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Author Topic: EMI Source: LG Refrigerator  (Read 1028 times)
KF9BD
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Posts: 61




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« on: March 13, 2019, 06:24:15 AM »

Finally found the major source of my S7+ EMI.  It is my LG refrigerator.  With everything in the house turned off and the refrigerator on the signal is S6.  I have placed three Mix 31 toroids on the power cord with very little change in the EMI.  I have sent an email to LG Customer Support notifying them of the EMI and asking for assistance. 

Anyone have any experience with refrigerator EMI?  The model of refrigerator is LFS28968ST.  The EMI is present across ~ 3.0 mHz thru 16 mHz.

Regard,

Danny
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N2AYM
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Posts: 120




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« Reply #1 on: March 13, 2019, 06:48:36 AM »

Even if they respond they are not likely to know of methods used for EMI suppression,
and it is possible your refrigerator has a unique problem. If not they may have dealt with
this issue before. If you do not get any effective help don't hesitate to contact the local
FCC office and report your receive interference issue and make sure to record the serial
number as well as the model number. LG may have had a production run problem and not
even know about it.
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W1VT
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Posts: 3187




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« Reply #2 on: March 13, 2019, 06:59:13 AM »

http://www.karinya.net/g3txq/chokes/type31.jpg
This chart suggests the optimum number of windings for stacked FT-240-31 cores.  
Sadly, Steve passed away recently.  Many amateurs who find that toroids "don't work" haven't used an optimum number of turns.
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KF9BD
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Posts: 61




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« Reply #3 on: March 13, 2019, 08:01:19 AM »

http://www.karinya.net/g3txq/chokes/type31.jpg
This chart suggests the optimum number of windings for stacked FT-240-31 cores.  
Sadly, Steve passed away recently.  Many amateurs who find that toroids "don't work" haven't used an optimum number of turns.

Thanks for the information.  I already have toroids on my antenna feedline with winds as described by the provided charts and confirmed with other research.  The toroids on the feedline have been effective at reducing/eliminating other EMI.  However, the EMI from the refrigerator is still getting through.

Regards,

Danny - KF9BD
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W9IQ
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Posts: 2907




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« Reply #4 on: March 13, 2019, 08:21:34 AM »

It could be that the noise is primarily conducted through the power lines, rather than radiated.

You may wish to try an in-line EMC filter such as Schaffner. Model: FN2060-20-06. This recently was reported on this forum as a fix for a pool pump with an integral VFD that was causing RFI problems.



- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
WB4SPT
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Posts: 755




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« Reply #5 on: March 13, 2019, 08:39:56 AM »

I am a bit surprised 3x mix 31 had little effect on the power cord.   At these HF freqs, I would tend to think the reefer is NOT directly radiating.  The corcom/schaffner line filter would be my next try. 
Does the noise correlate with compressor/fans or is it always an issue, even during defrost cycle, for instance?
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KF9BD
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Posts: 61




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« Reply #6 on: March 13, 2019, 09:38:50 AM »

I am a bit surprised 3x mix 31 had little effect on the power cord.   At these HF freqs, I would tend to think the reefer is NOT directly radiating.  The corcom/schaffner line filter would be my next try.  
Does the noise correlate with compressor/fans or is it always an issue, even during defrost cycle, for instance?

I was surprised the toroids did not work better as well.  The noise is constant, with no significant variation due to refrigerator operations.  When I place a sensing antenna, attached to a spectrum analyzer, close to the side of the refrigerator I see a significant increase in the noise floor with discernible peaks across the 3 to 16 mhz range.  If I disconnect the refrigerator from power the noise goes away completely.

What about using a Tripp Lite power line filter?  The specs indicate a 40 to 80 db reduction in RFI?  Just thinking the Tripp Lite component would be easier to install (just plug it in) and would be portable.

Danny
« Last Edit: March 13, 2019, 09:59:56 AM by KF9BD » Logged
WB4SPT
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Posts: 755




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« Reply #7 on: March 13, 2019, 10:29:12 AM »

Yes. I actually have a TL power strip with emi filter on my clothes washer.  They have basically have a pi filter inside.
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KF9BD
Member

Posts: 61




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« Reply #8 on: March 13, 2019, 11:01:30 AM »

Yes. I actually have a TL power strip with emi filter on my clothes washer.  They have basically have a pi filter inside.

We're you experiencing EMI from the washer?  Did the TL strip eliminate the EMC?

Danny
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WB4SPT
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Posts: 755




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« Reply #9 on: March 13, 2019, 01:08:02 PM »

actually, I put it on for the MOV benefits.   I don't have any local RFI issues to speak of, since I tamed down the Trane furnace.  I do still have some VHF junk coming out of a couple outdoor LED lamps.    No LG appliances, either.  Just the usual Whirlpool conglomerate stuff. 
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K0UA
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Posts: 3889




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« Reply #10 on: March 14, 2019, 08:42:36 AM »

Yes. I actually have a TL power strip with emi filter on my clothes washer.  They have basically have a pi filter inside.

We're you experiencing EMI from the washer?  Did the TL strip eliminate the EMC?

Danny

Yep, washers have Variable Frequency Drives in them now.  They are noisemakers. My LG washer makes some noise.
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KF9BD
Member

Posts: 61




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« Reply #11 on: March 14, 2019, 03:59:38 PM »

Yes. I actually have a TL power strip with emi filter on my clothes washer.  They have basically have a pi filter inside.

We're you experiencing EMI from the washer?  Did the TL strip eliminate the EMC?

Danny

Have you done anything to address the noise?  If so, what?

Danny ny

Yep, washers have Variable Frequency Drives in them now.  They are noisemakers. My LG washer makes some noise.
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K5LXP
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Posts: 6045


WWW

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« Reply #12 on: March 18, 2019, 10:58:11 AM »

 
We're missing the other half of the equation- what is the receive antenna?   Coupling/distance from the source can make a huge difference.  For all we know (at this point) the level of interfering emission may not be out of compliance but could be insufficient isolation from the source. 

Mark K5LXP
Albuquerque, NM
 
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W9IQ
Member

Posts: 2907




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« Reply #13 on: March 18, 2019, 11:11:02 AM »


We're missing the other half of the equation- what is the receive antenna?   Coupling/distance from the source can make a huge difference.  For all we know (at this point) the level of interfering emission may not be out of compliance but could be insufficient isolation from the source. 

Mark K5LXP
Albuquerque, NM
 

Mark,

Just an interesting data point:

15.103 Exempted devices.

The following devices are subject only to the general conditions of operation in ยงยง 15.5 and 15.29 and are exempt from the specific technical standards and other requirements contained in this part...

15.103(d) A digital device utilized exclusively in an appliance, e.g., microwave oven, dishwasher, clothes dryer, air conditioner (central or window), etc.

So the manufacturers are exempt from any emission requirements but if you as the owner/operator cause harmful interference by using the device, the FCC can require that you stop using it.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
KF9BD
Member

Posts: 61




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« Reply #14 on: March 19, 2019, 07:53:03 AM »

Interesting information.  As to the receive antenna, the antenna is in the attic above the second floor of the house.  The refrigerator is on the ground floor of the house.  Certainly not the best of situations.  I tested the circuits again to confirm that the noise source was the refrigerator, and, it certainly is.  I reached out to LC customer support about a week ago, but, haven't heard from them as yet.  If they don't provided assistance, I will pursue installation of an EMI/RFI filter in combination with the already installed toroids.

Danny
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