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Dominator
FM Broadcast Antennas

 

Dominator 6M & 10M
5/8 Wave 6&10 Meter Antenna

 

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Be aware of Imitations

 

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Facts About Gain

 

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Original copper prototype of the Dominator NWE-34 Antenna
(1996)

 

Dominator NWE-34 radiation
currents displayed in CST.
Click Image For Large View

 

Dominator FM Broadcast Antenna Installed on Commercial Tower.

Click Image For Large View

 


The INFO

Beware of counterfeit antennas that look like the Dominator going under several different names and a new "7/8 wave" antenna that looks similar to a long 1/4 wave ground plane with an added gamma match. The outlet selling the antennas we are referring to misrepresented themselves as wanting to become a factory authorized distributor for Norwalk Electronics antennas. Once they received a sample of the Dominator, they have been determined to copy and / or modify the Dominators highly effective design. Without understanding the concepts behind what makes the Dominator a powerful antenna, they have plowed right into one mistake after another while claiming these changes have resulted in advantages that are non existent.

Claims like no tune gamma match, collinear, and 7/8 wave at 11 feet long when 10 feet is the full wave for FM, are all false. Their deceptive advertising would have you think you're being offered an improved product when in reality many of the parts used are substandard. Implying you don't have to tune a gamma match on a shunt fed radiator across a 20 MHz spectrum of VHF will at best result in a loss in gain at each end of the band. Collinear would indicate at least two active antenna elements fed in phase where being employed. Not one that's simply much longer then what produces maximum gain. Each modification they have made from the basic design of the Dominator has robbed more and more gain.

The latest creation being offered by this distributor looks like an overgrown 1/4 wave ground plane with the 45 degree radials incorrectly placed above the RF feed point. Making them unable to decouple the coax line from the antenna effectively. The antenna also uses a gamma match that has been installed either to befuddle the layperson or because the builder lacks knowledge of basic antenna design. When you extend the main radiator beyond 5/8 wave, simple 45 or 90 degree radials produce extremely high angles of radiation however, 45 degree radials can provide a 50 ohm impedance without a gamma match.

For many years ham radio operators have used this type of design for mobile satellite communications on the 440 MHz band because they recognize one of the few examples of where this extreme high angle of radiation is desirable. Nice when you are in your car communicating through amateur radio satellites, not when you're trying to hear your local FM station. When used as a 440 MHz mobile antenna the vehicle makes up a ground plane reflector with a 90 degree angle. Since we've posted this information, the builder has now added both a 45 degree set of radials and a 90 degree set. Nothing like stacking one bad idea on top of another.  It is almost amusing if it weren't so deceptive.

You can prove this to yourself for about $50.00 by building the competitions latest antenna. Purchase an inexpensive $40.00 1/4 wave FM ground plane on eBay. Buy a 102 inch stainless steel Citizens Band whip from Radio Shack. Remove the top 1/4 wave vertical element from the ground plane and replace it with the 102 inch whip or use two hose clamps to attach it parallel to the existing whip. You may have to trim the top of the whip to get a perfect VSWR. The measurements for 98 MHz will be about 7 feet 2 inches or 2.183 meters. This is a 3/4 wavelength ground plane. Not a collinear or a coaxial antenna.

The basic design is still flawed because it will inherently have a radiation angle of 30 degrees or more above the horizon. It does not matter if the radials are 90 degrees or 45 degrees out from the base of the antenna. The radiation angle is still about 30 degrees upward. One set of 45 degree radials at the feed point works best since this matches the impedance to 50 ohms with no gamma required. This produces a usable signal in close proximity to the antenna that rapidly fades as distance is increased because the beam of radiation has not been narrowly focused on the horizon.

The pictures at the bottom of this page show some of the many components used in the competitions antennas. They are actually using a low power 27 MHz Citizens Band gamma match on all of their standard antennas. These were designed for use with radios that supply no more then 12 watts PEP for intermittent communication service. Their Teflon gamma match or choice of any quality connectors are all expensive options that should be standard in FM Broadcast antennas.

Shown just below are two sketches of the builders new overgrown 1/4 wave. Their first example shows how they placed the radials in the wrong location above the feed point. This provides no RF decoupling and can cause the coax to radiate. Their second try has combined two ineffective methods of radial use with both 45 and 90 degree radials. The picture to the right shows the 7/8 wave clone of the Dominator and while their photo may look very similar to our Dominator it could never perform to the standards of the FM broadcast industry or even compare close to the specifications on their web page, further more not even come close to the out put power and coverage area of the Dominator. and neither one can lower the angle of radiation down to the horizon as they claim. This is shown in the radiation pattern below. 
  
      
7/8 wave ground planes  7/8 wave clone

 

High angle 7/8 wave pattern

Images below are expandable by clicking on the picture.

Here you will find a short video clip of the Clones gamma
match failing under the stress of voltages created at the
1 KW power level. The bottom of the tube has been cut
away to show the inside insulator failure.

Clicking the photo will play the video in Quicktime,
If you prefer Windows Media Player
Click Here

   

This photo shows the Clones gamma match open to
expose the small black plastic insulator inside. Notice
the large diameter white Teflon insulator and locking
stainless steel clamp on the Dominators gamma match.
The Dominators gamma tube is also insulated to prevent detuning as a result of snow accumulation.

   

In this photo we can see the insulating material used in
both gamma matches. The white Teflon can withstand
over 1,000 degree temperatures while the black plastic will
melt at a few hundred. RF heating of this dielectric material
will cause it to melt and short out the gamma match.

   

The Clone uses a low quality SO-239 connector on the
right. Notice the extremely tight clearances between the
center pins hex nut and outer ground jacket. This causes
a prime spot for RF to arc and an impedance shift. The
Dominators standard N connector is made of silver, gold,
and Teflon. N connectors are waterproof due to internal
rubber gaskets on the male connector.

 

The manufacturer of the clone uses a flimsy connector and bracket that has caused many failures. The screwed on "L" bracket makes a poor mechanical and electrical connection as you can see in the photo here. If you have a photo of your clone and how it has failed, please send it to AntennaInfo@virtual-comm.com

 

The Nylon spreader brackets are shown in this photo.
The Dominator bracket is formed completely around the
four loop support elements. The Clone bracket on the
right is just wedged in place.

   

One customer who purchased a clone couldn't figure out
why the shipping costs were so much higher until the oversized shipping box arrived at his door.

By removing the loop for shipping and using telescopic
tubing sections, our product fits in a box 56 X 7 X 5 inches and is much more economical to ship worldwide.
Compared to the photo on the right.

 

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