Radar system

Radar systems used by civilian airports (like this at Heathrow) and military operations are inadvertently revealing our existence to potential advanced alien civilisations because of the hidden electromagnetic leakage they emit.
Radar systems used by civilian airports (like this at Heathrow) and military operations are inadvertently revealing our existence to potential advanced alien civilisations because of the hidden electromagnetic leakage they emit.
Mick Lobb / Radar scanner - Heathrow / CC BY-SA 2.0