Magnatrons and Black Holes (Oh, do behave!)

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cuffs054

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I'm bored again so I thought I would share fun stuff with y'all.
First up. Are all magnatron tubes basically the same size or can they be built to any size. Along with that, if you take a maggy out of a 1K microwave and put it into a 2K microwave will it put out 1 or 2K. In other words are output ratings of ovens reliant on the power supply or size of tube?
Ah, the mysterious black holes. Assuming they do exist sucking cosmic stuff in like a five year old on his last piece of pissgetty do they ever get full? If full what are we left with, a giant black ball with ultra dense gravity? Does it sit where it was and burp or move around the galaxy perhaps farting out old planets?
A dream trip for me would be going to see the CERN LHC. Lets say the boys do succeed in creating a Higs Bosan, what the hell are they going to do with it? Is it going to happy in it's magnetic tube or will it long to go create a new world?
As you can see, these are important questions to someone with too much time on their hands. I finally gave up my quest to get an answer to my half life of elements query. Except for the blood and the night time issue being a vampire and live forever could be interesting.
And then there is the "light year" issue that I find hard to believe. So much time so few useful things to think about.
Talk amongst yourselves.
 
The latest explanation I have seen about black holes is that they are like huge doughnuts, sucking in at one end and spewing out new star material from the other. Inside is like a Vitamix that recombines stuff.
 
Cuff's,

going back a few decades, a friend of mine with a unique sense of humor brought over a video to watch once. The title was "everything but the kitchen sink" Oh behave!!
 
Magnetron tubes are available in many diffrent types-they weren't always used to cook food-original use was in radar transmitters.Have seen some VERY large ones that were used in radars.And their magnets suck away any magnetic tools brought with a foot or so of it-Tools used to service these were non-magnetic.
Black holes are considered areas in space with a VERY powerful gravitional feild-so powerful in fact that even LIGHT cannot escape the feild-hence the name "Black Hole"If you are in space-----STAY AWAY-WELL AWAY-once you get caught in its gravitional feild-no escape!!!You then go thru the outer space "Vitamix"!
 
A magnetron tube looked at by itself will come in many variations. The device itself will set the operating frequency it oscillates at as well as the limits of how much power it can generate and be safe thermally. While a magnetron is fairly efficient at turning DC power into RF energy, they still turn about 30% of the power into heat which the tube must dissipate without incurring damage.

Commercial magnetrons will range from about 900Mhz to ~6Ghz and they usually are used for power generation in the ISM 'heating' frequency bands. The FCC set up these ranges of frequencies for Industrial, Scientific and Medical use knowing that high power RF generated for heating, or imaging or sputtering etc would make communications use of the ranges useless. The design of the magnetron and its internal physical sizes will set the frequency. Our common cooking ovens today all use 2.45Ghz at the frequency.

Output power is largely dependent on the power supply voltage and the current that can be delivered to the device. A bigger magnetron can dissipate more heat but run at lover drive voltage it won't make more power. Run too much input power into a small tube and it will make more power for a time.

While the magnetron is designed to generate the RF at a designed frequency, they aren't really very frequency stable. Temperature, power levels, loading etc can cause the operating frequency to drift around a bit. While this doesn't alter heating use, it adds limitations for radio communications and RADAR usage where the receiver needs an accurate transmitter frequency. As with other high power RF applications, once thought to always need a vacuum tube, solid state devices are becoming more popular at microwave frequencies. But for making a ton of RF for heating for low cost, magnetrons still rule the roost.
 
Has anyone seen pictures of the Russian scientist that put his head into a proton (photon?) beam. The only one I've seen is a left profile. It would be interesting to see a frontal view. Tolivac mentioned the large tube used in radar etc. Would you feel anything if you stood close to a large radar unit? I wonder what it would feel like?
 
At my workplace we used to have a few guys that were in the Navy and Coast Guard.They used to work on the ship radars and shore radars.You could feel "warmth" as the microwave radar heats you-or it could KILL you-cooked internally.While the ships were underway and everything was routine some of the personell would try to suntan on the radar antenna platforms on the ship-two big hazards while the antenna is rotating and radiating-the energy and getting pushed off by the rotating antenna structure-it has VERY high torque.Some tried using waveguides as chin up bars.BAD IDEA!Magnetron tubes need to have PULSED DC so as to make their internal resonant cavity structures "ring" therefore oscillate.The pulse modulator of the radar has a very large gas or high vacuum triode-tetrode tube running at up to 100Kv to generate the pulses.The whole modulator is often enclosed in an oil filled tank.And the PM tube is run in leaded enclosures to protect operators from X-Rays.Same with some of those large magnetrons.
I don't think sticking your head in ANY high energy beam is a good idea-suprized we didn't have to fill out a fatality form here!Also a rule--unwitten-NEVER look into a waveguide!!!!!At very least RF burn-at worst-DEATH!!Only way I would "look" into this is if the RF source is locked out and I have the key!This is a hazard for Radar techs,UHF TV transmitter techs.For the microwave oven-the half wave voltage doubler makes a DC pulse enough to make the magnetron oscillate.A steady DC would not be effective.
 
Tolivac, I always enjoy your posts, you seem to have some neat stuff to work around. Do you have to wear dilectric gloves, boots, etc. Going in another direction, could micro waves be used to heat water or for hydronic heating?
 
Microwaves for heating water

Microwaves are used for heating water all the time. They are fast and convenient for making soup or tea. But bear in mind that a magnetron itself is only about 70% efficient at turning electricity into RF energy (there will be some inefficiency in the power supply too). So the idea of bulk heating of water for climate control etc is less then desirable. Compare a magnetron to simple resistance electric heating, which is essentially 100% efficient so it isn't viable to use microwaves to heat with large scale.

One other statement that a magnetron needs pulsed DC to oscillate isn't correct, a magnetron will start fine with pure DC also. Random internal electron movement will cause it it quickly break into oscillation. Most microwave ovens don't have well filtered high voltage supplies but that is because the AC ripple on the DC line doesn't hurt anything and buying a bigger filter cap costs $$. The Panasonic Inverter power supply I rebuilt a while back has a fairly clean DC voltage to the magnetron.

A RADAR will pulse the magnetron for an entirely different reason, so that they can coax insane amounts of power out of the poor thing without exceeding it's steady state thermal capacity :)
 
I believe that they throttle the Inverter voltage to reduce the RF output, they don't appear to pulse the way traditional transformer/triac microwaves do.

I had planned on messing with one of those ovens at some point to measure the DC input voltage/current to the magnetron vs measured RF output. Alas I haven't had the time. It would be interesting though!

Internal photos of one of the Panasonic ovens I repaired here

http://www.automaticwasher.org/cgi-bin/TD/TD-VIEWTHREAD.cgi?43694
 
Yes,the DC input to a magnetron has to be pulsed-tried this myself-steady DC only generates radiation when its first applied,then when turned off.If its pulsed,or has high ripple voltages-as in a microwave oven-then the tube generates energy.I experimented with an old microwave oven tube and a small radar one-same results.I always thought DC would work-but doesn't try it if you have a scrap magnetron lying around-you will see!The magnetron in a microwave oven is "pulsed" with the high ripple voltage content voltage doubler power supply.The invertor power supply will supply a pulsed output to the magnetron-just at a higher frequency The invertor powerf unit has variable output-hence variable output power from the magnetron.-but the results are the same.The Navy and Coast Guard guys said the same thing-that was what prompted me to try it.
 
Rex - I find zero information anywhere that states a magnetron needs an interrupted DC supply to make it oscillate. If this were the case surely one of the half dozen magnetron data sheets I have just read would have called out what the input waveform would need to be to make it work. If you could point me to any information to the contrary I would welcome it. Please forgive my skepticism, I'm not trying to be contentious, but it just doesn't jive with what I have seen.

This page has a very good explanation of how a cavity magnetron functions.

http://www.radartutorial.eu/08.transmitters/Magnetron.en.html

Under the Transient Oscillation paragraph they describe how the tube starts oscillating, no mention of the need for any external excitation from power supply variations.

Cuffs - Are you asking if the Panasonic Inverter pulses the magnetron for power level variation? The answer to that is no, it is a variable DC voltage. There is likely some ripple due to less then perfect filtering and regulation, but this is unintentional, and I contend unnecessary for the oven to function.
 
Rex/Tolivac

One question I always had and never found out is what kind of radio station do you work at? Is it a Rock, Talk, News, or NPR station? I'd like to know where to tune in.

Oh, and microwave exposure happens in the Air Force too, when my brother was in the AF, he marshalled aircraft and often was "zapped" by their radar. It's one reason why today, he has some issues (that are service connected because of this).
 
 
Informative but the editing and pace is too fast, same as movies & TV nowadays (sound and image bites).  I'd have to watch it 10 times to catch all the details.  Aging is apparently dulling my head.
 
Aging is apparently dulling my head.

We should start a club!

I blame some of it on the Internet. With a constant barrage of emails, texts, looking stuff up etc. attention spans have gone to nothing. I have trouble sitting to read for any period of time now.

I want my pre-Internet brain back...
 
Phil:In the magnetron tube description you link to-they don't really mention specifically WHAT sort of power supply the magnetron actually runs on.Just know with microwave ovens its high ripple DC that comes from a half wave votage doubler-and in radar transmitters its the output of the pulse modulator that feeds the cathode of the magnetron.The anode side of the tube is grounded of course so it can be connected to the waveguides.The positive pole of the power supply feeding it is grounded.
Robert: I work at the Voice Of America Short Wave transmitter plant in Greenville,NC.This is the last operating VOA transmitter plant in the US.There used to be one in Delano,Ohio,2 in California,and another site in North Carolina.The other site is closed,its towers demolished.There used to be a receive site-"C"site where the program from Washington DC was received on terrestrial microwave or phone lines.That all changed when VOA went to sattelite distribution.C plant was closed in 1995."A" transmitter plant was closed in 2006.Hopefully the last site will remain open.Short wave is used becuase that is a standard to many people in other countries.Unlike Internet,Cell phones,Satellite transmissions the SW broadcasts can enter other countries on the other side of the planet-Target areas try to jam the broadcasts.Keep in mind internet,Cell phone networks adn such can be shut down or content blocked.Satellite recivers are banned in some countries in the Middle East.At this plant they have 3 GE 250Kw transmitters,3 CEMCO 500Kw transmitters-run at 250Kw one amplifier.At one time both 250Kw amps were used to get 500KW-at that poiont the transmitter costs Thusands of dollars per hour to run.Hence the power reduction.The site has two other 500Kw transmitters,run at 250Kw A BBC SW55,and an AEG-Telefunken S4005.This equipment is old,CEMCO transmitters are almost 70yrs old.A testament to Continental Electronics Quality.We keep em playing-parts made by a machine shopand we try to reuse what we can.The GE trasnsmitters are almost 50Yrs old.Designed in the 50's the CEMCO's were designed in the late 30's.The AEG adn BBC transmitters were built in 1985.About 35 yrs old.Parts for these hard to get,too.VOA bought up the last lot of S4005 parts some years ago.I can't give out the frequencies we use here-you can look them up at VOA's website,or get a copy of the World Radio Handbook.Available at large bookstores or libraries.The programs broadcast here go to Cuba,South America,and Africa.The plant could broadcast to anywhere in the world if needed.This night all is quiet-other nights we have to deal with broken tune drive chains,Blown variable vacuum capacitors,birds on transmission lines and so on.We have to be very careful out here-High voltages.The grounding hook is your freind when you have to work on equipment.One man was killed out here years ago.More safety measures have been used here than in the past.
The link to the collider was good-except understanding the operation thru the Rap music made it harder.Like text or spoken voice better.Hate Rap music as well.
 
Rex - Indeed both the commercial oven magnetron as well as a pulsed RADAR magnetron are fed a non-steady DC current. But what I contend is that it is not required to make the tube oscillate.

Both applications have reasons for the pulsed DC input, commercial oven would be cost and RADAR it is to increase power output without exceeding steady state power handling.

But were it required to have the DC input to the tube pulsing in order to get it to oscillate the data sheets for the commercial magnetrons would state this. I contend a magnetron will work fine on low ripple DC, but I'd love to know otherwise if this is the case.
 
Phil: looked at that Radar site some more you linked and they spoke of the most commonly used radar transmitter-the "POTs" type-Pulsed Oscillator transmitter-the magnetron being fed with pulsed DC input.I will have to dig up my RCA tube manuals and look at the Magnetron data-the multi volume RCA manuals had some magnetrons.The other transmitter was a "PAT" type-Power Amplifier Transmitter-this used an Amplitron that would be fed from a lower level RF source and the Amplitron tube amplifies it.Amplitron a Magnetron that has an input--so it could act as an amplifier.Besides radar transmitter they were used in particle accelerators.Klystrons and large power tubes used in those,too.One of our transmitters uses a PA tube that could be used in accelerator applications.
 

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