Tom, W8JI wrote:
"A reflector does not reflect anything. It radiates."

Call a parasitic element anything you like, but the convention has
already set in.

Kraus tells the Yagi-Uda story on page 246 of his 3rd edition of
"Antennas". He writes:
"He (Uda) found the highest gain with the reflector about lambda/2 in
length (they must be near resonance to get excited properly) and spaced
about lambda/4 from the driven element, while the best director lengths
were about 10% less than lambda/3."

Uda`s reports were published between March 1926 and July 1929. There has
been much fine tuning since then.

On page 245, Kraus writes:
"When the parasitic element is inductive (longer than its resonant
length) it acts as a reflector. When it is capacitive (shorter than its
resonant length) it acts as a director."

Shortwave broadcast station I worked in about a 1/2 century ago used
parasitic arrays of horizontal antennas. They were called "curtains". We
did the adjustments of reflector phasings near the earth. The reflectors
had feedlines like the driven elements, but were connected to
short-circuit stubs instead of a transmitter. The shorting bar location
was adjusted for the proper phase lag behind the driven element. It`s
easier than trimming the reflector.

We hung sampling loops from the driven element and reflector and fed
them to an RCA WM-30-A phase monitor exactly as were used in medium wave
broadcast stations for maintenance of directional arrays.

You could have used such a phase monitor to check the phase difference
introduced by a mobile loading coil. It is an oscilloscope fitted with a
precision phase shifter which identifies which of the 4 quadrants the
phase difference falls in and the number of degrees.

The parasitic reflector performs the function of reversing the direction
of much of the energy traveling toward it. Someone in this thread said
it can be 99% effective. I also recall reading somewhere that if you are
constructing a 2-element parasitic array, you`ll get more gain from a
director than from a reflector. Our broadcast plant was behind our
reflectors so it made sense to protect it in spite of perhaps a slight
gain penalty.

Best regards, Richaed Harrison, KB5WZI