How to calculate thermal noise contributed by an LNA?
You just need to determine the noise level at the input of the LNA.
The LNA has 60 dB Power gain so at the output the signal has a 60 dB higher power level.
If the LNA was noiseless, then the noise would also be amplified by 60 dB (same as the signal). However, the LNA isn't noiseless, it has a NF of 1.5 dB that means that it adds 1.5 dB to the noise level. So the noise level at the input of the LNA will be amplified by 60 dB + 1.5 dB = 61.5 dB.
Example:
At input of LNA:
Signal = -60 dBm, noise = -100 dBm
S/N ratio = 40 dB
At output of LNA:
Signal: Signal level + 60 dB = -60 dBm + 60 dB = 0 dBm
Noise: Noise level + 60 dB + 1.5 dB = -100 dBm + 61.5 dB = -38.5 dBm
S/N ratio = 38.5 dB (1.5 dB worse due to NF = 1.5 dB).