Richard Fry wrote:
"This post started with a question about a 28" loaded whip operating on
10 meters presumably to be used in a mobile application."

As Richard Fry noted, the vehicle and its position affect the antenna`s
pattern. Also at 10 meters, a 1/4-wave whip would be little more than 8
feet long. A 28" whip is less than 1/3 a resonant length. Capacitive
loading to make up the missing length is probably impractical. A loading
coil is lossy but practical. Best choice is likely the 8-ft whip. A CB
whip can be trimmed to resonance on 10-meters.

If one wanted an antenna to fit between poles about 1/4-wave apart, one
could use a 1/4-wave folded dipole, which is resonant due to its
1/2-wave circumference. Gain is only 0.5 dB less than a full 1/2-wave
dipole. Like a small loop, the small folded dipole can be resonated with
a high-Q series capacitor. Arnold B. Bailey in "TV and Other Receiving
Antennas" gives the resistance of the 1/4-wave folded dipole as 6000
ohms at center frequency. This would require transformation to a lower
impedance. Another resonant antenna that fits a 1/4-wave space is
square and 1/4-wave on each side. It`s about 35 feet of wire for 10
meters and has a feedpoint resistance of 100 to 200 ohms depending on
its height over the earth. Over good earth, feed one of its vertical
sides in the center. Over poor earth, feed a horizontal side in the
center. See ON4UN`s "Low-Band DXing" Chapter 10 for details on large
loops.

Best regards, Richard Harrison, KB5WZI