KC4US's New Antenna System

posted 3/15/17

 

Lew - KC4US recently purchased an Eagle One vertical antenna.  He and Dan - KK4OFR decided to try an experimental installation of the new antenna.  Below are the results.

 

Lew has been using a Force 12 vertical flagpole antenna for some time now.

Keith - WA8ZWJ was curious about how Lew and Dan had interfaced the antennas as Lew's description said they had connected the two verticals together.  Keith was curious how they had phased the two antennas.  He imagined there was some kind of T in the coax line to feed both antennas.

He was totally wrong on that account.

 

Here's a look at the current set up.

As you can see, the Eagle One is taller than the Force 12 flagpole antenna.

After Keith asked Lew how they had phased the two antennas together Lew sent these photographs.

 

Here's what Lew has to say about the new installation.

"I really don't know how electrons think or if they do, but I think of antennas as creating an electric fields in space.  Now if you think of a cylindrical field around the Force 12 and another around the Eagle 1, it seems like being that close together and in perfect sync that they would enhance each other and look like a larger diameter field.  So now we have a fat antenna at the bottom and a skinny one at the top.

You will not find an explanation like that in any book I don't think, but feel free to use it without fear of patent infringement.  It might perhaps change the radiation pattern slightly, it did noticeably lower the VSWR readings.  If we ever get more consistent conditions, between Dan & myself we should be able to determine if we have a real increase in performance or if we just have a talking point.

I thought that Charlie would like the "bifurcated flagpoles" name. "

Keith was a bit confused by the name in that there is actually only one flagpole antenna.

Here you can see how the antennas are supported.  The antenna tuner is on the ground to the left.

 

Here's Lew's photo of how the two antennas are connected.

 

Keith says "If you look at the photo called "close up" (see the photo below) that I have attached, I do not see any coax feed to the antenna system.  I am going to assume that it is hidden by the wooden structure that supports the original vertical antenna.

 Knowing that the Eagle One is a plastic device with a cable that runs up the center, the coupling devices are not actually making any contact with any antenna structure on the Eagle One but they are simply supporting the structure of the Eagle One.  In a sense, the distance that they separate the antennas would be the phasing distance for the two verticals.

What I think I am seeing is the feed line wire that runs up the center of the Eagle One is connected to the bottom clamp that secures the two antennas together.  (see "close up" again)"

Keith continues - "If that is the case, the driven element of the Eagle One is simply shorted to the bottom of the original vertical by the clamp.

However, I fail so see how your tuner can determine how, what, why and where to tune.

I am unable to process the math that might explain all that!  It makes my head ache just to think about it.

Trying to imagine what kind of radiation pattern may be set up is a good question too!

Obviously, the most important part is that IT IS WORKING!

I guess I am trying to put too much head time into the whole process!

If it works don't fix it!

Thanks a ton sir! "

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Here is the Chief of the IOOK Technology Center - Charlie - NN3V's response...

"WOW!  

This is a difficult matter to address.

I looked at the pictures because in order to analyze antenna matters a good physical understanding of the structure is vital.

So, my first conclusion is that some time is needed with EZNEC antenna radiation analysis to get some mathematical insight into what is going on.

Obviously, based on the series of emails, the antenna works.  No need to spend any time in analysis.

Enjoy it.

However. To assess the physics, and quantify the effects, a bit of better definition of the architecture is needed.

Specifically, a good understanding of the wavelength relationship between the size of the Force 12 and the size of the Eagle 1 is needed.

Depending on the frequency in question, each antenna presents a somewhat different radiation pattern relative to the wavelength of the frequency.

So there is a modification of the radiation pattern from each antenna based on frequency.

Therefore, in the near field, the electromagnetic effects will be different in their additive contribution.

That additive contribution will change the radiation pattern for each transmit and receive frequency.

Regardless of the situation, as long as the reactive impedance of the antenna is not totally bizarre, and antenna tuner capable of presenting a similar impedance from the transmitter, and capable of handling the input power and reflected power from the antenna , it will do just a fine job in allowing maximum power output from the transceiver, even  the actual radiated power from the antenna might be zilch even though the SWR is one (1).

73 de NN3V

Charlie"

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Addendum..3/15/17 PM

What is not obvious about the pictures, is that the white flagpole is metal. The wire inside the new antenna is connected directly to the driven element (flagpole). I discussed this with Lew this morning. 

De, K1MAX

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Lew has been using the set up on the IOOK nets but with current band conditions it is difficult to make any serious conclusions!

Good luck Lew!

Yes, I am sure we all know that today will be...

"A beautiful day in The Villages!"

Best 73...