Inverted V Antenna Design
by Martin E. Meserve
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Antennas | Inverted V Antenna
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As you can see from the diagram on the right,
this antenna gets it's name from the shape. It's really just a dipole with
the center raised on a mast and the endpoints near ground. By raising the
center point, the horizontal space requirement is reduced and only one tall
support is required. Although not the same as a dipole at the recommended
height of 1/2 wavelength above ground, it is still very effective when space
is a premium.
Another characteristic is that there is a shortening
of the radiator element by 3 to 5 percent. This will cause an antenna, that was
initially meant for another configuration, to require some pruning once installed.
Yet another characteristic is the radiation pattern.
A standard dipole generates a horizontal ratiation pattern in the shape of a
figure 8, with maximum radiation broadside to the antenna. The Inverted-Vee
tends to be more omni-directional and radiates equally in all directions.
For best results with this type of antenna, the
Apex Angle should be kept between 70 and 110 Degrees. Below 70 Degrees the
radiators start to become parallel to each other and signal canceling will
start to occur. Above 110 Degrees the antenna starts looking like a standard dipole,
minimizing any of the feed impedance and shortening effects. The optimum
Apex Angle is 90 Degrees.
The Data Input section, below, is set up for
you to enter data. You only have to fill in the text boxed with known data
and the rest are calculated. You can choose to specify a frequency of operation
and let the web page calculate and use that for the Radiator Element Length.
Or, you can specify your own value for the Radiator Element Length. Any time
you change any of the input data, the output data is automatically re-calculated.
A few things to note are:
The equations behind this web page are really
just a geometric solution, so, this page can be used with any type of
wire antenna, dipole, trap-dipole, folded-dipole, etc..
It's OK to mix and match dimensions. The web
page does all calculations in US/Imperial measurements and converts on input
and output, as necessary.
The Radiator Arm (Ra) length, in the diagram,
is measured from the Apex to the top of the End Support and thus includes
the Radiating Element AND the End Insulator. The Input Data area provides
space for specifying them both separately.
If the Support Height (Hs) is not set or
set to zero a small height (0.001 Ft) is assumed to avoid some divide-by-zero
If you select any of the Check Boxes, some
of the input data areas will be grayed out and not allow any input. To
re-enable these input area Un-Check the appropriate Check Box.
If too much data is left undefined, the program
will start to make some assumptions. It may be benificial to start this way,
see what the program comes up with, and then adjust the input data. For example,
if you only define the Radiator Element and End Insulator length, the web page
will assume a Apex Angle of 90 Degrees and calculate the rest of the information.
You can then make changes as you see fit.
I tried to intercept all possible entry configurations
and error conditions but a few still remain. I will fix them when I get around
to it but if there is something that really bothers you, send me email.
Using a Center Frequency of
x for the Dipole,
yields a length of x.
Reducing this by x %,
to account for the Inverted Vee configuration, we have a length of
Use the Inverted-Vee value, calculated above, for the Radiator Element
Fix Apex Angle at 90 Degrees
Apex Angle (Deg.)
Horizontal Space (A)
Mast Height (Hm)
Support Height (Hs)