Correction: the base inductor was 75uh
On Thu, 20 Apr 2006 19:06:17 GMT, John Ferrell
wrote:

I don't find the Helix feature in my copy of EZNEC+ V4.
I believe I can get the same results by inserting an appropriate load.
It will just be a little more cumbersome.

I was not aware that the feeding of the radiator was affected by the
driving source. My "lab models" require a base inductance to get the
radiator into a range I can feed. I have not been including that in
the models.

I added a base inductor of 100uh(r=3) and got the results you
predicted. The 28 foot radiator is now showing -3.75 dbi gain!
Lesson learned!

The matter of the phase angle and the feed point voltage is currently
over my head, I will study it further.

I am using the TLW program from the Antenna Handbook to determine an
appropriate match. I have not tried to verify those calculations with
a lab project YET!

Once again, thank you for the assistance. I was getting pretty
frustrated...
de W8CCW John

On Thu, 20 Apr 2006 18:23:34 GMT, "Cecil Moore"
wrote:



Take a look at the phase angle between the feedpoint voltage
and the feedpoint current for the 28 foot version and try to
figure out an efficient matching network. That phase angle
is ~89.95 degrees. The feedpoint voltage is 1400 volts for
only 1.2 watts input. The feedpoint impedance is about
1.2-j1400 ohms.

Try using the helix feature to install a loading coil in the center
of the 28 foot antenna. The gain will drop as expected but the
feedpoint impedance will be easier to match.
John Ferrell W8CCW
John Ferrell W8CCW