Topband: K9AY Loop questions

[K9AY]

>from Mark, N5OT [answers follow questions]

> Question 1 - I have seen plots on K9AY loops and their relative gain is 
> way down on 160 compared to 80.  Of course, they work great on 160, 
> certainly with a preamp.  Does this mean you could make one for 80 that 
> was half the size and it would still work well?  Is there something 
> magical about the size that Gary designed them to be?

Nothing magical about the size -- as a loop, the signal capture is 
proportional to the enclosed area, and the published dimensions are the 
maximum that allow it to work on 80M with a simple resistive termination. So 
yes, you can make a smaller loop for any frequency and use more preamp 
gain -- until the point where its inefficiency keeps you from reaching the 
band noise floor.

> Question 2 - is there any reason you could not build one 10 feet above the 
> ground and use a ground plane of 3 or 4 elevated radials?  Over very 
> sandy/rocky soil, wouldn't that give me better control of my antenna 
> ground than (more) difficult-to-manage (i.e. hard to bury and keep buried) 
> in-ground radials?

There have been reports of successful -- and unsuccessful -- elevated 
installations with radials on a garage, carport, even an aluminum pool 
cabana. If you try radials, the first four should be directly under the loop 
wires for maximum counterpoise effect.

 For a height of 10 feet, you can simply use a wire straight down to a 
ground rod. Make sure it's straight down -- symmetry is important to keep 
the extra vertical wire length from having a big effect. Back a few years, I 
tried a loop raised to 7 feet and it worked fine, with no changes detected.

73, Gary
K9AY