Toroidal Coil Signal Propagation and Exposure at 200-3000Hz, 500-1000W, 1-6ft Elevation

Strange Coil, Unusual Propagation? (TORUS, TOROIDAL SHAPE)

Hi, newb here... am trying to hunt down some answers on how a specific coil will
propagate transmission under a few different conditions. 
Photos of the coil and more details can be found at this link ;

http://soundofstars.org/1vendorsdanielnunez/coilissues.htm


The basic questions I have are listed below - would greatly appreciate any menaingful
feedback 
1.) Does the geometry of the coil affect signal propagation

For example, would this type of design tend to dampen propagation

Past the near field or would it work like a normal RF antenna?

2.) How far will the coil transmit frequencies in the range of 200 to

3000 Hz, at power levels between 500 to 1000 watts, given the

characteristics of the coil at elevations ranging between 1 to 6 feet?

3.) How do we calculate the ""permissible exposure levels" for this unit,

given inputs from # 1 above, for distance ranges of 1 to 20 feet

from coil?

tags ; antenna, torus,toroid,radio, frequency, engineer, engineering, signal, propagation,

Donald, I'm not an RF expert but as no one else seemed to want to have a go, I will...Firstly I will stop short of saying this is a scam, but looking at the prices ($100+ and up) for these coils which are basically made of copper wire and plastic, one has to wonder.Yes, he has a patent on it, but that does not mean it is as groundbreaking as he makes out. He claims that the coil produces a more uniform field in all directions.  Antenna theory tells us that if you want gain, you get it at the price of directivity, ie the narrower the beam the higher the gain.  For power transfer applications you would want the maximum power in one direction - towards the receiver - not uniformly distributed like this.  And I'd expect to see diagrams of field strength on the site or in data sheets, which are conspicuously absent.If these coils do have as omnidirectional a field as they say, they'd have applications in broadcasting RF or even AF to finite spaces (eg for those museum tour guide devices).  But even then vertical dipoles have a donut shaped field which puts out power horizontally (where you normally want it)  but not vertically (where it is of no use).I'd do some basic antenna theory study (eg here) and then ask the guy some questions.  But it seems to me they just look really pretty and one of the suggested areas of application (PEMF therapy) is not exactly mainstream.  And again, the huge prices for a few dollars worth (at most) of copper wire and plastic ring strong alarm bells.

David,I just had a bit of time to look at this and share your suspicions. In addition to everything else, these antennas are much less than a 1/4 wavelength in size  at 3000 Hz which means they aren't going to be very efficient at radiating at that frequency, let alone at 200 Hz.I can believe that these antennas are very omnidirectional though, since they are probably as close as you can get to an isotropic radiator.https://en.wikipedia.org/wiki/Isotropic_radiator

David thanks so much!  This actually helps a lot!  Yes, I realize the cost

per coil is high, my understanding after speaking with the developer of the coil is that the cost is mainly associated with the labour and time associated as all the coils are hand wound manually or "walked" he says it takes quite a long time to make each one he also showed me the costs he pays for the wires, which it turns out is pretty high - I hadnt know previously how expensive copper wiring had become.  The most helpful thing here from what you said though for me, i that  the coil should NOT typically be able to broadcast far, thats actually what I am hoping for.  Am wanting to do experiments with broadcasting frequencies at different power levels but I want to make sure everything I am doing is within normal FFC compliance.
What I am really hoping to find are formulas that I can apply to this coil type so I can compute the values associated with my inquiry for #1 and #2 above

A vortex coil is tiny compared to the wavelength, so the quasi-static approximation applies and the coil emits an approximately-dipole magnetic field. The farther the observer is from the coil, the more closely the field resembles a dipole field. The coil is a number Z of identical, slightly-tilted, one-turn rings, all in series, carrying current I. Let Aring(N) be the vector area of ring N (so N varies from 1 to Z-1), with vector direction perpendicular to the plane of ring N. All the rings have the same magnitude |Aring|, but different directions (due to the tilts of the rings). The different directions are the vortex effect. The vortex effect affects the magnetic field close to the coil. Far from the coil, the field will be a dipole field. The vortex effect will slightly reduce the size of the dipole field, but will not affect the shape of the dipole field. If the rings were tilted ninety degrees, we would have a classic toroidal coil, with zero dipole field.
We could slide each ring around the coil until all the rings are on top of one another, making the coil a standard solenoidal coil. This would eliminate the vortex effect, while leaving the dipole field unchanged.
If we put power into a vortex coil, most of the power will be converted to heat by the resistance of the wire. A small amount will go into the dipole magnetic field. An even smaller amount will go into the radiation field. At these frequencies, a vortex coil makes a good dummy load. The open construction permits airflow to cool the coil.
A general note on wireless-power systems: The hard part is not transmitting power wirelessly efficiently. The hard part is preventing the wireless power from showing up where the power must never show up.

Thanks Peter for that analysis, more in-depth that I could do, but confirms my feeling that these coils are nothing much out of the ordinary for most purposes.

Donald,If what you want is to test transmitters and NOT broadcast far, I'd suggest a dummy load. This is the proper way to test transmitting equipment.  Here is one possible source.
https://www.dxengineering.com/search/part-type/dummy-loadsMy experience with the dry dummy loads is that there is some small RF leakage (so a nearby receiver would detect a signal) but it is attenuated enough to meet safety requirements.The MFJ-264 or similar should be suitable for the power levels you want to use and cost less than $100...

Hi Elizabeth, thank you so much for the feedback!  This help a lot actually!  :)What I am actually hoping for IS to transmit an omnidirectional field AND I am hoping the transmission is NOT effectively delivering signal at longer distances,so this really is good news.  What I am hoping for is to deliver the signal within approximately a 15 to 60 foot radius of the transmitter.  Its ok (and preferable)  if the signal is greatly dampened past that distance.If I explain my purpose more here, perhaps this would  help.My purpose is to observe effects of broadcast signals on biological specimens ranging from microorgansims to plant species. 

Hi Elizabeth!  Thanks again for you kind and insightful feedback! I would like to be able to broadcast at power levels ranging from 500 to 1000 watts within at least the ULF range without crossing FFC boundaries, and if I could experiment within the human audible range and even in the Khz and up regions that would be great too.  I would rather not have to erect a local faraday cage or anechoic chamber due to the expense, time, effort associated with that.   If I understand you correctly, you are saying that a transmitter that is comparable to a "dummy load" would by virtue of its design operate well within FCC requirements for the type of experiments I want to run?
 I would like to be able to broadcast at power levels ranging from 500 to 1000 watts within at least the ULF range without crossing FFC boundaries, and if I could experiment within the human audible range and even in the Khz and up regions that would be great too.  I would rather not have to erect a local faraday cage or anechoic chamber due to the expense, time, effort associated with that.  

Peter, really appreciate this detailed and comprehensive feedback, thank you so much!  :)This is great news that a vortex coil functions as a dummy coil!  Very relieving to hear everyones feedback!  Are there any maths / formulas you know of that I could enter the values of the coil specs, power, frequency ranges and be able to estimate propagation distances at field strengths / power levels?

I wrote "dummy load", not "dummy coil". In the RF/radio world, a dummy load converts all the input RF power into heat, without radiating anything. Dummy loads are used for testing transmitters.Yes, there are methods for calculating the performance of coils. Classical electromagnetics texts (Smythe, "Static and Dynamic Electromagnetics" is a good one) and antenna-design texts (Kraus, "Antennas" is a good one) cover the material. The first step is to obtain the dimensions and details of the coil in question. From this, you develop an electromagnetic model of the coil, which will give the fields emitted for a given current applied to the coil. From this, you can calculate the signal induced in a receiving coil.In the quasi-static case (where all dimensions and distances are small compared to the wavelengths of the frequencies in question), Neumann's formula (named after Professor Neumann who published the formula in 1846, is quoted by James Clerk Maxwell in his papers and books between 1867 and 1891, and is covered in modern electromagnetics texts) uses a double integral to calculate the general case of the coupling between two coils.Where do you want your 500 to 1000 watts to go?The vortex-coil websites I looked at, all seemed pseudoscience and fantasy to me.Magnetic fields do have angular momentum. See Feynman's "Lectures on Physics" volume two for details.

Hi Peter, thanks for the direction on this!  About where we want the power output to go ; only in a local environment with an estimated max radius of distance traveled being between 15 to 50 feet in range.  Can I ask if you or anyone here might know of a person who could calculate the performance of the coils using the dimensions and details of the coil and who could develop the electromagnetic model of the coil, so we can obtain the fields emitted for a given current applied ?  And then as you said, calculate the signal induced in a receiving coil?

Donald,If, as you said, you want to subject biological specimens to RF fields, I would think that you'd want a strong (and known) field in the area of your specimens. I doubt that either a dummy load or the vortex coil will give you that since they will turn most of the power into heat.
In both cases, the majority of the power that you transmit will be dissipated as heat so you won't get much of an RF field out compared to the power you are putting into it. You would be much better off with a small wattage transmitter connected to a reasonable size dipole or loop antenna.If you really need a strong field similar to what would be generated by an AM radio transmitter, you either need to find an AM radio tower to put your samples near or you will need a screen room or similar to attenuate the RF outside your test area.
I think for this project you will want an RF Field strength meter...

Donald it sounds like you need to study antennas and RF propagation a bit.A dummy load converts ALL the RF power into heat and does not radiate at all.An antenna converts all the RF power into electromagnetic radiation - how it distributes this depends on the antenna design.  It is relatively easy to concentrate the radiation horizontally or vertically around the antenna, a bit more difficult to beam it mostly in one direction, and not very easy at all to radiate it equally in all directions (like a star or our sun).So putting 500-1000 watts of power into a dummy load or the vortex coil does not accomplish a lot, as most of the power will be wasted. rather use less power and use an antenna to distribute it as an RF field.Also, it is well nigh impossible to create a strong field nearby and have it become almost nothing further away.  The best way to do that is to have a coil and send power into that, and put your subject INSIDE the coil.  This is the principle of RF heating and inductive cooktops.  The dimensions, number of turns, etc of your coils for this would vary with the frequency you used.  Low frequencies need a relatively large coil with many turns of wire.Lastly, the wire in the vortex coils looks pretty standard.  A well known wholesaler not known for their bargain prices offers a roll of 105 ft / 32m of 15AWG / 1.5 mm diameter enamelled wire for 30 bucks.  Hardly accounts for the multi $100 prices for the vortex coils.Another warning bell.

David,You just prompted an interesting thought.I'd be willing to bet that the RF field inside a vortex coil is much higher than it is outside so a giant vortex coil might work for this. You'd need a lot of wire, a framework to support it, and some way of inserting and removing the samples but it just might work...

Correction: Smythe's book is "Static and Dynamic Electricity".

A solenoidal coil has a strong field inside the coil, and has open ends for easy sample insertion and removal.

https://web.archive.org/web/20151002101400/http://home.comcast.net/~traneus/thesis.pdf Chapter 7 describes how to calculate the quasi-static magnetic field of any coil, by modeling the coil as a large number of straight-line segments.

Mulling over this problem, it would seem to me that you may be able to use a Helmholtz coil  to generate a know B field, and some plates to generate an E field.This would give you a known quantity  within a workable volume.See this  document for some interesting comments.In the past I worked on a system that used a 100Km  suspended power transmission cable and a 20Kw audio modulator (used to modulate an AM broadcast transmitter) to push 20Kw out onto the cable. The radiated power was a few watts over the audio band.Cheers,Richard

Peter, the references you provided are absolutely helpful!  I would like to find someone to compute this electromagnetic coil model and derive the formularesults for me - is that something you could do?  I am willing to pay a service, consult fee for this, to you or to anyone else that would be willing capable?  If this is not something you are interested in thats totally ok, would be open to receving direction from anyone on here as to how I could locate an expert to do this?

I cannot help you with your calculations. Look for electromagnetic-modeling software packages. You need to study classical electromagnetics and radio regulations.

For a practical example using a spiral magnetic field, look up "tokamak".