" concept (SPG) and will take a look at
the quality of the grounds (we plan to remove and clean all the obvious
ground connections, especially the main/heavy ones around the battery.)

I'll let you know how things turn out when we work on it next week after the
new wires show up.

Thanks for taking the time. 73

....hasan, N0AN

"Richard Clark" wrote in message
news
On Thu, 31 Mar 2005 07:05:54 -0600, "hasan schiers"
wrote:


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

Thanks. I have a 70's vintage Standard Handbook for Electrical
Engineers somewhere. It may list the materials and dissipative
factors.

Ted KX4OM
On Tue, 29 Mar 2005 12:26:01 -0800, Roy Lewallen
wrote:

I should also mention that the requirements for an insulator depend
heavily on the application. An insulator which results in a lot of loss
when a large electric field is present might produce negligible loss
when the field is weak. For example, an insulator at the base of a very
short or half wavelength high vertical, or at the end of a dipole, has
to be pretty good in order to minimize loss, because the electric field
is high at those points. On the other hand, a poor quality insulator is
just fine at the base of a quarter wave high vertical or the center of a
half wave dipole, since the electric field is low at those points.

Roy Lewallen, W7EL