[Lowfer] Fw: K9AY's comments regarding recent thread on the K9AY antenna

[Steve Ratzlaff]

I've forwarded some of the recent comments to Gary K9AY and asked if he 
wished to comment. His reply is given here.
Steve
----- Original Message ----- 
From: "K9AY" <k9ay at k9ay.com>
> Steve,
>
> I don't mind making a few comments for the list:
>
> There have been two basic views on how the K9AY Loop operates: 1) a 
> close-spaced phased array, and 2) a type of directional coupler. The "DF 
> loop with sense antenna" analogy is the same as a directional coupler, 
> just more identifiable to hams.
>
> The close-spaced phased array can be useful as an intuitive visualization 
> aid, but with the phase gradient around the loop, you really can't reduce 
> it to a simplified model with two distinct short verticals. Still, there 
> are phased array type behaviors -- the correct terminating resistor value 
> corresonds with equal currents at the feed and terminated end, and a 
> reactive termination shifts the phase and moves the takeoff angle of the 
> rearward null.
>
> I find it most useful to consider the loop this way -- if the terminating 
> resistor is zero, it's a small loop; if the resistor is infinite, it's a 
> bent wire monopole. The optimum resistor value balances the two modes, 
> creating a single structure that combines the functions of a loop and 
> sense antenna.
>
> The antenna also has the characteristic "small loop" behavior in that the 
> induced current is proportional to the loop area. Thus, doubling the 
> enclosed area gives you 6 dB gain (in practice, it's less, since it's not 
> an ideal small loop). I have verified this with loops of larger overall 
> size, and with hexagonal loops that have more area than the same wire 
> length in the original delta shape.
>
>
> 73, Gary
> K9AY
>