Building an Underground Earth Probe Antenna for 0 – 14 MHz TX/RX

Thank you to Jean-Marie Polard (F5VLB) for letting us know about his work in creating underground "earth probe" antennas that work for both RX and TX between 0 - 14 MHz, and are especially good at VLF and below. He writes:

Can't install an antenna at home? Madame refuses the masts, taut son? One solution, The Earth probes antenna.

Our group (https://www.facebook.com/groups/earthprobes/) started in January 2019. At first everyone made fun of me, the professionals called me crazy and today with more than seven hundred members, we installed underground antenna systems and the results are there.

Between 0 and 14MHz, in transmission and reception, it works!

This system dates from 1914/1918 but has been brought up to date.

It doesn't take much to get started, just the urge to try.

Mad of vlf - elf - ulf ? come here https://www.facebook.com/groups/VLF.ULF.ELF/ nearly 1000 members are waiting for you.

So when? Welcome everyone.

To access the Earth Probes and VLF.ULF.ELF groups you'll need a Facebook account. The groups contain a number of research papers documenting the concept, and the photos section. From the photos, an earth probe antenna appears to consist of two long grounding rods spread over a distance, or a grounding rod and long buried wire, combined with a balun.

An example of an underground antenna setup from a 1935 shortwave magazine.
An example of an underground antenna setup from a 1935 shortwave magazine.

18 comments

  1. snn47

    Please remember, the main intention to have a concealed antenna for transmission and reception, was not that such concealed antennas have a better performance than simple above earth antennas, only that you have adequate performance.

  2. snn47

    Does anyone have the title and reference to the NBS article?

    With a few meter of cooper wire from a discarded transformer I received signals down to 77.5 kHz. The picture shows the use of a chicken-ladder as feeding line, which is for symmetrical antennas, while the use of the ground stick and buried wire is asymmetrical. It can be argued that the feeder line can be attributed for part of the signals received transmitted, similar to the infamous self-tuners-boxes to which you could connect any length of wire above a few feet. A teardown made by QST in the 70’s showed only a few resistors inside with the feeding line and the resistors provided enough matching without the need for tuning.
    My point is you will receive signals even with a dummy load on the end of a feeder line, the question is only how well you will receive signals compared to a defined antenna setup.

    • Bertie

      You would probably get similar performance, by adding a 14 MHz low pass filter in the signal path from a normal uhv/vhf antenna. No would be my answer.

      If this works the way I think that it does, I would guess at least ~30dB less signal (say that the filter, soil, has a very gentle slope and is attenuating at a extremely modest 20dB per decade).

  3. Jack Wybenga

    This concept has shown up in various publications including QST in the 1960s. It was a joke, surprised it finds new victims every few years

    • Bertie

      If the entire RF spectrum behaved exactly the same, I would fully agree with you that it was a joke.

      But ELF (3 to 30 Hz is used to order submarines to rise to a shallow depth where it can receive some other form of high bandwidth communication) can penetrate seawater deeply, to the the full operating range of submarines. Because seawater is electrical conductive it attenuates most of the RF spectrum. A single ELF transmitter has 100% earth coverage. ELF transmissions are one way, and not very efficient a few megawatts of input power for a few watts radiated power.

      My suspicion is the the soil is behaving similar to the “skin effect” in a conductor, where higher frequency AC has a low penetration depth, and lower frequency AC has a much greater penetration depth. Both signals will be attenuated but with less unwanted signal, the wanted signal will be clearer. But the assumption would be that the soil is conductive, so what works easily at a shallow depth in swampland may not work at all in the middle of a desert.

      • Jack Wybenga

        There was a supposition that a surface effect came to play in Loran C, at 100khz, but propogation measuremen’s during a drought and after a hurricane showed it to be false. The submarine com link was at 17 kHz with a transmit power in excess of 2 Mw. Attenuation through water was logarithmic.

        • Truth

          That may well be the case now. But Clam Lake, Wisconsin (between 1985 and 2004) was the heart of ELF transmissions to US submarines at the very bottom of the ocean.

    • Rufus

      The concept has been used as a joke, yes. It has also been used by several militaries for fixed antennas that sacrifice some efficiency for the sake of survivability.

    • Jean Marie Polard

      when I started I get the same comments as you jack (new victims every few years). I told them, try it and come back to me. Now we have several ham radios using this system with success. Don’t criticize if you have not tested ! 73’s John

  4. Jake Brodsky, AB3A

    For those who are not thrilled with FB membership (I am not and never have been on FB), you might want to see http://www.vlf.it/ed/earthprobes.html for a bit more technical background. This discusses the “Earth Probe” in better detail for LF, VLF, and ELF (right down to the Schumann resonances).

  5. Bertie

    I’m never going to hand my personal data over to facebook to track me and shove ads at me (not a part of the Facebook stalker cult) just to read the linked posts.

    So what be the short summary ? That this is in effect an E-field dipole antenna that is using the soil to strongly attenuate signals above 14 MHz ?

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