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htgr2001
 Post subject: Antenna Simulation Project
Posted: Sun Apr 12, 2009 2:27 pm 
 
Lieutenant

Joined: Sun Apr 12, 2009 2:25 pm
Posts: 1
Hello guys,

I am not quite sure how to start this thread; I am involved in this little project to simulate (using a software package called FEKO) the radiation pattern of a few antenna types under a variety of realistic conditions.

Most of all I will be creating 3d models on the package of a few types of antennas.

To get your curiosity going I will post a few pictures:

Image
Very simplistic model of a 5 element Yagi Antenna (no boom)

Image Image
Radiation Patterns at 100MHz (left) and 95MHz (right)

I have used a few dimension formulas I found online to optimize the antenna for frequencies of 95.5 MHz. Still it seems to operate better at higher frequencies as you can see.

So at the moment where I would really appreciate your help is if you could provide or point me towards a reliable source of antenna dimensions.


 
   
 
nubbage
 Post subject: Re: Antenna Simulation Project
Posted: Mon Apr 27, 2009 7:42 am 
 
General
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 236
Location: London UK
Hi
You can find full design graphs and details in Amateur Radio publications, and be confident they have been well-tried and tested. This is about the only source of information in the public domain, since manufacturers protect their designs by secrecy.
I spoofed around this when checking my own designs and checking the Mini-NEC software. I shamelessly did this by photo-copying a side-on photograph of designs by a well-known European manufacturer, taking the usual dimension for the radiator as 0.5*wavelength minus 4%, and then scaling all dimensions. Thus I was able to arrive at spacings and lengths of all elements. It worked very well.

_________________
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nubbage
 Post subject: Re: Antenna Simulation Project
Posted: Mon Apr 27, 2009 7:46 am 
 
General
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 236
Location: London UK
On another point you raised: the bandwidth of a simple yagi, with no broad-banding of the radiator, is only about 6%. The first parameter to suffer degradation outside this bandwidth will be the front-to-back ratio.
Another point worth mentioning is that you might design a yagi with a good set of radiation pattern envelope (RPE) parameters, but the impedance match could be awful: like a VSWR of 6:1, not good.

_________________
At bottom, life is all about
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Posted  11/12/2012
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