[Icom] Auto Noise in MKIIG

[Larry Benko]

Rick,

Generally audio power line filters are either capacitors to
ground or a series inductor and parallel capacitor.  Their
primary intent is to stop alternator noise which is less than
a 100KHz.  As such they may attenuate RF noise but no guarantees.
"Filter cons" are generally PI(C-L-C) or Tee(L-C-L) filters
housed in small shielded enclosures with the purpose of
attenuating RF.  They come in various sizes based on DC current
rating and the RF frequency that the attenuation is spec'd for.
I also had fuel pump noise with my 2000 Toyota 4Runner. I found 
a small copper can (~1"x1.5"x1.5") that was open on 1 side.  I
built the equivalent of 2 "filter cons" of the PI type by
mounting 1000pF feed-through caps on the ends of the can and 
using inductors made from #43 ferrite material.  The inductors
were designed to handle >2A DC and the inductance was ~30uH.  The
can was then filled with RTV and mounted just where the wires came
out of the gas tank with a <1" connection to chassis (the wires
need to be cut as the filter goes in series).  My noise was worst
on 17m and this cleared up the noise completely. 

73,
Larry Benko, W0QE

Rick Gouge VER7RiK wrote:
> 
> Doug. Check out car audio power line filters, there small and large. I`am
> sure they would do the trick. 73 Rick VE7RiK
> ----- Original Message -----
> From: "Davies, Doug A FOR:EX" <Doug.Davies@gems3.gov.bc.ca>
> To: "'Icom'" <Icom@mailman.qth.net>
> Sent: Wednesday, May 15, 2002 8:40 AM
> Subject: [Icom] Auto Noise in MKIIG
> 
> > In researching how to eliminate the fuel pump noise in my pickup, I find
> > that the recommended way is to install "filter cons" on each lead where
> they
> > enter the fuel tank.  I finally located a couple of sources for these but
> > the price is in the stratosphere, roughy $36.00 US each, which is about
> > $100.00 Canadian!! <grin>  Pretty steep and they may not even do the job.
> > Does anyone know of a less expensive source for these things or have some
> > they would sell for a more reasonable price?
> >
> > In the event that I can't find any of these at a reasonable price, has
> > anyone manufactured a low-pass pi network filter and used it to get rid of
> > fuel pump noise?  I'm not beyond doing is myself but I wouldn't know how
> to
> > design one.  Thanks in advance.
> >
> > Doug  VA7DD
> >
> >
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