Art wrote:
"My present antenna, which is for 160 m and above, is about the size of
two shoe boxes and is less than 2:1 swr (50 ohm) across the band when
situated at the tip of my tower."

Outstanding! An effective antenna needs to be an appreciable portion of
wavelength in some dimension.

If Art`s antenna is an appreciable portion of 525 feet it can radiate
well on 160 meters.

Any length of wire carrying an RF current is capable of radiation.
Significant radiation from a short wire requires much current.

With a garbage can lid for a reflector, a helical antenna can be made.
Were it 3 feet across in diameter (0.9 meter) the helix might work on 3
meters as the diameter needs to be about 0,3 lambda. Terman gives
helical antenna information on page 909 of his 1955 opus. His best bets
for small antenas are the corner reflector and the Yagi.

Best regards, Richard Harrison, KB5WZI