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Cecil Moore · July 7th 06, 02:57 AM posted to rec.radio.amateur.antenna

wrote:
1.) You have a half-wave end-fed antenna. There has to be as much
common mode current leaving the end of that point and flowing down the
feedline as there is flowing out onto the antenna at that point. There
isn't any exception to this rule.

It certainly isn't that simple in a distributed network.
The currents into the end of a half-wave section are certainly
unbalanced at X and Y but the current amplitudes are pretty low.
5 watts into 5000 ohms is only about 30 mA. 1/4WL back at the
shorted matching section at ++, the currents have to be close to
balanced because of the short. The coax connection at A and B is
closer to the short than it is to to X and Y. The current down
the coax braid at B does NOT have to be equal to the current at
the feedpoint at X since they are a good percentage of 1/4WL
different in location. And common-mode current can form standing
waves so common-mode current maximums and minimums exist depending
upon location on the feedline. The lumped circuit model strikes
(out) again.

X
+--A----------------------------
|
+--B--------Y
--
73, Cecil http://www.qsl.net/w5dxp