Through-Ground Radio. (Below 500 KHz)

Discussion in 'Homebrew and Kit Projects' started by KJ4JAE, Dec 30, 2009.

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  1. AD7N

    AD7N Ham Member QRZ Page

    I have always been fascinated by this portion of the spectrum. A fun fact I found is any signal below 3Khz is unregulated by the FCC.

    Also, I came across AA5TB's excellent page on the topic of VLF,etc.:

    For those who are interested too, check out the INSPIRE experiment: (warning:turn down speakers, loud lightning sound when visiting site):
    INSPIRE is an experiment to receive and analyze natural VLF sources.

    His comments are quite in line with what you've posted so far.

    I also remember finding a page that claimed several records of QSOs at different frequencies. Do you have a link to that effect?

    Thanks for posting this! I may pull together a small ground antenna and try out that experiment with local AM stations!!
    Last edited: Jan 9, 2010
  2. WD6ELU

    WD6ELU Ham Member QRZ Page

    5KHZ +8.7 KHZ for gold detection?


    Like your son-in-law I too am heavy into gold prospecting. From what I read he was successful in locating gold deposits with the injected ELF signal? What did he use for a receiver?

  3. KJ4JAE

    KJ4JAE Ham Member QRZ Page

    Yes, excellent links!:)

    To answer your question, is THIS what you were looking for:

    Both very exciting links with logs of previous long distance qso's using these methods.

    I'm sure you'll be quite amazed with the A.M. broadcast band experiment... I was.
    Try plugging the input of an old SW receiver to the "Earth Dipole" and compare reception of signals below 2 MHz to an above ground antenna with the same receiver. You'll be a believer.
    Glad to see some interest in this.

    Ohh, and here's four more awesome links... Food for thought!:

    Keep us posted and don't forget to rate this thread :);)!!!!
    Last edited: Jan 9, 2010
  4. KJ4JAE

    KJ4JAE Ham Member QRZ Page

    Thankyou very much!!! :)
  5. KD0CAC

    KD0CAC Ham Member QRZ Page

    I have heard some on this subject before , like a Nova program , but now & here , look to be some good sources to play with .
    I have some friends that are into the giga-Hz [ up to 24 Ghz ] , but this seems to just draw me more , VLF .
    I am only getting internet at coffee shops , so do not have enough time , often to go through all the links like I would like , but I will as time goes by .
    But I had a question that I have not noticed yet , what kind of distances are possible with these types of frequencies .
  6. KD0CAC

    KD0CAC Ham Member QRZ Page


    I stopped at our local consignment shop , mentioned the low frequency stuff , and he took me over to a shelve with a HP 3586B & a HP 3586C selective meter , 0-32MHz .
    Just checking to see if these are good units for his subject ?
  7. AD7N

    AD7N Ham Member QRZ Page

    Thanks for the links!
    Yes, the site was the one I remembered finding. Thanks! I'll keep the thread posted when I have time to setup a ground antenna and AM broadcast reception.

  8. K7ELP

    K7ELP Ham Member QRZ Page

    My son in law used dousing rods for the receiver, but it was so unreliable that he gave it up.
    I think the best part of the MFD system was that of matching the impedance of the amplifier to the earth by moving the rods.
  9. KJ4JAE

    KJ4JAE Ham Member QRZ Page

    6.2 Miles is claimed by one person in the links with Earth Dipoles and a 1 KiloWatt audio amp., 250 Kilometers is claimed using Earth Dipole for transmitting and VLF loop for receive.

    I've gotten around 1 Mile.
  10. M0WAN

    M0WAN Ham Member QRZ Page

    Many years ago I conducted some experiments with trying to transmit straight audio through the ground - was it you who contacted me via my VLF web page regarding my experiences? I don't have the e-mail on this computer so can't check right now.

    I was able to transmit audio several hundred yards using a TX 'base' of two earth stakes placed about 50 yards apart. The audio was supplied from a single chip amp outputting about 10 watts RMS via a step-up transformer to better match the resistance of the ground. I don't recall exactly what the transformer characteristics were, but it was found using trial & error - it was most likely a mains transformer (UK 230 volt) with a 6, 12 or 24 volt winding.

    The low voltage secondary was fed from the amp's output and the primary was connected to the earth stakes. The transformer had multiple primary tappings to accommodate a range of mains voltages and one of these was selected to to produce a current draw by the amp similar to that when the amp was working into the correct 4 ohm load - a good and simple way to get the impedance match close to ideal without the maths.

    The important point I want to make is that I didn't experience the strange distortion that you did. OK, the audio wasn't hi-fi quality, but then I was using a CB mic and tended to drive the amp to clipping anyhow! Mains hum was the biggest problem and it was this, the difficulty in filtering it out and the trouble I had in trying to find a suitable quiet location that made me eventually abandon the project. I'm wondering if your distortion was caused by magnetic hysteresis in the transformer core? By applying a high frequency 'bias' in the same way as is done with analogue magnetic tape recording it is possible to overcome this. Is this what happened by accident in your case I wonder when your speech was superimposed on the tone?

    Anyhow, pity I abandoned it in some ways as I had built a transceiver, complete with PTT mic and all! (still got it somewhere.) Brings back memories of taking the family out on picnicks as an excuse to stick in a couple of earth stakes and just sit and listen (and occasionally call), in the hope that I would one day hear a like-minded person answer or calling CQ! I never did, but what it did do was to get me interested in natural VLF phenomena.
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