"Bill Everhart" wrote:
I've been wondering: If a shortwave transmitter was put on Mars could
I pick it up - at night I mean? Would I need an external antenna?

Interesting question. When Mars is at its closest point to Earth, it's still
about 35 million miles away. Only a tiny portion of the transmitted power
would arrive on Earth (the rest would "miss" us and go out into space in all
directions).

The "free space path loss" between Earth and Mars at 15 MHz would be 211 dB.
That's a HUGE loss. At UHF and microwave frequencies the path loss is even
greater, BUT the use of very high gain dish antennas both on Earth and Mars,
as well a low noise figure receivers, makes communication possible. At HF,
antenna gain of more than about 10 dB is hard to obtain. And the
atmosphereic noise at HF is a killer for weak signal reception.

Plus, you'd have to be listening at a time when your side of the Earth was
facing "their" side of Mars, and the E and F layers of the ionosphere were
NOT refracting signals.

BTW - I tune down.

Huh?

Art N2AH