grounded vs ungrounded RX coil

[Monk]

My first "inclination" is to have separate return paths for Tx and Rx coils, i.e 2 ground returns. But as with all things having to do with EMI and grounding, it's 20% inspiration and 80% perspiration......

[greybeard]

i've been experimenting with a couple of HH versions and have been using the 'audio' grounding techniques that I was taught as a lad.
this doco ( fig 10.7 on page 3 ) has a drawing showing current flow and earth paths. you'll also need to find some info on shielding technuques to add to this knowledge.
http://www.analog.com/static/importe...0Grounding.pdf

my idea is that the coil is just like an extra component of the metal detector but it has a high level signal ( tx ) and a low level signal ( rx ) located at the end of a cable. and i treat the shield on the cable in the same way as i'd treat the electrostatic shield on a coil. my earth common point is as close to the detector electronics as is practical.

[dfbowers]

i've been experimenting with a couple of HH versions and have been using the 'audio' grounding techniques that I was taught as a lad.
this doco ( fig 10.7 on page 3 ) has a drawing showing current flow and earth paths. you'll also need to find some info on shielding technuques to add to this knowledge.
http://www.analog.com/static/importe...0Grounding.pdf

my idea is that the coil is just like an extra component of the metal detector but it has a high level signal ( tx ) and a low level signal ( rx ) located at the end of a cable. and i treat the shield on the cable in the same way as i'd treat the electrostatic shield on a coil. my earth common point is as close to the detector electronics as is practical.

Thanks..

That seems to be my conclusion by arriving there the hard way.