Author Topic: Disrupting Inductive Neck Loop Earpiece with EMP?  (Read 18764 times)

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Offline ShidoshiTopic starter

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Disrupting Inductive Neck Loop Earpiece with EMP?
« on: November 13, 2010, 06:23:49 pm »
I have currently made a small handheld EMP device originally from a 9V battery which later got converted into 8x9V batteries which was outputting 52.5V and down to 45V after a half hour or so, 500mAh batteries **** big time, will go on to 3000mAh once I figure out all the kinks in the current design though.

The reason for creating this small EMP is to block out the inductive neck loop system which students are using to cheat on their exams, they use an MP3 player and a wireless earpiece which captures the magnetic resonance at about 300Hz - 5300Hz, some even go to 8500Hz. Since I wasn't able to replicate this low output, I tried the EMP method.

The pulse works fantastically at around 1m range with some grounding issues however, the original design was only intended as a demo and at the original 9V nothing happened with the increase of power I managed to get the multimeter to show me 200V output from 8x9V batteries lol. At about 1m range the earpiece picks up the EMP as do 3V pc speakers, I need the pulse to be received in a 10x10m room though.

I was also thinking of digging up an ancient HAM schematic to output somewhere near the magnetic resonance the earpiece works on, if HAM and submarines can do it why can't we?

I'm seriously stumped as to what the best option for our centre is, one more point, it is important that the device can run on a small current, well actually, should be covert, able to be mobile, say in a backpack with a few 9V batteries or other power source that is small enough to conceive in a bag.
 

Offline JohnS_AZ

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #1 on: November 13, 2010, 06:48:20 pm »
It would be a hell of a lot easier to detect their transmitter, and expel them from school.
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Offline allanw

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #2 on: November 13, 2010, 06:56:27 pm »
Wait, why can't you notice them using an earbud?
 

Offline ShidoshiTopic starter

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #3 on: November 13, 2010, 07:05:59 pm »
to JohnS_AZ:

1 device that can block a whole room from current and future attempts to cheat on tests or extra staff to strip search each individual student and violating their rights... I think the cheaper and easier method is to not encourage students to try and cheat and not get caught but to study and pass their exams on their own and in turn raise the school's standards.

Some educational institutions have staff that take money from students to mark them as present and give them a solid report, a recent TV report on some New Zealand universities demonstrated this.

Just attempting to stay one step ahead. Of course if anyone is caught we will try to expel, however expulsion not every time works in our favor, there are many variables to take into consideration.


to allanw:

Magnetic resonance, some devices can be as small as 3mm in diameter and so far down the ear canal that they can't be seen without probing something down their ears.
 

Offline JohnS_AZ

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #4 on: November 13, 2010, 07:11:36 pm »
Okay.  I don't know a thing about these inductive neck loop things. Can you point to a web page that talks about the technology?

The point:  Figure out what the transmitter is doing, and build a bigger,more powerful one. Maybe blast them with Neil Sedaka songs from the 70's.   ;D
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Offline Fraser

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #5 on: November 13, 2010, 07:11:47 pm »
  Shidoshi,

When I first saw your message I was thinking 'what the heck !' but having seen your reason I understand your drive behind this project.
I have used what could be termed EMP emitters in my work life but they use much higher powers than you are talking about here and are not exactly portable ! They would also damage anything electronic within 10m so aren't really appropriate  ;D

You have not detailed your circuit so I have no idea what you are using in terms of a pulse generator or power amplifier stage. Any decent EMP device with any sort of effective range will need a significant ERP and the pulse repetition frequency (PRF) will have a significant effect on average current consumption.

My usage of EMP was to disrupt or damage electronic semiconductor junctions, yours is really more of a jamming application which is somewhat different. In the Cold War days the 'Woodpecker' could often be heard as it stepped through the HF spectrum. I once listened to that signal moving up from around 2MHz to over 30MHz knocking out thesignal on each of my fifteen HF receivers as it did so...... it was capable of completely disrupting my comms links while it was present. I would suggest you consider building a mini 'woodpecker' by feeding a swept pulse oscillator into a reasonably powerful RF power amplifier that feeds an inductive loop around the exam room. The swept frequency should be at a reasonably slow rate in order to create a intermittent jamming signal that covers all frequencies between 300 Hz and 10kHz. The less spectrum friendly option would be to build a spark gap transmitter as that would produce broad spectrum RFI. One can easily be built using a simple 555 oscillator driving a car ignition coil with the EHT jumping a 5mm spark gap and feeding a long piece of wire or large loop.... a most unpleasant  experience for anyone receiving it on an earpiece !

Now the legal bit…. Making a powerful EMP device or jammer of any description may be deemed unlawful in many countries and is definitely so in the United Kingdom. You always have to consider the effect the EMP device or jammer will have upon legitimate users of the RF spectrum. Broad band RFI producers can be a very anti-social act. Consider legitimate hearing aid users.

Your establishment should carefully consider it’s legal position and should also consider stopping the problem in a simpler manner. If the technique of using an inductive earpiece is known, the students may either be searched on entry or regular checks on their ears made. The only hearing aids fitted should be to those with a medical condition. The KISS principle applies !

I will not provide the circuit details needed for an EMP device or a jammer as they are freely available on the NET and personally I do not wish to be associated with such a device in a civilian environment.  
« Last Edit: November 13, 2010, 07:16:04 pm by Aurora »
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Offline ShidoshiTopic starter

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #6 on: November 13, 2010, 07:35:08 pm »
Transmitter/Receiver specs: http://www.ioffer.com/i/spy-micro-invisible-earpiece-wireless-earphone-cheat-143294781?source=eisi

EMP Schematics: http://www.freeinfosociety.com/electronics/schemview.php?id=2279 (REV.01)

Students with hearings-aids or pacemakers are segregated. Building the Woodpecker and feeding a pulse through an inductive loop around the room won't only be concentrated within the 10m2 room but will also spread in every other direction too, right? Since a parabola wouldn't be feasable, I think that even though this is a great suggestion, I would like to hear some more suggestions before thinking seriously about your method, Aurora. Ahh, also the spark gap method is rather noisy, is it not?
 

Offline JohnS_AZ

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #7 on: November 13, 2010, 07:39:39 pm »
I still don't understand. What is actually transmitting the signal that these earbuds receive?
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Offline ShidoshiTopic starter

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #8 on: November 13, 2010, 07:42:33 pm »
Speaking of cold war, what are your thoughts on a ELF/ULF/VLF transmitter? Been trying to figure out how the Russians used ZEVS in submarines and to replicate that method somehow or if feasable at all outside of water...

The signal is on a neck loop system using magnetic resonance. The inductive loop system uses a magnetic pulse to transmit VLF magnetic vibrations. The earpiece picks up the magnetic resonance at a short range and using a miniature speaker/magnet converts the magnetism to audio. Very similar way normal speakers work but on a much lower frequency range.
 

Offline ShidoshiTopic starter

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #9 on: November 13, 2010, 07:46:05 pm »
Some of these manufacturers state that this system is un-jammable, in theory this is not true. We beleive that nobody has gone public with their methods yet ;)
 

Offline .o:0|O|0:o.

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #10 on: November 13, 2010, 07:52:10 pm »
should be covert, able to be mobile, say in a backpack with a few 9V batteries or other power source that is small enough to conceive in a bag.

Really? Why?
 

Offline ShidoshiTopic starter

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #11 on: November 13, 2010, 08:01:33 pm »
Some examinations are conducted outside of a classroom environment.
 

Offline Fraser

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #12 on: November 13, 2010, 08:14:48 pm »
Shidoshi,

Nothing is unjammable  ;)

I have had a think about your situation over my dinner. I am an RF tech so magnetic loop links are not my speciality. I don’t think my idea of a swept pulse oscillator is going to be that effective in your very low frequency application.

From what I know of the system you are up against, it does not use a modulated carrier and is basically audio being fed into a loop at a high enough level to reach an inductive pickup in the earpiece, I presume the inductive pickup feeds a high gain audio amplifier. This is using the basic principle of close proximity inductive coupling, so to disrupt it you would need to generate an intense magnetic field that is actually a single frequency of say 1kHz. The earpiece inductive pickup would detect that field and reproduce an annoying 1kHz tone in the users ear  :)  You have two obstacles..... near field versus far field flux density and the challenge of driving a very low impedance loop with an audio frequency power amplifier. The manufacturers of hearing aid loops know how to deal with these challenges but I regret I do not. You could consider speaking to a hearing aid inductive loop vendor and establishing whether one could be used as a jammer by feeding in a 1KHz oscillator tone which the unit would radiate into the room.

Another approach is the BLACK BOX Hoax ! Construct a black box and fit some fancy digital meter to it with a bright flashing LED, then advise all students that an inductive earpiece detector will be deployed in the room. Anyone found cheating will be dealt with harshly. Bluff will sometimes work.
« Last Edit: November 14, 2010, 06:26:22 pm by Aurora »
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Offline ShidoshiTopic starter

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #13 on: November 13, 2010, 08:27:15 pm »
HAHAHAHAHA nice one! That is pretty fun until it's discovered to be a hoax!

Yes, it does contain a high gain amplifier indeed.

1Khz sounds right on, I had that thought last night but my mind ventured elsewhere. I never thought of the possible obstacles however. Great participation on your behalf Aurora, much appreciated!

I will speak with some manufacturers right away, thank you for the heads up on that!

Will post any obstacles/progress on here as soon as I know of anything new!

By the way, you don't happen to have a handy working schematic for a 1Khz transmitter would you? Mr. Google will be happy to comply if you don't, I can only assume ;)
 

Offline Fraser

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #14 on: November 13, 2010, 08:51:46 pm »
Shidoshi,

1 kHz transmitter....Hmmmm that is a bit of a challenge ! I suppose the audio amplifier could be considered a 'transmitter' but a pretty unconventional one !  What you will need is a single loop around an area driven by a powerful Audio Frequency amplifier that does not mind feeding what is effectively an extremely low impedance at audio frequencies. Some clever loop drive circuitry will be required and I regret that I do not have that knowledge and Google seems very quiet on the schematics side of hearing aid loop drivers.

I thought about using a standard reasonably high powered audio amplifier feeding into some form of step down impedance transformer but I do not know of one that will step 4 Ohms down to milliohms. If you connect a loop directly to the amplifier output I suspect you will quickly overheat the PA stage and kill it just as may occur with a shorted loudspeaker.

I think you will need to do some hard Googling on driving very low impedances at audio frequencies. There are many manufacturers of the loop amplifiers but very little detail of what they contain in terms of design.

The 1kHz tone may be produced using a simple 555 circuit in astable mode.... if you use a square wave it will produce quite a distorted sound ....... it would be like a loud mosquito in their ear  ;D

On a side note.... If you are successful in your desire to deploy a countermeasure against cheats, imagine what will happen when you first switch it on.... you will hopefully see all the cheats with pained expressions on their faces as a solid 1kHz tone drills into their ear  ;D They will want that earbud out of their ear canal pretty quickly or else suffer considerable discomfort and distraction during the exam  ;D ;D ;D
« Last Edit: November 13, 2010, 08:56:08 pm by Aurora »
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Offline cybergibbons

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #15 on: November 13, 2010, 09:16:35 pm »
I don't understand why people would go to such lengths to cheat... but anyway.

These are just the same as inductive loop hearing aids in use everywhere in the UK. I've set up quite a few temporary induction loop systems using hired kits, and it's very easy. If you aren't worried about sound quality, an audio amp connected to a long length of mains flex will do the job. Connect to a signal generator doing pulses of 1kHz at extremely high level, and you'll quickly find the students cheating - they'll be the ones ripping the earpieces out of the side of their heads.

Just be warned, anyone with hearing problems and using a hearing aid will experience the same.
 

Offline tyblu

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #16 on: November 13, 2010, 09:25:57 pm »
This is fascinating - I didn't know these earbuds existed. Was actually interested in making something similar for my final school project, last year. Looking online yields versions with receiver and power circuitry stuffed into a AAA battery-sized package, connected to the ear bud. This will only get smaller, 'til it fits in your ear like a hearing aide - in fact, this probably already exists as it was the size I was going for in the project.

If I were in your shoes, I would consider multiple smaller-range devices, such as what you have, to ensure you stay below certain SAR measurements and be able to selectively turn off the jamming signal near some individuals whose electronics are of vital importance (pace makers, and whatever other gadgets we'll be using in the few years to come).

Good luck! Would love to hear more about this.
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Offline cybergibbons

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #17 on: November 13, 2010, 09:26:16 pm »
The proper kits are current mode amps rather than voltage mode. A good audio amp can drive very low impedances, and a long length of flex is easy enough - buy a 100m length of 0.5mm2.
 

Offline NiHaoMike

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #18 on: November 13, 2010, 10:30:59 pm »
Remove the whole motivation to cheat. Allow them to have some references (notes or even a textbook) and design the exam to be based on applying the knowledge. It's pointless to make them remember reference materials - they'll remember it after lots of use - so have them learn how to actually solve problems. In the end, they'll forget the stuff that doesn't count and remember the stuff that does.
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Offline .o:0|O|0:o.

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #19 on: November 13, 2010, 10:58:19 pm »
Remove the whole motivation to cheat. Allow them to have some references (notes or even a textbook) and design the exam to be based on applying the knowledge. It's pointless to make them remember reference materials - they'll remember it after lots of use - so have them learn how to actually solve problems. In the end, they'll forget the stuff that doesn't count and remember the stuff that does.

In some countries they complement written examinations with oral examinations, where you are expected to solve a problem on a blackboard in front of a board of examiners, while explaining your steps as you proceed... None of this multiple choice* "who wants to be a millionaire" nonsense - the real world doesn't work like that ....but you can automate the marking process and save money that way.

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« Last Edit: November 13, 2010, 11:03:19 pm by .o:0|O|0:o. »
 

Offline marianoapp

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #20 on: November 14, 2010, 12:31:08 am »
you could also buy your own earpiece and walk among the students while they are answering the test.. as soon as you start receiving something you'll know how the cheater is
 

Offline NiHaoMike

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #21 on: November 14, 2010, 02:56:09 am »
In some countries they complement written examinations with oral examinations, where you are expected to solve a problem on a blackboard in front of a board of examiners, while explaining your steps as you proceed... None of this multiple choice* "who wants to be a millionaire" nonsense - the real world doesn't work like that ....but you can automate the marking process and save money that way.
At my university, multiple choice exams are very uncommon for the higher level classes and just about all the exams either allow "bring your own references" or supply some sort of reference sheet. What I like the most are "practical exams", where the whole objective is to either fix something that doesn't work properly or create something using the supplied materials. Basically a good simulation of a real world situation.
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Offline ShidoshiTopic starter

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #22 on: November 14, 2010, 04:12:06 am »
Quote
you could also buy your own earpiece and walk among the students while they are answering the test.. as soon as you start receiving something you'll know how the cheater is

Some devices transmit up to 10cm, that would be an uncomfortable moment for both parties. The longest ranged devices state they can transmit 70-100cm which would mean the source could come from the pocket rather then a neck loop system, either way there would be certain uncertainty, also the system can be triggered on/off by the operator via a switch as soon as someone approaches.
 

Offline NiHaoMike

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #23 on: November 14, 2010, 05:20:05 am »
They'll just find some other way to cheat. But if you allow use of reference materials and redesign the exam to account for that, clever tricks to hide information would not offer much advantage if any. (You'll still need to prevent unauthorized sharing of answers but making different versions of the exams would make that useless. Maybe even make subtle changes that cheaters probably would not notice but would greatly change the answer.) In other words, to quote Dr. Ehsani (a power electronics professor at Texas A&M), "Make cheating obsolete."
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Offline Bored@Work

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Re: Disrupting Inductive Neck Loop Earpiece with EMP?
« Reply #24 on: November 14, 2010, 10:07:00 am »
If they can cheat with an MP3 player, then I would also say the exam questions are asked the wrong way. It sounds they are parroting exams. Exams where it is just checked if people can repeat what they have memorized, like a parrot, instead of checking if they understood the subject.

But anyhow, if you roughly know the frequency these devices use, build a receiver. You don't have to decode the signal, just detect its presence. You will need something like a (hand-held) loop antenna (loop antenna, because of the low frequency). A cap in parallel with the loop antenna to  get a resonance frequency in that kHz area you are interested in. Then an audio pre-amplifier (simple two-stage transistor or the like). And then you can rectify the output to display signal strength on some meter.
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