Topband: Adjusting termination resistance

K9AY k9ay at
Wed Dec 28 18:14:48 EST 2005

>I use W8JI's technique for my K9AY loop system (homebrew). I use an SWR 
>analyzer feeding a small amount of RF into the system, and adjust the 
>termination resistance SWR for minimum at 1.830.
> John, W4NU

John and all,

With a K9AY loop, as with a Beverage, minimum VSWR is not a measure of 
antenna performance, although it may happen by coincidence.

In an installation using an accurate 9:1 transformer, with typical ground, 
the lowest VSWR will occur near the ~400 ohm optimum termination resistance. 
But, for example, if your transformer is 4:1, the termination still needs to 
be 400 ohms, not the 200 ohms that will give you the lowest VSWR.

73, Gary

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