Whoops, I see I did "Building the Antenna", not "Second Example". There is
something wrong with "Second Example", because the dimensions are about the
same as "Building", but the coil is almost twice as big.

Tam/WB2TT
"Tarmo Tammaru" wrote in message
...
Jerry,

I ran EZNEC on this, using the QST dimensions, and got what seem to be
reasonable results.

Resonant frequency = ~7.11 MHz
Impedance = 21.15 + j1.17

For those who obviously did not read the QST article, the 25 uH loading
coils are 1.7 meters from the ends. Total length is 10.64 meters, and
height
is 6 meters. Over real ground, maximum gain is about 6dbi, straight up,
and
about 3 dbi at 30 degrees elevation.

Tam/WB2TT
"Jerry" wrote in message ...
October's QST has an article "Designing a Shortened Antenna" pp 28-32.
It
gives an example of a shortened dipole for 40 meters at 7007 khz. Dipole
length of the half-sized dipole [p30 "a second example"] is 10.61
meters.
This is 20 feet off ground using #12 wire. The formulas give a solution
of
XL= +j1776 ohms or an inductance of 40 microhenries at 30 degrees from
each
leg.


I tried to simulate this antenna on EZNEC. A 10.61 meter antenna at 7007
khz
gives impedance =11.33 - j 881.2 ohms.

If EZNEC is correct wouldn t I need an inductance of +j881.2 on each
leg
of
the dipole, rather than +j1776?

--
Jerry