Build a small jammer

Hello, because my sister is in front of her mobile phone all day, I want to build a jammer myself to paralyze the mobile phone network within a radius of up to 3m. Is there any instructions for this? And a jammer with such a small radius in the home is actually legal! operate?

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Topsignaljammer  2022.3

This is not legal. If the jammer is only working on your own property, that's a gray area, but to fully jam a nearby cell phone it has to affect a phone at a distance, so the jammer won't stay on the property unless it's a few acres in size .

Do-it-yourself requires a lot of experience and measurement equipment to get the jammer to jam in a targeted manner, rather than flattening other frequencies at the same time. If you absolutely need something like this, order a cell phone jammer for a few euros in China! It doesn't make it any more legal either, but these things are better than what you can get without spending a lot of money.