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Thread: Through-Ground Radio. (Below 500 KHz)

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  1. #1

    Default Through-Ground Radio. (Below 500 KHz)

    Hi fellow Hams, I'm J.B.Young III . KJ4JAE.
    My work has recently been menchaned in the international magazine
    Monitoring Times, specifically in the column Below 500 KHz, by Kevin Carey, WB2QMY. December 2009 issue. My work should also soon be up on Renato Romero's site:http://www.vlf.it/

    I'm sharing this with you, because I was recently in the hospital and almost died. I have years of work on this project and don't want my work to be lost. My attempt to publish a book on it has failed.
    I only wanted to recoup some of my R&D costs, but looks like I better go public now. The Schematics I've included (thumbnailed) are my property (Empire CO.) but I am sharing them to all who want to build the circuits as long as noone uses my designs for their own financial gain.
    Feel free to copy the circuit diagrams to your computer or hard copy them so you can distribute them to other hobbiests. These circuits are strait out of my notebook (scratch pad) and are drawn by my own hand.
    the writing is not the best, since I usually scribbled in a hurry, excited about doing more experiments but having the desire to record my efforts.
    For years now, I've been experimenting (allong with many other hams) with trying to transceive through the ground.

    A lot of people are familiar with the VLF signals that cause currents to flow in the ground beneath our feet. Some of these signals are man made, and some of them are naturally occuring, such as 'Sferics and the famous 'Whistlers' believed to be caused by lightning.

    These signals can be recieved with loop antennas in the air, other antennas, OR can be directly tapped into by sticking copper probes into the ground, a few feet apart and connected to a vlf receiver, or even a high gain audio amp! (filtered to take out 60 Hz power line buzz).

    I wanted to see if anyone who frequents QRZ, was in to this sort of thing like me, and share all my knowledge about it.

    The receivers are simple, see first attachment. All you need is an op-amp, a LM386 N-4, 8 ohm speaker, battery, and two ground probes along with a handful of resistors and caps.
    No need for an a.m. demodulator circuit, the audio amp will do that for you through the process of auto-rectification.

    To transmit through the ground isn't as easy. A lot of people believe it's impossible to achieve (at least, with any distance at all) and have given up. I know a ham who buried an antenna and transmitted at 1 Kilowatt and could receive the signal only a few FEET.

    However, they were going about it the WRONG way.
    I also tried for a long time to transmitt with only one rod poking in the ground, could never make it work.

    UNTIL I tried sticking 2 rods in the ground a very wide distance apart and hooked the output of a high voltage/low current audio amp I homebrewed to them. THEN the signal traveled very far.
    For instance, my current transmitter delivers about 170 Volts (peak to peak) to the two poles, the signal is an A.M.modulated carrier at 17 KHz. The poles, which are copper pipe, are about 300 feet apart and go about 3 feet into the ground.

    I can pick up the signal with my receivers up to about 1/4 MILE away!
    I hav my portable receiver in a nice handled case and hook the two receive probes to it through an earphone jack. The poles on the receiver need only be placed a short distance apart (about 3 feet).

    The farther the tx poles are seperated, the farther the signal will transmit. Same thing for the receivers, put more seperation between the ground rods and the more sensetive the rx becomes.

    My first several transmitters were just audio amps, they put only audio into the ground. Although I could pick up the signal a good distance, it was always badly distorted. I always play a c.d. player with music into my transmitters when experimenting, unless I have someone else around that can speak into a mic (which is not very often).
    I couldn't understand why the transmision was garbled, when my Tektronix O'scope showed a perfectly clean signal with the ground rods attached and the tx running.

    So I decided to make a tape of me generating various audio tones, speaking the frequency over the tape, starting at 300 Hz and going to around 20 KHz. I softly spoke each frequency in between each change.
    I went out into field around my house to listen... The audio tones came in clear but my speech again was GARBLED. UNTIL the tape reached the 8 KHZ tone. For some reason, when I made the tape, I spoke "Eight KiloHertz" WHILE the tone was running, instead of before I generated it.

    While standing there in the field, I heard for the first time, crystal clear voice come over my receiver. I was breathless...

    Then I repeated the experiment over and over, wondering why my voice could only be understood with around a 5 to 20 KHz tone RUNNING IN THE BACKGROUND. (Anybody figuring this out yet?)
    It took me a while, but I theorized that because of velocity factor (the fact that r.f. travels at different speed based on frequency through conductors) and other factors, that since speech and musics' frequencies vary over many octaves, that the individual waveform componants were arriving at my antennas at different times and out of phase/sync.
    Based on this theory, I thought to myself. If I only transmitt a SINGLE frequency and A.M. modulate it, it should work.

    After all, that's EXACTLY what my audio amp had done in the first place.
    When the 8KHz tone was transmitting and I spoke, my voice was being linearly mixed with that signal by the amp. In other words, my voice was "riding the back" of the 8KHz sinewave much like an A.M. carrier

    I then constructed an A.M. Modulator using the XR-2206 chip, amped the output up from about 2 volts peak to peak to around 170 at 17 KHz, and the rest is history....

    It's now been several years since I finally completed my first two fully functional Underground VLF Transceivers and had my first underground QSO, between me and my neighbor across the street. On Monday 9-18-06 I saw the ultimate success of my efforts. Using 4 copper rods hammered into the ground about 3 feet, (2 in front of my house and 2 in front of his) with a seperation between mine of 40 feet and his 20 feet AND over 200 FEET between the two independant systems, I had the pleasure of talking to another person THROUGH THE GROUND with crystal clear sound and LOUD modulation.
    I have included the FULL schematic of the final transceivers on the last thumbnail.
    Theorectically, this sytem will go as far as you want it too, you need only seperate the poles farther apart. The system appears to go about THREE times as far as the poles are seperated.
    You want a range of 6 Miles? Seperate the poles by 2 miles.
    This sounds VERY impracticle, but there ARE uses for such a system.
    Suppose you wanted to have a covert 2 way intercom between two houses seperated by a river.... or seperated by a street like my neighbor and I.... Radio can be eavesdropped on, a wired intercom would be impossible because of the river or street, you get the picture.
    Besides it's FUN!!!
    I hope there will be lots of comments and interest...

    To answer some questions beforehand, I use the untuned wideband audio amp as the reciever, with a high pass filter of around 300 Hz, so I can listen and demodulate any signal I detect from 300 Hz to around 400 KHz. I have monitored NDB's and just bout anything else you can imagine in that frequency range. The 100 KHz LORAN C, should be the first thing you hear when turning up the gain pot on the receiver. Using a tuned A.M. receiver seems to do nothing to increase the range, I've already tried it. I used a Palamar VLF converter with the ground probes feeding it, and the converter plugged into my AOR 8200 tuned at 3017 KHz (listening to 17 KHz) and have almost the exact same range as with my hombrew receiver.

    The second attachment shows the receiver with a .01micro Farad cap shunted across the input, and a .22nano Farad cap between the receiver and ground rod.
    The first cap stops signals above 400 KHz (namely A.M.Broadcast Transmitters) and the second cap provides a highpass critical frequency of 30 Hz, this makes the receiver start amping max at 300 Hz (Critical frequency times 10) which reduces power line buzz at 60 Hz and asscociated harmonics to an acceptable level.

    I've also included the XR-2206 schematic for an A.M.modulator for connecting a c.d. player or microphone circuit (also thumbnailed) that forms the basis of an A.M. Transmitter that will go from about 10 Hz to 1 MHz.
    The XR-2206 can be bought from Unicorn Electronics for about $3, and the TL082 is about 30 CENTS (also bought the LM386N-4's from them for about a Dollar a pop.



    I'm interested to see some reponses and make contact with other experimenters.

    Have fun (I have!)
    -73's.
    Attached Images Attached Images
    Last edited by KJ4JAE; 12-30-2009 at 01:55 PM.

  2. #2
    Join Date
    Aug 2009
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    Default

    That is the subject of submarine communication. The US and Russia have ELF transmitters working aound 80 Hz range (not kHz) using rodes separated by a distance of 50 km range. To produce a few watt of radiated power, a dedicated power plant is needed.

    That is the ultimate QRP communication and the signal can be heard all over the globe.
    73, Jim AD2U /6

  3. #3
    Join Date
    Mar 2008
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    SoKY
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    Default

    Just read the article in MT a few days ago. Interesting stuff indeed.
    Sorry to hear about you health issues. Have you thought about self publishing the book? Write it up on a computer and then go to Staples or Kinkos and get it printed out.
    World War II began turning around when the Allies landed near Italy's toe and gradually advanced up her leg.

  4. #4
    Join Date
    Dec 2004
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    Shropshire, UK, SY10. Locator IO82LS
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    Done it with audio (music) using about 1.5W between a Victorian cast-iron fence with a number of posts in the ground and the ground wire for a domestic telephone (ground generally not used these days). The "electrodes" were about 10 yards apart and the reception distance a little under a mile. There was a fair amount of QRM, mostly harmonics of the mains frequency.

    I have the feeling that the telephone "ground" may have actually been continuous most of the way, nevertheless it worked well. It was well over 30 years ago when we had far less electrical and electronic equipment to cause QRM.

  5. #5

    Default

    Thanks for the suggestion, but I think the best way now is for me to just get my information on the internet. I really need a good cheap (or free) program to professionally portray my schematics, instead of my hand drawn notes. I just wanna get my work out there.

    I certainly DON'T claim to be an expert in the field... Just an experimenter who has found a way that works. There's no reason that anyone else should have to go through the years of mistakes that I did while trying to make it work.
    The method I'm using is called "Ground Conduction". It's NOT transmitting Radio waves through the ground in a conventional method. Rather, inducing currents in the ground by forcing a potential difference (Voltage)between two points in the ground at VLF R.F. frequencies which causes currents to flow outward (not just STRAIT between the two points).

    I'm certainly not the first to use it. A German Physicist named Heinrich Barkhausen theorized that he could listen in to Allied field phones during WW2, by using a high gain audio amp to pick up the Eddy currents generated by the phones (which used 1 wire and the GROUND as the return circuit. He was successful, using the seperated ground rod (dubbed Earth Dipole) method from MILES away. My thoughts were "If he could pick up unintentional long range communication currents in the ground, surely I could devise a system to do it 2 way (transceive) by using intentionally generated currents.
    In WW2, the Allies used an intentional system to communicate between trenches, that I'm sure was very similar to mine.

    I tried for years to transceive with strait voice (audio) but could NOT make it work.
    My Velocity Factor theory is just that, a THEORY.... there maybe much more complex things involved including the QRM that ModS menchaned, and the fact that the ground has a capacitance that produces an automatic 90 degree phase shift. The D.C. resistance of the ground is 100's of MegOhms per INCH. If you stick two poles in the ground, congradulations, you just made a capacitor, that will even show up on a capacitance meter. Two conductors seperated by an insulator IS a CAPACITOR, not to menchan the moisture and mineral rich dielectric most good ground has. The a.c. impedance of the Earth Dipole system is MUCH lower however, arguabkly around 30 Ohms per foot based on certain variables.

    My point is that A.M. modulating a VLF carrier and using the Earth Dipole method for t.x. and r.x. DOES work and can be made from simple circuits that take only hours to build and VERY cheap parts.
    I feel triumphant because many people told me that I'd NEVER get more than a few feet through the ground. I KNEW they were wrong and finally proved it to them.
    For now this system has these advantages.
    1. It's covert... Who's gonna be sticking poles in the ground to try to listen in on your 2 way intercom. (Laser, fiber optic, and radio shortrange point to point intercom systems can all be eavesdropped on).

    2. You can directly control how far it transmitts. When you use this system, it creates currents that run strongest directly between the two points of the ground poles, then rapidly dissapate in strength with distance from the poles.
    The Eddy currents produced at long range which are responsible for the results ModS got are too far in QRM to ever be able to pick them up now.
    There is almost NO above ground R.F. energy created.
    Even the most well equipped "snoop" probably isn't gonna have a sensitive VLF reciever like I do... And I can only pick up a signal "in the air" if I hold the antenna RIGHT AGAINST THE GROUND DIRECTLY IN BETWEEN THE TWO TX POLES. Move a few feet away and the signal dissapears. Since the underground R.F. signal (current)is taking an infinite number of expanding paths to reach the return circuit ground rod, the phases of the currents as they take different (longer or shorter) routes, causes MULIPLE PHASE CANCELATIONS WHICH NEGATE ANY ABOVE GROUND/TRUE R.F. TRANSMISSION.

    Imagine this: Lets say you applied an audio signal to a 100 K Ohm resistor. You take a Dremel tool and gently rub off all the casing of the resistor on the top, so you can get VERY small VOM probes to the resistor's conducting surface.
    If you could measure the voltage between any number of two points on the resistor substrate, you would find that the current flowing between any two points in the resistor are NOT the same. Most of the current is directly between the two resistor leads, then exponentially decreases, because of physics similar to Inverse Square Law, as you move toward the resisistors outer surface. It's no different when you place two poles in the ground seperated by a wide distance, EXCEPT that you have just applied a signal to a resistor that has no defined boandary.
    The current will flow from one pole to the other. but do so in gradually diminishing quantity as you move away from the poles... this degredation of signal CAN be calculated and proven mathematically, based on all the variables, including the makeup of the ground.
    The thing is, these primary currents produce Eddy currents which induce and "disturb" other currents in the ground at MUCH longer ranges than the primary currents, who's effects are still a mystery.

    I'm no expert, but trust me, I know what I'm talking about... I've been experimenting with this since I was 17 and am now 35. AND I'm a well-rounded Electronics Engineer with years of study and experience.

    A radio electronics book I checked out at the Mercer County Kentucky Public Library got me into this whole thing way back in '91.

    Already an avid C.B.er, SWL, and scanner hobbiest, I was amazed and inspired by the Authors' claims that there was a whole "new world" of mysterious signals beneath our feet, in the ground, and that this world was seperate from above ground signals.
    Their experiment in which they plugged a guitar amp into two ground poles and could hear them with a high gain audio amp 2 miles away, using two other ground poles had me trippin'!
    I've been obsessed ever since.

    Although there is some truth in their claims, the two worlds are not entirely seperate. For instance, listen up NDB (Non Directional VLF Nav-aid) monitorers/enthusiasts and A.M. Broadcast Band Enthusiasts, VLF radio signals travel further than any other R.F. signal and propagation gradually diminishes as you move up in frequency. This is because the distance between the ground and ionosphere acts as a "wave giude", it is also because these signals penetrate the ground further than any other and cause currents, and are intimately associated with the ground...
    As the lower half of the wave entcounters the ground, IT SLOWS DOWN and causes a BENDING effect that keeps the wave in contact with the ground and causes it to follow the curviture of the Earth.
    Because of this, at these frequencies, above gound transmissions can be monitored by the current alone they produce in the ground.
    Earth dipoles in many instances actually beat above ground antennas from the A.M. Broadcast Band, on down. There is almost no noise above about 100khz when hooking them into a SW receiver, because the noise is common at the two points and are cancled by the Common Mode Rejection of most receivers.
    I can attest to this from seeing it with my own eyes (and ears) and doing it myself.
    I can pick up NDB's and ANY nearby A.M. Broadcast station with 2 ground poles better than any ferret rod A.M.receiver or above ground VLF antenna (for VLF NDBs). Don't believe me? Try it yourself.
    Bear in mind that the Earth Dipole Antenna IS directional when using it to receive above ground (conventional) radio transmissions.
    Much the same as a loop antenna it "hears" from two sides and "nulls" the other two directions.
    Signals coming in parrallell to the poles "see" the energy from the approaching r.f. wave at the same time, therefore producing no difference in voltage in between them. Waves encountering the poles in the direction they are "alligned" 'see' the wave at diffent parts of the phase cycle, since this is two different voltages (and this is exctly what causes the wave to produce moving current in the ground) this voltage can be amplified by a reciever and demodulated.

    For more earth Dipole theory checkout the affore given link or do a Google search.

    One more thing I'd like to menchan... the transmitter circuits I've shown are DANGEROUS. They use a bridge rectifier STRAIT from the 120 Volt LINE, (besides fuse of corse) to generate 170 VDC.
    Notice that you MUST use a Line Isolation Transformer of suitable current rating for these circuits to work AND to protect yourself against electric shock.
    These circuits WILL NOT WORK without an Isolation Transformer to remove the circuit's reference to ground and cause it to "float" so that it only sees the two ground poles as an output and NOT every other ground line in your area (including your neigbors').
    Your transmitter (if using my designs) could draw up to several r.f. Amps while operating (depending on pole seperation and ground conditions). Don't worry about frying Earth Worms, underground animals, ect, as the voltage and current will be spread a over a VERY large area.

    I'm looking forward to answering more questions.

    -73's
    Last edited by KJ4JAE; 12-31-2009 at 01:30 PM.

  6. #6

    Default More "Earth Mode" ground conduction links.

    Here's another excellent link to an Amatuer Operator's work on VLF transmission through the ground:
    http://www.scribd.com/doc/2412122/earthcomms

    They claim to have actually acomplished over 250 KM QSO's using the Earth dipole method (and with loops at the receiving end) and using data modes instead of voice!

    And yet another awesome link of work done by Amatuers in this exciting and mysterious field:
    http://homepage.ntlworld.com/lapthorn/earthmode.htm

  7. #7
    Join Date
    May 2001
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    Ivins, Utah
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    Very interesting to read.
    I have a son-in-law that is heavy into metal detectors for gold deposits.
    Several years ago I built him a audio transmitter for that purpose and develolped a circuit that actually measured the impedance of the ground between the two stakes that were in the earth. The circuit went on to match the impedance of the stakes to the impedance of the amplifier.
    As I recall we used a solid state amplifier with an output impedance of about 8 ohms. The a audio transformer connected in reverse to step up the impedance from 8 ohms to several K ohms. The resulatant signal was of a much higher voltage.
    His theory was that injecting a certain frequency into the earth caused the gold ions to polarize a certain way and with a handheld receiver he was able to walk in the area of transmissions and locate buried gold.

    If anyone is interested, I will try to find my notes and diagrams.
    73
    Ned

  8. #8

    Default

    I'd be interested in the "impedance match" with the ground calculations and circuitry you used. Specifically, did you use air core coils or toroids and which composition/diameter ect.

  9. #9
    Join Date
    May 2001
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    Ivins, Utah
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    Here are the documents for my circuit. The extra picture shows my reasoning for measuring the impedance. The frequencies I used were 5khz and 8.7khz.
    Ned
    Attached Images Attached Images

  10. #10
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    Aug 2008
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    Mpls. , MN.
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    Just wanted to post , so I can come back to this later .

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