On Jun 16, 8:06*pm, tom wrote:
Jim Lux wrote:

Don't forget that DirecTV radiates a LOT more power than a typical deep
space probe. AND they often have a higher gain antenna. A geosync relay
satellite might have 96 TWTAs, each several hundred watts, on it,
feeding a very clever multiple feed dish which is many meters in
diameter (look at Thuraya, for instance).

Wow. *96 TWTs with several hundred watts each. *From a satellite. *And
what's the efficiency?

So these are powered by what? *Small nuclear reactors?

Certainly not solar panels.

tom
K0TAR

Not all will necessarily be on at the same time.
Typical narrow band coupled cavity TWTAs can get over 50% efficiency
(DC in to RF out)
Yes Solar Panels..10kW would not be unusual.

See, e.g., http://en.wikipedia.org/wiki/ASTRIUM_E3000 ... 14 kW of
power from 45 m^2 of solar panels and 4500kg of satellite..

This is so far beyond what is used in the scientific space program
it's mind boggling. But, hey, out of the $1-2B cost, the TWTAs are
probably only 5-10% of the total, and there are definitely quantity
discounts.