Assume a middle school or home hobby lab with a bunch of breadboards, jumper wires, and 3.3V microcontrollers fast enough to toggle IO at RF frequencies (if not at the fundamental, at lower harmonics of the toggle frequency). Assume a digital IO toggle frequency right in the middle of some random HF or VHF band. Assume that the school or hobbyist are unlikely to have access to a calibrated spectrum analyzer.
So, to help encourage best practices:
Are there any good jumper wiring guidelines to reduce the chances of a breadboard (or set of breadboards) radiating EM outside various limits (FCC Part 15 in the U.S., etc.)?
e.g. maximum length of jumper wires, maximum loop area with respect to the nearest ground return, minimum termination resistance of a circuit loop, etc.?
Best Answer
There isn't a reason to worry about exceeding limits with a breadboard, the FCC allows for building of single devices with no testing:
The point at which you may get in trouble if you are unintentionally radiating large amounts of RF on bands that are in use by people that care. For example: A electronic billboard was leaking RF on a cellular band, the phone company saw the leak with their equipment and complained to the billboard company. If the company didn't fix the leak they then could complain to the FCC, and they could take action with fines, ect.
It's unlikely that you'll build an unintentional radiator with a breadboard that would get someones attention. You might however build an intentional radiator (like an FM radio) that could disrupt a radio a few 10's of meters away. If you're building an intentional radiator that's a different story.