Magnetron frequency - Page 1
Forum section: electronics / beginners

author: testtube44
author_rank: Regular Contributor
timestamp: September 26, 2018, 10:39:40 pm
content: I have a weird idea, what would happen if you replace a magnetron's magnets with electromagnets and vary the magnetism. Could you change the frequency of the microwaves?

author: drussell
author_rank: Super Contributor
timestamp: September 26, 2018, 10:52:25 pm
content: The frequency is mostly influenced by the physical geometry.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 26, 2018, 11:36:56 pm
content: Buy a YIG.https://en.wikipedia.org/wiki/YIG_sphereYou are on to something!

author: GeoffreyF
author_rank: Regular Contributor
timestamp: October 12, 2018, 01:27:26 pm
content: As others said, the frequency is based on the geometry.The Magnets are big.If you crack the beryllium ceramic insulator while taking a magnetron apart, and you inhale even some dust - you could get berylosis, a fatal disease. With the voltages and energies involved in a Magnetron, if you have to ask, don't. Be thoroughly versed in every single aspect of these devices before you do anything.

author: chris_leyson
author_rank: Super Contributor
timestamp: October 12, 2018, 02:32:23 pm
content: For a standard microwave oven magnetron the anode insulator IS NOT beryllium it's ceramic. I don't know why people people persist with this myth. Read a data sheet for an oven magnetron and there won't be any mention of beryllium. Similarly if it were berylliun there would be a mandatory warning sticker on the magnetron. I work for a company that designs and manufactures microwave ovens so I know what I'm talking about. I've even got some on my desk, in fact a lot of the engineers have one or two lying around, some take the magnets out and one guy cut one in half to show people what the anode block looks like. If anything is going to kill me it won't be the non existant berillium oxide it will be a 4kV inverter and I'm going to make damn sure that doesn't happen. Big high power radar magnetrons, berillium oxide insulator maybe, read the data sheet but little piss ant 1200W ones no. Rant overAnyway, back on topic, some magnetrons have an integral electromagnet to control output power, National YJ1530SP is one examplehttps://www.relltubes.com/filebase/en/src/Datasheets/yj1530sp.pdf. Also, the power spectrum from a magnetron is basically crap, it could easilly be 100MHz wide so it's no good as a signal source, might make a good jammer though. If you want to use a tube try a reflex klystron if you can get one.

author: rsjsouza
author_rank: Super Contributor
timestamp: October 12, 2018, 05:42:36 pm
content: Quote from: chris_leyson on October 12, 2018, 02:32:23 pmOr use them as ray guns (Kreosancomes to mind)

author: chris_leyson
author_rank: Super Contributor
timestamp: October 13, 2018, 12:55:12 am
content: QuoteLOLCavity magnetrons are pretty cool for a tube technology that is nearly 100 years old and if properly matched will achieve 75% efficiency. There is a very good IEEE paper on the history of cavity magnetron developmenthttps://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6735528I've already started collecting my ray gun parts. If I had access to a lathe I would machine it down to the strapped anode block which would make a nice geeky paper weight.

author: german77
author_rank: Regular Contributor
timestamp: October 13, 2018, 01:15:54 am
content: As far as I know magnetrons contains berilyum oxide witch is pretty dangerous it's dust form. I would never use or modify with a lathe.

author: coppice
author_rank: Super Contributor
timestamp: October 13, 2018, 01:29:05 am
content: Quote from: chris_leyson on October 13, 2018, 12:55:12 amMagnetron like devices started appearing not long after the simple triode valve, yet it took over 30 years until the modern cavity magnetron was developed in 1940. I was actually taught about magnetrons by someone who was a research student assisting in that development in Birmingham in 1940.

author: chris_leyson
author_rank: Super Contributor
timestamp: October 13, 2018, 01:40:12 am
content: Quotereally. If in doubt go read the data sheet for the magnetron in question.

author: GeoffreyF
author_rank: Regular Contributor
timestamp: October 13, 2018, 02:00:03 am
content: Not all microwaves use berylium ceramic but many do. There is no reason not to take apart a microwave and see what is going on but to poo poo precautions is irresponsible.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 13, 2018, 04:21:37 am
content: Remember that if you change the operating frequency too far higher or lower, you will start causing illegal radio interference.Domestic microwave ovens operate in the 2.4GHz ISM band, and large industrial microwaves in the 915MHz ISM bandISM = Industrial, Scientific and Medical. There are around a dozen of these frequency spectrum bands where unlicensed use is permitted. The original WiFI, and BlueTooth also operate in the 2.4GHz band. Note that you can't use WiFi or BlueTooth if you are close to a microwave oven. I need to move my kitchen computer farther away from the microwave.Ref:https://en.wikipedia.org/wiki/ISM_band

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 13, 2018, 05:40:01 am
content: AFAIK, BeO is white and Al2O3 is red (colored with Cr2O3, in essence making it ruby ceramic).Tim

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 13, 2018, 06:27:24 am
content: Quote from: german77 on October 13, 2018, 01:15:54 amDid you read the post three above yours?

author: drussell
author_rank: Super Contributor
timestamp: October 13, 2018, 10:22:55 am
content: Quote from: GeoffreyF on October 13, 2018, 02:00:03 amDo you have any evidence to back up this claim?

author: chris_leyson
author_rank: Super Contributor
timestamp: October 13, 2018, 11:53:41 am
content: It's also urban legend that BeO is pink, as far as I know manganese makes the ceramic pink. Eimac also made a few special conduction cooled tubes. For example, 4CS250R BeO conduction cooled, 8873 was designed to be conduction cooled and used a separate BeO block. Then there are huge numbers of RF power transistors and mosfets that use BeO and they have to be treated as chemical or special waste. So it's a case of read the data sheet rather than repeat urban legend.https://www.cpii.com/docs/library/9/Operating%20Hazards%20Sheet.pdfhttp://www.tubecollectors.org/eimac/archives/8873(73).pdf