[VHFcontesting] Re: VHFcontesting Digest, Vol 5, Issue 15

Joseph H. Taylor joe at Princeton.EDU
Tue May 6 16:36:52 EDT 2003


N6TR wrote:

> ... The two element quad is a great antenna, but as you add more 
> elements, it becomes less clear that you are really getting much 
> advantage.  Maybe someone ... can explain why.


Yes, and that's why the "quagi" became so popular.

The two-element quad may be thought of as a stacked pair of two element 
yagis with the element ends bent toward each other until they touch.  The
stacking distance (1/4 wavelength) is much less than would be optimal, but
even so there is significant stacking gain around 1 or 1.5 dB.  As you add 
directors and lengthen the boom, the stacking distance of the equivalent 
"pair of yagis" becomes much more seriously less than optimal.  Long yagis 
need much wider spacing than 2-element yagis in order to yield significant 
gain over a single one.  Hence, as you say, you don't really get much 
advantage from using full-wave loop elements instead of half-wave linear
elements.  

On the other hand, you certainly don't lose anything by using full-wave
loop elements.  If they are mechanically convenient, it can be a good way 
to go -- hence the popular UHF/microwave "loopers".

                           -- 73, Joe, K1JT



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