[Antennas] Building A Coil

Sun Aug 24 22:20:54 EDT 2008

Your short loaded whip is not really in any way 1/4 wave. 
The inductor simply resonates the antenna's capacitance.
There are two ways to get a shortened 1/2 wave antenna.
Why would you want to do this, it's asked? Because a 1/2
wave antenna with its impedance in thousands of ohms, is
MUCH less subject to ground resistance losses.
How to do it?
One way is to wind the 1/2 wave helically on the antenna 
mast. This actually requires about a full wave of wire, which
means a LOT of wire turns and is a MAJOR chore. Maybe 
not so practical on any of the "DC bands". ( As compared to
10m, say. ) The other way is like the Radioshack "No-Ground
CB antenna", where the antenna seems to be a 1/2 wave 
off center fed, with most of the antenna being in the feedline,
and the length of the feedline also being an impedance matcher.
So yes, it actually IS possible, altho not by purely "electrical"
means, if you're thinking of just adding L and C type loading.
Maybe this helical winding would be practical on 20m, altho still
a lot work - the only articles i have seen using helical wound 
antenna shoot for 1/4 wave resonance which means winding 
about 1/2 wave of wire. -Hue Miller K7HUE