In article ,
Jeff Liebermann wrote:

Anyway, 900 MHz yagi antennas are kinda pedestrian. Getting something
to work at VLF frequencies is a real challenge.

Not all that hard, really. All you have to do is lay out a redundent
pair of oil pipelines along the proper courses, and you can make a VLF
rhombic large enough to be seen from geostationary orbit :-)