# Producing Alternating current of high Frequency.

1. Dec 4, 2012

### amk_dbz

As the title suggests, how are very high frequency AC produced?
A AC generator must have a limit to the rotation velocity of the coil, mustn't it?
Any help would be appreciated.
Thanks.

2. Dec 4, 2012

### the_emi_guy

How high in frequency are you thinking about?

3. Dec 4, 2012

### Staff: Mentor

You can use electronics to generate everything up to several GHz, and electromagnetic waves (and corresponding transitions in atoms/metals for photons of specific energy) for higher frequencies.

4. Dec 4, 2012

### yungman

Look into electronics, they have crystals, oscillator circuits that generate RF and then amplify the higher current.

5. Dec 4, 2012

### sophiecentaur

The words "Radio Transmitter" come to mind as a possible answer for you. You can buy equipment off the shelf that will give you 250kW at 20MHz or 20kW at 500Mhz. But that's not done with rotating coils.
I'm not sure the highest frequency that has ever been generated with a rotating generator but I believe 400Hz is / was used for the AC supply in aircraft. One reason for using such a (comparatively) high frequency for this application is that motors and transformers can be made a lot lighter than if you use 56/60Hz. I wouldn't be surprised to be told of special rotary equipment having been made to generate tens of kHz or even more, though - before power radio valves were available.
You mention high rotation rates as a possible problem - True but it is possible to have many poles on a rotor, which can produce multiples of the basic rotational frequency. But there will be limits, imposed by the Inductance of this sort of generator (or distribution and load equipment), which would compromise performance.

6. Dec 4, 2012

### amk_dbz

Thank you all for your Help.......In addition to information provided, I found another method to generate high frequency AC, which is to use oscillatory circuits.
Thank you