Art, KB9MZ wrote:
"Personally, I see antennas gyrating towards smaller antennas where
radiation per unit length will finish at the top of the heap."

Kraus, W8JK is somewhat famous among many reasons for his experience
with close-spaced antenna elements.

On page 184 of the 3rd edition of Kraus` "Antennas for All
Applications", is Figure 6-12 containing an ordinarily-spaced broadside
driven-array of two dipoles and a driven array radiating in the plane of
the two dipoles (an end-fire array), the W8JK array.

A feature of the W8JK array is close-spacing (1/8-wavelength). Gain of
the W8JK array is a tiny bit more than that of the 4X wider-spaced
broadside array. It`s a pity if you don`t have a copy of Kraus
available.

Kraus says in his earl;ier 1950 edition of "Antennas" on page 295:
"The end-fire array of two side-by-side out-of-phase 1/2-wavelength
elements discussed in Sec. 11-3 produces substantial gains even when the
spacing is decreased to small values."

To my eye, the W8JK array resembles the Adcock antenna if so spaced and
polarized. The 1955 edition of Terman has the Adcock on page 1050.

Terman has a comment on page 906 of his 1955 edition regarding
"Close-spaced Arrays-Super-gain Antennas. A review of the behavior of
broadside and end-fire arrays make it appear that in order to achieve
high gain it is necessary that the antenna system be distributed over a
considerable space. However, the antennas of Figs. 23-35 and 23-39
obtain enhanced directivity by employing antennas that are closely
spaced. Moreover, it can be shown that an end-fire (like a Yagi) type of
array that is short compared with a wavelength can theoretically achieve
any desired directive gain provided enough radiators are employed and
they are suitably phased. Such antennas which give great gain using
small over-all dimensions are referred to as super-gain antennas."

Read on. There is a fly in the ointment. Terman says:

" 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; this is illustrated by Fig. 23-36. The result is a practical limit
to the amount of gain that can be achieved in compact antenna systems,
since as the radiation resistance goes down the fraction of the total
power dissipated in the antenna loss resistance goes up. The Yagi
antenna of Fig.23-39 andf the corner reflector represent about the best
that can be achieved----."

So, Art may be on to something to some extent.

Best regards, Richard Harrison, KB5WZI