Thanks Hoov,

It would seem to me, with my limited technical know how that these z-tems etc will show somewhat similar to what a transducer of a fish finder would show. The cone of signal increases in diameter the deeper you go. Using a fish finder in 8 feet of water will give you a very narrow view. Deeper water will enable you to get a visual of a wider range.

Of course the deeper one goes the less the resonance.

Is this an appropriate analogy??

TIA

Don