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Reason for booms geometry/placement on a log periodic ?

Externet

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Good day.
Horizontal log-periodic antennas in the market feature one boom above, the other under and the alternating elements mounted to their 'sides' as below.

Is there a reason why the booms are not built side-by-side instead ?

More images for this at ----> https://www.alibaba.com/product-detail/New-TV-Antenna-32-Element-Log_60314349738.html

1631734054428.png


The question would imply the elements attaching on top and under the booms instead of near and far sides as shown; and turning the whole assembly 90 degrees if wanted to show as horizontal.
 

FvM

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You understand that the elements have to be connected with alternating phase? I don't see how you can achieve this with side-by-side feed-line design.
 

vfone

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The Log Periodic elements are half-wavelength dipoles (LPDA, log periodic dipoles array).
These dipoles are fed with a specific phase, which is obtained by a cross-coupled connection between antenna elements.
For this kind of connection the simplest way is to use two booms.
Could be used only one boom, but the connection between dipoles would be much complicated, because need to isolate the elements from the main boom.

 

crutschow

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The question would imply the elements attaching on top and under the booms instead of near and far sides as shown; and turning the whole assembly 90 degrees if wanted to show as horizontal.
So the question is, what happens if you rotate the booms 90° along its axis and have all the elements in the same plane (but still on two booms).
It may not make any difference, but that could affect the phasing between the elements.

So why would you want to do that?
 

RCinFLA

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It is just physically easier way to get the alternating phase and required boom parallel impedance.

There are some TV antennas that use a single support boom with criss-crossed high impedance balanced wire pair transmission line to interconnecting the elements with plastic insulators to support elements from the support boom.
 

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