[TowerTalk] need ideas for 4-square elements

[Jim Lux]

>In other words, the idea is to get from here to there as
>quickly, cheaply and effortlessly as possible.

An admirable goal... then, if it doesn't work like you thought, you've got 
time to try something else..


>
>K4SQR of Comtek systems says ELNEC shows the close-spaced array to have 10
>dB F/B and 4.9 dBi gain. I get similar results with EZNEC. While this isn't
>stellar, it's quite a bit better than the delta loop, especially if I can do
>it with minimum effort and cost. (BTW, K4SQR also says it's OK to feed the
>system with one of their hybrid couplers, as long as the phasing lines are
>1/4-wave long at 80m.)

Indeed, this is true, the hybrid coupler is basically a 90 degree device 
(although, is it broadband enough... most transformer based 90 degree 
hybrids have some lumped L and C)

And, as long as the TL to the element is 1/4 wave, you're getting the 
current forcing effect..


>3. Are the 1/8 wave radials going to result in much lower efficiency (bear
>in mind that there are a lot of them)?

Probably not "much lower", most of the current is at the base of the 
vertical, and the image current in the ground plane is also highest close 
to the base.  As you move out, there's significant coupling to the ground 
from the radials, so return currents will flow into the radials, whether 
they're connected or not.

>
>and most important:
>
>4. What's the easiest, cheapest way to extend the elements?

At some sacrifice in efficiency, why not start by just putting a loading 
coil/matching transformer at the base of the existing verticals, just to 
see how well it works.  This will also reduce the mutual coupling between 
the elements (because physically short elements have less coupling). Mutual 
Z is the bane of phased array design anyway..

Easy, minimal hassles, etc... 4 new pieces of coax, 4 little loading coils 
lashed up out of #10 bare wire wound on a mailing tube or PVC pipe or 
something, and test that sucker out..


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