----- Original Message ----- From: "Howie DeFelice" howied231@hotmail.com To: amsat-bb@amsat.org Sent: Friday, July 03, 2009 3:14 PM Subject: [amsat-bb] Lunar link budget
Hi Domenico,
I could be wrong but I think your budget is correct for a regenerative transponder but for a bent pipe transponder we need to add the uplink noise to the downlink noise where
C/N (total) = 1/((1/C-Nup)+(1/C-Ndn)) which in this case would be about 6.7 dB.
Still pretty good, but would probably be better even at the lower microwave freqs. If we used PSK31 exlusively, even 2.5 KHz many simultaneous QSO's.
Howie AB2S
Hi Hovie AB2S
I agree with you and this is why I writes....................290 kelvin but (probably more)
The gain of the 2 meters antenna on the Lander is 3 dBd = 5.14 dBi Assume that the Noise Figure of the 2 meter receiver is 0.5 dB = 35 kelvin and the sky temperature as seen by the 2 meter Lander antenna looking at the earth is conservatively 290 kelvin but (probably more ).
At microwave frequencies where the gain of the antennas of the Lander are higher and higher than 3 dBd and the antenna pattern is very narrow who will automatically and precisely point the antennas toward the earth and who will compensate the pointing to follow the libration movements of the moon ?
73" de
i8CVS Domenico