On page 6-29 it says: " "Experience has indicated that a secrion of wire
approximately one half wavelength long, wound on an insulating form with
linear pitch (equal spacing between turns) will come close to yielding a
resonant quarter wavelength. Therefore, an antenna for use on 160 meters
would require approximately 230 feet of wire, spirally wound on the
support. *
______________

Such a helical may come close to resonance, but unless the overall
length of the helical structure approaches 1/4WL, its radiation
resistance (Rr) will not be as great as if a naturally resonant,
straight, ~quarter-wavelength conductor is used.

Lower Rr for "monopole" antennas will reduce the radiation efficiency
of these systems -- if they are not using a zero-loss r-f ground
connection.

RF