"Arthur Harris" wrote in message
t...

"CW" wrote:
Very little power is necessary in space. I had a QSO with an astronaut
on
MIR with a 3 watt ht. With nothing in the way, it will go on virtually
forever.

The signal will decrease by 6 dB every time you double the distance. MIR
was
about 250 miles above Earth, and you could establish communicaion with
fairly low power when it was overhead. On the other hand, Mars is about 35
million miles away! You'd need a LOT more power and antenna gain to
contact
Mars.


I presume that the Mars rovers do not have extensive antenna arrays, nor
more than a few watts of power. Of course, NASA does have large receiving
arrays..