Are 5 GHz telephones safe?

[Terry Given]

I do not see the relevance of the copper skin depth here. Are you talking about the excitation of
the what, ions in the brain? I am not sure of that. It's my understand that 10 mm is perhaps enough
to change human metabolism for bone healing and that brain cells don't need much current to be
provoked. In fact picoamperes might do nicely.

the relevance is simply this: electromagnetic theory holds for *ALL*
frequencies, big and small.

I know in the literature you fellows use there is a lot of talk of Cu skin depth. Is copper the
culprit with electromagnetism radiation then? It's interesting but what has this to do with the
power law I was referring to? I was not referring to invasively entering the body.

no, skin effect is a manifestation of electromagnetism. When AC current
flows in a conductor it generates a magnetic field. This magnetic field
cuts through the conductor, affecting the conductors impedance (ie
current is *not* distributed evenly throughout the conductor, but is
concentrated at the surface. The skin depth d is the depth into the
surface at which current density has fallen to 1/e ie 37% (just like an
RC time constant). By the time the conductor radius is > 5*d, *all* of
the current flows in that 5*d worth of material - none flows in the
inner bit. high frequency coax is sually built with a hollow center
conductor, for this reason. And skin depth is a function of material
resistivity & permeability, and frequency.

For Cu d = 66mm/sqrt(frequency)

Unfortunately much 50/60Hz design work is done by ignoring these
so-called high frequency effects. They are still there, but the low
frequency requires correspondingly large dimensions before it becomes
significant. Its often ignorable in small transformers, but by the time
you get to 1MVA+ its important all right.

You are talking about 10mm and I have measured the ELF at 100 meters! So this kind of boggles my
poor brain what you are referring to. Aha, 5 GHz is very low invasively then, that is what you are
referring to? Most likely. Nothing stops ELF short of nu-metal, Faraday cages, and so on. Okay, we
are talking at cross purposes but the basic equations are the same, fine.

exactly.

Terry (neither drunk nor trolling)

Thanks, I was worried.

I was what, glad to read that it is the same stuff. This is what I suspected
but I have only personally played with, tested, and messed around with
mostly 60 Hz electromagnetic radiation.

I have used the simple power law of 1/r or 1/r[2]squared or 1/r[3]cubed.

It works. I have also seen that taking two lines I can cancel out the radiation
to a large degree because the phase of the waves do cancel each other out.
You know, the right hand rule in physics. High school stuff.

depends how close you look. If the wires are infinitely thin, and occupy
the exact same space, then cancellation is perfect. But of course they
are not, so it isnt.

As the voltage increases, a host of other effects come into play which
maximise the allowable distance between conductors, which of course
screws up this cancellation.

Another trick is to twist the wires together. The EM field is
directional, so a pair of conductors carrying equal and opposite
currents, with two twists, generates two fields, of opposite direction,
with a center-to-center spacing that of the twists. If this "twist
pitch" is very small compared to a wavelength (which at 50Hz is several
1000km) then the two opposing fields pretty much cancel each other out.

This is not trivial and not what the resident experts and geniuses say BUT
IT IS WHAT THE INDUSTRY HAS DONE TO MINIMIZE THE PROBLEM.

What industry?

Try electric blankets which no longer radiate as they used to.
How? They placed the wires together. It's so simple and safe and effective.
They were ELF generators placed right up against the body.
Not a good idea. And extraordinarily simple to completely well almost completely solve a problem
even if there was not a problem. I forget now. Pregnancies were one of the first indications. Not
getting pregnant, although you all could joke about that, but miscarriages.

Try schools where the children were getting headaches.
An engineer comes in and balances the fields by making sure the neutrals are done correctly.
This actually happened. Nothing complicated. Someone had separated the wires in the walls
unnecessarily when building the school. Just a case history that always stuck in my memory. An
electrician actually, not an engineer, just balanced the neutrals, not even knowing any of this
stuff.

And another thing that is not so funny are the blood disorders on those who work on high power
lines. Yes, electrocution is the first job danger. But the second are the medical issues which
Washington State once studied in detail, yes? You all should know about that.

I do not see why Maxwell has to be brought in here, but if you can direct me to a source, then
fine.
It's a simple power law.

in a trivial case yes. As others have mentioned though, it can get a lot
more complex depending on the adjacent materials & geometries.

I don't see what the fuss is about except what? Solutions should be as simple as they can be until
they are not correct.

ELF and what you all are discussing may follow the same laws, but the health problems are quite
different since ELF penetrates. I guess we were talking at cross purposes.

There has been some interesting work on the effects of low power EM
radiation on proteins and DNA.

As Roger Penrose pointed out, it's amazing that humans ever understand anything anyone else says,
especially when I chime in

<snort>

Cheers
Terry

 

[Rich Grise]

I'm always out of line but I was not denigrating Mr. Woodgate. I was just bringing up the place
where what he said was not true.

The problem is, what he said _is_ true, and your changing the subject in
an effort to make him wrong - or maybe call it "using a different kind of
equipment to refute his statements" is at best marginal, and at worst
fraudulent.

Of course you get different numbers with a magnetometer than you get with
a field strength meter! They're measuring different things!

You're out of line measuring something different from what he is
measuring, and then claiming he's wrong because your numbers don't
match.

That's the same kind of insidious weaseling that got antismokerism
installed as the new national religion.

Thanks,
Rich

 

[Treeline]

The problem is, what he said _is_ true, and your changing the subject in
an effort to make him wrong - or maybe call it "using a different kind of
equipment to refute his statements" is at best marginal, and at worst
fraudulent.

What he said is not true for "ALL" and that's what I was bitching about.
It's not true for ELF which does follow the simple power law because
ELF follows anything. You can't stop ELF. It's like the current administration.
What a great pun, if I may say so.

So I stand behind my original assertion.

Let me give you an anecdote. Mr. Woodgate is a revered fellow.
So is Albert Einstein, so here this goes:

One time Wolfgang Pauli went to the blackboard and said:
"What Einstein says is not so stupid..."

What that has to do with the power law is well empowering

Of course you get different numbers with a magnetometer than you get with
a field strength meter! They're measuring different things!

Like what? Clue me in, that's why I post to the internet.

What's the different between my measuring the milliGauss of an ELF field
and whatever you measure with your field strength meters?

Are you sure it's not the same thing, just a different frequency?

I am measuring the 60 Hz field in terms of magnetism because that is what the meter converts it to
but it is a field measurement. I am really measuring the 60 Hz emanations, discharges, effusions,
et cetera. I am calling it milliGauss because that is what the meter says but it's really measuring
the 60 Hz field.

Now what does your field meter measure and how? I could look this up on the internet but forgive
me. It's snowed out and I have to go and make track in the snow.

Chew on that while you think up more aspersions to cast upon me.

If I'm wrong, then give it to me logically. You're using ad hominem arguments.
That won't work with me. Whoever said I was human?

 

[Treeline]

no, skin effect is a manifestation of electromagnetism. When AC current
flows in a conductor it generates a magnetic field. This magnetic field
cuts through the conductor, affecting the conductors impedance (ie
current is *not* distributed evenly throughout the conductor, but is
concentrated at the surface. The skin depth d is the depth into the
surface at which current density has fallen to 1/e ie 37% (just like an
RC time constant). By the time the conductor radius is > 5*d, *all* of
the current flows in that 5*d worth of material - none flows in the
inner bit. high frequency coax is sually built with a hollow center
conductor, for this reason. And skin depth is a function of material
resistivity & permeability, and frequency.

For Cu d = 66mm/sqrt(frequency)

Unfortunately much 50/60Hz design work is done by ignoring these
so-called high frequency effects. They are still there, but the low
frequency requires correspondingly large dimensions before it becomes
significant. Its often ignorable in small transformers, but by the time
you get to 1MVA+ its important all right.

1MVA+ =?= 1 million+ volt-amps?
how big is that as a transformer? 2 meters? just asking.
thanks for the explanation. explains why 250 mA can kill and will skim across the body, if i
understood you correctly? well, it shorts out the heart's rhythms but i wondered why it skimmed
across the body if one was not careful, and across the heart is a big no-no.

depends how close you look. If the wires are infinitely thin, and occupy
the exact same space, then cancellation is perfect. But of course they
are not, so it isnt.

As the voltage increases, a host of other effects come into play which
maximise the allowable distance between conductors, which of course
screws up this cancellation.

Another trick is to twist the wires together. The EM field is
directional, so a pair of conductors carrying equal and opposite
currents, with two twists, generates two fields, of opposite direction,
with a center-to-center spacing that of the twists. If this "twist
pitch" is very small compared to a wavelength (which at 50Hz is several
1000km) then the two opposing fields pretty much cancel each other out.

wonderful, wonderful, where were you when i had this problem:

measuring brain waves, let's say, mostly around 10 Hz, really 6 to around 20 Hz

the wires at the time are not shielded, for various reasons at that time
the wires are about 2 meters in length
the wires are stranded and thin and again, not shielded

how many twists would you have suggested based on what you wrote above?

the current is probably picoamperes and the volts are maybe 10 millionths of 1 volt
i was measuring only volts, really, microvolts
and also computing frequencies and phase angle octants with discrete FFTs

i just twisted the wires as comfortable as i could, around 1 twist every couple inches or so?
i would braid the wires as i used to braid things like a child, must be still a child for i found
this very easy to do if there were only 3 wires

now if there were over 24 wires, we have a problem but that's for another post
then we might need a thicker, shielded-grounded cable conduit

the simple case, 1 signal wire, 1 reference, 1 ground for the 3 wires of 2 meters in length,
braided

but what would have been ideal to get rid of 60 Hz noise? how many twists in 2 meters would you
reckon? it was a problem. we had filters and filters but what a PITA.

There has been some interesting work on the effects of low power EM
radiation on proteins and DNA.

Recent work too? I recall first reading about this when Wertheimer and Leeper first published their
stuff which caused a wild reaction. She was a student of Becker, the fellow who lost his lab
because he kept the USA Department of Navy from wiring up Wisconsin with ELF, presumably to look
for USSR missiles and stuff. Becker wrote _The Body Electric_ I mentioned previously.

I think some fellows in Italy did the very first lab experiment showing ELF could affect human
cells.

But when I read the actual studies, it seemed so small. Granted that you could double the rates of
leukemia if you lived within 200 meters of 128,000 KVA or more wires, that is, within a 2+ mG
field, but that was from 2 to 4 cases per 100,000. That just did not get me all worked up. Too bad.
The headlines were terrific and the response, awful, just full of rhetoric and counter-rhetoric!

Even if statistically significant, practically it did not seem especially powerful. Now if it made
you depressed, well, those who have to live near high-powered lines might be depressed as though
who have to live near railroad tracks. In any case, I moved away from high-powered milliGauss
fields but I became more depressed! Maybe it was self-medicating.

Gets complicated, yes?

<snort>

Cheers
Terry

getting a cold? snort

 

[Don Klipstein]

Err, you're so far off that it's ridiculous.
Microwaves operate on 2.45 (or is it 54) GHz.
3*10^8m/s /2*10^14Hz = 1.5*10^-6m, or what's commonly called infra-red.
(treble the frequency and you get green)

Microwaves operate at 2.4 or so GHz. 2.4 GHz is a popular frequency for
cordless phones.
Other popular frequencies for cordless phones range from a bit under a
GHz to a few GHz but less than 10. Some may be only a few hundred MHz.

- Don Klipstein ([email protected])

 

[Terry Given]

1MVA+ =?= 1 million+ volt-amps?
yep

how big is that as a transformer? 2 meters? just asking.

not very. perhaps 1.5m x 1.5m x 1.5m

thanks for the explanation. explains why 250 mA can kill and will skim across the body, if i
understood you correctly? well, it shorts out the heart's rhythms but i wondered why it skimmed
across the body if one was not careful, and across the heart is a big no-no.

thats pretty much it (he says, well outside his area of understanding.
still, never let that stop me before...)

wonderful, wonderful, where were you when i had this problem:

measuring brain waves, let's say, mostly around 10 Hz, really 6 to around 20 Hz

the wires at the time are not shielded, for various reasons at that time
the wires are about 2 meters in length
the wires are stranded and thin and again, not shielded

how many twists would you have suggested based on what you wrote above?

the tighter the twist, the better the cancellation. BUT inter-wire
capacitance goes up, as does cable length and hence resistivity. most
cables require a bend radius about 10x cable diameter to prevent
insulation creep & hence degradation/failure. look at a piece of CAT5 -
about one twist per centimetre for 10mbps/100mbps.

the current is probably picoamperes and the volts are maybe 10 millionths of 1 volt
i was measuring only volts, really, microvolts
and also computing frequencies and phase angle octants with discrete FFTs

i just twisted the wires as comfortable as i could, around 1 twist every couple inches or so?
i would braid the wires as i used to braid things like a child, must be still a child for i found
this very easy to do if there were only 3 wires

to attenuate 50/60Hz (differential mode) this would be just fine. dont
forget common-mode noise though.

now if there were over 24 wires, we have a problem but that's for another post
then we might need a thicker, shielded-grounded cable conduit

the simple case, 1 signal wire, 1 reference, 1 ground for the 3 wires of 2 meters in length,
braided

but what would have been ideal to get rid of 60 Hz noise? how many twists in 2 meters would you
reckon? it was a problem. we had filters and filters but what a PITA.

I invariably use CAT5 cable, its cheap and comes pre-twisted. STP is
real handy stuff...

Recent work too? I recall first reading about this when Wertheimer and Leeper first published their
stuff which caused a wild reaction. She was a student of Becker, the fellow who lost his lab
because he kept the USA Department of Navy from wiring up Wisconsin with ELF, presumably to look
for USSR missiles and stuff. Becker wrote _The Body Electric_ I mentioned previously.

I recall reading a few years back (New Scientist IIRC) about an
experiment showing proteins lining up under the influence of an EM
field. ditto with gene expression. Mostly I think it shows that the
"heating is the problem, not enough energy = no problem" argument is no
longer valid.

I think some fellows in Italy did the very first lab experiment showing ELF could affect human
cells.

But when I read the actual studies, it seemed so small. Granted that you could double the rates of
leukemia if you lived within 200 meters of 128,000 KVA or more wires, that is, within a 2+ mG
field, but that was from 2 to 4 cases per 100,000. That just did not get me all worked up. Too bad.
The headlines were terrific and the response, awful, just full of rhetoric and counter-rhetoric!

these are trivial compared to a recent study on the leukemia rates of
children living near gas stations - 11x to 15x or so.

years ago a buddy of mine was in the NZ army engineering corps, and led
a study on the health effects of radar installations. They went through
the medical records of all NZ soldiers, and found no correlations at
all. They also found no 65 year old armourers, and painters didnt make
it past 70. Conclusion: bugger EM fields, stay the hell away from nasty
chemicals.

Even if statistically significant, practically it did not seem especially powerful. Now if it made
you depressed, well, those who have to live near high-powered lines might be depressed as though
who have to live near railroad tracks. In any case, I moved away from high-powered milliGauss
fields but I became more depressed! Maybe it was self-medicating.

Gets complicated, yes?




getting a cold? snort

no, a gram of coke

Cheers
Terry

 

[John Woodgate]

I read in sci.electronics.design that Michael A. Terrell

Yes, the microwave ovens were there first!

Information from the IEC:

The new International Standard IEC 62209-1 was developed jointly by the
IEC, by the European Committee for Electrotechnical Standardization
(CENELEC) and by the IEEE, who worked together informally through common
membership in various technical committees. This is the first of a
multi-part series of standards and it covers devices, such as mobile
phones, with a frequency range of 300 MHz to 3 GHz.

This is about measuring SAR by a method compatible with both European
and US exposure provisions.