Fisher PF-18
The Fisher PF-18 sheath fault locator manufactured during the late 1990's transmits phase-synchronously at 5 and 10 Hz (to avoid the 7.8 Hz Schumann resonance), is equipped with earth probes, and the receiver also equipped with earth probes is directional. Although designed for sheath fault locating, in principle it could be used for soil resistivity mapping. I have demonstrated its use for through-the-ground binary communication.
They show up every now and then on fleabay.
If anyone is wondering "what does something that actually works have to do with LRL's?", the right answer is "what does anything electronic have to do with LRL's?"
--Dave J.
|