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Author Topic: Dishwasher motor noise on all frequencies.  (Read 5785 times)
KE0JWA
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Posts: 4




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« on: August 18, 2017, 07:24:45 AM »

I am pretty new to ham radio so I am a bit lost.

I am getting motor noise from my dishwasher on all frequencies.  I was wondering where to put some torrids, or if they would help at all?

Not sure where to start and would appreciate any advice on where to start.

Thanks.

Randy
KE0JWA
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KC2MMI
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Posts: 812




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« Reply #1 on: August 18, 2017, 10:19:49 AM »

If it is RFI being broadcast from a sparky motor, that's a spark gap generator and nothing will help until the entire motor assembly is in a Faraday cage. Replacing the motor or cleaning the brushes and shaft contacts might help if it is just old age and dirt, or replacing it with a different type of motor (Is it slip rings that have no contact noise?) could do it.

If it is just EMI going out the power cord, then try choking it AT the motor, as well as again where the power cord exits the metal dishwater case, if there is one.

First try asking the manufacturer, they often have RFI suppression kits that they don't admit exist, until you've gone to a supervisor.

Our dishwasher just sings quietly while she works, not much of a problem. That's what happens when you cheap out and hire mechanical house servants, nothing but problems.
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G4LNA
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Posts: 146




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« Reply #2 on: August 18, 2017, 11:04:33 AM »

Without hearing the noise it's difficult to advise, it could be the motor if it's got brushes or if the machine is fairly new, it could be one that has a digital motor driver, our Miele which has a digital motor drive creates merry hell and I haven't found a way to stop it, damned thing costs enough.
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KE0JWA
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« Reply #3 on: August 18, 2017, 11:16:56 AM »

This is a brand new dishwasher....hard to tell what kind of motor it has.

You know I think the best idea might be to run the dishwasher at bed time......right?
« Last Edit: August 18, 2017, 11:31:12 AM by KE0JWA » Logged
KC1BMD
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Posts: 612




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« Reply #4 on: August 18, 2017, 11:20:27 AM »

A bedtime run is not a bad idea, if it's a relatively silent machine Smiley.

I have some minor motor noise from my washing machine. I tried some snap-on ferrites but no relief. Of course, it doesn't help that I cannot determine where the noise is actually coming from (radiated vs. conducted,...common mode vs. differential mode...). If your dishwasher is anything like my washing machine (just me and the wife, YMMV if kids are involved Smiley), it doesn't run very often, perhaps once a week and then only for a couple of hours. So I try to plan my on air time around it. However, if you use it often, then I certainly can understand your desire to solve rather than ignore it. That would be like my furnace draft inducer motor noise, which is really annoying in Winter because it runs so often. I've not been able to solve it with an RFI kit from Trane, nor with snap-on ferrites, so I have to put up with it unless I get a better idea. Nevertheless, it's certainly worth asking the manufacturer and doing a little experimenting to see if the fix is simple. Unfortunately, in my experience, the noise problems are consistently one step ahead of me.
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KM1H
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« Reply #5 on: August 18, 2017, 03:10:10 PM »

Quote
Trane, nor with snap-on ferrites, so I have to put up with it unless I get a better idea. Nevertheless, it's certainly worth asking the manufacturer and doing a little experimenting to see if the fix is simple. Unfortunately, in my experience, the noise problems are consistently one step ahead of me.

What frequencies are affected and is there a peak band? Can you tune well below the AM Broadcast band?

Most snap on chokes are pretty useless as they are for the actual ham bands for 40 and up and individually have very little choking action, and certainly not the actual RFI fundamental frequency.

Carl
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KC1BMD
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Posts: 612




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« Reply #6 on: August 19, 2017, 05:41:03 PM »

The noise is fairly broadband Smiley). I work 40-10 and 40/20 very much affected across both. I'm out of ideas.
« Last Edit: August 19, 2017, 05:43:16 PM by KC1BMD » Logged
KAPT4560
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Posts: 384




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« Reply #7 on: August 20, 2017, 03:35:52 AM »

 Is this plugged into a wall outlet or wired to a junction box? Is the chassis/cabinet ground (green wire?) secure and is it really a ground?
 I went around our (older) house with an AC outlet tester and was fairly horrified at the number of 'no grounds' and reversed Hot/Neutral terminals.
 Is there is a 'switching' power supply for the motor controller, that cam make a lot of noise on AM.
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KH6AQ
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Posts: 7718




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« Reply #8 on: August 20, 2017, 09:13:00 AM »

Ferrite cores on the AC power cable are usually the first thing to try. The FT240-43 core is available from several suppliers. JPM Supply and Mouser sell them for around $10. The downside to this core is that only a couple of turns will fit with the AC power plug and this does not provide a high common-mode impedance. Stacking cores helps; the impedance is proportional to the number of cores and to the square of the number of turns. For example, if the core impedance is 100 ohms for one turn it's 400 ohms for two turns.


https://www.jpmsupply.com/Toroid-Core-FT240-43-Ferrite-p/38021.htm

http://www.mouser.com/ProductDetail/Fair-Rite/5943003801/?qs=sGAEpiMZZMs2JV%252bnT%2fvX8PSq2BULPkJLFOO3yrB4H3E%3d


G3TXQ shows eight to twelve turns providing a high impedance throughout the HF range. Eight turns on one core is equivalent to one turn through 64 cores.

http://karinya.net/g3txq/chokes/


DX Engineering clamp-on cores might work. Two or three turns of the power cores should fit on a DXE-CSB-750P ferrite core. Five cost $33 and I'd arm myself with two kits.

https://www.dxengineering.com/parts/dxe-csb-750p



« Last Edit: August 20, 2017, 09:23:42 AM by KH6AQ » Logged
KH6AQ
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Posts: 7718




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« Reply #9 on: August 20, 2017, 10:00:55 AM »

If the dishwasher is plugged in, and not hard-wired, the outlet will be in an adjacent cabinet. In this case a plug-in AC line filter is an option. A Google search shows several plug-in AC line filters but not many with current ratings high enough for a dishwasher (>10A?). Here's a 20 amp filter.

http://www.onfilter.com/products.html?s=20ASF2



And here's a 10 amp filter.   

https://www.amazon.com/X10-XPPF-Plug-Noise-Filter/dp/B0002M5OJI



The MFJ-1164B could work but it's not UL-listed and I would not use it. Unless the MOVs have series fuses (the schematic shows no MOV fuses), or the MOVs have integrated thermal protectors, the unit could not be UL compliant.
« Last Edit: August 20, 2017, 10:22:21 AM by KH6AQ » Logged
KC1BMD
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Posts: 612




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« Reply #10 on: August 20, 2017, 02:48:35 PM »

To all: Please ignore my comments about the Trane furnace noise. It was a sidebar comment when I was commenting on the OP's dishwasher noise. I didn't intend to hijack this thread with an unrelated issue. Again, my apologies.
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KM1H
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Posts: 2633




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« Reply #11 on: August 22, 2017, 03:19:30 PM »

Quote
Ferrite cores on the AC power cable are usually the first thing to try. The FT240-43 core is available from several suppliers. JPM Supply and Mouser sell them for around $10.

It has been $4.26 at Mouser for years; my #1 choice for ferrites.
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VK2LEE
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WWW

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« Reply #12 on: October 13, 2017, 05:00:15 AM »

Although We are being told that We have the most expensive electricity in the World, We have what is called OFF PEAK electricity which is much cheaper than the two peak day time rates. the Off Peak rates is from 10pm until 7am next morning, so, it is best to use the dishwasher and clothes washing machine etc during the night.  My 4 year old LG Dishwasher and LG Washing machine don't make much noise at all, apart from when they finish and they BEEP BEEP BEEP .. Naturally I'm NOT using My HF transceiver during these hours... Hi Hi...  unless there is a contest on... Hi Hi...

Lee  VK2LEE 
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28 years as VK2LEE - The 1st 3 letter L call ever issued - in 1986 -
WB4SPT
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Posts: 498




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« Reply #13 on: October 17, 2017, 06:32:14 AM »

Although We are being told that We have the most expensive electricity in the World, We have what is called OFF PEAK electricity which is much cheaper than the two peak day time rates.

Lee  VK2LEE 


YOUR problem is not generation cost, since hydro is quite low.  The problem is the 330million folks living below you buying a large percentage of your capacity!  over 60 TW.   Grin
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WB4SPT
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Posts: 498




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« Reply #14 on: October 17, 2017, 06:34:14 AM »

I am pretty new to ham radio so I am a bit lost.

I am getting motor noise from my dishwasher on all frequencies.  I was wondering where to put some torrids, or if they would help at all?

Not sure where to start and would appreciate any advice on where to start.

Thanks.

Randy
KE0JWA

Randy;   have you discovered what type motor you have? 
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