[TowerTalk] Fixed Quads

[KI7WX@aol.com]

For folks interested in wire antennas and using natural supports, I could use 
a bit of advice.

In preparation for the upcoming contest events I'm looking at erecting some 
fixed quad loop "beams".  The loops will be hung from a catenary line running 
(length wise) NE/SW -> e.g. Europe.  I have about 50 feet of length to play 
with and the height measures out at 85 feet above ground.  That's pretty 
spiffy as it'll place the center of 20M diamond shaped loops at around 1 
wavelength and 40M about 1/2 wavelength which should be decent for both 
bands.  It will get higher with time as the trees grow .... ..

With that setting, I want to suspend loops for both 40 and 20M from this 
line.  Looking at a driven element and reflector with ~20' spacing for 40M 
and probably 4L on 20M using 10 feet between elements (30' total).  Two 
questions for the group:

(1) Does shape of the loop matter much?  From my reading it appears that 
cubes (diamonds) are credited with very slightly more gain than equilateral 
triangles.  I'll probably do the pragmatic thing and use what ever shape is 
easiest, but curious what experience teaches here. It probably doesn't matter 
except on paper.

(2) For rotatable quads it's obviously possible to build multiband arrays by 
nesting the loops for higher bands within the loops for the lower bands.  
It's not immediately obvious to me why interaction is not a problem, but I 
accept the results.  For my situation, erecting "nested" elements will not be 
too practical and would likely result in a twisted mass of wire and much 
frustration.  

Taking a page from the yagi book, I have pondered "interlacing" the elements 
to take better advantage of the available catenary length.  For example, the 
40M outer elements could surround the 20M elements to give a larger spacing 
on 40. Alternatively I could add a couple 10M loops inside of the 40M loops.  
Stuff like that.  Has anyone played with this type of arrangement that can 
offer practical advice?  

Cheers,

Mark
KI7WX/4


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