Solderless breadboards are extremely handy. You always hear, of course, that you need to be careful with them at high frequencies and that they can add unwanted capacitance and crosstalk to a circuit. That stands to reason since you have relatively long pieces of metal spaced close together — the very definition of a capacitor.
[Ryan Jensen] did more than just listen to that advice. He built a circuit and used a scope to investigate just how much coupling he could expect with a simple digital circuit. Better still, he also made a video of it (see below). The test setup shows a single gate of a hex Schmitt trigger inverter with a sine wave input. The output transitions ring and also couple back into the input.
Of course, the circuit is simple. Some additional decoupling might have helped some. Still, [Ryan’s] circuit isn’t atypical of something you’d see on a breadboard, so his points are still valid. Another thing that can help is mounting the breadboard on a solid ground plane.
Towards the end of the video, [Ryan] guts a breadboard to show what’s inside. We’ve seen people do surgery on the breadboard internals before, but if you haven’t seen one eviscerated before, you might find it interesting.