I think I understand that common mode chokes are important on small
loops and other low-output receiving antennas, in order to prevent
signals being received on the shield of the feedline and passed
through the matching transformer primary at the antenna end, to join
the desired differential-mode signals on the coax which then go to
the receiver.
But what about the case of a different termination at the antenna
end, such as a preamp or an active antenna amplifier unit? Does the
same still apply, or does the termination in the output of that
amplifier attenuate the common mode currents sufficiently to make the
common mode choke unnecessary?
73, Pete N4ZR
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