[RFI] AC Line filters- Direct-Drive Washers

dgsvetan at rockwellcollins.com dgsvetan at rockwellcollins.com
Fri Apr 4 14:14:32 EDT 2008


Sorry to hear about yet another QRN machine.  Your experience does lead to 
some questions, however:

1.  Have you determined how the noise is propagated within your house? 
(ie:  Is it ALL power line conduction (and subsequent radiation off house 
wiring), or could it be a combination of power line conduction and 
radiation directly from the pc cards and drivers within the machine?)

2.  What is the orientation of your 80m antenna relative to the machine?

3.  What are the noise levels like on 40m and higher bands? 

While I have no direct experience with the Harmony machiens, I do have 
prior experience with their industrial bretheren, variable frequency AC 
drives.  Bad news. 

It would not surprise me if the digital controller electronics actually 
contain filters and design details that are necessary for the controllers 
to even operate in such close proximity to the variable speed drive 
systems.  In any case,  minimizing coupling between your antennas and the 
machine/house wiring combination is a good place to start while waiting 
for the warranty to expire.  Another thing you can do while waiting is 
prepare some "sniffer" probes to use with your receiver, a spectrum 
analyzer (if you can get one), or an oscilloscope.  The sniffers are 
nothing more than insulated lengths of coax made to have anywhere from 1 
or 2 inches of exposed center conductor to maybe as much as 5 or 6 inches 
exposed.  BTW:  When I say "exposed", I mean without shielding braid.  Be 
sure to leave the center conductor dielectric in place so that you are not 
probing around with a bare wire!

The idea is to set the machine into normal operation and "sniff" around 
the power cord, control panel, and all around at cabinet seams and 
openings to see where the strongest signals exist.  Do that before opening 
up the cabinet.  Once you know the hot spots, then go at it, but be sure 
you can reassemble that which you took apart.  Don't be surprised if you 
end with control boards and wiring all over the floor.  The best news (for 
you) would be to find that it's all in the power cord.  That means you 
could probably leave the machine alone and place a big hunkin' line filter 
right at the cord entrance to the machine.  (See K9YC's comments.)

If the problems are, in fact, from multiple sources within the machine, 
you will probably need to use the "divide and conquer" approach to EMI 
investigation, which means isolating the various sections or stages as 
much as possible and then applying shields, filtesrs, etc, as required. 
Keep in mind that you may not be able to kill it all to a point low enough 
to preclude some interference.  So, that goes back to either relocating 
antennas or finding other activities when the laundry is being done. 

Best luck and please keep us informed.

73, Dale


"Paul Christensen" <w9ac at arrl.net> 
Sent by: rfi-bounces at contesting.com
04/04/2008 09:04 AM

<rfi at contesting.com>

Re: [RFI] AC Line filters- Direct-Drive Washers

For the past year, I have been fighting an issue with my own GE Harmony 
direct-drive clothes washer.  It's a great clothes washer, complete with 
serial I/O port to the dryer and a touch-screen display.  Unfortunately, 
under 47 CFR 15.103(d) such appliances are still exempt from the specific 
technical and certification standards, notwithstanding the general Part 15 

requirement that a user of such a device holds no unconditional right to 
use when it causes harmful interference to another service.

I suspect that the last time this section within Part 15 was revised, it 
wasn't foreseeable that appliances like clothes washers could hold as much 

processing power as a personal computer.  The amount of RFI being 
by this washer is mind-boggling.  On 80M, it is producing signals at +50 
dB/S9 every 50 kHz or so on my Icom 7800.  If this RFI was loosely coupled 

to a resonant dipole, I imagine that its effect could be heard to the same 

extent as some QRPp transmissions -- it's that strong.

I have tried using some robust AC line filters on the line cord with zero 
effect, but I know that I need to dig deep and attack the problem closer 
the source.  However, I need to first let the warranty period expire.

I had an opportunity to speak with two of the GE Harmony designers.  They 
were quite surprised when I found their direct inline-dial numbers on the 
Internet.  In fact, one of the engineers was responsible for the entire 
digital interface.  The first words uttered, were "look, we're exempt from 

certification with that product."   No further assistance was provided and 

of course, this was the first complaint he had heard relating to the 

Anyone have any similar experiences with the new direct-drive washers and 
so, what specific remedy was used to mitigate RFI?  I am completely 
with the general concepts of RFI/EMI abatement, but I am looking for 
case-specific solutions with actual experiences with direct-drive washers. 


Paul, W9AC

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