If there were Martians and they had a SETI program, they would have no difficulty detecting Earth's radio and television transmissions. Human SETI projects are able to pick up the feeble transmissions, from beyond Pluto, of the Pioneer spacecraft, whose transmitter uses a few watts of power, similar to what a refrigerator lightbulb uses.
Earth has many transmitters using thousands to millions of watts.
These should be easy for Martians to detect. For example, the giant Arecibo radio telescope in Puerto Rico has a million-watt radar transmitter. It's used to bounce radio signals off planets, moons, comets and asteroids. It's so powerful that it could detect a steel golf ball on the Moon. They'd be able to learn something about our civilization.