14
votes
Accepted
What causes loss of power over lifetime of a magnetron?
A Magnetron is a "vacuum tube".
One limit on vacuum tube lifetime is cathode emissivity - the ability to provide electrons for the 'tube' to 'modulate'. Decay mechanisms can be complex but ...
- 152k
11
votes
Can I extend the the antenna of a magnetron with a cable?
Please don't play with magnetrons.
If somebody who knows what they are doing adds a properly matched waveguide to the output of a magnetron, they will be able to guide the energy further away.
If you ...
- 174k
9
votes
How is it possible that emitting electrons create alternating charges in the cavities of a magnetron?
There's an I. I. Rabi story here. During WWII, when the UK shipped their entire radar project to the USA (in order to avoid 1940 bombing, during Battle of Britain,) the prototypes and documents ...
- 11k
8
votes
What causes loss of power over lifetime of a magnetron?
I got one possible reason from this article:
"Each magnetron’s cathode has a special coating to enhance performance. Over time this material is consumed during normal operation."
Although that ...
- 81.4k
7
votes
Connecting microwave oven magnetron with coaxial cable (for a simple plasma torch)
it's not possible. You need to couple out the wave from the cavity, through an appropriately shaped waveguide. You can then convert that waveguide to whatever shape you want as long as you maintain ...
- 100k
6
votes
Accepted
UHF Tesla coil powered by low voltage?
Is it possible to use a 2.4 GHz magnetron as a oscillator for a Tesla coil? The short answer is no, definitely not.
The long answer is... well, long. Note that the following reasons are each, by ...
- 29.3k
6
votes
Connecting microwave oven magnetron with coaxial cable (for a simple plasma torch)
Is it possible? Yes. Can you afford that coax? Probably not, if you can't afford the waveguides. Power RF folks please correct me, but I'd imagine S-band waveguides are a low denominator, if not the ...
4
votes
Drive a magnetron with low power via a CCFL backlight driver
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 ...
- 81.4k
4
votes
Accepted
Can a lower voltage overheat a magnetron?
A cavity magnetron will be overheated by it's cathode heater if there is not sufficient bias voltage to operate correctly. Correct operation depends on thermal electrons being emitted in sufficient ...
- 4,622
4
votes
Can a lower voltage overheat a magnetron?
Magnetrons don't have varnish in them, it is likely to be the transformer. Try measuring it's Temperature, it shouldn't be more than 70 centigrade.
- 258
3
votes
Accepted
How is the frequency in the label behind microwave ovens determined? How could one measure the frequency?
It's worth noting that almost all home microwave ovens must operate within the ~2.4 GHz ISM band as that's the allocation of spectrum where they're allowed to operate for regulatory reasons. If they ...
- 20.6k
3
votes
How to generate microwave band frequencies like 85GHz? Is there a DIY device or parts kit to do this?
Searching for 76 GHz transmitter comes up with many hits, such as the following for a 76-81 GHz device, although it appears to be a sensor:
https://www.ti.com/product/IWR1642
Here is a transmitter for ...
- 7,645
3
votes
Microwave magnetron connections reversable F, FA?
As someone who works on Turbo Chef ovens on a daily basis, I can confirm that reversing the wires does not seem to matter whatsoever. I often come across ovens that have been serviced by someone else ...
- 31
2
votes
Microwave oven: How can I temporarily limit the startup load?
3 recommendations
Test or replace bulk Film cap (test by RLC meter @120Hz)
insert an Inrush Current Limiter (ICL) for rated current eg 120Vac, 10A a) 7 Ω to 0.08 Ω or b) 20 Ω to 0.18 Ω. (Slow ...
- 148k
2
votes
Accepted
Magnetron Working Principle
Can you explain me why when electrons go near the cavities, they start to resonate at microwave frequency?
It's not the electron that resonates. Or the cavity.
It's the electric field produced by ...
- 134k
2
votes
Magnetron Working Principle
I have just read the Wikipedia article as I also know very little about cavity magnetrons. It is much better. What I read from the wiki page the following is wrong/missing from the text above:
The ...
2
votes
Can a lower voltage overheat a magnetron?
Seems unlikely to me. The value of voltage you measure at the magnetron with an ordinary DMM will be a bit suspect because it's half-wave pulsating DC.
Check that the fan that cools the transformer ...
2
votes
Drive a magnetron with low power via a CCFL backlight driver
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)....
- 31
2
votes
Microwave Turntable Absorption
Microwave turntable are designed to absorb as little microwave energy as reasonably possible. The mini that I have seen made of glass but there probably other suitable materials.
When operating an ...
- 152k
2
votes
Is a microwave's cooking cavity of particular dimensions according to the characteristics of the input microwave feed?
I would think that the dimensions of the oven were engineered to match the magnetron Output impedance for maximum efficiency or transfer of power therefore minimizing standing waves or power reflected ...
- 21
2
votes
Accepted
Is a microwave's cooking cavity of particular dimensions according to the characteristics of the input microwave feed?
A domestic microwave oven's cavity is multimode. That means it fits many wavelengths across its major dimensions, so it's fairly unpredictable which modes will carry most energy. Once the turntable ...
- 174k
2
votes
How is the frequency in the label behind microwave ovens determined? How could one measure the frequency?
The people who design microwave ovens refer to the specifications of the magnetron.
For example, this Toshiba magnetron has an output frequency of 2450 +/-30MHz.
Some magnetrons are (mechanically) ...
2
votes
How to generate microwave band frequencies like 85GHz? Is there a DIY device or parts kit to do this?
For such a high frequency and relatively high power you would need to use a device called magnetron, similar to the one found in microwave ovens, but that would require high voltages which even ...
- 7,368
2
votes
Power supply for 9.4 GHz magnetron
A general scheme could be as follows:
Leafing through the text published at the beginning of the last century: "Introduction to Radar Systems" by SKOLNIK - Publisher McGraw - Hill, I found ...
- 2,215
2
votes
Power supply for 9.4 GHz magnetron
You can do this with a switch such as a thyratron or solid-state equivalent, a transformer and a pulse-forming network.
A paper showing the detailed design of the pulse-forming network (from which ...
2
votes
Microwave magnetron connections reversable F, FA?
I am yet to disassemble a magnetron and see weither the cathode has direct or indirect heating.
On the other hand, it doesn't matter much.
If it has indirect heating, the one side (probably the FA one)...
- 9,686
1
vote
Accepted
What dictates the current drawn by a magnetron's anode?
What dictates this current to the anode, 300mA?
and
What is the relationship with the output power?
Once the magnetron starts resonating, it emits an EM wave of a certain power, that power is the ...
- 473k
1
vote
Accepted
Understand magnetron monitor circuit
All the current through the magnetron goes through that HV capacitor. The average current through the capacitor is zero (or it would build up voltage until something broke). So the same current that ...
Only top scored, non community-wiki answers of a minimum length are eligible