[RFI] LG machines can be OK

Jim Brown jim at audiosystemsgroup.com
Sat Jan 27 17:10:51 EST 2018

On 1/27/2018 11:11 AM, Alex wrote:
> We purchased a LG washer (model WM3270CW) and dryer (model DLE3170W) 
> at the end of 2016 based on a Consumer Reports recommendation and 
> searching the net for *substantiated* reports of RFI problems (we 
> found none). 

Exactly what would you consider "substantiated?"

> After installation I checked with a FT-817 around the appliances and 
> found no significant RFI from either.

While we're all glad that you've found a good product that doesn't cause 
you problems, I would not consider your report "substantiated." Rather, 
I would like to see broadband waterfalls that cover a wide swath of 
frequency from an SDR connected to some sort of antenna close to the 
product and its wiring. Noise generated by electronic products that are 
not arcing tends to concentrated in frequency. There are broad "humps" 
of noise that repeat very 10 - 30 kHz and are unstable in frequency 
(generated by switch-mode power supplies and motor controllers), and 
there are steady (or pulsing) carriers (generated by microprocessor 
clocks and their circuitry.  Noise from these products is often much 
stronger (or absent) in different frequency ranges. The 33V power supply 
that SteppIR shipped me was MONDO noisy between 17M and 10M (like 20dB 
over S9 on 12M into the 3-el on a 120 ft tower 200 ft away!). Noise was 
present on lower bands, but not nearly as bad.

The most likely cause of RFI in a product that has a motor is a variable 
speed controller for it. Variable speed controllers are a strong and 
well known cause of RFI. They cause RFI when the motor is running, but 
are unlikely to do so when the machine is idling. Another likely cause 
is a switch mode power supply for on-board electronics.

73, Jim K9YC

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