Sunday, August 29, 2010

My RFI adventure

RFI affected IMac
I was spending an enjoyable afternoon with my Elecraft KX1 I was using the 20 meter dipole located in the attic. Then the unthinkable happened, my door opened with my wife announcing "Are you on the radio" Now she is either really excited about becoming a ham (NOT) or there is RFI somewhere it shouldn't be!!!! Julie has a photography business and my CW was scrambling her IMac screen, with only 2 watts from my KX1 to boot. Here is what I did, I removed all USB controlled devices put a load of snap-on chokes on the AC line. I found the screen  to be fine and I slowly hooked up all USB devices after each device was connected I transmitted and all was good. Soon the IMac was loaded again with all devices and no RFI. I thought to my self  "that was easy......way too easy"
There is a new mouse in town
Julie and the IMac are happy
As Murphy would have was too easy. Soon after the short lived RFI victory my door opened again with bad news. Well it boiled down to what seemed to me to be a very inconsistent RFI problem. It seemed to me anyway there was no rhyme or reason to how her IMac was picking up the RFI. I decided it was time to order out for help!!! I posted my problem on a forum called Nabble check out this site it is a fantastic resource for more than just Amateur radio. Well the emails started coming in and one common thread with the responses was that the IMac mouse is the problem. The emails explained  how
Possible impending death sentence

the mouse acts like an antenna, sometimes not until Julie touched the mouse. That made sense and had me understand how all seem to be well and it was not until she touched the mouse all hell broke loose with the IMac. So off came the snap-on chokes on the AC line and I swapped out the mouse and voila all was good. As for the the Mac mouse the jury is still out on whether he is doing a life of hard time or the death penalty.
Or condemned to hard time


  1. I had intermittent RFI problems as well - when operating on 12 or 15 meters, my computer's mouse & keyboard would lock up. The fix was simple, effective and cheap: just coiled up the slack in the mouse/kybd USB cables and secure the resulting coil with tie wraps. Problem solved. Wish they could all be that easy!

  2. Yes John I too had lockup troubles with my keyboard...during CQWW CW of all times. For me it was 6 turns of the keyboard cable around a snap-on toroid and all was well.

  3. Oh well, RFI can be very annoying. It is good you have solved the problems. We can reduce a lot of RFI with snap-on toroids. 73 Paul