Some calcs for you Victor,

4-turn loop, 2M each side, seperated by 1cm. The following tuning
capacitance is required for 60 KHz:

1mm dia. wi 60,180p
1.5 and 2mm dia. wi 65,580p

That's an awful lot and the tuning will be only a few tens of Hz wide.

If you have the capacitors, go for it.

If not, maybe an active antenna for your underground receivers?

BTW - the program is posted to ABSE. It won't go down to 60KHz, but you
can scale 1MHz results accurately.

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*