Help with vlf dd coil.

[douglas]

I've constructed a nice DD coil for my 6.59khz detector. It works well in all metal mode, but not in disc,. mode I want to improve it so it will work wilth the target id.. The TX coil resonates at 6.59 (roughly) I have a good null it will detect a coin from several inches. the RX is a 37 mh coil with a resistance of 96 Ohms. Can anyone help me.
Thank You.

[Geo]

I've constructed a nice DD coil for my 6.59khz detector. It works well in all metal mode, but not in disc,. mode I want to improve it so it will work wilth the target id.. The TX coil resonates at 6.59 (roughly) I have a good null it will detect a coin from several inches. the RX is a 37 mh coil with a resistance of 96 Ohms. Can anyone help me.
Thank You.

Rx coil has different phase shift than the original one.

[mikebg]

Douglas, you should adjust capacitance connected across RX coil. Adjustment is important not only for DISC mode, but also for elimination of GND signal in ALL METAL mode. For adjustment you need a ferrite rod, ferrite core or hot rock. Put GND BAL knob near to end position and change the capacitance until machine starts to eliminate signal from ferrite rod. Then check discrimination in DISC mode.