Click here to go to our main page on heat
Click here to go to our page on microwave auditoy effects (new for November 2018)
Click here to go to our page on the biological effects of electromagnetic radiation
Click here to go to our magnetron page (learn how a magnetron works!)
Click here to go to a page on microwave toilets
Click here to learn about medical applications for microwaves
How to test a microwave oven
The RF & Microwave Research Group (RFM) here does some interesting work on microwave heating, among other things.
http://www.ljmu.ac.uk/BLT/BEST/RFM/
History of Microwave Heating
Is located on this page!
Microwave ovens
On this page we deal with some of the topics of microwave heating. Don't look for any microwave cooking recipes, we all we know is that "bagel bites" taste better when you cook them in a "real" oven!
Heating is the microwave application that most people are familiar with. Often for less than $50, big-box stores will sell you a cheap microwave oven made in China that will heat up yesterday's chili from the inside out, using a magnetron, some waveguide and an antenna, operating at around 2.4 GHz.
Besides cooking, microwave heating has many industrial uses (drying paint or wood products), and medical applications (cell destruction, sometimes used to treat cancer or other illnesses.) There was recent inventor that wanted to develop a waterless toilet that used microwaves to reduce waste to ashes (click here to learn more). You can even use microwave energy to kill bugs that are infesting cereal grains. One huge market for microwave heating is for medical purposes.
Did you ever need to dispose of a CD full of data, perhaps proprietary or classified? Try putting it into the microwave oven for five seconds, then watch the fireworks! Here's a paper that attempts to determine the physics behind the mysterious crop circle patterns that emerge. Some people have too much time on their hands...
Here's a video on using a microwave to "repair" a CD...
Testing a Microwave Oven Part 1
What about that seal on a microwave oven? It seems to keep a lot of people up at night, buying and selling testers in what seems to be a billion dollar junk-science industry. For all we know these devices don't do anything at all, like homeopathy.
A leaky seal in the microwave oven is about the smallest risk in your kitchen, unless you somehow bent the door on the oven so there is a large gap (in which case it probably wouldn't latch and therefore not turn on). Even in bent-door case the only way you would get an injury would be to place your eye near the gap for a substantial time while cooking an entire frozen turkey, if you absorbed enough heat eventually you would get a cataract. Microwaves101 is a limited liability company, keep that in mind when you hire a lawyer and claim we caused you an ocular injury....
There is one "free" way to verify the seal.
If you have wireless in your house, and an ipad (or other netbook), put the ipad in the oven and close the door. Obviously, don't turn on the oven for the remainder of the experiment.... unless you were looking to upgrade your netbook and have archived the data on an external hard drive.
Then try to call the netbook though your home wireless network (tweet yourself or whatever makes sense in the future era that you read these words of wisdom). Your device should not respond. The wireless signal is the same frequency that you cook at, so if it is blocked one way, it is blocked the other. If anyone wants to do some math to determine the isolation needed to block a cell phone signal, please send it to webmaster@microwaves101.com
You could do the same check with a cell phone, but there is a question of accuracy as the cell phone is at a lower frequency. However, if the cell phone rings in the oven, you have a seal problem.
Microwave April Fool's Day Trick
This has gotta be one of the best microwave April Fool tricks ever, or use it any day of the year... let's say you are visiting your non-technical friends. While you are talking about the need for additional gun controls in the US, you get so excited you need to use the powder room. Find the wireless router and unplug it. Come back through the kitchen, and remark that it is important to check a microwave oven once a year, and when was the last time they checked theirs? Tell them it's simple, grab a one quart pyrex measuring cup (one liter if you are in a country that has good gun controls), fill it and put it in the oven and fire it up on high for two minutes. Then grab their netbook and prop it against the door... tell then if the door was leaking, the netbook wireless feature would pick up the 2.45 GHz signal with its 802.11H wireless card and would receive an instant message from the microwave in the rare case of a bad seal. Be as smarmy as you like, even say "everybody knows that". When the experiment fails to detect a problem, give them the netbook and ask them to go on-line to Microwaves101.com where this experiment is all explained, while you take time out to refresh your beverage. When the netbook browser fails to connect, tell them this has never happened before, and their microwave must be so bad it blew up the wireless front-end of their porn-box. Then tell them "it was and was only a small risk to take, but you and your children's health was worth it, right?" Ask them if they have noticed that their dog seems to have cataracts.... then either come clean or make up an excuse to leave. You can also laugh at them during your next visit when you find out that they bought one of those stupid leak testers...
Microwaves101 Magic Cell Phone Locker
Back to that cell-phone-in-the-oven idea.... how would you like to make a "magic cell phone locker" for your work place, so that no one is distracted by incoming messages while you are pitching some boring slides? Or you own a high-end restaurant where you don't want anyone to be disturbed? Or perhaps you work in a SCIF where cell phones are not allowed and the sleepy guard is getting sick of hearing phones ringing even though he told everyone to turn them off when he asked for them... Get an old microwave oven, cut off the AC cord, and voila, you have the ultimate cell-phone disruption-eliminator. Put a Microwaves101 Magic Cell Phone Locker logo on it, please. We'll let you know when that logo is ready....
Testing a Microwave Oven, Part 2
Ovens use tubes which fail over time, by measuring the temperature rise of a known quantity of water you can determine quite accurately if your 500 watt oven still musters 500 watts. See this site:
http://www.zyra.info/micropwr.htm
We did not check the math. This makes a good science experiment for a junior high classroom.
What is new in microwave heating?
Directed energy weapons (DEW)
The use of high power microwaves as a weapon is limited only by the imagination. USA Today discusses some of the potential uses, including the "pain ray" and another scheme to melt the guidance systems of missiles aimed at aircraft while they are taking off or landing.
One defense contractor has been working for ten years on what they call the Active Denial System, which is a more marketable term than "pain ray". It uses W-band electromagnetic energy focussed into a narrow beam (think about how much antenna gain you get with a meter dish at 94 GHz). So far, defense customers have NOT lined up to buy this, and DARPA has said "Hell, no"! However, one Los Angeles jail has a remote control version for crowd control, thanks to a grant from the Department of Justice.
In spite of the marketing hype and safeguards to turn off the ray after a few seconds, exposure can be extremely dangerous, as it is actually frying your skin. None of the fielded versions permit the operator to continuously illuminate a subject, for good reason. If it fell into the wrong hands, a good hacker could bypass that "problem" pretty quickly no doubt. If you are a terrorist, you might like to get your hands on this to use as an instrument of torture. But the argument is, why bother, when a $0.99 disposable lighter can do the same thing?
The system that has been filed so far is very expensive. The high power is generated by vacuum electronics gyrotron, which requires a cryo-cooler for its high temperature superconductor (HTS) magnet. It takes hours to cool down, so it must be left on all the time. The system drinks a large tank of fuel every day, or it must be plugged into an electrical panel that can provide copious amounts of AC current, like that special GM Volt car outlet that some rich people have in their garage. You can read about the cooler in this paper which you can find by Googling:
Pulse Tube Cryocooler for Rapid Cooldown of a Superconducting Magnet by M.A. Lewis et al.
Below, Rachel Maddow explains the conops of the pain ray:
If you think you might be in a situation where you might be exposed to the pain ray, what can you do to reduce the effect? Wrapping yourself in aluminum foil is not going to work, as any holes in that "armor" are still in for a burn.
Microwaves101 exclusive theory, remember where you read this! If you study different videos of the pain ray in action, you'll see "show-off" people trying to stand in front of the beam as long as they can. The people that can take the beam the longest are invariably old geezers. Is it because they are such a tough old birds and can handle pain? Not really; it is because their skin is dried out and therefore does not have the dissipative properties of normal skin. So if you want to attack a facility that possesses the pain ray, send your oldest, most dried up comrade to get the job done!
What is the future of the pain ray? The initials FMS come to mind... foreign military sales. If your country won't buy it, other less ethical regimes will. Gotta serve the Raytheon stockholders!
Long ago, Raytheon Company's legal department told us never to mention their good name on this web site, or the penalty might include "termination". Gentlemen, that option is no longer available to you.
Variable frequency microwave (VFM)
Did you ever wonder why doesn't someone invent a microwave oven that doesn't need a stupid turntable to prevent hot spots in your potatoes? Well, it has been done, and it is called variable frequency microwave (VFM). Here the microwave energy is frequency hopped every 5 microseconds or so, to that the pattern of energy distribution is randomized. Don't look for this technology under the Christmas tree yet, it is expensive and therefore relegated to industrial applications such thermal processing of semiconductor wafers.
Microwave drill
Here's some info on a "microwave drill" that works by heating the crap out of anything you want to put a hole in (except metal):
http://www.trnmag.com/Stories/2002/103002/Microwave_drill_melts_concrete_103002.html
Microwave auditory effect
This is related to heating caused by microwaves. Dating back to WWII, people have reported being able to "hear" microwaves. The phenomenon has been studied over the years, and was named the Frey Effect, after one researcher, who is in our Microwave Hall of Fame. Learn more about "MAE" here on Microwaves101.