Larry D. wrote:
"The reason I wanted to try 5/8 wave is because I have had the Solarcon
A 99 1/2 wave ground plane for 10 meters up for about 5 years and it is
an excellent antenna for DX."

OK. A comparison of unattenuated field strengths at one mile from
various verticals is given on page 20 of the "Vertical Antenna Handbook"
by Capt. Paul H. Lee, USNR, K6TS:

1/4-wave, 196 mv/m

1/2-wave, 236 mv/m

5/8-wave, 276 mv/m

Power varies as the square of the voltage. One can see the difference in
the field strength is hardly worth the effort for an amateur to try to
increase the length of his antenna. It`s about a 3 dB gain from 1/4-wave
to 5/8 wave.

A 5/8-wave at 10 meters is 1/2-wave at 12.5-meters (24 MHz).

A 1/2-wave at 10-meters is 0.4 wavelength at 12.5-meters (24 MHz). One
could resonate it with a series capacitance at the antenna.

Best regards, Richard Harrison, KB5WZI