I've got this ancient 2008 Dell CRT monitor I still use sometimes for retro gaming, and whenever someone runs the microwave in the kitchen nearby, the screen gets these weird horizontal lines and flickers like crazy. Is this electromagnetic interference? How does a microwave actually mess with electronics that aren't even plugged into the same outlet?
Yep, that's electromagnetic interference - microwaves emit a lot of radio frequency noise when they're running, and that energy radiates through the air and gets picked up by your CRT monitor's cables and circuitry. CRTs are especially vulnerable because they need high voltage to create the electron beam that draws the image, so any stray electromagnetic energy can mess with that beam and cause the flickering and lines you're seeing. The outlets don't need to be connected for this to happen since the interference travels wirelessly through space. You could try moving the monitor farther away from the kitchen, using shielded cables, or just accepting it as a quirk of older tech - newer LCD monitors handle this way better because they don't rely on that high-voltage scanning system.
You're absolutely right that it's electromagnetic interference - microwaves pump out a ton of RF radiation to heat food, and that energy radiates out in all directions, not just into the food chamber. CRT monitors are particularly vulnerable because they use electron beams scanning across the screen, and stray electromagnetic fields can deflect those beams and cause the flickering and lines you're seeing. The radiation doesn't need a shared electrical outlet to affect your monitor; it travels through the air and couples into your monitor's circuitry and cables, which act like antennas. You could try moving your monitor farther from the kitchen, shielding the cable with foil or a ferrite clamp, or just accepting that your retro setup has a quirky relationship with modern appliances - honestly, it's kind of a nostalgic reminder of how finicky older electronics were.
Electromagnetic interference is definitely what's happening here. Microwaves operate by generating intense RF (radio frequency) radiation at around 2.45 GHz to excite water molecules in food. That energy doesn't stay neatly contained - it leaks out through seams and vents, and your CRT monitor's cable acts like an antenna picking up those signals. The unshielded analog signals running through old monitor cables are particularly vulnerable to this kind of noise, which shows up as those horizontal scan lines you're seeing.
The thing the other answers don't mention is that CRT monitors are actually pretty sensitive to RF interference because of how they work. The electron beam is being constantly steered by magnetic coils, and when stray RF gets into those deflection circuits, it literally messes with where that beam is supposed to be hitting the screen. Modern LCD/LED displays are less affected because their signal paths are digital and shorter. With your setup, the best fix is usually just moving the monitor further away from the kitchen, or shielding the monitor cable - wrapping it in aluminum foil or using a ferrite clamp on the cable can help absorb some of that RF noise before it gets to the circuitry.
electromagnetic interference is exactly what's happening - microwaves leak RF energy all over the place, and your CRT's long unshielded cables act like tiny antennas picking up that noise. i noticed the same thing years ago when i had an old tube monitor in the office, and swapping it for something newer made the problem vanish, though honestly the cables are what matter more than the monitor itself. shielded cables and distance help, but nothing beats just moving one device farther away if you can. the flicker you're seeing is the electron beam in your CRT getting jostled by that stray radiation interfering with the deflection signals.
How far away is your kitchen from where the monitor sits? Yeah, it's RF interference for sure, but here's what everyone glossed over: your cables aren't the only problem - CRT monitors are inherently vulnerable because they need high voltage constantly running through them to generate that electron beam, so they're basically already "noisy" receivers. The microwave's 2.45 GHz radiation gets picked up by everything nearby, but your old CRT amplifies it way more than a modern LCD would. If you want it to stop, try moving the monitor farther from the kitchen, wrapping the cable in foil or a ferrite clamp, or just accept it as the price of retro gaming.
CRT monitors are basically giant antennas for electromagnetic noise, which is exactly what you're running into. Your microwave generates radio frequency energy at 2.45 GHz to heat food, and that energy doesn't stay neatly contained - it radiates outward in all directions. The long cables connected to your monitor act like little pickup coils for that RF noise, and since CRTs refresh the screen by sweeping an electron beam across it thousands of times per second, any electrical interference gets turned into those flickering lines you're seeing.
Here's the thing though: everyone's focusing on the cables, but the real culprit is usually your monitor's power supply and video cable together. The power cord brings the noise in from the wall, but the video cable - especially if it's an old unshielded one - is what actually carries that interference directly into the monitor's circuitry. If you want to test this, try moving the video cable away from the microwave or wrapping it in some aluminum foil (grounding one end to an outlet's ground pin with a short wire). That usually helps way more than people expect.
The bigger issue is that older CRTs were never designed with the amount of wireless interference we have now. When your monitor was made, microwaves weren't as common in every home, and they had fewer safety regulations about RF leakage. Modern devices have better shielding, which is why you don't see this problem as much anymore. If it really bothers you during retro gaming sessions, keeping the microwave at least a few feet away or waiting until you're done playing is the simplest fix.
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