[RFI] 160 meters RFI caused by low voltage bookcase lights

Jim Brown jim at audiosystemsgroup.com
Mon Sep 29 14:54:28 EDT 2014

This is a VERY VERY VERY common problem -- yet another dirty switching 
power supply.

The easiest cure is to replace the power supply with a linear supply.  
First, you must measure the voltage and current. Then look for a linear 
supply having the same voltage and current rating, break the cable 
between the supply and the lights, and splice in your linear supply.

Depending on the current you need, you may find a vintage wall wart that 
provides sufficient current.

A variation of this solution if the supply can't supply the current is 
to add a suitable lead-acid battery that you can trickle charge from the 
linear wall wart.

It is often possible to kill the noise with a suitable ferrite choke.
Study k9yc.com/RFI-Ham.pdf

You will need a choke on both the AC and low voltage sides of the noisy 

73, Jim K9YC

On Mon,9/29/2014 10:25 AM, Don Kirk wrote:
> Late last week I encountered interference on 160 meters which was repeating
> at 41 khz intervals, and this morning I was able to track the problem down
> to low voltage bookcase lights at my neighbors home which is 430 feet
> away.  I created a website to document this case which includes a link to a
> youtube video that contains receive audio of the noise, and my simple
> website URL is http://sites.google.com/site/bookcaselightsrfi/
> The signal was S9 on 160 meters (approximately 15 dB above my noise floor
> when using a 500 hz receive filter), and it could be heard up into the 80
> meter band.
> We (my neighbor and I) will now dig into his low voltage lighting system to
> see what we can do to eliminate the interference.
> Just FYI,
> Don Kirk (wd8dsb)
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