[RFI] RFI on 40 meters tracked down to Solid State Mini Fridge

[Jim Brown]

On 1/13/2025 9:16 AM, Don Kirk wrote:

> Next step will be to try various filters that I have on the power cord to
> see if we can eliminate the RFI.  Note: The fridge plugs directly into a
> 120 Vac outlet (no external power supply) and it uses a 2 prong plug.  It
> also has a power jack if you want to power it with a 12 Vdc 3 amp power
> supply.
Hi Don. Thanks for the NAQP QSO.

The unit is feeding common mode RF current to the power system in that 
home, which is acting as an end-fed long wire. The first thing I would 
try is to wind the power cord through a #31 Fair-Rite 2.4-in toroid 
following the recommendations  in my 2018 Cookbook for the transmitting 
chokes. Alternatively, wind as many turns as you can through a 1-in i.d 
#31 clamp-on, WITH THE TURNS BEING IN ORDER AROUND IT! See Fig 28b and 
28c in RFI-Ham.pdf at kyyc.com  If the power cord isn't long enough, or is 
too big, add a choke into a short section of power cable. Wind that 
choke with as many turns as you can in a single layer of #18 zip cord. 
This choke is for maximum effectiveness on the lower bands.

Traditional power line filters are unlikely to do much, because they 
need access to the chassis of the source for their differential mode 
networks to work.

73, Jim K9YC