Topband: [Topband] Inverted "L" vs." T"

[Guy Olinger, K2AV]

> Hi All,
> I have been following this thread for a while and have a question about 
> how accurate the results are for a ground plane antenna are using EZNEC 5.

EZNEC 5 is the graphical interface which runs a version of NEC in it. The 
ham version "shells" NEC2. It will use either a Minninec or Summerfield 
ground. Both of these have their limitations and gotchas.

If  you obtain a NEC4 license from Lawrence Livermore Labs ($$, and a signed 
agreement with a federal agency) then you can pay more $$ and get EZNEC pro 
which runs W7EL's compilation inside the EZNEC graphics. This level requires 
a registered USB key that enables the program. There is an intermediate 
version, "Plus" which has all the extra graphical stuff and no limit on 
segments, but does not run NEC4, it's still NEC2.

With the NEC4 version you can bury conductors in the model, etc. Even then 
DIRT is such variable element that predicting GROUNDWAVE measurements at a 
distance is still partly voodoo, because of the unpredictable absorbtion of 
vertically polarized radiation in the quarter to half mile of DIRT around 
the antenna. Absorbtion can change depending on rain (or not) and whether 
the sun is out (or not), only a partial list of the variables.

This makes comparative measurements of various wire vertical configurations 
at the ground very difficult with antennas with minor variations in the 
elevated conductors.

In your model you might want to try a receiving antenna 20 miles away and 4 
miles up.  Jack the power if the rx antenna doesn't show anything in the 
displayed decimal points.  Magic power is free and doesn't run up your power 
bill.

73, Guy.