On Wed, 29 Oct 2003 02:52:33 GMT, "BuckEye" wrote:


"Lancer" wrote in message
.. .
On Tue, 28 Oct 2003 23:10:42 GMT, "BuckEye" wrote:

I agree to all of the above except a 1/4 wave is a 1/4 no matter what. A
so
called loaded 1/4 is a loaded antenna not called a 1/4 anymore. Once a
antenna has been shortened by any means, shorter than the physical 1/4
wave
antenna ( 1/4 wave including the velocity factor ), top hats, loading
coil,
or ant other ways it is not clamed to be called a 1/4 wave anymore.
I did say 1/4 whip on the post, as most everybody should have known it
to
be the 108" antenna.


I don't know where Doc is heading for with his statement, but a
shortened antenna ( like the Xterminator) is 1/4 wave "electrically"

Velocity factor isn't a factor when you determine antenna length,
except certain antennas that are made from transmission line.

Maby you can explain how a antenna is 1/4 so called " electrically 1/4 " if
it is not a 1/4 wave like a 108" whip.
If it has a coil in it it, and shorter than the 1/4 it is a loaded antenna
NOT a electrically 1/4 wave equivelement .
If that was the case then a very loaded antenna that was 12" tall NOT 8'
could also be called a 1/4 wave "electrically"
What makes then a antenna 1/4 wave "electrically", because it matches the
50 coax?

A coil in a short antenna cancels out the capacitive reactance making
the antenna resistive at the operating frequency. The coil makes it
"electrically" a 1/4 wavelength. More than likely it won't be 50
ohms, usually quite less, unless some kind of matching is used at the
base.



Velocity factor IS importment when cutting a element to the proper
length.
Typically a antenna element can range from .91 to .99 of the true open space
length.


The number (.91 to .99) are correct for the difference between an
antenna in free space and erected near earth. Its not from the
velocity factor of the antenna.
Its because the antenna is close to the earth and other
conductive objects (tree, buildings and power lines) which present
stray capacitance that tunes the antenna lower in frequency than a
free space antenna. Its called "end effect" and is more prevelant
the closer an antenna is other objects.