On 8/27/2020 10:39 AM, Mike Flowers wrote:
Sometimes, a line or cable is just the right fraction of a specific wavelength
to act as an efficient antenna, and RF will find it's way in.
These issues are often prevented simply by practicing the proper bonding
within the station, providing a counterpoise for any end-fed antennas
(verticals, random wires), and using an effective ferrite choke at all
antenna feedpoints. The feedpoint is where the feedline connects to the
antenna (up in the air, or at the end of the end-fed wire). Without this
choke, your feedline, and everything it is connected to, including stuff
in your shack and AC wiring, is carrying antenna current.
Note that non-resonant antennas, especially those fed with 2-wire line,
cannot be effectively choked.
Effective chokes you can build are here.
http://k9yc.com/2018Cookbook.pdf
Do NOT be a sucker for commercially made chokes, including those from
Balun Designs, Palomar, and most other ham vendors. They won't blow up,
mainly because they aren't doing anything useful.
73, Jim K9YC
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