Using mains wiring as an antenna

Make sure to brush up on your safety protocol if you undertake this project. The penalty for messing up when using live wiring as a radio receiver antenna is rather severe. But after reading about it in some old books [Miroslav] decided to give this technique a try.

We love the old-school chalk board he used to map out his test circuit. With safety in mind, he uses two high voltage capacitors in series. If these should somehow fail, there is also a fuse which would blow, disconnecting the apparatus from mains. But just to be sure, he isolated the circuit using a two coils. These step down the voltage, but would also burn out if hit with a voltage spike.

You can see the results he gets using the setup as an AM radio receiver in the video after the break. He tested against a meter long antenna and found that his setup far outperforms it. Actually, he found that a six foot extension cord which is not plugged into the wall will also outperform the 1m antenna. Something to keep in mind the next time the ball game isn’t coming in as clear as you would like.

Comments

  1. Nova says:

    Just a speculation but I’d guess this wouldn’t work as well if you had more modern metal conduit around all of your wiring. Unless the plugged in appliances could gather enough RF and pass it back into the outlets?..

    • Nova says:

      Also isn’t a 20turn to 55turn transformer a step-up in voltage?

    • N0LKK says:

      I would think more localities permit non-metallic sheathed cable, than those that mandate metal conduit for residential 120 V. branch circuits In my home the neutral is bonded to the ground bus at the service panel. In essence the leads to the primary coil in the transformer would be connected to ground. I think this is functioning by bring the neutral into proximity to the receiver. Could be equal performance could be realized by loosely wrapping a wire connected to the neutral around the receiver.

  2. Fred says:

    I was given a elec. kit when I was about eleven or so. ( yes dinosaurs still roamed the earth) that had a antena wire that pluged directly into the wall socket. I remember something about pico farads on the side of the plug. Years later we used it on a cryistal radio that I helped my son build. Worked like a darn. I still have it in the garage somewhere.

    • jimmy says:

      Fred–

      I too had one in a kit–made by Olsen Electronics (Akron Oh) in 1967. I still have the kit, and the instruction manual. The ANT (antenna) part is a single prong plug, with a 100 pF cap to block everything but RC signals.

      Variation on the classic “death cap”, ;-). Amazing what they sold to kids back then…

      • Quin says:

        The kit I had in the 80s suggested tying the short antenna wire to the cold water pipe or any other grounded source. I used the heater pipes, which were grounded at the furnace to both the cold water line and the electrical box neutral. Had a great little AM radio til the parts were needed elsewhere.

  3. Okian Warrior says:

    Okay, the reason this is wrong is not because it’s connected to the AC, but because an AC connected circuit is going to headphones that are mounted on your head.

    If you’re going to play with things like this, it makes sense to go the extra mile and make some sort of air-gap between what goes on your body and what plugs into the wall.

    Optoisolators are cheap and easy to use.

    Power the body side with a battery, and don’t even connect the grounds together.

    Rather than show projects like this, which admittedly are neat, I’d much rather see projects that show how to do things correctly.

    • JJ says:

      You’re already isolated from the main with the transformer, there is no need to add optos. Maybe the “infinte” power of the mains scares you but the circuit already have two capacitors acting as (big) impedances and a fuse. Physics don’t lie!

    • Americans (and many people around) are becoming little sissies. You can see that before, every kit has a kind of “dangerous” connection to the mains. How many did you know that died because of one of “those things done unpropperly”???

      It is nice to offer some danger. It riches the gene pool, the stupid people has a nice death and smart people keeps alive, enriching the gene pool :)

      • Zack Carlson says:

        I agree with the sentiment, but I don’t think stupid qualifies with people experimenting with radio antennae.. Foolish, but not stupid.

        However, if there was a facebook feature to implement this..

      • Homelypoet says:

        I remember rewiring all the switches in the house in the middle of the night when I was eight (I REALLY did not want to go to bed).

        Live Wire and all, I only electrocuted myself four times.

        Took a fortnight before it was sorted out.

  4. rj says:

    You know there are millions of products that just use magnetic isolation, like this, and this is no more dangerous than those? An isolated transformer is as good as an optoisolator.

    • Okian Warrior says:

      Millions of products which are UL approved, you mean?

      Yeah – I was just thinking about them. How they have to be packed in plastic and require safe build methods and undergo testing in a real laboratory.

      And have a long history of being safe.

      And I suppose building your own transformer is the same as using an optoisolator that costs $.30 and is rated for several thousand volts arc over.

      Get real.

      If there’s a mistake in that transformer setup, if the insulation isn’t rated for the voltage, or if there are two matching cracks in the insulation because he’s using surplus wire…

      …it will arc over and put 120 volts into the circuit…

      …connected to his head.

      Pert of doing electronics is to learn. Learn to do it right, where doing it right is important. It’s not that hard.

      • someonecool says:

        May I specify that an opto isolator can be rated for say, 7 kV, but I highly doubt the traces on the board can handle such a high voltage.

        Most of the time these opto isolators are in an SMD package, and the traces in that situation are close enough for an arc over.

        But yes, an opto isolator is much easier to get right on the first try compared to isolation transformer, at least in my opinion.

      • rj says:

        Oh, yes, because the UL applies magic pixie dust to turn all products they certify from always-dangerous to always-safe. And because it’s obviously guaranteed that the fuse and both capacitors will fail to a short and that the when 120VAC are across the primary winding, it will open the primary and short to the secondary. And then no other circuit component will die horribly when overvoltaged and thus 120V will be applied directly to your ear and not through a many mm air gap.

        The reason this design isn’t used is because it’s lousy for RF pickup (as a parallel dipole), not because it’s horrifically dangerous. I have been shocked in my ears by more SMPS chargers for consumer electronics than this design.

        P.S. I have a UL certified clock-radio that uses an antenna similar to this. They wound a small number of turns of wire around the power line coming in. Differences? No fuse, no capacitors, and 300V-rated insulation on the primary winding.

  5. Hal H says:

    Couldn’t you just tap the earth ground for your antenna?

    In an electronics lab in college we had a project to build an AM tuner from scratch. We tried it and it sorta worked. The trouble was that the lab was in the basement and it was hard to pick up any signals in the area. So the lab TA brought in an AM generator and we plugged some music into it. Then that signal wasn’t very powerful, so we stuck the antenna out in the ground plug of a wall socket. Then we tapped the ground with our project antennas and then we could get a strong enough signal. If the professor had seen it he probably would have failed us all. We thought it was awesome when it finally worked well.

  6. ejonesss says:

    can this be used for a transmitter so you can send signals all over town.

    maybe even tune into the right frequency used by the smart electric meters and jam the signal so the electric co cant read the meters remotely forcing them to come out to change the meter to the old meter and read them the old way.

    i say that because the new smart meters that can be read remotely send out a signal that causes a 2 stage static once an hour.

    • DainBramage1991 says:

      That depends on how much jail time you want to do. In the USA and most other places, that would be illegal in two or three ways, at least.
      1: Illegal signal jamming.
      2: Using an illegal transmitter on a frequency that you are unlicensed to transmit on.
      3: I’m sure the power company would find some way to charge you, either legally or civilly if you attempted to jam their signals.

      Not a good idea.

      If you are having a static problem with your part 15 rated electronic devices, do what everyone else has to do and invest in some filters.

      • proper.orfentik says:

        How do you know he’s not a licenced radio amateur?

        Granted, the part on signal jamming says otherwise – but who are you to hector him/her with your moralistic blathering’s? Just answer the question.

        The answer to the above is yes you can. Look up “power line communication”.

      • DainBramage1991 says:

        I know he’s not a licensed amateur because licensed amateurs know better than to do things like that. Why do you think I posted my reply? I am a licensed radio amateur with the highest class license in my country. I understand the laws in this country and most others regarding illegal transmissions and jamming. I also understand what the penalties are for breaking them. They range from small fines to many years of prison time.

        What you refer to as “moralistic blathering’s” (sic) I consider a cautionary statement.

      • proper.orfentik says:

        You claim you’re a ‘licensed (sic) amateur’? Tell me this, is power line communication against the terms of your licence? No is the answer.

        Instead of answering the question, you decided to saddle up on that high horse. Instead of saying it was possible and guiding him/her towards obtaining a licence, you broke out your rule book – probably putting him/her off for life.

        Also depending where you live, broadcasting without a licence is classed as a civil not criminal offence – the police have no powers of arrest unless your local/national radio authority/quango decides to prosecute. They can only do so if they have evidence of or witness you making a broadcast – just owning equipment is not enough to constitute an offence as it’s not illegal.

        You do not own the electromagnetic spectrum.

      • Matthew Wilkes says:

        “You claim you’re a ‘licensed (sic) amateur’?”

        Nice try.

        licensed |ˈlʌɪs(ə)nst| (also licenced )
        adjective
        having an official licence: a licensed taxi operator.

        I’m afraid that this error is yours, that’s two strikes.

      • DainBramage1991 says:

        This is getting old. “Licensed” is spelled correctly, BTW.
        I don’t claim to own the spectrum, but the FCC (in the US) does have full control of it and they have since 1934. That includes putting people in prison, as FCC violations are federal crimes. If you don’t believe me, look up FCC enforcement bureau on their website. Here’s the link:

        http://www.fcc.gov/enforcement-bureau

        If someone is “put off” by the rule book, then that person has no business transmitting anything anyway, and I am happy to be of service.

      • proper.orfentik says:

        I’m well aware of the American spelling for the word “licenced”, just as I’m fully aware of of the English spelling for “moralistic blathering”. Why you felt the need to append that with ‘sic’ who knows? One can only speculate that your argument was based on such thin and flimsy premise that you had to resort to pointing out perceived spelling errors in order to gain the higher ground.

      • Matt says:

        @proper.orfentik:
        I’m going to guess he quoted you with “sic” because you used an apostrophe inappropriately.

        *Your* usage of “sic” is just plain silly, though.
        And you’re just plain wrong (in both the “incorrect” and the “immoral” sense).

      • draeath says:

        For what it’s worth I hold a license as well (and oddly, use the “wrong” spelling for my country) and think it’s a bad idea as well.

      • solomon says:

        actually carrier current transmission is allowed under the FCC’s Part 15 regulations for unlicensed intentional radiators.

        obviously there are limitations to what you are allowed to do but you can learn all about that by looking up Part 15 on the FCC website.

      • proper.orfentik says:

        @ “Matthew Wilkes”

        Eh? You don’t get it do you? It’s not a ‘nice try’ because:

        a) I was being sarcastic.
        b) Licenced with an “S” is not a correct spelling in the “English” language. Your “American” dictionaries may include it but ours don’t.

        ..so there is no ‘error’ on my part. I suggest you “trot off”.

        @ Matt

        ‘Plain silly’? I don’t think so. My point was to point out the futility and sadness in pointing out someones spelling mistakes over the internet. Who gives a stuff? You can’t win the argument over the subject matter at hand , so you resort to pointing out grammatical and spelling errors – it’s pathetic! As for my ‘incorrect use’ of an apostrophe – I couldn’t give a flying fig.

        • Matthew Wilkes says:

          Well, you can’t win, no. Yes, it is an merkin dictionary that I used, as it is the one Apple ships, but even across the pond they’re sensible enough to include words used in the UK.

          If your dictionaries don’t include ‘licensed’ I humbly suggest that you get a new dictionary, yours has an omission.

          Is your mummy proud of you? Somehow I imagine she wouldn’t be if she saw this thread.

      • proper.orfentik says:

        Licensed is not used in England. The end. It doesn’t matter what your dictionaries say. We don’t use it. Some who use “American” spell check dictionaries might have been mistaken that it was also used in the “English” language – but it is not the case.

        As I thought. Instead of throwing some insight about the subject matter like @solomon has, you’ve resorted to the tool of the half-wit with your witless, limp wristed, soggy jibes.

        Thanks Matthew for your time, but I think you’re done.

        • L says:

          “Licensed is not used in England. The end.” Kind of like saying we don’t use colour in America, it;s not common usage but we don’t try to ignore it’s existance.

  7. M4CGYV3R says:

    “What could possibly go wrong?”

  8. Sparky says:

    What are the frequencies of the power line signals?

  9. KnightFire says:

    Er… Ah… could one use an antenna like this to receive OTA HDTV? I’d be interested in connecting it to the earth ground of my house.

    • raz says:

      Interested as well.

    • Eric says:

      It would be better, in my experience, to simply use whatever you used before the digital switch. the frequencies haven’t changed so much as the type of signal has. No need to get one of those ‘special digital antennas'(does anyone else laugh at those? I know I do.) if you already have an antenna on your roof.

      Direct answer; you MIGHT. It’s dependent on the way your house is wired.

      • draeath says:

        Those converters do just that – convert the digital signal back to analog NTSC (that the old TV can use). Just because the same antenna can receive the signal doesn’t mean the attached receiver can demodulate it.

    • draeath says:

      Unlikely.

      This works because those broadcast AM signals have large wavelengths, so the household wiring form a significant fraction of that wavelength.

      Broadcast HDTV has a much much shorter wavelength.

    • n0lkk says:

      In word;yes. For most receiving purposes the concerns stated about wave length are not a concern. The longer wiring may be beneficial, no harm in trying. I’m assuming you know enough not to connect a wire from the mains to an antenna input. Use a capacitor with at least a 200V. rating

  10. ejonesss says:

    DainBramage1991 i am sure that the power co would just come down and remove the meter and replace it with a new one and just start reading it in person for those houses that they cant read the meter.

    they couldnt get you for theft of service since the meter shows as unreadable.

    now if it showed as un normally low usage then they may be able to say theft of service.

    with recent blows to the various enforcement parts of the government laws are being more difficult to enforce.

    take the environment for examples.

    1. gas frackers can pollute the water and air and pay a fine and continue to polute.

    2. you can dump less than 50 pounds of freon into the air and not get busted (why do you think hobbyist scrap metal recyclers can get away with venting refrigeration units).

    • DainBramage1991 says:

      Interesting morality: it’s ok to commit acts of crime and fraud as long as you don’t get caught…

      The tough part is when you do get caught, and you will. I’m assuming that you are in the US from what you have said, therefor you should know that the FCC has stepped up their efforts on tracking down and prosecuting illegal spectrum users.

      • Matt says:

        Also,
        Licensed radio amateurs in the US are typically very happy to assist the FCC in finding unlicensed and/or illegal radio transmissions- particularly if they interfere with legal amateur operations (as I’m sure would be the case with a poorly designed powerline transmitter).

    • jan says:

      What’s it like living in a world of pure delusion?

  11. Miroslav says:

    Hi to all.

    The safety was achieved by:
    1. Complete separation of antenna winding from the secondary of circuit. There are layers of clear tape on windings, and wire is lacquered (regular transformer wire).

    2. Separation of mains voltage by TWO 1 kilovolt rated caps.

    3. Fuse.

    I think it is safe to say that this is safer than your regular AC mains connected clock (transformer only). It is going to blow only if there is a ligthning strike. Chances are, I will not be listening to the radio at that time.

    • Munch says:

      You’ve obviously never had a horizontal flyback transformer failure before, have you? They, too, have isolated primaries and secondaries, and they, too, use lacquered windings. They’ll last for years, until they stop lasting. See, with prolonged use, that lacquer breaks down, and will eventually arc over. Many a TV set failure can be traced to a failed flyback transformer, and when I was in the TV repair industry, maybe constituted around 30% of all failed units.

      OK, ok, they’re dealing with much higher voltages, but still, the point remains — why take the risk?

      • Miroslav says:

        Yes, you have some valid points there. Again, this will not fail on regular 120 Vac or 220 Vac voltage. Currents are small, voltages are small compared to flyback, usage is infrequent, and if this baby goes down, so will all the neighborhood electronic devices, which are not as well protected. In my whole life, I have once witnessed such event (lightning strike burning out a bunch of electronics). Other mishap was 380 Vac getting onto 220 Vac line (in Europe) :)))

        Why take the risk? My space is very small and constrained, so I have to at least try an antenna like this. And of course: I’m not claiming it is lightning proof. But *nothing* is lightning proof.

        For optoisolator folks: Power line distribution in hundred kilovolt range uses transformers, not optoisolators. Optos are mere toys compared to high voltage transformers.

        If I get more time, I will continue to pursue this line of antenna development. It looks like the 60 Hz hum is decreasing at higher end of tunning range, so this might end up being an ideal short wave antenna.

  12. BigBear says:

    where is detector?
    with one more diode it will work better.

  13. Hacksaw says:

    This is as old as radio… What is going on here is called carrier current transmission. Part 15 of the FCC rules allow for the UNLICENSED operation of a carrier current setup on the AM frequency band. The specifics are available but basically as long as the signal does not radiate more than 90 meters from the antennae(wiring in the house)it is legal.As far as connecting it to the distribution “grid” it will work just fine…up to the first transformer (unless the power company has bypass wires installed expressly to allow the signal to pass) if you google “high school radio” or “low power broadcasting” you will get more info on the subject than any human needs.

    • LarryL says:

      My college radio station had AM transmitters connected to all the dorm buildings in this fashion. I was always fixing those stupid things. I suspect that our transmitters couldn’t match variable load of the building’s wiring well.

  14. Ad5os says:

    It’s hard to tell which antenna is better in the recording just cause one was louder doesn’t mean it’s better. I just think this is a very bad idea for an antenna. As you can see I’m a ham Ad5os is my call. Anyway it’s very dangerous to have an antenna like this. He could of safely coupled the meter antenna next to a lamp cord and gotten the same if not better signals from the mains. But all the extra hash and noise on the mains messes up signals so the signal might be louder but way noisier.

    I think he could of figured out a better performing antenna with just a simple dipole so thAt there is an artificial ground and the antenna. In receiving and transmitting your ground is just as important as your radiating element!

  15. erich says:

    One may be able to replace the high voltage capacitors, fuse and primary winding with a 10 or 20 metre 1.5mm squared (10 amp rated) extension lead plugged in to a power point at one end and coiled up and placed near the the tuned circuit of the receiver I.e. what was the secondary winding of the air cored coupling transformer.

    Assuming a radius of about 0.7 mm for the Copper conductors, spaced about 2.5mm apart, with pvc insulation, this should give a distributed capacitance of about 12pf per metre between the ground wire and the active and neutral wires, as per

    C = Pi * Eo * Er * log e ( D / r ) * Length in Farads

    This would make for a capactive reactance of perhaps 600 ohms, allowing plenty of RF to flow for the purposes of inductive coupling, would raise fewer eyebrows among the safety management system types, and would allow experimentation with coupling.

    It should be pointed out to the hand wringing safety inspectors that had Miroslav done this in occupied Europe to set up a clandestine receiver he would have been a war hero!

    :-)

  16. echodelta says:

    As a ham I afirm the fact that the power lines are the source of most all man made noise. Why on earth would you want to receive noise. If we are talking AM MW and some shortwave a loop antenna is far better, if FM digital TV etc a meter down to a foot of wire is resonant with the higher frequency. They still sell plug in the wall (now digital) TV antennae in those tacky import sources. That’s one cap for $19.95 +S&H. The cheap clock radios that have that clip or coil of wire on the line cord that goes to the antenna terminal is for FM only the cord does the job of a floppy rabbit ear, just so so. Safe and clean listening.

  17. Dan says:

    I have emailed him asking if it 110V or 220V as it does not state anywhere the operating voltage. It does mention 60Hz but it is dangerous assuming one voltage, when it may be designed for another.

    Dan in 220V land

    • Miroslav says:

      I’m currently in Canada: 120 Vac / 60 Hz. This will work without saying on 220 Vac / 50 Hz lines as well, provided they are not within metal conduit or concrete walls with a lot of metal armature.

      It will work safely up to 700 Vac (700 Vrms * 1.41 = 989 Vac(peak)) as it is: there are two 1000 Vdc rated caps in series. Of course if you want to attempt that, add more HV caps.

      Voltage rating on a cap is DC: peak AC value is Vrms * 1.41. You must work with peak AC value here.

      Also: your voltage drop will be maximum on smallest capacitance capacitor! Use equal caps with equal voltage rating in series. Don’t play with this stuff if you are not certain what you are doing.

    • Miroslav says:

      I forgot to add: by “safely” I mean if one cap shorts out, you are still protected by the other one, fuse and separate antenna coil.

  18. Aussietech says:

    1) at one time, when AM ruled the waves, this (or something very similar) was a very common practice in commercial AM radios.

    2) all things considered, including a real earth on the south end of the input coil, this is actually a safer arrangement.

    3) it should provide greater inherent protection from induced charge from a nearby lightning strike than the external long wire aerial I put up and used as a kid.

    4) early “wireless” intercoms, no doubt sold in the millions, used a very similar arrangement to inject and recover a 100kHz FM carrier (that generally couldn’t make it through the local supply step down tranny, or even between phases in large buildings).

  19. Raven Rage says:

    As far as I understand this is a common practice…. I used to do this with an old walkie talkie when I was younger to get better reception. Granted its not the safest but honestly you can get hit by a car simply crossing the street….

  20. DeeplyShrouded says:

    Anyone remember the old Bell dial telephones? You’d hook a wire to the finger stop (that piece of metal near the Operator hole) and connect it to a radio. Lots of good reception there.

  21. Alfred says:

    This guy is pretty smart! But I didn’t get right one thing: first he makes use of a step down transformer but then it looks like it has an step up converter?! What should it supposed to do – step up the voltage stepped down by the two coils?

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