On 10/1/2025 10:46 AM, Howard Hoyt via TowerTalk wrote:
If you look at the magnitude of CM currents using an inductive pickup on
feedlines as I have you will see both CM chokes and grounding can reduce
CM currents at the shack, but the grounding is perhaps more problematic
Mostly good observations, Howie. but problems in the shack have NOTHING
to do with grounding, and everything to do with BONDING! Earth
connections are about lightning safety. If chokes solve problems in the
shack, some element of bonding is not done properly.
And when trying to measure CM on the line, we get into the obvious
problem of doing so without disturbing the system we're trying to
measure. Any conductors that couple to the line can do that if they are
large enough (as a fraction of wavelength, and depending on the
impedance of the common mode circuit at the point of measurement).
73, Jim K9YC
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