Grounding of ferrous and nonferrous objects- valid or invalid tests

Is the validity of dependent on frequency transmitted of a detector? Or detector disc system?

[m.youtube.com]

Multiple times previously stated on this forum, grounding not a good test. But these comments were about detectors generally transmitting at lower freqs. And I guess I could say had slower recovery speeds generally. Where actual grounding would it seem allow a detector to 'falsely see the nonferrous', but separating albeit very small distance wise- nonferrous object masked.

So where do we draw the line, if we accept the fact , video above, test performed are valid?

And this work of art shown here - coin fused to nail.
[www.dankowskidetectors.com]

And just in case the host responds here.
This question I have here is Fisher F75 related.
If a masked nonferrous is swung over from best approach angle for possible detection, which setup likely to be odds on favorite for alerting.
Running fast audio (if detector possesses) using multi tone, or using single tone using disc level 6. Assuming using the latter method may in fact allow the digging of more ferrous.
So which is the better dragnet of mask nonferrous?

Or would a site need to be hunted using both methods to be deemed F75 detector with associated coil 'dead' ?



Edited 8 time(s). Last edit at 02/10/2018 02:55PM by Sod-buster.