Talk:Microwave

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[edit] Uncategorized

Lumped-circuit analysis does not apply to microwave circuits because the microwave wavelengths approach the scales of the circuit. Distributed/transmission line analysis must be used instead. I have modified the first paragraph accordingly. Please do not revert.

Fbmyers 04:42, 11 October 2007 (UTC) Frankie Myers, fbm@berkeley.edu

[edit] Needs editing?

"There is also much more bandwidth in the microwave spectrum than in the rest of the radio spectrum."

Does not make any sense - does it mean "free (unallocated) bandwidth" ?

No, higher frequency (shorter wavelength) => more bandwith.

Again, makes no sense. Higher frequency => more *unallocated* bandwidth ?

No, it has nothing to do with allocated bandwidth, its sheer data capacity. Higher frequency = more bandwidth = higher data capacity.

For example, thats why 2.4GHz cordless phones have a clearer signal than 900MHz cordless phones. 2.4GHz is higher frequency than 900MHz, thus 2.4GHz has more bandwidth to transmit more audio data which makes the audio connection sonud clearer. Probably not the best example since the quality of the handset and phoneline are major factors but yapping about 802.11 bandwidth would probably just confuse you more.

Someone needs to clean up ths talk page. Up at the top it says I will pull out a knife after finding your home by your ISP address. Is that possible? Anyway... for some reason I cannot edit what is at the top of the page.

All this microwave talk is fascinating though!

This stuff about bandwidth is kind of misleading. Just because 2.4 GHz is higher than 900 MHz does not mean that there is more bandwidth to transmit a signal. The bandwidth is regulated by the FCC in any kind of commercial application, not by the frequency that is being used. An example will probably explain things best. Suppose you are broadcasting a signal that requires 10 kHz of bandwidth (typical AM radio). At typical AM broadcast frequencies from 540 kHz to 1600 kHz that means you could have (1600-540)/10=106 AM stations all operating at the same time (this is called frequency division multiplexing). If these stations were instead broadcasting in the range of frequencies from 540 MHz to 1600 MHz but still using 10 kHz each you could have (1600000-540000)/10=106000 AM stations all operating at the same time. Modern digital communication systems may require bandwidths of 10s of MHz. If you tried to use frequency division multiplexing to send a signal with a one MHz bandwidth in the AM frequency range you could only send one signal at a time: (1600-540)/1000~1. But in the frequency range from 540 MHz to 1600 MHz you could send over 1000 such signals. I hope it is clear that a 2.4 GHz cell phone does not use 2.4 GHz of bandwidth and that a 900MHz phone does not use 900 MHz of bandwidth.

Right on ! That's what I was talking about, higher frequency need not mean higher bandwidth ! Whenever someone says 2.4GHz, its a 'carrier frequency', there is some 'bandwidth' around the carrier frequency.

I hope I made it a little clearer. If you want a 6 MHz channel for TV, there are only 50 of them below 300 MHz but how many between 300 MHz and, say, 30 GHz? Also, the point about microwaves going through the atmosphere with less interference than lower frequency radio was simply wrong. Altaphon 23:34, 17 April 2007 (UTC)

Need diagrams people don't know where things are in the micro wave! Denden136 01:25, 9 May 2007 (UTC)Denden136

Just a bit of clarification on the discussion that is going on here. One of the people above is saying that the Microwave region of the spectrum has more "bandwidth" than others. The point the person is trying to get across is correct, but the way he/she is trying to get it across is misleading. The first thing to realize is that virtually no traffic that is in the "900 mhz" band or the "2.4 ghz" band actually operates with the specific carrier frequency of 900 mhz or 2400 mhz, respectively. Let's take the example of the 2.4 ghz band, and a common method of communication on that band, 802.11g. 802.11g has 11 channels, each of which uses a nominal amount of the spectrum above and below the primary carrier frequency given to that channel. The sum total of this nominal amount of spectrum "used up" by the channel is called the channel's bandwidth. For example, the nominal frequency of 802.11g CH1 is 2412 mhz, but it has a minimum and maximum frequency of 2401 mhz and 2423 mhz, respectively. This means that each channel in 802.11g uses 22 mhz of bandwidth. This of course is decided by how sensitive your equipment is expected to be and how much interference you will have to deal with. The better your equipment is, the narrower your channel bandwidth can be. It is therefore feasible to have a radio system operating in 900 mhz that can actually fit more information into the same amount of spectrum that say, 802.11g can, however, it is also true that because a system that has a higher base frequency has more "resolution" to it, your modulations can be bigger and more detectible, giving you more possible channels for a given modulation strategy.

Clear as mud? :)

The comment about Ku also being called P band is unattributed. P-band is traditionally a UHF band (225-390 MHz). It would be better if the comment were attributed (I can't say whether the comment is true or false) and that the generally accepted definition of P-band be included in the comment.

—Preceding unsigned comment added by 63.237.78.108 (talk) 14:48, 5 September 2007 (UTC)

[edit] can a microwaves oven be used for sterilisation?

I was just wandering if it kills bacterias and could be used to kill pests like lice or fleas on stuffed toys without adding water. Dominique

My friend says you can put your toothbrush in the microwave to sterilize it when you are sick. YesJesusLovesYou 07:03, 24 February 2007 (UTC)

As far as I know, most bacteria and parasites have water in their bodies, and I really can't imagine them surviving the ordeal of having its innards heating to boiling point. Viruses might be another matter, not being alive, I don't know if they necessarily need to carry water inside their shells. 66.227.95.240 00:40, 30 April 2007 (UTC)

as long as it wont melt you can sterilize it not with the radiation but with the heat if it will melt you would probly be better off boiling it for a few minutes or it might only take a few seconds but im going with a few hours just to be safe--Av1497 16:33, 21 October 2007 (UTC)

[edit] Differing Values

The Pozar reference appears credible, but the values for frequency and wavelength are significantly different than what's commonly taught at the university level, with wavelengths from 10 cm to .001 cm, and frequencies from 3*10^9 to 3*10^12 Hz. Source: http://csep10.phys.utk.edu/astr162/lect/light/spectrum.html Recommend updating the first paragraph and citing a better source. Mugaliens 16:58, 22 August 2006 (UTC)

[edit] Why are they called Microwaves?

This article needs a bit more history. Who called them "microwaves" and why? What parameter is "micro" - the wavelength isn't in the micron range, so what is the "micro"? Please expand the article to explain this stuff.149.167.200.118 05:09, 3 September 2006 (UTC)

[edit] Band links wrong/misleading?

The D, E, and F band links go to pages on radio frequencies. Is something wrong here?

[edit] Form of power?

Ok, if you put a light bulb in a microwave it turns on, couldn't this theroy be used to transport electricity through the air?

Yes. Look up Nikola Tesla. Altaphon 23:08, 17 April 2007 (UTC)

[edit] Turntables

Why do microwaves have turntables? Since the device is heating the whole compartment, do they really do anything? --David Youngberg 14:22, 3 November 2006 (UTC)

David, I believe this is because microwaves ovens do not evenly distribute the emitted microwaves to all areas in the oven. I think this question might be better addressed under the Microwave Oven entry. --Arterion 22:53, 15 November 2006 (UTC)
Actually this is because microwaves do not fill the entire oven. They actually only penetrate into whatever is being cooked by a few centimeters, and so there are large shadow regions in the oven. The turntable simply helps make cooking even. —The preceding unsigned comment was added by 88.108.79.57 (talk) 21:00, 6 February 2007 (UTC).
The generated electromagnetic field has nulls present in the cavity, similar to sines and cosines which make up the "wave". It is possible to place a small object at a certain point in a microwave oven where it will never be touched by the electromagnetic radiation (in the nulls), the turntable minimizes this effect as stated above.
Also, the penetration depth of the microwave is called the "skin depth" and is proportional to the permittivity of whatever it is you are cooking, it is not a constant of the microwave oven itself.

[edit] Microwaves vs. microwave

When talking a bout a term I am under the impression that the plural form is normally used. Should we then rename the article? --Tunheim 10:36, 31 January 2007 (UTC) In this case it's commonly used as an adjective, such as microwave communication. Altaphon 23:09, 17 April 2007 (UTC)

[edit] Misattributed discovery

They were *not* discovered by Max Lazarus.

[edit] Heating different states of matter

Can anyone tell me why it is that water in a gaseous state isn't heated as easily as water in a liquid state. It says it why it doesn't work with frozen water, but a gas is even less dense than a liquid, so wouldn't it more freely rotate. Is that why, because it is to free and their isn't enough friction? It makes sense, but is that true? 74.225.66.28 21:25, 21 February 2007 (UTC)

yes it is true--Av1497 16:36, 21 October 2007 (UTC)

[edit] Frequency Range

The paragraph about vacuum tube based devices doesn't really belong. It seems like useful information so I don't want to just delete it, but it's definitely in the wrong section, if not article. --Jw 14:12, 1 March 2007 (UTC)

[edit] Unsourced Comment

I'm relatively new in editing, but i'm trying to be bold. I am removing "For the proven dangers of microwave ovens visit this page http://www.ghchealth.com/microwave-ovens-the-proven-dangers.html" from Health Effects because it seems like original research and/or unsourced material. (Let me know if this is incorrect some way, I didn't see anything here about it. --Suamme1 18:04, 27 March 2007 (UTC)

Yes. If not on that ground, then on grounds of sloppy language, incongruous placement within the article, and placement in the incorrect article. I should have killed it earlier myself. Welcome to the Wikipedia vigilantes. It's not the most fun job in building the encyclopedia, but it's a necessary one.
Let me make it a bit clearer. External linked sites don't have to conform to the same standards of neutrality, etc of articles. Links may for example go to the personal or official sites of controversial persons, corporations or organizations that may be concerned with promoting and defending their products, views or selves, rather than with balance or reliable sourcing. This idea obviously necessitates judgement calls, and I figure you made the right judgement here. Sometimes a look at other edits by the same account can help understand where they are coming from. Jim.henderson 20:55, 27 March 2007 (UTC)

[edit] Irradiated

Today's effort to disconfuse the different kinds of radiation is a good effort but not entirely successful, as some kinds of EMR ionize while others don't. I hope you can get it right. Jim.henderson 17:42, 15 April 2007 (UTC)

I feel it is only fair to add other sides of the Health Effects discussion. The current presentation seems biased, and needs editing.

[edit] Biased view

I feel it is only fair to add other sides of the Health Effects discussion. The current presentation seems biased, and needs editing.

[edit] Naming

 Please help improve this article or section by expanding it.
Further information might be found on the talk page or at requests for expansion. (July 2007)

Who assigned the name "microwaves"? Was it simply because they are shorter than radio waves? -- Beland 15:40, 22 June 2007 (UTC)

[edit] Accuracy of health effects research

The references to the "microwaves are unhealthy" research are all to the original journal articles. This is insufficient to determine whether or not the conclusions of these papers have been accepted by scientific consensus. Wikipedia's summary also implies that these studies have implications for human health. Is this implication supported or contradicted by scientific consensus, if any? -- Beland 15:47, 22 June 2007 (UTC)

[edit] Radio Spectrum?

Why does the "Radio Spectrum" template appear at the bottom of this page, especially if Microwaves do not even appear within that template? Wouldn't it be more logical to have a "Microwave Spectrum" template, or just remove it entirely? The "Electromagnetic Spectrum" template already suffices. Alex Heinz 02:30, 7 July 2007 (UTC)