M3 wrote:
"Any designs for a small antenna to work on 160M ?"

Small antennas are inefficient.

Medium wave broadcast stations have operated from small plots with some
satisfaction. They once commonly operated from building tops in the
middle of the city.

Building top antenna systems were most often short verticals worked
against a ground plane. The broadcaster only wanted vertically polarized
radiation, radiated at an extremely low angle.

DXers want low-angle radiation too, but not 0-degree radiation. A
horizontal wire must be 1/2-wave high for low-angle radiation; more if
conductivity is good under the antenna.

The shortest vertical antenna with a groundplane has a null in its
radiation pattern directly overhead but most radiation is at low angles.

The efficiency of a vertical antenna over real earth is bad without an
excellent ground system. U.S. medium-wave broadcasters approach 100%
efficiency using 1/4-wave towers and 120 radials near the earth`s
surface. As antenna efficiency is: radiation resistance divided by the
sum of radiation resistance plus loss resistance, the short vertical
antenna (whip) has a low radiation resistance and poor efficiency. The
efficiency formula has a small numerator, thus a small quotient.

As most mobile operators have found, the short vertical antenna is not
the best choice. It is the only choice for an extremely restricted
space.

How can the best use be made of a small garden space? Jerry Sevick,
W2FMI is pictured adjusting his 6-foot high 40-meter vertical on page
6-24 of my 19th edition of the ARRL Antenna Book. There are several
other options in chapter 6 of the "Antenna Book". Get it or a similar
book and study applicabilities to your situation.

Antennas scale to most wavelengths.

Best regards, Richard Harrison, KB5WZI