Topband: Inverted V antenna!

[k6se@juno.com]

Don, W7DD wrote:

"I just modeled an inverted V antenna on EZNEC.  The apex height is at
87'(for an 89' tower), ends are 2 feet above ground, ground conductivity
is 1.5s/m, dielectric constant is 13 and 1/4 wave elements are 127.6'
long/side.  Frequency was 1.85mhz.  The ground description is for
Tucson,Az.

"The results show that it is a BETTER VERTICAL  than horizontal by 3dbi
at a elevation angle of 20 degrees to the horizon.  This is off the ends.
Horizontal is broadside."
==========
I used EZNEC v3.0 to model the same antenna that Don describes.  Because
the antenna is so low to the ground, I used the "high accuracy" method to
do the plots.  Using 1.5 s/m, the horizontal component is down 4.45 dB
from the vertical component at 20 degrees elevation.  I immediately
suspected that Don's description of the soil conductivity in Tucson was
wrong (1.5 s/m is not too much worse than sea water, which is 5 s/m).  So
I played around with the soil conductivity until I got the 3.0 dB
difference that Don mentioned, which turned out to be 0.0076 s/m (I left
the dielectric constant at 13).

With 127.6' of #12 AWG wire on each leg of the antenna, the resonant
frequency is 1.876 MHz, so I made all plots at that frequency.  The gain
of the horizontal compont broadside to the antenna is -4.76 dBi.  The
gain of the vertical component off of the ends of the antenna is -1.76
dBi,  which is 3.52 dB less than a grounded vertical antenna over the
same soil with a good ground radial system.

73, de Earl, K6SE