[Antennaware] EZNEC modelling

[David Gould]

Thanks for the input so far.

Ed K4SB asked how I determine the L-match components..  I use the 
following website to match what the model gives me to 50ohms.  The 
network I use is the second down on the right.  You do need to watch 
the units ie frequency as 10.125e6 and the results give inductance in 
nanohenries.
http://bwrc.eecs.berkeley.edu/Research/RF/projects/60GHz/matching/ImpMatch.html

The antenna is a 48ft vertical, 2.5inches at the bottom tapering to 
2inches at the top.
For the 10MHz example I am working on, that gives me
A coil of  4.3uh  (X=274) from bottom of antenna to earth.
A series capacitor 90pf  (X= -175) from bottom of antenna (top of 
coil) to feed line

I just went ahead and modelled it in EZNEC (V3) as I 
described...  And it gave absolute rubbish...  (I am NOT blaming the software!)
The feed impedance was given as 220 - j18,000.
I think this proves that my model is far from correct, but I don't 
know what to change to make it a true representation of my real life antenna.

I am happy with the physical implementation of the antenna,  I just 
want to play about with the model so I can get some idea of what 
effect different coils (of different Q) and different earth losses 
make to the antenna efficiency and SWR bandwidth.

73,
Dave, G3UEG