1KW &
3KW
This
antenna is perhaps the least understood of all FM broadcast
antennas. Some have suggested it's just a J-Pole and that the bottom
section does not radiate. Some argue the cone is a non radiating
transmission line to feed the top section. Others mistake it as a
3/4 wave ground plane that would allow the bottom 1/4 wave of the
main vertical section to radiate in a deconstructive phase and
create a peak gain about 45 degrees above the horizon. None of these
theories correctly describe the manner in which this antenna
functions.
The
coaxial cone serves several important functions. In some ways is
does mimic a transmission line with it's ability to confine or
shield radiation from the base of the center vertical radiator.
Because it's tapered, it transforms the impedance of the antenna so
that it can be efficiently matched to 50 ohm coax. The cone is also
tuned to act as an effective counterpoise and has both transmission
mode and antenna mode currents flowing through it. Transmission mode
currents are confined within the cone and antenna mode currents are
allowed to radiate constructively on the outside of the cone.
Let's
examine how this principle allows us to simulate a collinear
antenna. Normally the end fed antenna will begin to will begin to
radiate from its base in a phase that is deconstructive once the
wavelength is increased significantly beyond 1/2 wave. Pass this
point and the peak gain begins to shift in favor of an upper 45
degree lobe where it is wasted. This is why it is essential to
confine the radiation from the lower 1/4 wave section of the center
vertical element. Allowing the longer top section above the cone to
radiate constructively with the currents on the outside of the cone.
Dominator NWE-34
radiation currents displayed in CST model.

Advancements
in computer antenna modeling software have made it easier to
understand how the Dominator NWE-34 produces more gain then any
single other commercially manufactured FM broadcast antenna. CST
Microwave Studio is an exceptionally accurate software tool that
provides 3D Electro-Magnetic simulation of antennas. The image
displays both the magnitude and phase of all radiation currents
along the antenna at a driven phase angle that produces maximum
current. Clicking on the image above will open a GIF video that
shows the currents at all driven phase angles throughout the 360
degree RF sinewave.
Magnitude
is displayed with color intensity and referenced to the chart on the
right. This chart shows the magnitude in amps per meter for the
corresponding colors. Phase is also indicated by opposing colors at
the positive top and negative bottom of the chart. The Dominator has
obvious characteristics not typically found in antennas other then
collinear types. It has 3 separate radiation currents with two
allowed to radiate freely in a phase that is constructively combined
in the far field. The third current is in a deconstructive phase
with respect to the other two and has been confined within the
tapered coaxial skeleton cone.
It is the tapered 1/4 wave coaxial cone that sets this antenna apart
from others. It allows the longer top section of the main radiator
to radiate freely while the deconstructively phased radiation on the
lower 1/4 wave of the main radiator is confined within the cone.
Since the base of the cone and the base of the main radiator are
excited by opposite phase polarities, the currents allowed to
radiate on the outside of the shielding cone combine constructively
with the longer main radiator extending above the cone. Total
currents radiated by the cone are divided into its four vertically
tapered radials. This provides noticeable gain over a dipole on the
distant horizon.
Understanding
the Cartesian radiation elevation charts.

Now
that we have covered how the CST model reveals radiation currents
from the tapered coaxial cone and upper main radiator constructively
combine together, lets look at how this compresses the Dominators
beamwidth in the far field to produce it's 3 db gain over the
dipole. The Cartesian charts show the normalized field in relation
to the elevation angle above and below 0 degrees horizontal.
Normalized field is the technical term for the relative amount of
field power density the particular antenna can produce at the given
elevation angle, with 1 being equal to 100% of its maximum radiated
RF field. Clicking on either image above will open a
larger version.
The
half wave dipole shown in red has a broader less compressed slope
then the Dominator shown in blue. This wastes power by radiating it
well above and below the horizontal plane. The dipole is still
radiating 50% of it's maximum field at an angle that is -60 degrees
from horizontal. In comparison, the Dominator field is reduced to
50% at an angle of -47 degrees from horizontal and it's down to 33%
at -60 degrees. Effectively refocusing the power wasted at undesired
angles into a tighter beamwidth that is 3 db stronger then a dipole
at the critical 0 degree elevation angle.
Because
the Normalized fields are relative to the specific antennas full
power field, it is not apparent how the beamwidth effects the two
antennas Effective Radiated Power in comparison to each other. We
only see the percentage of the individual antennas full field at any
given angle. If we were to lay the dipole chart over the Dominator
chart and used the Dominators Normalized Field as the reference
point for peak field power, the differences would be clear.
The peak
field for the dipole would only reach approximately 0.75 or 75% of
the Dominators peak Normalized field. Placing it 3 db lower as a
result of wasted energy at angles that are not useful to VHF
broadcast propagation. The Dominators compressed beamwidth not only
increases gain, it reduces on site RF exposure levels with limited
downward radiation making it easier to comply with safety standards.
The
Dominator® antenna was developed for FM Broadcast in 1996 by
Norwalk Electronics. It is a high gain vertically polarized .82 wave
Coaxial antenna. It is the coaxial cone at the base of this antenna
that allows us to go beyond the standard 1/2 wave and 5/8 wave
designs while forcing the angle of radiation down on the horizon.
The Dominator® has the same vertical gain as four stacked circular
polarized bays fed in phase and mounted over a forty foot section of
tower.
This
antenna uses a highly efficient Teflon insulated gamma match that
eliminates any coils or matching transformers. That enables shunt
feeding of the .82 wave main radiator, keeping it DC grounded for
added lightning protection. This also gives the antenna it's ability
to handle high power levels. The standard model is available with a
gold pin Teflon insulated weatherproof N or SO-239 connector
recommended for up to 1 KW input. Higher power versions are also
available such as our 3 kilowatt using a Teflon 7/16" DIN
connector and heavy duty gamma match.
Beware
of poorly constructed clones that look similar to the Dominator®.
One distributor in Slovenia is selling an antenna that has been made
to look like the factory authorized product . Clones are not factory
authorized and are advertised with inflated gain figures. Please
visit our "Dominator vs. Clone" page for more information.
Norwalk Electronics guarantees no single other FM broadcast antenna
can produce a stronger signal or you can return the antenna to us
within 30 days for a refund.
The Dominator® is professionally
manufactured using high grade 6063 magnesium alloy aluminum tubing.
This antenna is currently in use by hundreds of stations around the
globe from Alaska to South America. It has proved itself to
withstand severe weather while providing a strong reliable signal.
The Dominator® also offers unique
possibilities for use in emergency or temporary situations where an
effective, easy to install antenna is required. Be prepared for the
unexpected as changes in weather patterns can cause a severe weather
system to strike at anytime. This has forced some stations into the
awkward position of having to reach their listeners after the loss
of the transmitter antenna and or tower.

- Polarization:
Vertical
- Max.
power: 1 KW. standard model
(3 KW. high power)
- Max.
wind speed: 100 MPH
- Radiation
pattern: Low angle omni
- Material:
High grade 6063 alloy aluminum
- Impedance:
50 ohms
- Gain:
5.15 dbi / Power Gain = 2
- Connector:
N or SO-239
(7/16" DIN for 3 KW.)
- Wavelength:
.82 wave
- Lightning
protection: DC grounded radiator
- Weight:
Approx. 8 pounds
- Frequency
range: 88-110 MHz.
(Tunable)
- Wind
load: .7 square feet
- VSWR:
1:1 at tuned frequency
- Length:
9 feet
- Bandwidth:
5 MHz @ <1.5:1
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