"AI4QJ" wrote in
:


"AI4QJ" wrote in message
...

note the independence of coil size and location on the
monopole.


The location on the monopole may make a difference. Since a standing
wave is present, the location on the antenna will define the amount of
current in the coil. Mounting near the feedpoint is at a high current

Yes, the complete picture is that:
1. more inductance is needed the further that a single small loading coil
is located from the base; and
2. loss is due to I^2*R, so locating the coil further up decreases
current, but increases required inductance and inherent R.

The above mean that the optimum efficiency is often from a coil located
closer to the middle than to the top or bottom.

It seems reasonable that a stand alone coil can be characterised as a
transmission line having a delay that equates to an electrical length in
degrees, radians, wavelengths or a velocity factor. In fact the
inductance calculator at http://hamwaves.com/antennas/inductance.html is
based on that approach and shows the calculated value of Beta.

But, it is the suggestion by some that the coil simply replaces an
equivalent electrical length of the monopole conductor irrespective of
the coil's location that is inconsistent with 1 above.

A further issue is the accuracy of the estimate of the coil's electrical
length when represented as a transmission line. Using the length of the
wire in the coil (as is sometimes done) is too simplistic. The Corum
paper referenced at the calculator above describes a method that appears
to be more reliable.

Owen