Roy Lewallen wrote:
I'm
particularly targeting Cecil, and others who have bandied about a lot of
pseudo-analysis about electrical length, reflections, and the like.

Balanis would be surprised to know that you consider the material that
he teaches in his classes at ASU to be pseudo-analysis. Some of the
stuff I have posted is in Balanis' book, _Antenna_Theory_ which you
haven't read. In particular, he says: "Standing wave antennas, such
as the dipole, can be analyzed as traveling wave antennas with waves
propagating in opposite directions (forwards and backwards) as represented
by traveling wave currents If and Ib in Figure 10.1(a)."

I'm just wondering how you can be so sure that what I have offered is pseudo-
analysis and which of the following statements you disagree with. Please
be specific.

1. The feedpoint impedance of a typical traveling wave antenna is in the
hundreds of ohms since there are no reflected waves.

2. The feedpoint impedance of a standing wave antenna is the result of
superposition of forward and reflected waves (which cause the observable
standing waves).

3. At the feedpoint of a 1/2WL resonant dipole, the forward current, reflected
current, and forward voltage are all in phase. The reflected voltage is 180
degrees out of phase. This results in a purely resistive low-voltage/high-current
ratio for the feedpoint impedance.

4. The above relationship is true for any dipole, 1/2WL or physically shorter,
that has a purely resistive feedpoint impedance. (No resistive loading)

5. The phases of the signals at the feedpoint are known. The phases of the signals
at the open tips of the dipole are known. Any loading used in order to increase
the electrical length to 1/2WL must maintain those known phase conditions in
order to achieve a purely resistive feedpoint impedance.

On page 18, in Figure 1.15, Balanis shows how a 1/2WL dipole is achieved by
flaring out the last ~1/4WL of an unterminated transmission line. He says:
"As the section of the transmission line begins to flare, it can be assumed
that the current distribution is essentially unaltered in form in each of
the wires."
--
73, Cecil http://www.qsl.net/w5dxp



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