Then the book is incorrect assuming you are using statements corectly
Art
"Richard Harrison" wrote in message
...
Art Unwin wrote:
"You place another element closely (behind usually) to the driven
element such that with a "critical coupling" the feed impedance
increases to the desired level."

That`s not the way it works. More coupling lowers the feed impedance.

Check under "Close-spaced Arrays -- Super-=gain Antennas" on page 906 of
Terman`s 1955 edition:
"A characteristic of all close-spaced arrays is that as the ratio of
size to antenna gain is reduced, the radiation resistance also goes
down;---." The Yagi antenna of Fig.23-39, and the corner reflector,
represent almost the best that can be achieved in a compact array."

Notice that Terman said "almost". There`s always hope, but looking for
more gain by element spacing changes has been thoroughly investigated.
This is akin to to drilling in a field which is already overdrilled in
the search for oil.

Moving elements closer together brings the radiation resustance down.
The elements don`t know if a coupled element is ahead of the driven
element or behind it. It brings the drivepoint impedance down for the
driven element. Impedance adjustment is done through transformation.

Best regards, Richard Harrison, KB5WZI