Pictures like those:
http://imageshack.com/a/img673/7211/yUX1yW.jpg
http://www.longrangelocators.com/for...1&d=1419076081
shows that the ahead-orientated ferrite-antenna with its 2 different windings already
acts as some sort of directional-receiver.
But this is just a very simple amateurs-solution because the coils are so close together
and they can't detect left right which is absolutly important.
If this LRL stuff should have a chance to work usefully, 4 seperate ferrite-antennas are needed!
6 would be even better, to check out the vertically field strenght.
And its not good to include directly some sort of retro-metal-detector-circuit into
such LRL-device, because even if the MD is fully switched off,
the round, DD or omega coil of it will suck away or disturbs the weak long-wave EM-fields.
But highest priority has a useful signal output !!!
With one stupid LED or a beeper this doesn't work and sweeping the coil into
find direction also doesn't work because it would be like turning an AM-radio
away from its (best) reception position!