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Admin

Simple Dipole Antenna

67 posts in this topic

I have two same grids, lets fin out how it will be in thi  combination (simple ilustration):

(simulation without optymalization shows inceasing gain from 17.2dBi to 19.6dBi)

double grid.jpg

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,,,where did you get this from? - such a thing is not possible...???!!!

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1 hour ago, Admin said:

such a thing is not possible...???!!!

That's what my fellow senior radio amateurs tell to me :)

 

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Measured very roughly, when the dimensions of the system are accurately measured the results will be different

Thats the basic grid - 17.3 dBi

grid - simple.jpg

 

That's double grid: 19.8dBi

double grid A.jpg

double grid A_patern.jpg

 

option B -  it does not work: 16.9dBi

 

duble grid B - does not work.jpg

 

conclusion: doubling the reflector area gives ~~~~ 2.5dBi or more of the gain.

 

I will show real pictures later, will be mechanically difficult.

I think I can get a few dB more by improving the feed.

Edited by eco32

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,,,this is a bit stupid..!!
,,,you'd better use a parabolic offset...!!!

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9 minutes ago, Admin said:

,,,this is a bit stupid..!!
 

This requires an explanation as to why you think it is stupid.

 

11 minutes ago, Admin said:

,,,you'd better use a parabolic offset...!!!

Of course not, such a grid reflector is best for dipole feed that have parabolas smaller than 10xlambda

BTW, it is prototypingc, parabolic offset will be consider in other project. Here we consider the "siple dipole" feed and exploration, what we can do. @Admin do you agree with me?

 

 

 

 

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It was concept picture,  it has one focal point

dual-grid 2.jpg

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conclusion from simulations and from experiment:

shape is ok, gemetry is wrong!

diuble grid C a.jpg

double grid C.jpg

 

Why?

The ratio of focal length to aperture size (ie., f/D) known as “f over D ratio” is an important parameter of parabolic reflector. Its value varies from 0.25 to 0.50.  calculator: https://satlex.de/en/fdratio-params.html?diam=90&depth=15

in my case is  f/D = 0.16 => Geometry is wrong - may it be that with other type of feed will be more profitable. Any parabolic antenna larger than 120cm is horrendously expensive, building big grid antennas is reasonable.

Example from Czech Republic: https://www.ok2kkw.com/wsjt2006/23cm2008.htm also for Earth–Moon–Earth communication (EME).

120cm grid.jpg

 

 

 

Grid vs double grid with siple dipole fed without small  reflector as case  above 13.5dBi VS 17dBi

 

one grid with simple dipole 13.5DBi.jpg

double gdid - siple dipole 17dBi.jpg

 

 

I DID IT, AND YOU DONT HAVE TO!

 

 

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Simple design with a corner reflector. 14dB, 10dB in the main direction, with additional  work with  the elements, you can probably improve the main beam. The structure is similar to my latest grid (17dBi), but simpler. Important detail : standard model  feed was changed to revers direction of radiation - director is Reflectors and reflector is director. Useful when you don't want to build a parabola

 simple dipol with corner reflector 14dBi.jpgsimple dipol with corner reflector 14dBi Diameters.jpg

simple dipol with corner reflector 14dBi EL patern.jpg

Simple dipol with corne reflector.png

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,,,eco32, what program do you use for simulation...!!!

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19 minutes ago, Admin said:

,,,eco32, what program do you use for simulation...!!!

Matlab (not yet able to use CST)

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two dilpes with corner reflector: Gain increases, but at the expense of side lobes, in some applications this is unacceptable

details: Yagi feed is reversed and it has two reflectors

 

normal mode dual - patern.jpg

 

side lobes:

corner dual sidelobes.jpg

how it looks in "normal mode:, feed litle yagi was not reversed:

design:

normal mode_design.jpg

patern

normal mode.jpg

 

normal mode dual - patern.jpg

Edited by eco32

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,,,executes a single reflector with two antennas spaced at a distance greater than 143 mm between them...!!!

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On 15.11.2023 at 4:04 PM, Admin said:

,,,executes a single reflector with two antennas spaced at a distance greater than 143 mm between them...!!!

10dBi in main direction, same a single dipole with corner reflector

crap.jpg

Edited by eco32

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