Long (1000ft) coiled loop of 18-24g wire. What frequency would this setup produce?

Thread Starter

RogueRose

Joined Oct 10, 2014
375
I read a post where someone who suspected they were very convinced that they had some spy device recording and possibly transmitting frequencies within the home (the experience was 4-5 years of consistent happenings that never replicated when they frequently travelled, so I was somewhat convinced they were experiencing something).

A responder told this person that they needed to make a coil of wire (single strand, didn't say gauge, but i'm guessing 18-24) by placing 100 nails or tacks in a row with spacing of 5-10mm between each - so a total of 50-100cm (12.5 - 25 inches) and another row 5 ft across from the first with the same tacks/nails and same spacing. They were then to take a wire and run it in a zig-zag, back and forth starting at the tack 1 on side A then to tack 1 on side B, loop back around to tack 2 on side A the to tack 2 on side B and repeat until the end. After this run a wire from the beginning of tack 1/side A, and also connect a wire to the last tack (100, side B) and run these leads to a audio amplifier speaker output.

So this wire "coil" is 1,000ft (maybe a little longer by a couple ft). He was then instructed to play music through the device turned up all the way. 9unless it was a high end stereo of like 100-150 watts RMS, but he said 20-40 watts RMS was fine and would generate constant noise in any recording device in the house.

Now from what I understand, the amplifier boosts whatever signal the source is, and being music it is almost always 20-20,000 Hz, so I would suspect this loop would generate frequencies in that range as well. IDK if there would be harmonics generated as well which may get up in the megahertz range, but I would suspect for them to get any where near the 80MHz as the 15th harmonic of 20KHz would only be 320KHz and at the 15th harmonic I would think it would have lost most of it's power not to mention the music would vary so much the frequencies would be all over.

So, is there anything to this idea or was the poster just being trolled? I was thinking that the size of the wire would be important, especially when wattage of the amp is taken into consideration as it would heat the wire. Most speakers are 4 or 8 ohm, with 8 being more usual.

All are AWG standards diameter
gauge: 24g - Length: 1000ft - diameter: .511mm - cross sectional area: .205mm^2 - resistance: 25.6 ohms
gauge: 22g - Length: 1000ft - diameter: .644mm - cross sectional area:.326mm^2 - resistance: 16.14 ohms
gauge: 20g - Length: 1000ft - diameter: .812mm- cross sectional area: .518mm^2 - resistance: 10.15 ohms
gauge: 18g - Length: 1000ft - diameter: 1.024mm - cross sectional area: .823mm^2 - resistance: 6.39 ohms

15g = 3.184 ohms (8 strands of 24 gauge which could be gotten from a single cat5 cable with the wires run in parallel/twisted together at the ends)
17g = 5.064 ohms (8 strands of 26g cat5 cable run in parallel)
 
Last edited:

Papabravo

Joined Feb 24, 2006
16,511
I don't give the story much credibility. 1000' of wire by itself doesn't produce any frequency at all, and the gauge has less than no impact on what it will do. As a load to an amplifier it may or may not radiate over some distance in the audio frequency range. Anything above the audio range will no doubt be substantially attenuated. Assuming a VHF spy device, it would hum along without much in the way to bother it especially if it was an FM device.
 

BobTPH

Joined Jun 5, 2013
3,505
I think the idea is that it would insert sound at the point of the microphone, not that it would jam the RF signal. No idea whether or not it would work.

Bob
 

tcmtech

Joined Nov 4, 2013
2,867
For anyone to be spied on they usually have to hold some sort of social value and or significance to justify the spying of which the vast majority of those who think someone is spying on them generally fit into the category of being people that no one would ever care anything about regarding what they say or do.
 

Papabravo

Joined Feb 24, 2006
16,511
I think the idea is that it would insert sound at the point of the microphone, not that it would jam the RF signal. No idea whether or not it would work.

Bob
As I understood what he was talking about it was replacing the voice coil of the speaker with 1000' of [magic wire] of woven onto an arrangement of tacks. Inductance is inductance after all.
 

Tonyr1084

Joined Sep 24, 2015
6,082
I highly doubt that story is true. Not saying what you heard was untrue or what you're saying - that this story circulated - is untrue, I think the story itself is untrue that taking 1,000 feet of wire and making a loop of wire (especially the part of zig-zagging the wire among nails) would really do ANYTHING. Except maybe blow out the amplifier.

Here's something I didn't hear - something I actually did (and the reason why): My first wife was suicidal. One particular night she was in trouble and I quickly dialed 911 to get emergency help to the house. As I happened to dial 911 someone locally (never found them) was broadcasting on the Citizen Band (CB) radio running illegal power and came bleeding in over my stereo (turned off), my TV (turned on) and over my phone line. PHONE LINE! Not cell phone. I had no choice but to throw her in the car and drive her to the hospital myself. (end of that part of the story)

The next day I decided I was going to find this guy. Knowing absolutely nothing about loop antenna other than they're directional, I set out to build one. I used wire out of a very large transformer, the fine wire and took a 16 inch bicycle rim and began rapping the wire around the circumference (with a stick to provide slack so I could remove it). Made about 100 turns, then took it off the rim. Four folded it into approximately 400 turns, then wired the ends to a coax and plugged it into a small portable hand held walkie-talkie radio and set out to find the guy. The very next night he was at it again, but my antenna did nothing to indicate any direction; the experiment was a bust. But just out of curiosity I decided to key down (transmit). As soon as I did my microwave oven blanked out. I thought I blew it out. But when I hit the CLEAR button the time came back on.

I started experimenting with it and inadvertently discovered some things that posting them here would probably be prohibited, so don't ask what those findings were. But sitting about 20 feet away from the microwave oven it had an affect on the control board.

Now, this isn't a story I heard or just made up - this actually happened. I would not advocate rebuilding this circuit because there's a remote chance it could lead you to getting into trouble - possibly with the FED's. So don't try it.

But as for the story you heard - a 1,000 foot length of wire coiled into some sort of five foot diameter loop will likely do nothing to stop someone from eavesdropping on someone. It's more likely they'll gain access to your computer and turn on the mic to listen to your conversation - or maybe turn on your web cam and watch what you're doing. But there ARE devices and programs to combat such things. However, a giant loop of wire will probably do nothing. I say "Probably" because I don't KNOW that for a fact. But I think the general consensus is that it won't do anything.
 

shortbus

Joined Sep 30, 2009
8,726
My thoughts on this story is the person is assuming the loop of wire would become a 'Faraday cage", to keep out the 'bugs'. Which it won't.
 

Alec_t

Joined Sep 17, 2013
12,160
I don't think zig-zagged wire would make a vey good antenna, since the fields generated by any two adjacent runs of wire would cancel out.
 

Tonyr1084

Joined Sep 24, 2015
6,082
The post states a row of 100 nails spaced approximately 5mm to 10mm apart. Assume 7.5mm for the sake of argument. That's 750mm or 0.75 meters long. The post also instructs to construct another row of nails spaced in the same manor, and then space the two set of nails 5 feet apart. So, approximately 2 1/2 feet by 5 feet will equal a length of 15 feet in circumference (rectangular). IF we take 1000 feet of wire, that's going to loop 66 2/3 times around. That's not very many turns. And lets assume it's magnet wire 22 gauge. I just don't see what that's going to accomplish. But then again, when it comes to coils (from my earlier post) I haven't the experience to speak with any authority. Still, I just don't see what 67 turns on a coil that size will do. Well, I said "I don't see it".

Now, my experience not withstanding, a stereo pushing 40 watts - lets assume 65 volts peak DC voltage on one of the output stages, that's going to push little more than 600 mA. Well, that seems like it wouldn't hurt the amp IF the wire resistance is around 110Ω. Exactly what that is supposed to do - I just don't see.

Well, I've had enough fun with this post. I think I'll sit back and copy the mail.
 

BobTPH

Joined Jun 5, 2013
3,505
Again. I think the varying magnetic field it creates at audio frequencies is expected to induce a voltage in the microphone circuit of any listening device overwhelming any audio the mic was picking up. I doubt that it would work though. The zig zag design of the "coil" seems wrong for this purpose. Winding a coil all the way around the house would have more of a chance of working.

Bob
 
Top