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[TowerTalk] from w4bsg

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Subject: [TowerTalk] from w4bsg
From: (Tom Rauch)
Date: Wed, 11 Aug 1999 08:02:13 -0400
> Michael forwarded a note concerning noise on 40M, in a Ford Diesel
> pickup.
> A comment was made that, even if the source under the hood was located
> with a probe- the ID of the source would not be known.

I have a F250HD Diesel. The noise comes from the solenoids that 
open the oil lines for the fuel injectors.

The entire wiring harness to the injectors radiates, and the antenna 
picks it up. When I switch to a dummy load, or remove the antenna 
and leave the feedline connected, the noise in mine vanishes. I can 
also hear it on my home antennas, when I point them at my truck. 

You can measure it with a e-field probe, or a clamp on current 

It also disappears when you let off the accelerator or downshift 
because the injectors stay closed while braking with the engine. 

The injectors reach over 1000 volts on mine during field collapse, 
they drive my scope off scale.
> A mystery like this is usually solveable- the use of the probe, and
> reference to a manual for ID of the source, is my recommendation. Even
> deisels have electrical circuits that can be less than well designed, from
> an interference standpoint.
> When you find the source- Bitch to Ford and let us know, as well.
> (please)

Calling Ford does no good. They have no cure. If anyone is 
interested in what I did, e-mail me. I reduced mine about 30 dB, 
and now it is only S5-6. If anyone completely cured theirs please e-
mail me.

73, Tom W8JI

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