[RFI] AC Line filters- Direct-Drive Washers

Larry Benko xxw0qe at comcast.net
Fri Apr 4 10:22:12 EDT 2008


Perhaps it is now too late but why not return the offending appliance?  
I bought a new large screen TV recently and told the store that I would 
return it if it produced interference to the HF spectrum.  I even wrote 
that condition on the sales slip prior to signing it.  Then of course 
purchase with a credit card.  Fortunately the TV I bought was clean.  As 
consumers our ultimate power is in the "pocketbook". 

As an aside, since most of the interference produced by these appliances 
is common mode current on the AC power cord and it should be fairly easy 
to take a clip on current probe and connect it to a small hand held 
receiver before purchase (if the store has the appliances powered).  
This solution has other problems in that if there are 100 other 
appliances all plugged in the common mode current you measure may be 
from some of them.  Still an S9+50 signal should jump out with this test.

Perhaps we could really use a database of appliances that are "clean" 
but that would be a huge amount of work since one person's idea of a EMI 
quiet appliance would not match another person's.  Good luck with your 

Larry W0QE

Paul Christensen wrote:
> 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 its 
> 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 generated 
> 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 to 
> 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 
> problem.
> Anyone have any similar experiences with the new direct-drive washers and if 
> so, what specific remedy was used to mitigate RFI?  I am completely familiar 
> with the general concepts of RFI/EMI abatement, but I am looking for 
> case-specific solutions with actual experiences with direct-drive washers. 
> Thanks.
> Paul, W9AC
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi

More information about the RFI mailing list