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[RFI] RFI from 12 volt refrigeration

To: <rfi@contesting.com>
Subject: [RFI] RFI from 12 volt refrigeration
From: ka5s@earthlink.net (Cortland Richmond)
Date: Tue, 4 Jun 2002 12:23:32 -0700
I suggest that you install a robust common-mode RFI filter as close to the
compressor as practical, to keep noise out of your vessel's power wiring. 
Any number of pre-packaged powerline filters are suitable for the HF
frequency range. I do not know which are legally suitable for a marine
installation, and you will have to deal with that, and with your insurer. 

Ad-hoc, you may find you can coil up ten or 12 feet of the power wiring in
a foot-wide coil (still close to the unit), adding and subtracting turns as
needed, that will be broadly resonant at 20 meters, and so reduce the noise
radiated. This is a technique often used as a Balun on beam antennas.

There seem to be no FCC regulations setting limits on noise from automotive
digital devices (they are exempt). However, other nations have different
rules. There _are_ Marine standards in Europe (though I am not at the
moment able to refer to them). There may be NZ/AU standards, and you may
find that a product you bought in the USA exceeds the limits they impose. 

In any case, there IS an FCC Part 15 requirement that devices not cause
harmful interference. Quite apart from fixing the problem with what you
have on hand, you should write to Danfoss for their solution, and copy the
FCC (or your home radio authority) so that it knows such problems do exist.
If the FCC receives no complaints, it assumes there are no problems, and
this later comes back to bite us, as radio users, when the FCC accedes to
proposals to increase permitted interference levels -- since the existing
ones cause no trouble!

Good luck!

--- Cortland Richmond
--- ka5s@earthlink.net
--- EarthLink: The #1 provider of the Real Internet.

> [Original Message]
> From: Harry and Jane Hungate <wcx7106@xtra.co.nz>
> To: <rfi@contesting.com>
To: <rfi@contesting.com>
 > Date: 5/16/2002 8:38:35 PM
> Subject: [RFI] RFI from 12 volt refrigeration
> Have you any suggestions for eliminating RFI created by the electronic =
> module (in effect, a solid-state commutator for the hermetically-sealed =
> compressor) manufactured by Danfoss, and used by practically all =
> manufacturers of 12 and 24 volt dc refrigeration.  My system, Danfoss =
> part number 101N0200 creates electronic pulses over a wide range of =
> frequencies, but I would most like to eliminate those on 20 meters, =
> specifically in the range of 14.050 to 14.090 MHz, the frequencies I use =
> for HF email (AirMail).  Many other cruising sailors would be grateful =
> for a solution.
> 73, Harry Hungate
> S/V Cormorant
> cruising in New Zealand
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