8.970KHz Earth Mode VLF Amateur Radio Saga Pt 1

8.970KHz VLF Amatuer Radio The Dreamers Band

8.970KHz sounds like something you would see associated with a hearing test not amateur radio. In this instance we have been attempting to send a signal roughly 3 miles through the ground via earth mode propagation (conduction?). The antenna (grounding) system consists of two 8ft ground rods spaced roughly 35ft apart. 8.970KHz AC at around 140 watts is being injected into the ground between the two ground rods.

The theory is the ground is more or less a large conductive sheet of infinite resistors or a giant crazy voltage divider circuit. No matter how much current travels the short path between the two ground rods some must travel through other paths. So at the other end 3 miles away we have two ground rods around 50ft apart connected to and HP receiver in theory if current is present it should travel between ground rods and show up on the very narrow waterfall in Spectrum Lab.

Rockford Fosgate Punch 200.2 Power Amplifier / HP DPS-800GB Power Supply

Rockford Fosgate Punch 200.2 Power Amplifier / HP DPS-800GB Power Supply

So far no luck! we still have many other options to try such as magnetic loop antennas, more power, father spaced ground rods at the transmitter site and many things we haven’t thought of yet.

The station consists of:

  • PC computer running DL4YHF’s Spectrum Lab (AMAZING MUST HAVE SOFTWARE!)
  • Spectrum Lab has been configured in QRSS 3 – 60 and DFCW 3 – 60 for the tests
  • Rockford Fosgate Punch 200.2 car stereo amplifier
  • HP server power supply DPS-800GB 13.7v @ 69 amps
  • Two ground rods 35ft apart directly connected to the 4 ohm output of the amp
DL4YHF's Spectrum Lab transmitting QRSS 3 mode

DL4YHF’s Spectrum Lab transmitting QRSS 3 mode

I would appreciate any suggestions from hams that have had success with earth mode transmissions.

Links related to the subject.

VLF Using Earth Mode – Sub 9kHz Amateur Radio

G3XBM Earth Mode Blog – Sub 9kHz Amateur Radio

VLF Amateur Radio Roger Lapthorn G3XBM (PDF)

G3XBM YouTube Channel

More pictures of my crappy test setup

Thanks for reading as always don’t forget experimenting = learning = prepping!