Live Wire Antenna


Posted on Feb 7, 2014

Using live or neutral wire in AC household wiring as receiving antenna. Of course, this is possible only with high voltage capacitor inserted between the receiver antenna terminal and live or neutral wire. AC wiring antenna solution was mentioned as some type of last resort, when no other antenna can be installed due to space contraints. Ground conductor can be used as Earth ground.


Live Wire Antenna
Click here to download the full size of the above Circuit.

Old books recommend cold water pipe as ground connection, but I`m not sure whether this is good/practical/allowed any more. They also recommend "one good condenser" for antenna connection, not 2 in series. I guess people were braver then :) I decided to test this system myself. I made a small 2-transistor medium-wave AM receiver, with headphone output. To reduce main LC tank circuit loading, HF is taken from a capacitive divider of variable cap and 5 nF cap. Smaller voltage drop exists on larger capacitor due to its smaller capacitive reactance Xc=1/(2*pi*f*C). Voltage taken from main LC circuit decreases as higher frequencies are received: smaller capacitance of variable cap takes on more of capacitive divider voltage. This was deemed to be unimportant for fairly narrow range MW tuning. Received high frequency is demodulated at the base of first transistor and then amplified as low frequency in the first and second transistor. Calculated frequency range is approximately 700 kHz - 2800 kHz. To protect myself and my receiver, I decided to use two high voltage capacitors in series, antenna coil galvanically separated from remainder of circuit, and fuse. If high voltage spike is somehow able to penetrate through both 1 kV rated capacitors, it will blow open the fuse. Failing that, antenna coil (0. 3 mm diameter wire, 20 turns) will burn out, with no further damage done to receiver (or user). Hopefully. :) Several tests were...




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