Submarine communication with low frequency electromagnetic signals


BBC Horizon show - episode "The Mysterious Mr. Tesla" presented by Bob Symes in 1982


Introduction: Radio waves do not travel well in electrical conductors like salt water. This means that submarines have to approach the surface to receive communication signals. However, electromagnetic signals of low frequency can penetrate seawater, and the lower the frequency the deeper they reach. 


Transcript from the video starting at 4.46 (Note that the show was presented in 1982).
"ELF, extremely low frequency* will be most important for the United States submarine fleet in years to come. Could submarines be protected by a development of Tesla's wireless work?"


*3 to 30Hz


"Submarines are at their most vulnerable when they approach the surface to communicate with their headquarters. To change that, the US Navy is building two giant wireless stations up near the Canadian border, in Wisconsin and Michigan. Each of them will radiate under 4 Watts just enough to light a doll's house but the power behind each transmitter will be enormous. The station at Clam Lake needs two aerials each 14 miles long. That's because the signals, like the Woodpecker, will go out at extremely low-frequency (ELF) which requires special arrangements. Because ELF is low frequency it takes a long time to send a message, but it does penetrate the ocean to great depth. Vessels like the newly-launched Ohio will be able to receive operating orders without ever rising to the pedals at the surface." 


"Most 'Teslarians' believe that the great man described ELF transmissions in his patents and that the US Navy went back to these papers for the concept. But what did Tesla actually say? 'It is necessary to employ oscillations in which the rate of radiation of energy into space in the form of hertzian or electromagnetic waves is very small. The lowest frequency would appear to be 6 per second.' All credit to Tesla for even thinking in this area but it comes clear from the context that he was describing the sending of electrical energy without wires through the earth and not the sending of radio waves through the sea."


@infobook tweet




"Riding the Airways: Ultra-Wideband Ambient Backscatter via Commercial Broadcast Systems" via Disney Research
Excerpt from the paper:
"Use of "all available ambient radio sources from FM radio stations, to digital TV stations, all the way up to cellular networks for backscatter communication. This technique is depicted in Figure 1, which shows several commercial broadcast systems operating at frequencies from 80 MHz to 900 MHz."
Here the energy harvesting nodes use an UWB antenna and broadband switch to backscatter all ambient sources to a Universal Backscatter Reader (UBR). The reader then selects the strongest set of RF sources in the environment and combines
them when decoding the backscatter data."



"Ambient backscatter techniques utilize the ever-present cloud of TV and cellular signals already in the air."


"The team was able to demonstrate communication from node to reader over 22 m (72 ft) when using ambient signals from broadcast towers, and over 50 m (164 ft) with data rates of up to 1 kbps by simultaneously harnessing 17 ambient signal sources."



Power line networking (PLN) - Broadband over power lines (BPL)

Wi-Fi box does not reach distant room? Impress the signal on the power circuitry of the house.
Plug the Wi-Fi in an electric socket in one room and take it from an electric socket in another room!
Use an adapter plug that bounces a wireless signal along the wired circuity of the house.
Power line networking (PLN)
« Power line networking (PLN) uses existing electrical wiring, whether in a building or in the utility grid, as network cables, meaning they also carry data signals. It can be a means of extending an existing network into new places without adding new wires.[7]
For example, a computer could be wired to a router as follows: an adapter is connected to a router of an existing wired local-area network, via its network port. A second adapter is connected to an Ethernet-ready device like a computer. When both adapters are plugged into their wall sockets they will have a network connection via the electrical wiring in between the two wall sockets being used.[7] Some networking devices, such as routers or switches, also have power line connectivity built in. This adds no new wires since they need to be plugged into the wall to operate anyway.
The power line is transformed into a data line via the superposition of a low energy information signal to the power wave. Since electricity is 50 or 60 Hz, data is transmitted at at least 3 kHz to ensure that the power wave does not interfere with the data signal.[8] A technical challenge is that, because the power wiring is unshielded and untwisted, the wiring acts as an antenna, so that the wiring emits radio energy, causing interference to the existing users of the same frequency band. The power lines can also act as receiving antennas, and receive interference from radio signals.[8] In many jurisdictions such transmissions are illegal. The U.S. is an exception, permitting limited-power wide-band signals to be injected into unshielded wiring, as long as the wiring is not designed to propagate radio waves in free space[9][10]. »
Broadband over power lines (BPL)
« Broadband over power lines (BPL) is a method of power line communication (PLC) that allows relatively high-speed digital data transmission over the public electric power distribution wiring.
BPL is based on PLC technology developed as far back as 1914 by US telecommunications company AT&T[1]. Electricity companies have been bundling radio frequency on the same line as electrical current to monitor the performance of their own power grids for years. »

(2016/4/13) "Facebook is building a new way to connect to the internet, employing millimeter-wave technology to connect buildings to the larger internet without fiber optic cable."
"Terragraph is notably similar to Starry, a new wireless system developed by Aereo CEO Chet Kanojia, which launched in January. Both Starry and Terragraph transmit data in the millimeter wave spectrum, and employ a phased array of antennae to maintain a narrowly beamed signal. But while Starry touted proprietary antenna technology for increased range and signal strength, Terragraph is based on the open WiGig standard, which has been publicly available since 2010. The open standard means third-party hardware can more easily be built with Terragraph-friendly antennae, including phones, cars, and home Wi-Fi routers."