satellite communication - size and noise?

[liberal]

satellite communication

as we konw ,the effective noise temperature of the satellite earth station is 30K.Now i use a 6m Ku antenna and a receiver with 60K effective noise temperature and 44dB Gain,and i measure the receiver's output noise (i want to konw the noise i receive from the satellite)in 1MHz bandwidth ,it is -52dbm.
and when i use a 0.6m Ku antenna and a receiver with 60K effective noise temperature and 58dB Gain,and i measure the receiver's output noise in 1MHz bandwidth ,it is also about -52dbm.
then i cal that the noise in front of the receiver(noiseless) is -96dbm with 6m antenna and -110dbm with 0.6m antenna. the biger of the antenna ,the biger of the noise?

 

[kspalla]

satellite communication

Q: the bigger of the antenna ,the bigger of the noise?
ANS is No. bigger antenna have more gain than smaller antenna.
The result, total system gain is different for both cases.
This result in noise floor to shift to high.

 

[nandopg]

Re: satellite communication

The evaluation of a satellite dish is performed by comparison of a parameter called G/T, which is the gain to noise temperature ratio. The bigger the G/T the better the antenna is. So to comapare just noise temperature is meanless, as if you had no atenna at all the noise would be 0!!

If you check on the procedures for commissioning a satellite dish you will see the G/T measurement is one of the most important parameter to be measured.

NandoPG