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Saturday, December 31, 2011

Live AC Wire or Neutral House Wiring Antenna

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Live wire antenna
or how to use live or neutral wire in your home as receiving antenna for long wave, medium wave, or short wave

Warning

Warning: use of this antenna is not recommended if you do not use fuse, separate antenna coil and high voltage capacitors to connect to high voltage live wire. You risk death otherwise. Be careful and use all safety precautions. Always assume that neutral wire might be live as well, if improperly wired. Even if properly wired, it can become live due to a fault.

Live wire / neutral wire antenna

I was looking through some old radio books - mostly tube designs - when it was mentioned that it's possible to use 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 constraints. Ground conductor can be used as Earth ground.

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 :)

Receiver circuit and antenna connection

I decided to test this system myself. I made a small 2-transistor medium-wave AM receiver, with headphone output. To reduce main 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). Received high frequency is demodulated at the base of first transistor and then amplified as low frequency in the first and second transistor stage. Calculated frequency range: 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. :)

Simple MW AM direct receiver schematic with live wire antenna connection shown.

Coil, variable capacitor and receiver circuit. Headphones can be of low or high impedance.

Testing

Several tests were done: first with 1 m wire antenna, without ground connection. Four nearby AM stations were received, 3 were identified for testing. Latter tests were done with live wire antenna, neutral wire antenna, and power cable antenna NOT plugged into the outlet.

Connection setup with live wire (black wire) connected as antenna. Male power plug not plugged into the outlet.

DSCF0525.AVI

Video Link...
http://www.youtube.com/watch?feature=player_embedded&v=zZHjitGCBno

Testing video with live wire as antenna. Antenna is plugged into the AC outlet during the video. This changes main receiver LC circuit frequency somewhat, so re-tuning is necessary for maximum sound output. Sound is weak because it is coming from the headphones only, so weaker stations cannot be heard in the video.

Read More...
http://www.arthropodsystems.com/LiveWireAntenna/LiveWireAntenna.html

Back in the 1970's AM-FM Stereos came with a little T-Antenna. Made out of flat TV Antenna Wire. It was the Standard Antenna wiring at the time. This was before RF Cable came into wide spread use for TV Antenna wiring. Since the Flat TV Antenna wiring was not shielded. It made a pretty good little Antenna for Radios. I suppose that the T-Design was supposed to improve reception. But, I discovered that a longer piece of flat antenna wire, actually worked better. I also discovered that pretty much any type of un-shielded wire could be used for a Radio Antenna. I think that single strand copper wire works better than multi-strand wire. But, I usually just try what ever type of wire that I have available, when the need arises for better Radio Reception. The old Copper Single Stranded Telephone wire works pretty well for this purpose. I have tried different Configurations. Straight, Looped and T's. But, the thing, that makes the biggest difference, is, putting your Wire Antenna near or in a Window. I also had an actual FM Radio Antenna, back in 1976. I had moved to Wichita Falls, TX and they had No Rock n Roll Station there!:( I grew up in Azle TX, near Fort Worth and my favorite Radio Station was KZEW, "The Zew" (Zoo). An "Album Rock" Station. They played the whole songs, not the shortened "Radio Cuts". And I liked Q102 as well. It cam out just before The Zew wen out of business. I could not get any of the Dallas Rock Stations on my Home Stereo. But, sometimes I could get them on my Car Radio. Depending on where in the City that I was. It was staticky and the signal faded in and out. So, I figured there was a chance, with a better antenna. So, I bought a 10 to 15ft (don't remember the exact size now) FM Antenna at Radio Shack. It worked great!:) I was able to listen to my favorite Radio Stations on my Home Stereo!:) The signal dis degrade with Weather Changes, such as certain types of Clouds. Sometimes, the Clouds would cause other even more distant Stations to come in too. I kept that Antenna for at least 15 years. I used it as a TV Antenna, wen I moved back to Azle, a few years later. It wasn't as good for TV reception. You had to choose, to either aim it for the best VHF or UHF reception. So, I mounted it on a pole, close to a Window and would just reach out and turn it when I wanted to get a better Signal on a Certain Channel. I never did get one of those Electric Remote Antenna Turners, like I planned...

Don