On the admittance of a monopole driven from a coaxial line

A simple formula is described for the apparent admittance
Y(ka, b/a)
of a monopole of fixed length
h
and radius
a
when driven from a coaxial line (conductor radii
b
and
a
). If
Y(ka, b/a)
is known at
n
values of
ka
with
b/a
fixed at
(b/a)_{2}
and at m values of
b/a
with
ka
fixed at
(ka)_{1}
, it can be evaluated from the given formula for all combinations of
ka
and
b/a
in the two ranges of
n
and
m
. It is assumed that
kb \ll 1
and
h \gg (b-a)
.