Magnatrons and Black Holes (Oh, do behave!)

[kb0nes]

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.

 

[neptunebob]

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).

 

[vacerator]

Don't

watch the food cook!

 

[cuffs054]

KB, my head is swimming now! Maybe I should have thought of a different question!

 

[tomoldcars]

Large Hadron Collider explained

Or how science moves.

http://https//www.youtube.com/watch?v=f6aU-wFSqt0

 

[cuffs054]

Yo Bro, that's smokin'

 

[DADoES]

 
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.

 

[kb0nes]

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...

 

[tolivac]

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.

 

[kb0nes]

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.

 

[tolivac]

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,tone of our transmitters uses a PA tube that could be used in accelerator applications.