Roy, W7EL wrote:
"No, the example with the positive reactance is at a frequency below
parallel resonance, where the reactance goes the other way than it does
just below normal resonance."

Just as the usual folded dipole selected for a particular frequency is
1/2-wave, the usual folded monopole is a 1/4-wave. Shorter or longer
antennas are used and harmonically related frequencies may or may not
have convenient drivepoint impedances depending on which harmonic.

The folded monopole is usually tuned to be a short-circuit stub at some
particular frequency and it has the shield side of the coax also
connected to an elevated radial system to keep signal off the outside of
the coax, and it replaces the "missing half" of a dipole. The ground
plane leaves the radiation up to the vertical antenna element.

The folded monopole antenna is a resonant system with distributed
constants.

Terman says on page 893 of his 1955 edition:
"As a result, the impedance of an antenna behaves in much the same
manner as does the impedance of a transmission line (see Sec. 4-7)"

Sec. 4-7 is found on page 98. Here Terman says:
"The expression "Transmission-line impedance" applied to a point on a
transmission line signifies the vector ratio of line voltage to line
current at that particular point. This is the impedance that would be
obtained if the transmission line were cut at the point in question, and
the impedance looking toward the load were measured on a bridge."

In the case of a short-circuit 1/4-wave stub, Terman has Fig. 4-10(b) on
page 99 of the 1955 edition. At the load, the short at the antenna tip,
the power factor is shown lagging by 90-degrees which by my electronics
dictionary is:
"Laggibng load - A predominantly inductive load - i.e., one in which the
current lags the voltage."

What`s more, the 90-degree lag persists almost unchanged until a point
is reached nearly 1/4-wavelength back from the short.In the folded
monole, that would approach the drivepoint.

If the folded monopole were lengthened beyond 1/4-wave, an abrupt flip
to a leading power factor angle of nearly 90-degrees would be
experienced on passage through the 1/4-wave resonance point. The phase
variations become less abrupt at subsequent flip points as any added
90-degree points become farther removed from the antenna tip
short-circuit. The frequency is getting higher so that the antenna
appears longer in terms of wavelength or the antenna is gaining in
number of 1/4-wavelengths some other way to produce multiple phase
reversals.

Best regards, Richard Harrison, KB5WZI