Design this high performance sector antenna that you find very similar to what is available from commercial manufacturers.
My initial approach was to design a ?Franklin Array? omni antenna because I?ve done the Meanderline with a reflector before and it?s a no performer, I did not try the COCO yet as soldering the joint is difficult, basically this antenna is a centre fed dipole with a ?U? shape for shift phasing instead of a coil, so far so good, the design seems to be good but the result was not very promising, the theoretical gain I can get is within 2-3 dBi only!, (aerialix design performs much better than this!)
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I was not happy with the result so I revised my design again, this time I put a 123mmX123mm reflector at the feed point with a distance of L1/2 from the feed , to my surprise the gain jumped from 2-3dbi to 3-4 dBi! well that is interesting! an increase of 1db (obviously because of the reflector), the sphere also changed from a typical omni pattern to a directional pattern with 30 degrees of beam width horizontally and about 10 degrees vertically, I modify the reflector with different dimension from 1wavelength down to 1/4, after making lots of adjustment which are all based on wavelength, the only size that seems to show a good result is by using the L 1/2 x 1 size, there was no difference with the gain, however the beam width improved a lot! from 30 degrees to almost 118 degrees! my modelling seems to give me a good result, I continue adding more reflector until I reached the top and bottom of the element with an extra 1/4L from the tip of the element, to my surprise the gain increased from 4dbi to 11.5dbi! the beam width stays the same. I?ve check the svwr and it is within the acceptable figure which is 1.2 – 1.5, the design seems to be ideal for a sectored antenna, it is now time to put everything in practice!. I will post all relevant result from the modelling program later on, meanwhile; I will start to make the ?sectored antenna?.
Article by Dan Santillan at his blog at http://thekrome.blogspot.com/
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