Sunday, December 4, 2016

Dirty Balun - Common Mode Choke Info

I stumbled across this on the web, and snagged it for my website. Great info from G3TXQ on the subject. I plan to buy some Amidon FB-31-1020 ferrite beads and rework my common mode choke at the feed points of my antennas, when I move them to a higher perch.

I've used the air-core version wound from feed line on my yagi's and dipoles since the 1970's to keep stray RF out of the shack, but it's easy to see the improvement in EMI blocking with the FB-31-1020 ferrite beads simply slipped over the feed line at the feed point connection. Here's his chart.

Be sure to check out his website for load of great info at