Thinking about how the Grabbit Ears work

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#1
I did some thinking about how the Grabbit Ears work.

I think it goes something like this.

The upper and lower fractalized antennas are out of phase with the center bowtie. That would mean that they interact funny with the center bowtie, canceling out signal. It is well known that attenuators can be useful in combatting multipath. This is essentially what the fractalized elements are doing.

Being fractalized, they also are better at non horizontal polarization (and worse at horizontal polarization)....which often is the case with mulipathic signals. As they are reflected they rotate polarization. Thus further increasing the the out of phase cancelation aspects of the multipathic signals. These signals are greater on the fractalized antennas and cancel the multipathic signals out more than they do horizontal primary signal.

The key is to increase S/N ratio or Primary Signal to Multipathic Signal.

When multipath is not a problem, then rotating them 90 degrees so that the bowtie is vertical and thus not contributing much to the system would give you better captured signal from the dual in phase center fed fractalized elements.

What say you?
 
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EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#2
Let's see if I can clarify.


You have a 2 bay center fed fractalized bowtie antenna....with out of phase bowtie at the center feed.

So when the non fractalized bowtie is vertical and thus pretty much a non factor (unless they are acting as stubs...hmmmm) you have a fractalized 2 bay antenna. This works better than a single bowtie even if its not quite as good as a non fractablized 2 Bay.
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#3
When rotated where the center bowtie is now horizontal and thus more active as an antenna (with horizontally polarized tv signals), and it is out of phase with the upper and lower fractalized antennas, signal cancellation is taking place. The way this cancellation happens serves to increase the Signal to Noise or Signal to Multipathic Signal....while at the same time reducing the Primary signal but to a lessor extent....thus increasing the Signal to Noise ratio.

Does that make sense?
 

EscapeVelocity

Moderator, , Webmaster of EV's Antenna Blog
#4
Why does it do that?

Because the Fractalized antennas are more sensitive to rotated reflected multipath signals than the primary single bowtie. While also being less sensitive to the horizontal primary signal than the primary single bowtie.
 
#5
Here is my un-educated opinion about Grabbit Ears. I am not a student of antenna theory.

I believe that the key to this is 3. It is a three bay, and each fractal is made of three angles.

Why is 3 the important part?

1. That's what my Father in heaven said to do. (Father, Son, Holy Spirit).

and

2. For the somewhat scientific explanation of the operation of Grabbit Ears, let's consider multipath.

When two reflections of the same signal come together, we have a canceling effect, rendering them null. So now both paths are gone. What if you had a third way in...
 
#6
EV,

Take a look at the picture markup of Grabbit Ears.

If each of the angles were extended as if they were all bowties, they make seven bowties with their openings a few degrees from one another all around the antenna.

I think this is where the flat omni-directional aspect comes from.

The number of those would be seven. (The perfect number and again, odd to overcome multi-path as the earlier post.)

The arrangement per side is sort of 3-1-3. (All individually odd and the sum is also odd.)

Cancelling is mostly removed due to the "odd" points of collection.

What do you think?
 

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