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I was going to post this in the "Rhombic and V-type antennas" thread, but this may warrant a thread in its own right. Let's start with my Chireix from post http://www.digitalhome.ca/forum/showpost.php?p=1104790&postcount=936 I had initially called it a simplified Gray-Hoverman, but holl_ands pointed out in post http://www.digitalhome.ca/forum/showpost.php?p=1106880&postcount=937 that this design dated back to the 1920's under the Chireix name
  • It has a rhombic shape... check
  • It's connected at one end... check
  • It is not connected at the other end... check
Without the reflectors, the channel 14 to 51 gain ranged from 7 to just under 10 db with SWR from 1.5 to 3. I played with the size/scale to get the maximum gain at right angles to the diamond. I noticed as I increased the size in relation to lambda, the direct of the maximum gain lobe slowly shifted towards the open end of the diamond. To maximize the forward gain, I had to tilt the 2 diamonds forward into a corner-reflector shape. As the size got even larger, the max gain lobe came even closer to the lengthwise direction of the diamond, and I had to angle the 2 diamonds even closer together.

I thought about posting the angled rhombic-like version in Area 51, but decided that the huge size made it impractical. I could model more gain, using a lot less wire, by putting up reflectors behind the double-Chireix.

The main difference is how the non-connected end is handled in the 3 versions...
  • Chireix has an "air gap" in the diamond shape
  • A simple Gray Hoverman has horizontal elements extending sideways from the air gap
  • A "classic rhombic" uses a terminating resistor
The obvious next questions are...
  • How well would a terminating resistor work in a Chireix or a simple Gray Hoverman?
  • How well would an air gap and horizontal end elements work in place of a terminating resistor in a classic rhombic?
 
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