[TowerTalk] Fixed Quads

[n4kg@juno.com]

Re:  Full  Wave Loop antenna elements   de N4KG

Chapter 4 in the W2PV  Yagi Antenna Design book
discusses loop antennas.

Table 4.5, estimated gain and self resistance vs shape,
is especially interesting.

Shape   Sides    Gain     R (ohms)
		  dBi

Triangle	    3	 2.70	105
Square	    4	 2.99	120   (same as diamond)
Pentagon  5	 3.10	126
Hexagon   6	 3.16	129	
Octagon   8	 3.22	132
Circle	  oo	 3.28	135

The Triangle is obviously the simplest to install from a
catenary and is only 0.3 dB below the square configuration.
Pullout ropes at the bottom corners need only be tied off
at approximately 1/2 the apex height because of the 60 degree
apex angle.  For a diamond shape, the tieoffs would need to be
at least 1.5 times the apex height due to the 90 degree angle.

If you have the room to achieve a 120 degree apex angle
(tieoffs at twice the apex height), with an 85 ft apex, I 
would recommend a 2L (or 3L) inverted vee Yagi because
it will have a greater effective height.  40M beams play
VERY WELL at 80 to 100 ft.

Several years ago, I had a 2L Delta Loop suspended from a 
20 ft boom at 120 ft, fixed at 60 degrees.  It was a KILLER
antenna, covering all of Europe, Middle East, Indian Ocean,
North, Central, and even South Africa.

A 2L Loop or Inverted Vee Yagi can be made reversible using 
identical elements, each fed with 3/8 WL of coax, and switching 
both the center and shield of the feedline.  The open 3/8 WL line
looks like an inductance at the center of the unfed element,
effectively loading it to look like a reflector.  K1ZZ had such
a system in place several years ago.

The best way to avoid interaction is to use Foreward Stagger,
i.e., place higher frequency elements in front of lower frequency
elements.

de  Tom  N4KG






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