RadioBanter - View Single Post

March 7th 06, 10:37 AM posted to rec.radio.amateur.antenna

wrote:
My obviously-overloaded must-be-pea-sized brain sure has trouble thinking
of current which is NOT flowing, since my basic internal definition of
"current" is something like "electrons flowing past a point".

Forward current is a traveling wave and is flowing. Reflected
current is a traveling wave and is flowing. Both can be
represented by phasors. But since they are traveling in
opposite directions, their phasors are rotating in opposite
directions and their superposed sum always add up to the
same constant phase angle = zero (in a thin wire).

Given a 1/2WL (-90 deg to +90 deg) thin wire dipole fed in
the center (at 0 deg) with 1.0 amps, the standing wave current
magnitude on the antenna is cos(theta) and the phase angle
is a constant zero degrees from end to end. Reference: Figure
14-2, page 464 of "Antennas for All Applications", by Kraus
and Marhefka, 3rd edition.

If the phasor sum of two currents is not rotating, it is not
flowing. Since phasors, by definition, change phase at a rate
of (2*pi*f) and the standing wave current doesn't change
phase at all, I don't think standing wave current is a phasor.
Standing wave current is what we measure on a standing-wave
antenna like a 75m mobile center-loaded bugcatcher.
--
73, Cecil http://www.qsl.net/w5dxp