High frequency electromagnetic energy. hazardous? legal?

[thadman]

Tesla Coils and Plasma Loudspeakers are characterized by an extremely high frequency electrical resonance. This resonance is modulated to produce energy in the audio bandwidth.

I am curious as to what frequency ranges are non-hazardous and/or not regulated by the government.

As far as I understand, the government along with private parties use certain frequency bands for military / communication purposes (ex. RF). Reproduction of a device that emits significant electromagnetic radiation may interfere with these operations. In addition, the resonance of the transducer could couple to these signals and produce undesirable levels of noise.

Also, high frequency electromagnetic signals contain a lot of energy. I believe radiation is emitted. These signals can be hazardous to humans if they contain sufficient energy (ex. Microwaves).

What frequency ranges would not have the aforementioned effects? Could anybody offer further insight on this?

Thanks,
Thadman

[Inductor]

Originally Posted by thadman

Also, high frequency electromagnetic signals contain a lot of energy. I believe radiation is emitted. These signals can be hazardous to humans if they contain sufficient energy (ex. Microwaves).

Maybe overreacting, but, I don't think Mr. Tesla died young.

[Andrew Eckhardt]

Anything in the kilohertz is not going to bother you unless you find a way to drive more than a milliamp or 2 right through you, by direct conduction or standing around an antenna with either lots of directivity or maybe kilowatts in. Oddly, I've taken direct hits from the collectors of TV flyback circuits (what is that 15kHz?) at maybe 1000 volts or so and did not get shocked, just burned at the point of contact. (Didn't affect me none. {tic, tic}) The resonance isn't a real big factor in safety, except that it's easy to make big voltage that way.

[scott wurcer]

FCC Part 15 is a good place to start. No serious commercial product should seriously/deliberately violate it. Hams can and do get involved on both sides of this issue.

ARRLWeb: FCC Part-15 Rules: Unlicensed RF Devices

[Andrew Eckhardt]

In other words, if no one can detect it outside your yard, it's kinda legal to boot.

[thadman]

Originally Posted by Andrew Eckhardt

In other words, if no one can detect it outside your yard, it's kinda legal to boot.

Interesting point. I failed to consider that.

A tesla coil utilizing vacuum tubes could oscillate at an incredibly high frequency. I believe Krytron tubes can theoretically switch in nanoseconds. Are ultra high frequencies hazardous to human health? How would one establish an upper frequency limit for radiation?

Thanks,
Thadman

[bob91343]

Scott has it correctly. FCC is the authority here, in the USA. Its rules and regulations (what's the difference between a rule and a regulation?) specify what levels are permissible.

Yes, hams are supposed to be in compliance, and in fact most of them are. Part 15 is for the general public and part 97 for ham radio specifically.

Both documents are available on line, probably from fcc.gov in the appropriate section.

There is much mass hysteria on this topic. Most of it is worthless.

[Andrew Eckhardt]

I really never thought much about Tesla coils, but I think some are still made with spark gaps as switches, which probably have breakover speeds at ionization that rival any semiconductor or valve. But the oscillation frequency is still determined by the LC circuit. It's only the harmonics that reach into gamma rays (well, not really)

Yes there are national, maybe even international spec limits for any known kind of radiation. I figure you're worried more about health issues than EMI/RFI compliance. I can't tell you the name of them or where to even look. You're good to worry about the frequency. X-rays spook me. Anodes over 30kV give me the heeebeeegeeebees.

[wakibaki]

Virtually all frequencies are regulated by governments worldwide, from ULF submarine communications up to the infrared. Emissions below some levels are insignificant dependent on frequency. Depending on your definition of insignificant...

Beyond that there is the unregulated ultraviolet (although sunbeds are regulated) then regulation takes over again with x-rays, and gamma rays. So the entire electromagnetic spectrum apart from a small band round about the visible light frequencies are regulated.

There is a great deal known about this subject, and a good deal unknown.

The radiation to which you refer and which is damaging is more properly called 'ionizing radiation', which is a subset of frequencies. None of the frequencies involved in radio transmission are ionizing radiation, it's all higher frequency than light. Radio can heat things up though, as in microwaves.

There is also particle radiation. This is the emission of high-speed sub-atomic particles from radioactive substances. Again, this can be hazardous, but it has nothing to do with radio (despite the name radioactive), or any kind electromagnetic wave in the conventional sense.

The average solar (electromagnetic wave) irradiation at the earth's surface (all frequencies) is about 200 watts/square metre, but this is only a ballpark figure, the figure is low at the poles and varies seasonally.

This is not the so-called 'cosmic radiation', which is again particular, although some of these do originate in the sun.

The FCC is the US body responsible for regulation of the radio spectrum, and I guess the AEC for ionising radiations.

Stray emissions from electronics are regulated in Europe on the basis of EMC, or electromagnetic compatibility.

Segments of the band are quiet as the grave by comparison, some are filled with the echoes of tropical thunderstorms.

It's a very difficult subject because it raises a lot of strong feelings around the health issues, partly because these can only really be decided by critical examination of historical data which is currently not exactly plentiful or of unimpeachable provenance and you can't get the data unless you expose some people to some risk and a balance has to be struck involving commercial interests that impinge on us all that at the same time stops somwhere short of unleashing a second Dr. Mengele.

w

[thadman]

Originally Posted by Andrew Eckhardt

I really never thought much about Tesla coils, but I think some are still made with spark gaps as switches, which probably have breakover speeds at ionization that rival any semiconductor or valve. But the oscillation frequency is still determined by the LC circuit. It's only the harmonics that reach into gamma rays (well, not really)

I've considered powering a Tesla Coil by a two-cavity klystron oscillator, which is capable of producing an UHF resonance.

This is why I'm worried about the health issues associated with electromagnetic radiation. I'm not sure how high I can go before dangerous radiation levels are produced. I know the "health" issue is ambiguous, however are there any rules of thumb I could use to determine an upper resonant frequency limit?