[TowerTalk] 4SQ for 80M

[Jim Lux]

At 01:35 PM 9/1/2005, Vojtech Ritzko wrote:

>I am planning 4SQ for 80M. I have problem with space, due to property 
>limitation.
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>Does anybody compared:
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>4SQ with ë/4 spacing, but only ë/8 long radials
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>Versus
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>4SQ with ë/8 spacing with ë/4 long radials
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>TNX
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>OM8AW

I'll give you a theoretical take.  Others will no doubt give you some 
practical experience.

Closer spacing makes for higher interelement coupling, the feedpoint 
impedances will probably be lower, so the IR losses (assuming everything 
else is identical) will be higher. The resonance will be higher Q, and the 
coupling changes faster with frequency, so it will be harder to get good 
phasing. Some depends on: would you use lambda/8 phasing or lambda/4 
phasing (or some variant with a bit more phase shift than the physical 
distance (like W8JIs scheme), which increases the forward gain a bit).

Think of something like a W8JK beam (two parallel dipoles fed out of 
phase).  As you move the two closer together, the directivity increases, 
but so does the loss, so the overall gain doesn't increase all that much.

On the other hand, the length of the radials (assuming you're planning on 
putting them on the ground) isn't really frequency dependent (the 
propagation speed in the wire is much slower than in free space, so a 
quarter wavelength long wire is a much larger fraction of a wavelength hwen 
the wire is buried in, or on, the dirt).  Most of the current in the 
antenna is close to the base, and it's the same for the radial 
network.  Lots of wires close to the base is probably more important than 
few wires farther out.

If I had the choice, I'd go for 1/4 wave spacing and short radials.  Easier 
tuning and operation, mostly.