Power combining multiple magnetrons

Thread Starter

rfwi

Joined Jan 2, 2021
2
Hi everyone.
I want to create high-powered microwave output by combining multiple magnetrons.
Currently I'm stuck with a problem that simply attaching a second magnetron to a waveguide doesn't work. It seriously increases heating of both magnetrons compared to running my setup with one magnetron attached. Even when second is unpowered, first one heats substantially.
I'm asking you for any advices, articles or books containing information how to properly build waveguide and power combine multiple magnetrons. Preferably something with details on geometry calculation - proper placing of magnetrons, waveguide interconnections, etc.
 

andrewmm

Joined Feb 25, 2011
1,466
@rfwi
under the rules of the forums, and the dangerous nature of what your doing.
I am not certain what help we can give you .

A serious research project on using multiple magnetrons can be found here
https://ieeexplore.ieee.org/document/563168

magnetrons have the "feature" that that phase lock to another power source.
so if you fire two magnetrons at each other, even if they are on slightly different frequencies, they will both end up at the same frequency. Apart from the undesirability of this, ( you want power combining , which if phase locked, will have in phase and anti phase spots, a stirrer needed ) means the pulling is pumping power into each magnetron, causing a reduction in efficiency , QED more heating of the magnetron,

A wave guide multiplexer / joiner is required , such that the microwave energy from one does not feed into the other.
At microwave oven frequencies of around 2.45 GHz ( water resonance frequency I think ) is quiet large.

i am certain you have seen, but if you do a google, you will see multiple examples of "microwave oven guns" made with multiple magnetrons.

but that is definitely outside the forum,
 

bertus

Joined Apr 5, 2008
21,364
Hello,

What is your intention of the use of combining the powers of the magnetrons?
As said, we do not support any dangerous intentions.

Bertus
 

Janis59

Joined Aug 21, 2017
1,332
Yepp, quoted article is very interesting. I have bit interested about high power plasma creation into mulikilowatt scale magnetron system. Firstly, only 2.45 GHz magnetrons are powerful enough, all others except probably the very special military technique are few Watts scale, whilst kitchen magnetron may be found as 0.8..1 kW as 2...2.2 and even 3 kW. The hardest is HV feed of magnetrons. When used a clasic tech of MOT plus voltage doubler, the waveform is pulsed. Thus the plasma will be pulsed thus the noise will be just killing.Therefore DC feed is mandatory but in that case the voltage platoe where generation is happening is extra narrow, for example 20-30 V on the 3 kV bias. By the way, each magnetron have it individual and changing by the time. Thus, the DC/DC SMPS with CV/CC combined regime is only solution. The only suitable wavequide form-factor is WR-430, betcause that other available for this frequency cannot be exploited over about 1/2 kW. Okay, now You have generating monster, transmitting in the LAUNCHER. Launcher have to be screwed onto CIRCULATOR having two outputs. In straightward direction must be attached THREE KNOB TUNER. Exists slightly cheaper two knob tuner, but I cannot to recommend it. So, the backway output of circulator must contain the WATERLOAD aka water cooled high power MW resistor with attached MICROWAVE DIODE on which the simplest scale microammeter will show You the tuning point where back rolling wave is completely cancelled. So, in the output of tuner You set the slightly over 1/4 wavequide with closed end-cup (=mirror) thus where the forward and backward waves are interferring about 1 inch from exit of tuner, the plasma may beat-through the air. With stipulating that it becomes ignited there. Therefore in that point the special double-wall quartz pipe is fixed cooled betwen walls by absolute non-polar coolant called MICROWAVE FLUID (damn expensive). Inside the pipe is tiny argon flow organized and 1-2 MHz HV oscillator driven by current reader. The flame is just brilliant, but the cost of project is between 3 and 5 thousands USD (sorry). Work without tuner will blow the magnetron to the hell flashlikely, and the same without the circulator. If Your power is larger, I dont know ANY producer making those components over 3 kW, thus something must be invented to add the power AFTER the multiple tuners.
 

Janis59

Joined Aug 21, 2017
1,332
PS: if the aim is to kill the drones over territories where they are prohibited, say airports, military etc, then up to 1 km afar the 2.2 kW is enough, You need no more. In that case the open rupor antenna is highly trustable load impedance, thus in this narrow case may omit the circulator and at best case even tuner. Just launcher plus antenna. However such death-rays weapon is highly effective, but far more dangerous as the worst explosive. Probably that is true reason behind why every airport is not equipped with such.
 
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