ON7YD wrote:

If you calibrate the loop it is not nessecary to use an untuned loop. If
you use a tuned loop the output voltage will be much higher (factor Q, can
easily be 100 or more). This will allow to measure at larger distances.

I think there is a point in using an untuned loop (or at least one with low Q).
It should be less affected by nearby objects than a high-Q loop.

/Christer
sm6pxj