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Comment by godelmachine | Hacker News Reader

The CPU colloquially called the processor does this. When you feed a program to the CPU, it switches between logic gates (read - transistors turning on and off), to process the program. As the processing elements switch between power levels of 0 and 1 (0V & 5V / 0V & 12 V), there are electromagnetic fluctuations.

These EM fluctuations are the emmissions we are talking about here.

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I highly doubt that cpu is the emitter. More probable is some long path on mother board, used for data communication.

The CPU is comprised of millions / billions of transistors which switch on and off multiple times (which depends on the base clock frequency).

Yes, it's the bus traces between CPU and RAM. From linked paper: "When data is exchanged between the CPU and the RAM, radio waves are emitted from the bus's long parallel circuits."

I don’t think the FETs generate enough EM on their own? It’s probably the inductors on the motherboard charging and discharging as a result of the FETs that cause the EM whine/hum?

Another likely source is the power supply, which has coils by the dozens and will react to varying loads of computational work. The cheap ones are already all over the radio spectrum even when you don’t want them to be.

The transistors also have a drain and a source :)

The transistors in a modern machine use a minuscule amount of power and don't have enough area to make an antenna. You need to find a way to affect an output pin of the chip. Address lines for example will do a decent job, and the lower bits of the address are easy to control with a program.

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