shielding

[Tseeker]

Is there any type of material that can be used to fabricate an extra shield cover for the top of the coil? The idea being that if the magnetic field cannot extend upward then the energy must be forced downward achieving greater depth.

 

[gilfordberry]

An interesting proposition. First, shielding the emf from the top of the coil won't make the signal stronger on the other side unless the shield reflects the transmit signal (can't be grounded) and the reflected signal happens to be in phase with the original signal. With relatively long wave length signals from VLF machines, though, this phase difference wouldn't be substantial, so the signals would, probably, be additive, but not as clean as you would hope, causing some chatter in the transmitted signal (and doubtless the same chatter in the received signal). Shielding one side of the receive coil, though, is certainly an option - and this shield should be grounded. It wouln't add any signal strength to the transmit coil but will stop received signals from above the coil. I think White's used to make (maybe still do?) a coil to use under fences and in areas of high interference that shielded the top of the coil.