Power Grid Radio Telescope
The North American Power Grid is the Largest Radio Receiver Ever Built
Yes friends, the biggest and probably most sensitive radio receiver that costs nothing to build - because it already exists!
A vast array of wires and cables totalling billions of kilometers in
length, stretched out over vast areas of the Earth's surface.
Signals can be digitized at many points simultaneously. These signals are then analyzed via Fast Fourier Transform and other time/frequency domain methods. With a large enough set of sampling stations, noise and non-useful signals can easily be filtered out, leaving what we want.
If filtering proves infeasible, the entire grid can be shut down some night using nonlegal methods. This will provide a few precious minutes/hours to listen to the cosmos with a higher sensitivity than ever imagined.
The entire grid is interconnected though (mostly) magnetic transformers. These pass signals of wide enough frequency range. For example, currently a system is being examined by the FCC called "Broadband over Powerlines" or BPL. It uses certain frequencies to transmit TCP/IP packets over power lines.
From a docket submitted to the FCC by the National Academy of Sciences Committee on Radio Frequencies:
p.3: "While radio astronomers make observations at many frequencies that could be affected by emissions from BPL systems, CORF is particularly concerned about the following frequencies..."
Location: http:// www7.nationalacademies.org / corf / CORF_5_3_04_Filing_2.pdf # search=%22 powerline%20 radiotelescope%22
If the NAS is concerned about interference, it is obvious that powerlines can carry such frequencies over long distances, evidenced by existing BPL systems' usage of them. However, the BPL sytems they mention may be home-use (short distance).
For Access Broadband over Powerlines (ABoP), some useful information:
http:// en.wikipedia.org /wiki / Power_line_communication
In particular, the frequency range of 20-350 KHz is what interests us. It may be narrow from an astrological viewpoint, but the sensitivity and scope is enormous. Later in the same Wikipedia entry, the range 1.6-30 MHz is mentioned for the carrier.