« on: Yesterday at 22:35:46 »
Quote from: opportunity
I'm using 400W of microwave energy, standard stuff, launcher, etc, into cable, fed into a coil system around a magnetic rod.I suspect that your magnetic rod is just an idle bystander in this circuit.
Low-frequency magnetic fields (eg 50Hz) travel through iron about 100-1000 times easier than through air or vacuum (we say iron alloys have a relative magnetic permeability μr of 100-1000).
- If you want to carry a lot of magnetic energy in a transformer, you want to ensure that the magnetic field passes through the iron, not through air
- This means that you need an iron core shaped like a circle or rectangle, with no air-gaps. This forms a magnetic circuit.
- In practice, power transformers are often assembled from thin iron sheets shaped like the letter "E" and/or "I".
- So a rod is very inefficient as a power transformer, since most of the magnetic path is through the air.
At high frequencies, the magnetic rod would not carry a magnetic field nearly as well as it does at 50Hz; in fact it is probably worse than a vacuum in that it would exclude the electromagnetic field.
- I suspect that any power transfer in your circuit is just leakage through the air
In some ways, microwaves behave more like water than like 50Hz AC or like 9V DC from a battery.
- You need to carry microwaves in pipes (a "waveguide")
- The microwaves will squirt out through any gaps in the pipe (even quite narrow gaps)
- The microwaves will spray out from the open end of the pipe, and go everywhere
- Anything near a gap in the pipe will get wet (irradiated by microwaves)
- A solid or stranded wire won't carry microwaves much better than a solid or stranded wire will carry water
- If you try and make it turn sharp corners, it is likely to go everywhere
- It is more like plumbing than the familiar electrical wiring
PS: Please clarify "magnetic rod": Is it a:
- Permanent magnet? These are "hard" magnetic materials, and make really poor transformers, even at 50Hz
- Conductive iron rod? The skin effect would prevent microwaves from entering it to any significant depth
- Insulating ferrite rod? 5GHz probably exceeds its maximum frequency
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