OK, I know that radio waves don’t really work well in the ground, but it is the best analogy I could think of for this question.
Back in the mid 1960’s, I remember reading an article in Popular Electronics, or similar magazine, about building a device that allowed people to communicate through a device that transmitted through the ground. It worked basically like a radio, but used a ground pole instead of an antenna. I remember that the range on it was at least a mile or two and that it worked better when the earth was wet, like a day or two after a good rain. This was a setup that they showed how to build and was simple enough for home construction.
I have never seen nor heard of such a setup since.
Has anyone heard of this, know what it is called and have any information about it?
From what stranger wrote, I’m not sure exactly what it is. Nor have I ever looked into this Stubblefield ground radio system in detail, or exactly how it works. My best guess is that stranger read some article in the 1960s about transmitting ELF of VLF radio signals through the ground. Producing such low frequency radio signals is quite trivial for amateurs with little technical knowledge. As would be transmitting them into the ground. Not much practical use in amateur terms, as one can trivially get much better distance using an antenna. However, I can see some people doing it for the “gee whiz” novelty aspect.
For those curious about the possibilities of amateurs transmitting radio signals over the air in the Very Low Frequency band, search “lowfer” on Google. Radio enthusiasts using 1 watt transmitters, and transmititing antennas just 50 feet long (the max allowed in the US by the FCC), routinely communicate with each other hundreds of miles away.
I’m told that ELF signals bounce through the polar ice rather nicely. I believe the navy used to take advantage of this during the cold war era to allow their subs to communicate all through the arctic region. The bandwidth was pretty limited, but unlike on land, the signals travelled for very long distances through the ice.
I’m 10 years late to the topic, but I remember the article you are referring to. As I remember it, the “transmitter” was an audio amp with the output going to 2 ground rods, and the “receiver” was an audio amplifier with the input going to two ground rods.
All the old Pop Electronics (where I think I saw it) and the Electronics Illustrated are on line at some electronics magazine site, but I don’t have the motivation to go searching for that article.
Technically the article isn’t about radio communication, but instead is short-range conduction. The Model 1882 Wireless Telephone has a good detailed review of the early conduction and induction systems.
VLF is in pretty common use for submarine communications, both from ground stations and airborn (see E-6 and E-4 aircraft). It has certain characteristics that make it a good strategic choice and can penetrate oceans to 20+ meters.
ELF has better ground penetration capabilities (and is used to send signals from deep mines) but we’re talking bits-per-minute sorts of bandwidth. VLF is more late 70s MODEM speed.
In WWI the British (I don’t know others) employed field telephones that only had one wire between sets, using the ground as the… well, ground, to close the circuit. Problem was, the Germans wised up to this and used a device that allowed them to pick up the signal through the ground, letting them listen to the conversations going on across no mans land.
I believe old style telegraph lines operated on the same principle.
Channel capacity (bits per second) is proportional to bandwidth. Bandwidth itself doesn’t mean bps. But it is a good thing to know.
Bandwidth is the difference between the lowest and highest frequency of the channel you’re using. If you’re sending data in a 2.5GHz band, a tiny percentage range of frequencies gives you a nice bandwith. If your trying to send something at around 1KHz, even having a range from 300Hz to 3KHz isn’t much bandwidth. And then you are taking up the entire ELF range just for one channel. VLF isn’t much better.
Then you throw in all the noise issues in the bps equation and things get even worse. Humans have a lot of stuff that throws out LF noise and Nature doesn’t help either.