Mike and Tom,
The ion source is probably a plasma (arc, if you will) that is unshielded
and radiating nicely, probably on any wiring within the unit. If the
unit's housing is plastic, you have a nice transmitter.
Mike is on the right track, but before you go encasing the unit in hardware
cloth, there are a few tricks you might try. Since you own 4 of them, Tom,
maybe you could do "exploratory" surgery on one of them to see what the
internals are like. Of course, be sure to unplug the unit and use an
insulated probe to short out everything you see so as not to get a residual
zap. Tricks worth looking into would include installing by-pass caps
around the ion source, maybe placing a shield around it (but useless if you
can not ground the shield), and trying to determine if the ion source is
directly line-operated or if it uses some sort of power supply. Important:
does the unit have a 2-wire or 3-wire line cord? If it has only 2-wires,
true grounding of anything internal is pretty much a lost cause.
On the other hand, we have a whole-house electrostatic filter that is part
of the HVAC system (installed on the furnace). It does not generate free
ions, but does create high voltage and apply that (via current limiting
resistors) to a pair of grids that form the actual filter in the airstream.
No RFI at all from this unit unless it arcs - a sign that the filters need
cleaning.
Let us know what you learn if you decide to open up one of these gems.
73, Dale
WA9ENA
Michael
Neverdosky To:
<mikenever@earthl cc: RFI@contesting.com
ink.net> Subject: Re: [RFI]
Electrostatic filter rfi
Sent by:
rfi-bounces@conte
sting.com
06/28/2004 01:16
PM
Tom Berry wrote:
>
> On Mon, 28 Jun 2004 11:41:23 +0000, you wrote:
>
> > The noise was similar to that of the Sharper Image Ionic Breeze Quadra
filter
> If anyone knows how to stop the noise from them please let me know.
I can think of one way but it is ugly.
Put a grounded faraday cage around the unit.
I would try 1/4" welded hardware cloth (metal screen) to make
the cage as a compromise between airflow and coverage. Completely
enclose the unit and ground the cage well.
good luck
michael N6CHV
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