Surfmaster PI Larger Coil

[Joe Prime]

I have the older White's Surfmaster PI+ and like it very much.

I am thinking, however, that a larger coil would speed up my beach hunts.

Is this a relatively straight forward mod? Could I wind my own coil? OR is their someone to do it for me?

Appreciate any help I can get.

Thanks, Joe

[homefire]

Larger coils are no problems.

Just be willing to loose the smaller stuff doing so.

Go to the Coil Board.

Tones of info.

[maikl]

With the "Dual Field Coils Pi" will be held on sensitivity to small items... http://www.geotech1.com/forums/showthread.php?t=16691 But for a large coil is bad pinpointer.

[mikebg]

Joe Prime, the timeconstant of GND signal depends on conductivity of soil and diameter of TX coil (in square power). When we increase the diameter of TX coil, the timeconstant of salty beach signal comes close to timeconstant of valuable targets and magnitude of GND signal increases.

The dual field configuration can not improve the GND signal.
Attached figure illustrates what happens with dual field coil above conductive ground. The secondary field generated by eddy currents in the ground seems as if there is a dual field coil with the same size of TX coil buried as mirror image (relating to surface plane).

Think for the mirror coil as a target which moves inside the earth together with movement of original coil. When the original coil increases height, the mirror coil increases depth. When the original coil inclines, the mirror coil inclines in opposite direction.
The maximal smart diameter of monocoil for salty beach is 25 cm. Only if the beach is dry or wet but not salty, you can use larger coil diameter.

[maikl]

mikebg i do not have near the sea beach i check your theory. But Whites most of its beaches detectors for the Dual Field coils: 300mm larger the outer coil and an inner smaller coil 150mm. I think that is the maximal diameter of smart monocoil for salty beach is 300mm.