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[EDIT] My real question here is: can a magnetron from a microwave oven be used to output low power microwaves? If so, how can I achieve this? If not, what is a source for low power microwaves? In this context, low power means that I don't intend to output microwaves that are dangerous to a human being.
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Is it feasible/reasonable to drive a microwave oven magnetron from a CCFL backlight driver? From what I've seen, the voltage produced by the CCFL driver should be in the ballpark what a magnetron accepts.
I want to use the radiation for measurements, so I don't need the high power a megnetron would typically produce and a lower power rating makes this feel much safer.

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  • \$\begingroup\$ what is a source for low power microwaves? Actually that question is off topic (shopping question) but I'll give some hints: an RF signal generator, for example: rigolna.com/products/rf-signal-generators Note that these are budget models but can generate a whole range of frequencies. If you want only a single frequency things are much more affordable, take a look at: minicircuits.com/WebStore/Oscillators.html Minicircuits also sell amplifiers that you can use to get to the signal level you need. \$\endgroup\$
    – Bimpelrekkie
    Commented Mar 22, 2020 at 20:16
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    \$\begingroup\$ I'm assuming you're an RF engineer (or learning to be one) otherwise you might be unable to get the result you want from these devices. You need to understand microwaves before being able to work with them. If terms like "characteristic impedance", "signal reflections" and "impedance matching" mean little to you then you have some studying to do. \$\endgroup\$
    – Bimpelrekkie
    Commented Mar 22, 2020 at 20:19
  • \$\begingroup\$ "I want to use the radiation for measurements" - what sort of measurements? How much power do you need? \$\endgroup\$
    – Bruce Abbott
    Commented Mar 22, 2020 at 21:24

3 Answers 3

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If you can somehow get 4 kV out of a CCFL driver it should work. I don't think so!

A magnetron doesn't start conducting until about 3.9 kV, then it conducts heavily like a 4 kV Zener.

The safest way to do it would be to make a power supply by pulsing a car ignition coil, arranged so it puts out a positive voltage to the anode. You will need something like a scope soldering iron transformer for the filament, which takes 3.3 V & about 11 A.

If you want a smooth output, you will need a capacitor rated at more than 4 kV and a string of at least 5 1N4007 diodes as well. Preheat the cathode to limit the voltage before applying the HT.

Put the high voltage on the anode, as the soldering iron transformer insulation is not designed for 4 kV, or use the filament winding of a microwave transformer.

The other option is a 7.5 kV neon sign transformer and a bridge of 4 strings of at least 12 1N4007s (preferably 15, to handle the peak voltage if the cathode is not preheated). Neon sign transformers are rated at o/c voltage & s/c current, &, as far as I was able to find out, a 30 mA transformer produces about 26mA at a tube voltage of 1/2 the transformer o/c voltage, so it will give you about 24.4 mA RMS (about 22 mA average) at 4 kV. Magnetrons normally run at about 300 mA, so it will produce about 1/14 of the normal output power. Keep it away from your eyes though. Check out this advice by Neil_UK on Magnetron, and Microwave - Electrical Engineering Stack to someone else contemplating using a magnetron outside of the oven. It will not only give you a good laugh with his sense of humor, it is very good advice.

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    \$\begingroup\$ 'KV' is kelvin-volt. 'kV' is kilovolt. Capitals matter! \$\endgroup\$
    – Transistor
    Commented Sep 5, 2020 at 12:14
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    \$\begingroup\$ thanks, that answer works way better. there seems to be a lack of guides out there that tell you how to do stuff with these things safely. the DON'T-EVER-DO-IT's aren't helpful. \$\endgroup\$
    – iamnotgoodwithcomputer
    Commented Sep 7, 2020 at 21:09
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Is it feasible/reasonable to drive a microwave oven magnetron from a CCFL backlight driver?

No, magnetrons require a high DC voltage and a CCFL driver will output AC.

Also, a magnetron can't be operated on a lower voltage to get lower power output. A magnetron tube is designed for a certain power output and it will only work at or close to that power output.

I urge you to get a much, much better understanding of how Magnetrons and (high power) RF works before even considering experimenting with this. Any sane Electrical engineer will strongly advise you not to experiment with a magnetron before you have proven your knowledge on the subject.

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  • \$\begingroup\$ The idea was to use the CCFL driver instead of the regular microwave transformer to limit the total power that goes into the system. The voltage levels are very comparable between the two and I could step them up or down with an additional transformer. But I see, how this approach is flawed. Thanks for preventing me from cooking my intestines. \$\endgroup\$
    – iamnotgoodwithcomputer
    Commented Mar 22, 2020 at 15:17
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The CCFL driver will be too weak to drive the magnetron. You have to use a high voltage supply that can deliver more power. Try building up a high power flyback driver (or a similar HV supply >4kV). Then, connect the output to a capacitor (a simple homemade saltwater capacitor will do) and then to the magnetron via a spark gap. Hook everything else up in the configuration of how a microwave oven magnetron is normally connected. The filament supply needs to be one that can deliver at least 4V at 10A and above. You may notice that the set-up that I had is very similar to how a Tesla coil is run. The spark gap can be played around with for numerous effects.

Just make sure that you don't stare directly into the magnetron, and you should be safe. And don't be stupid like me to touch the metal body when the whole thing is running. To make sure you don't kill your magnetron, put a cooling fan on it too. If you don't know if it is working, grab a neon screwdriver and place it NEAR(not on). If it lights up good, you're good to go. JUST NEVER TOUCH THE METAL PARTS. You won't die, but you won't feel good either.

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  • \$\begingroup\$ What is a "salt water capacitor?" Water capacitors require pure water, not salt water. \$\endgroup\$
    – JRE
    Commented Jun 30, 2021 at 6:11
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    \$\begingroup\$ Saltwater used in a bottle. Foil wrapped around the bottle acting as one terminal of the capacitor. The other terminal is made using the saltwater in the bottle. In this case, the dielectric is the plastic bottle itself. Of course, water can be used as the conducting medium too. In the link you show, water is used as the dielectric. That's not what is happening here. \$\endgroup\$
    – Tomiko
    Commented Jul 1, 2021 at 12:10

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