[Elecraft] 12 meter K3 RFI from nearby FM station

[Jim Brown]

On Thu,2/11/2016 10:55 AM, Jon Zaimes wrote:
> Yes, that is the case. Hearing it on both of my K3 transceivers with only
> the 12v power cable connected, nothing else (listening on speaker).

I'm assuming this means nothing at all plugged into the back of the rig 
-- no control, no audio, nothing to the BNCs, nothing to the Aux power 
jack.

By all means choke the 12V DC cable. Since the RFI is VHF, this IS an 
application for a "string of beads" choke. #43 clamp-ons would be the 
weapon of choice, either single turn or two turns. #31 would also work. 
What you want is a clamp-on with two turns through it, a short length of 
the power cable, then another clamp-on with two turns, a short length of 
cable, then another clamp-on with two turns, and so on. Select the size 
of the clamp-on to fit the number of turns. Turns should be widely 
spaced. Do NOT run two turns through a string of clamp-ons -- that will 
take the resonance too low in frequency to work at 90 MHz.

You can see data for the choking Z of individual Fair-Rite parts with 
one, two, and three turns on the data sheets for those parts. Click on 
the part number in the table of parts to get that data sheet, then 
scroll all the way down for the impedance plots. You may need to click 
on that to get the three turn plots.

73, Jim K9YC