EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: skyler on January 04, 2014, 11:19:28 pm
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I willing to try really hard on working with Extremly Low Frequency or Low Frequency waves to get a signal through the earth a few Km.
How can I go about putting a signal at the frequency (probably near 10 kilohertz) into the ground?
I have some 47 amp 600 volt MOSFETS, FCA47N60F, those may pump a lot of power in the ground.
I have been searching for schematics Everywhere, but just nothing shows up.
I know it is possible, I have seen some amateur radio really low frequency contacts through the earth.
I know it is slow-speed CW, but that is still worth the joy of experimenting.
Thanks for the help
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Do you have a few kilometers of land available for the antenna?
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i wonder if you can find a long stretch of power line and inject a signal into it.
that might be a reallllllllyyyyy bad idea though.
How about old rail road tracks?
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How about old rail road tracks?
Emphasis on old, do it on active ones and you'll cause so much trouble you'll be in jail before you can switch it on. Power lines sounds like a pretty bad idea too
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I thought I heard you can do it with ground rods
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look up the 'omega' system - it was used to communicate with submarine whilst the were submerged at sea, now decomissioned.
Here's a link th the aerial unit they had in victoria.
http://en.wikipedia.org/wiki/VLF_Transmitter_Woodside (http://en.wikipedia.org/wiki/VLF_Transmitter_Woodside)
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I was thinking something like the first comment on this question I asked on electronics stack exchange
http://electronics.stackexchange.com/questions/81584/can-earth-be-used-for-communication (http://electronics.stackexchange.com/questions/81584/can-earth-be-used-for-communication)
"For transmitting, microphone input, impedance match an audio amplifier output to rods inserted into the earth. When receiving, match that rod impedance to the input impedance, speaker for output. It will work like an intercom, but with party lines. "
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Do this experiment: Take an audio amplifier or transistor radio. Disconnect the speaker and connect the audio output into two probes in the ground. Use a crystal earpiece (or a very sensitive audio amp and hedphones) whose input is conected to two ground probes and see how far you can go and hear the audio (maybe a few cm initially). Experiment.
Not radio as we know it but it is wireless communications and was used in the early days to communicate across rivers etc. It could be applied with anything from keyed AC waves to modern low signal digital modes eg WSPR.
There was a UK cave radio design using VLF published in Sprat from the G QRP Club. This was a voice transceiver and was called the Heyphone (after the developer John Hey G3TDZ). See http://bcra.org.uk/creg/heyphone/introduction.html (http://bcra.org.uk/creg/heyphone/introduction.html) . Also see http://ke7hr.com/caveradio/ (http://ke7hr.com/caveradio/)
http://users.tpg.com.au/ldbutler/Underwater_Communication.pdf (http://users.tpg.com.au/ldbutler/Underwater_Communication.pdf) is good background on underwater communications.
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antennas and systems for simple transmitting and receiving in this band need not be BIG or very complicated.
A fellow in the UK Roger G3XBM has reported success using what he describes as an Earth Electrode antenna. Some details here:
https://sites.google.com/site/g3xbmqrp3/antennas/earth-electrode-antennas (https://sites.google.com/site/g3xbmqrp3/antennas/earth-electrode-antennas)
He has also posted some in his blog which can be found here:
http://g3xbm-qrp.blogspot.ca/ (http://g3xbm-qrp.blogspot.ca/)
also, anothe rgood resource and starting point is here:
https://sites.google.com/site/sub9khz/ (https://sites.google.com/site/sub9khz/)
Particularily:
https://sites.google.com/site/sub9khz/earthmode/vlf-xbm-blog (https://sites.google.com/site/sub9khz/earthmode/vlf-xbm-blog)
Roger has been in hospital lately and has not been well but is on the mend. I am sure he would answer questions on his experiments if asked.
Good luck.
cheers, Graham ve3gtc
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antennas and systems for simple transmitting and receiving in this band need not be BIG or very complicated.
A fellow in the UK Roger G3XBM has reported success using what he describes as an Earth Electrode antenna. Some details here:
...
cheers, Graham ve3gtc
Thanks Graham - good resources there. :)
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In a recent QST I saw some people who were playing with 200khz at like 100 or 200 watts. I can not remember which issue though.
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How about old rail road tracks?
Emphasis on old, do it on active ones and you'll cause so much trouble you'll be in jail before you can switch it on. Power lines sounds like a pretty bad idea too
What sort of problems would a signal on a railroad track cause? I would think as long as the stuff isn't touching the wheel of the train when it crosses, they wouldn't notice a thing, and I don't think the VLF would interfere with VHF or UHF train radios.
Also, so powerlines have 3 phases and a ground or neutral wire right? So If I did (not saying by any means I will) I would connect it to gnd/neut?
If I did that I would probably do old railroad lines anyway, and I probably won't do it anyway at all and stick with ground rods, but maybe some day!
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How about old rail road tracks?
Emphasis on old, do it on active ones and you'll cause so much trouble you'll be in jail before you can switch it on. Power lines sounds like a pretty bad idea too
What sort of problems would a signal on a railroad track cause? I would think as long as the stuff isn't touching the wheel of the train when it crosses, they wouldn't notice a thing, and I don't think the VLF would interfere with VHF or UHF train radios.
Also, so powerlines have 3 phases and a ground or neutral wire right? So If I did (not saying by any means I will) I would connect it to gnd/neut?
If I did that I would probably do old railroad lines anyway, and I probably won't do it anyway at all and stick with ground rods, but maybe some day!
you never know what a harmonic or parasitic diodes could do to your signal, thought I am not sure if its frequency is high enough to worry about that, but you really don't want to get caught fucking with train systems, you will potentially get a alphabet soup enema if caught doing that. Plus you never know what kind of equipment you will effect with a high power RF transmission, for all you know the engineers did not add enough decoupling capacitors to something and its enough to effect some microcontroller, especially in such close proximity to a antenna. Some old equipment might be out of spec for EMI resistance and engineers probobly never thought to design the train electronics to run ontop of an antenna.
and with old railroad tracks you should make sure that they do not connect to new railroad tracks.
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Loop antennas are probably your best bet. You could even use a ferrite rod for receiving.
Basically your operating on the magnetic part of the EM wave.
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Loop antennas are probably your best bet. You could even use a ferrite rod for receiving.
Basically your operating on the magnetic part of the EM wave.
For that low of a frequency, I bet i'd need a pretty big loop to transmit!
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Loop antennas are probably your best bet. You could even use a ferrite rod for receiving.
Basically your operating on the magnetic part of the EM wave.
For that low of a frequency, I bet i'd need a pretty big loop to transmit!
Small antenna's have a small aperture so aren't very efficient. The loop is fairly easy to design and construct. I wouldn't no where to start to feed and impedance matching train track.
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Tapping in to a district heating pipeline?
http://en.wikipedia.org/wiki/District_heating (http://en.wikipedia.org/wiki/District_heating)
I have no idea.
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lol, how about hooking a transmitter up to the super collider in Geneva?
or a roller coaster
those should make nice loop antennas... :wtf:
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It would be hilarious if 20 years from now somebody found a mysterious black box under a barely used railway, connected to the OP's house. >:D
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i read about goverment plans to deploy vans that would unwind huuge low frequency antennas in order to communicate with nuclear submarines in case that the submarine communications transmitters were hit with nuclear weapons.
I wonder if there was any plans to use power lines or railroads or other large metal objects.
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I vaguely remember an old magazine back in the 1980's had an interesting experiment on this kind of stuff, I am from the UK, and so it was probably EE, ETI, PE, or likely PW*. The author was trying to emulate the field telephones/telegraphs used in the trenches during World War I, and so used the same rifle bayonets that they would use a ground. Also used very high impedance headphones much like you would use with a crystal radio set. But I do remember him trying to experiment with open field bayonet wired ground antennas to communicate wirelessly as apparently they did this to avoid running overhead wires in "no mans land". Not so sure, it is 30 years ago since I read the article.
I couldn't get my head round it at the time, as I was only a kid and simple DC battery circuits were more than enough for me. I could never comprehend how you can get a flow of electrons without a return loop - and using battlefield mud with bayonets. Damn! :-//
* ETA: Everyday Electronics, Electronics Today International, Practical Electronics, Practical Wireless. Other mags I would lust over were the Elektor and Maplin Catalogue and their later brief magazine. Also Television magazine was good, though I only got into that when I apprenticed as a TV engineer.
Elektor was a bit too highbrow for me at the time. I could only dream of the equipment needed to fab double sided PCBs and make 20MHz digital frequency counters vs Veroboard or single sided PCB given with the mag to make an FM bug or whatever. haha. Nostalgia.
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I used to work on Decca Navigator transmitter chains and we used to pump kilowatts into the ether for comparatively small returns.
As others have implied, grounding is a big factor and by this I mean acres/hectares of copper wire buried under the ground. One US Navy station I read of had 10 square acres of earth plane!
The one-wire military field telephones were simply a basic telephone that used the ground as one side of a two-wire circuit. Nothing more fancy than that. The isolated wire was steel not copper.
With VLF you have to use VERY slow signalling rates. For example, Decca - on behalf of the MoD - did experiments transmitting signals over Moscow, with the then weekly BOAC (BA forerunner) having a special recording receivers in them. It was all to do with guiding bombers.
One of the signal sequences involved transmitting a special 'marker' signal of 10 seconds in length. They found that whilst the main frequency transmissions were heard, the 10 second inserts were NOT!
BTW, if you are thinking of using railway lines, do NOT short them together - some remote rail lines use a short between rails to turn signals to red (especially in Canada).
One benefit, it's unlikely GCHQ or NSA will even think of checking out those frequencies regularly.
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The modern-day experts on VLF comms, at least in the amateur world, are the Lowfer guys. Google lowfer and learn. (This is in the unlicensed 160-190 kHz band. They have achieved distances of 1000s of kms with minuscule radiated power.)
Someone asked if the OP has a few kilometers of land for the antenna. What I want to know is, does the OP have a tunnel a few kilometers deep? Because how else could it matter whether you can communicate that far "through the earth"? Guess I'm still unclear on the original question. Ground wave normally refers to communication between points on the surface of the earth.
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I used to work on Decca Navigator transmitter chains and we used to pump kilowatts into the ether for comparatively small returns.
As others have implied, grounding is a big factor and by this I mean acres/hectares of copper wire buried under the ground. One US Navy station I read of had 10 square acres of earth plane!
The one-wire military field telephones were simply a basic telephone that used the ground as one side of a two-wire circuit. Nothing more fancy than that. The isolated wire was steel not copper.
With VLF you have to use VERY slow signalling rates. For example, Decca - on behalf of the MoD - did experiments transmitting signals over Moscow, with the then weekly BOAC (BA forerunner) having a special recording receivers in them. It was all to do with guiding bombers.
One of the signal sequences involved transmitting a special 'marker' signal of 10 seconds in length. They found that whilst the main frequency transmissions were heard, the 10 second inserts were NOT!
BTW, if you are thinking of using railway lines, do NOT short them together - some remote rail lines use a short between rails to turn signals to red (especially in Canada).
One benefit, it's unlikely GCHQ or NSA will even think of checking out those frequencies regularly.
So if I shorted the railway lines, every red light would trigger down the whole line? How would they control that, is this saying there are segments of small track not electrically connected tracks to isolate seperate lights resulting in a smaller antenna?
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@skyler:
In remote areas of countries with rail track that have few stations, therefore population, trains are, for all intent and purposes, out of touch with traffic control.
Frequently the trains on this type of line are both long and heavily laden. Additionally, these are single tracks with two-way opposing traffic.
The rail line is electrically divided, that is for continuity purposes, so each mile or two is separated from the next part of the track.
When a train is present on a section of track, the tracks are shorted together. This short is detected by standalone signal lights, at either end of the section, which display a red when in this condition. The signal lights are bi-directional - the red will face in both directions.
In Canada, when the First Nations people want to protest, they often use battery booster wires clipped to the track which effectively stops all rail traffic. Rail lines frequently cross First Nations treaty areas so they are, in effect, the landlord!
In India they use a 'tag' or 'token' system, which frequently fails. In single rail areas there is a box which is used to hold a 'token' or marked device. The driver takes the token with him to the other end of the single section where he leaves it in another box.
In theory, the drivers cannot enter the single rail section without the token. They often do, and hundreds of people die as a result of these diver short-cuts.
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I used to work on Decca Navigator transmitter chains and we used to pump kilowatts into the ether for comparatively small returns.
As others have implied, grounding is a big factor and by this I mean acres/hectares of copper wire buried under the ground. One US Navy station I read of had 10 square acres of earth plane!
The one-wire military field telephones were simply a basic telephone that used the ground as one side of a two-wire circuit. Nothing more fancy than that. The isolated wire was steel not copper.
With VLF you have to use VERY slow signalling rates. For example, Decca - on behalf of the MoD - did experiments transmitting signals over Moscow, with the then weekly BOAC (BA forerunner) having a special recording receivers in them. It was all to do with guiding bombers.
One of the signal sequences involved transmitting a special 'marker' signal of 10 seconds in length. They found that It whilst the main frequency transmissions were heard, the 10 second inserts were NOT!
BTW, if you are thinking of using railway lines, do NOT short them together - some remote rail lines use a short between rails to turn signals to red (especially in Canada).
One benefit, it's unlikely GCHQ or NSA will even think of checking out those frequencies regularly.
wouldn't the train short the tracks? It is a big lump of metal after all. on another note I don't think the kids at the NSA even know about ELF/VLF.
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Shorting the track with the train wheels indicates the section is occupied by a train. The train itself only sees the next section light as it enters the section. If it is red the driver does an emergency stop, wheel damage and track damage not a worry. thus shorting the line stops the train and it then occupies 2 sections of track. If the driver hears 3 bangs the same, as then there is a dead signal and a stopped train about 500m ahead because the driver or brake guard has gone down the track 500m and attached the 3 track squibs to the line as a warning. Beats the alternative of hitting another train at 60 kph.
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https://www.researchgate.net/publication/319702287_THE_HISTORY_OF_EARLY_LOW_FREQUENCY_RADIO_ASTRONOMY_IN_AUSTRALIA_8_GROTE_REBER_AND_THE_'SQUARE_KILOMETRE_ARRAY'_NEAR_BOTHWELL_TASMANIA_IN_THE_1960s_AND_1970s (https://www.researchgate.net/publication/319702287_THE_HISTORY_OF_EARLY_LOW_FREQUENCY_RADIO_ASTRONOMY_IN_AUSTRALIA_8_GROTE_REBER_AND_THE_'SQUARE_KILOMETRE_ARRAY'_NEAR_BOTHWELL_TASMANIA_IN_THE_1960s_AND_1970s)
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Is here any reason why you cant use more conventional techniques, like (presuming there is a hill in the way) NVIS?