The signal is imperceptible outside a 1980s truck.

On a modern vehicle if you are more than a foot away from the door it can’t be measured.

They are cheap devices without much long range punch, but effective for the range they cover.

Yes most are made in China, Taiwan, or Vietnam, but that doesn’t matter if you are checking them. Frankly the cheaper one don’t even cover that range.

Long range stuff like radar jammers are doing very different shit.