Tom, K0TAR wrote:
"What I meant was, none of the elements of a yagi are resonant, except
perhaps the driven element."

That`s usually right. The reflector is lengthened and directors are
shortened to conveniently produce phase relations which determine
reinforcement or repression in directions as desired.

However, this is not the only way. Commercial broadcast curtain antenna
arrays use parasitic elements which have the same length as the driven
elements in some instances. Short-circuit stubs repalace drive lines in
the parasitic elements, and these are adjusted for the desired phasing
instead of adjusting element lengths.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:

That`s usually right. The reflector is lengthened and directors are
shortened to conveniently produce phase relations which determine
reinforcement or repression in directions as desired.

However, this is not the only way. Commercial broadcast curtain antenna
arrays use parasitic elements which have the same length as the driven
elements in some instances. Short-circuit stubs repalace drive lines in
the parasitic elements, and these are adjusted for the desired phasing
instead of adjusting element lengths.


That's a nice trick. Of course that still means they aren't resonant
since you just displaced the "center" of the element. Seems a good way
for a broadcaster to be able to adjust the pattern if needed after
construction.

I seem to remember an HF wire antenna project that used that method to
go from driven plus reflector to driven plus director to get a
reversible beam. I also remember a set of 5 slopers that were in the
ARRL antenna book or handbook that could be steered.

Oh well, way off topic here now. cul

Tom
K0TAR

Tom, K0TAR wrote:
"Of course that still means thery aren`t resonant aince you just
displaced the "center" of the element."

Kraus describes adjustment of the phase between driven and parasitic
elements on page 320 of his 1950 edition of "Antennas":

"The parasitic element may have a fixed length of 1/2 wavelength, the
tuning being accomplished by inserting a lumped reactance in series with
the antenna at its center point."

In my case, the "lumped reactance" was a tuned stub adjusted to the
desired phase difference between parasitic and driven elements as
indicated by an RCA WM-30A phase monitor.

Best regards, Richard Harrison, KB5WZI