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Bjørn

Sat Oct 06 2007, 03:49PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Rather, can anyone answer my question about microwave ovens? Why 2,45Ghz?

It seems like it is a combination of being an available frequency and practicality.

Shaun

Sat Oct 06 2007, 04:01PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

"The hotel called him to investigate it, and he measured no output from the antennas. He thought the phone company was just trying to pull one over on him, so he called them and had a tech come out, sure enough all the racks inside were empty."

The placebo effect in action!

As for the microwave oven frequency, I doubt they actually decided to set the frequency at 2.45 GHz, rather they probably just decided to make consumer magnetrons a standard size, and at the particular size they picked, the frequency just happened to be 2.45 GHz. That frequency is also supposed to drift a lot, depending on its surroundings, temperature, etc. which means frequency can't be that important or else it would have been made to be stay much more reliably on that one frequency.

Zum Beispiel

Sat Oct 06 2007, 04:37PM

Registered Member #514 Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295

When people start talking about the dangers of eletric fields I just say that with all the eletric fields in use since the the late 19th century, we would have noticed if there were any (serious) effects.

Like if mobile phones really were that dangerous, I doubt we would still be using them. Like every 10th person using a mobile phone gets cancer from it, I think we would notice.

If there are 1000 people working in a building, it is relatively likely that 7 of them get cancer. A transmitter tower on the buildings roof makes no difference.

Chris Russell

Sat Oct 06 2007, 07:11PM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Correlation does not imply causation so answer is *you don't know*, and you can't say it doesn't just from lack of observational evidence, you need *evidence* which proves it doesn't - that's how I get poked most of time.

This is a common logical fallacy, and lies at the root of many a tinfoil hatter's rantings -- it is exceedingly difficult to prove a negative. One cannot say "X must be true because there is no concrete proof that X is false." If someone asks you to prove that EM radiation does not cause cancer, you might demonstrate the error by asking them to first prove there's no such thing as leprechauns.

You simply cannot prove that EM radiation does not cause cancer through some undefined, possibly unknown mechanism. The best you can hope to do is provide counter-examples where cancer rates do not correlate to EM exposure. Here in the US, there are several sites that are home to little-known VLF transmitters, with radiated power well up into the hundreds of kilowatts. If 50/60Hz radiation is truly that harmful, one would have to expect to see amazing cancer rates clustered around the transmitter. For higher frequencies, try having a look at cancer statistics near some of the other extremely high powered military trasmitters, such as PAVE PAWS, which generate nearly half a megawatt of power at frequencies not much lower than cell phones. Again, if EM radiation causes cancer, one would expect to see a deadly swath of cancer appear in the direction the transmitter is usually aimed.

So, I nowhere really found why is frequency of 2450Mhz specifically used in ovens? Few Ghz up or down should make nothing special.

It really is nothing special. The resonance myth is just something that has been passed along over and over by people who don't bother verifying their information. Originally, microwave ovens operated in the 900MHz range. Later, it just so happened that 2.5GHz was available, and microwave ovens started operating in that range. One reason for the change might have been to allow the resonant cavities inside magnetrons to be made smaller, leading to a more compact microwave oven. As an interesting aside, since water absorbs RF more and more as frequency increases (up to 20GHz or so), the newer 2.5GHz ovens tend to cook large food items less evenly than the old 900MHz models -- the RF cannot penetrate the food as deeply. Not really a big issue unless you were microwaving a turkey or something. I suppose a 15Ghz microwave oven could be made that would burn the outside of your food, while leaving the inside cold.

You might also have a look at the chart here:

It illustrates how well water vapor absorbs microwaves at various frequencies.

Tesladownunder

Sun Oct 07 2007, 01:54AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Here is a little EM radiation meter I have.
I think specs were vague and a little in the tone of protecting your health.
Shown here with a magnet and then moving so responds to low Hz fields. In fact it will even turn on by shaking outside. Possibly earths magfield?
Last pic thows a mains cord with perhaps 20W load. Doesn't register (usually) with no load.

In regard to the RMIT/Cellphone/HV pylons causing leukemia/brain tumours etc. There are millions of opportunities statistically to make associations. It is hard to do double blinded randomised trials in this are so results will always be suspect. Usually only the positive studies get to the news. Negative studies may be less likely to be published and end up as a poster presentation in some obscure conference.
At present my offhand reading suggests to me that the risks of these are less than a few moments in a car on a public road.

I wonder if the good professor smokes or lives around smokers?

TDU

Marko

Sun Oct 07 2007, 12:48PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Guys, thanks a lot for these replies.

bjorn wrote ...
One of the properties of truly random events is that people will recognise clusters in the events, that means that normal people are not able to judge the statistical difference between a real cluster and an imagined one.

How true that is. As well as people will recognize faces and pictures on TV screen 'snow' or voices on acoustic white noise.

This probably isn't much different at all.

BTW;

Chris Russell wrote ...
Here in the US, there are several sites that are home to little-known VLF transmitters, with radiated power well up into the hundreds of kilowatts. If 50/60Hz radiation is truly that harmful, one would have to expect to see amazing cancer rates clustered around the transmitter. For higher frequencies, try having a look at cancer statistics near some of the other extremely high powered military transmitters, such as PAVE PAWS, which generate nearly half a megawatt of power at frequencies not much lower than cell phones. Again, if EM radiation causes cancer, one would expect to see a deadly swath of cancer appear in the direction the transmitter is usually aimed.

I was just looking around for cancer rate maps and comparisons like this

Cancer is, not surprisingly, most common in heavily urban areas, *and* you'll find largest number of GSM transmitters and overhead wiring there to. So I don't know how could one easily prove anything, especially when I have no clue about the potentially damaging mechanism, unlike the case with radon.

Where could I find locations of at least those major (100kW >) microwave transmitters?

Making a comparison map like that would be the least thing I can do.

This is a common logical fallacy, and lies at the root of many a tinfoil hatter's rantings -- it is exceedingly difficult to prove a negative. One cannot say "X must be true because there is no concrete proof that X is false." If someone asks you to prove that EM radiation does not cause cancer, you might demonstrate the error by asking them to first prove there's no such thing as leprechauns.

Yeah, but most people will be much less paranoid about existence of leprechauns than their health.

As I think it makes no sense trying to fight this and all I can do is keep mouth shut;

In regard to the RMIT/Cellphone/HV pylons causing leukemia/brain tumours etc. There are millions of opportunities statistically to make associations. It is hard to do double blinded randomized trials in this are so results will always be suspect. Usually only the positive studies get to the news. Negative studies may be less likely to be published and end up as a poster presentation in some obscure conference.

I can find and sum up all the negative studies I come after, but I will be retaliated by even bigger bunch of positive studies, no matter if they involve lies about microwave ovens or orgone energy - probably all that matters is that word 'science' is found in the article.

Nobody appears to have made enough large-scale double-blind experiment yet.

I don't know everything, these 'scientists' know more, and I should shut up.

PS. As it looks now this thread may belong more to EM radiation than general science, so I'l let Chris/mods to decide if it should be moved.

Marko

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