On 14 Jan 2005 12:25:54 -0800, "C Bun" wrote:

Anyone interested in science and outer space exploration knows that
today Huygens probe had just now successfully landed on Titan,
Saturn's largest moon. The probe began transmitting radio beacon
siginal at 11:25 CET, and the Green Bank radio telescope in West
Virginia, USA, picked up this faint but unmistakable radio signal (2040
MHz) from the probe.

My wondering is, considering the huge distance between Titan(Saturn)
and Earth, and the undirectionality of the beacon radio signal (not the
ones modulated with scientifically data that will be picked up by
Cassini and relays directionally to Earth), the telescope in WV must be
very very sensitive. Can anyone estimate what sensitivity it has, and
compare it with a regular radio receiver (say, 0.1uV)?
The key isn't as much sensitivity of the receiver. That is seriously
limited by background noise anyway to something around .5 microvolts
unless you use synchronous detection. The game at Green Bank and the
others is the huge gain over an isotropic radiator the big dish gives.

If an 8 ft dish gives about 40 db, an 80 ft dish is about 60db, 800
foot dish (like Aericibo) 80 db gain over an isostropic radiator.
When you have 60db in the antenna system, ta picowatt becomes a
microwatt, and a microwatt turns into a watt.