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Though there is a plethora of information regarding appliances and such that emit RFI/EMI and how to attack the issues, I have one that is eluding repair when trying various methods. I have a Maytag refrigerator, which by the way I have asked for and am awaiting help from Maytag, that emits an S9 +20 dB noise (-53dBm, or 0.5mV into 50 Ohms) across several amateur radio bands.

This prevents me, an amateur radio operator, from using those bands. I have tried ferrite clamp-on devices. I have put as many as 6 of the ferrites on the power cord to no avail.

  1. Will a larger toroidal ferrite with the cord wound through it would be a better killer of the RFI?
  2. Or are there other methods that have been tried and found to work?

This is a big problem so I'm interested to hear from anyone on how they have had the good fortune in trying different things for similar issues.

Ecnerwal
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tedson
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    Wouldn't the ferrite on the cord only help if the cord is acting as the antenna? If the signal is coming, for example, from the control board with the metal frame of the refrigerator as the antenna, I don't see how the ferrite would help at all. – manassehkatz-Moving 2 Codidact Jan 24 '23 at 19:12
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    Interesting question. Not quite sure if this is the best page for it or one of the others might be better. Model of the fridge might help. – crip659 Jan 24 '23 at 19:15
  • Depending how it's coupling, if along powerlines, you might look at putting a "surge capacitor" (which also serves as a "facility emi filter") on it. Mine are (the fast) part of my overall surge suppression system. Delta CA603, just a happy customer... CA302R is a bit less expensive. – Ecnerwal Jan 24 '23 at 21:14
  • Do you know for sure it's the refrigerator, in that if the unplug the refrig, the RFI goes away? – SteveSh Jan 24 '23 at 21:56
  • And what is S9 referring to in "S9+20 dB"? – SteveSh Jan 24 '23 at 21:58
  • Also, what amateur bands are being affected? Are they the HF bands, 3 MHz - 30 MHz? – SteveSh Jan 24 '23 at 22:01
  • What kind of cable are you using to go to the antenna? Is it 300 ohm twin lead? Coax? Something else? – SteveSh Jan 24 '23 at 22:06
  • I’m voting to close this question because it does not have to do with home improvement issues. – RMDman Jan 25 '23 at 01:11
  • I'm going to suggest this question gets moved over to the Electrical Engineering site. – SteveSh Jan 25 '23 at 01:13
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    @RMDman -- I flagged this for migration to hamradio or EE -- it needs to stay open though lest the Stack system reject the migration – ThreePhaseEel Jan 25 '23 at 03:27
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    That said: what model is your fridge? This very well could be an appliance that's gone off the reservation and started violating Part 15 due to damaged filter components in some of its electronics, given how many fancy digital gizmos modern appliances have... – ThreePhaseEel Jan 25 '23 at 03:29
  • Seems like a great fit for [ham.se]. Of course, they'll probably want more details over there, too, but who knows, this may be more than clear enough for folks who know what he's talking about... – FreeMan Jan 25 '23 at 12:38
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    Questions need to have enough detail that they wouldn't be closed on the receiving site. I'm closing this for now since there are too many unanswered comments. It can be reopened and migrated after editing for more detail, or a new question can be opened on the appropriate site. – BMitch Jan 25 '23 at 14:03
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    The specific affected bands and the specific model of fridge would be good to get sorted. I explained and linked more explanation of the "ham-jargon-only" noise level. – Ecnerwal Jan 25 '23 at 18:50
  • All else fails: add as many milk jugs of water as possible to the freezer, wait a day or two, then you can turn off or unplug the fridge when you need radio silence. – dandavis Jan 26 '23 at 01:26

1 Answers1

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A ferrite core is useful a higher frequencies; but if you're in he lower ham bands, there are a few things that might help.

  1. Bond the doors to the refrigerator cabinet with braided copper bonding straps. If possible, use available screw holes. N.B. drilling into the cabinet can accidentally pierce refrigerant pipes and vacuum insulation, effectively destroying the fridge.

RFI Filter

  1. Put a simple radio frequency interference (RFI) suppression filter, AKA electromagnetic interference (EMI) filter, shown above, in the power cable. For best results, the filter should be mounted inside the fridge cabinet, screwed to the metal shell before the power cable, but if that is not practical, tuck the power cable inside a can connected to the cabinet, with the RFI filter (still bonded to the cabinet) between cable and an extension cord to the mains. Such a filter can be found for US$8, though you might need a different filter for bands of interest. or can be made by the user from a torroid and a few capacitors. The values of the inductor and capacitor depend on the bands to which you listen.
DrMoishe Pippik
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