"Reg Edwards" wrote
Does it bring more than 1dB gain with it?
73's
Richard Clark, KB7QHC
===============================
Richard, asking such awkward questions you get more insensitive to
people's feelings every day.
Are you not aware that a decrease in gain of even less than 1 dB can
lose a contest?
Reg, G4FGQ
__________________

This post started with a question about a 28" loaded whip operating on 10
meters, presumably to be used in a mobile application. The concern of the
post was how to model the antenna to determine whether it would have the
pattern of a 1/4 wave or a 1/2 wave vertical radiator.

But for a mobile application the affect of the auto body, the local
environment, and even the direction the car is pointing can alter the
free-space pattern of the antenna more than the difference in the relative
radiation patterns of 1/4-wave and 1/2-wave verticals -- and particularly so
for VHF/UHF antennas.

If 1dB of antenna gain is so critical to amateurs, suggest that more
attention needs to be paid in its system design to the operating environment
of the antenna. Some NEC programs make it fairly straightforward to model
the net patterns of antennas as mounted on vehicles, and should lead to a
better understanding of antenna performance in the real world.

RF

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