BH and AP vertical clearnce

Do AP’s and BH’s of the same FREQ still need 100’ of vertical clearnace when using a CMM?

If not…is there any instance where the 100’ of clearnace between them IS actually needed?

Cheers

They don’t really recommend the same freq. for your Ap and Bh’s.

We have done this very thing with as little as 20ft of seperation