[HQRP] Diesel Noise - Ford PowerStroke

[J.D. Stevens]

I gave up trying to operate from my 1994 Chevrolet gasoline powered 
suburban because of locally generated noise at about S8. All of the 
noise came in through the antenna, which was mounted on the back bumper. 
In one experiment, I put the radio on the ground a few feet away from 
the truck and ran it off a portable battery. The difference in 
background noise between having engine running or not was about 6-8 S units.

I was never able to isolate any specific noise source by running a 
"sniffer" around the truck. The noise sounded like computer hash.

The best suppression I found was a combination of an antenna based 
blanker with a short sense antenna on the RF end on the radio and DSP on 
the audio end. It was such a pain to get everything adjusted, I gave up 
anything but FM communication from the truck.

I assumed that a diesel rig would make everything much quieter. Maybe not!

   Dave
   K5ERP

Ron Sparks wrote:
> Quite some time ago I posted a query as to why my F-350 Diesel was creating
> about 2-5 S units of rpm related noise.  A big clue was when Paul Gobel told
> me his was the same and that the injectors used high voltage to trip.
> 
> That was absolutely right!  The doggoned things use 110 volts (yes 110!) to
> fire, due to the very high pressures involved.  Basically each injector is a
> miniature hydraulic pump with crankcase oil at several hundred pounds (about
> 600 psi) in the main supply rail.  The 110v PWM signal then opens a valve to
> let this high pressure oil act on the back side of a piston which then
> compresses the fuel until a spring loaded poppet opens at about 2700 psi and
> injects direct into the cylinder.  All this is nicely described for all you
> Ford diesel owners at: http://www.intellidog.com/dieselmann/injector.htm
> 
> As for the QRM.  I got rid of one S unit by putting a ferrite bead around
> the cable bundle from the computer.  I have gotten rid of another S unit by
> improving grounds (especially between the hood and chassis).  As to the last
> one or two S units -- I now have to find a way to shield the high voltage
> wires to the injectors.
> 
> More later -- happy rovering,
> 
> Ron, AG5RS
> 
> 
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