Radio frequency amplifier and error rate

Hi, I am designing an RF link. Before my spectrum analyzer, I have an RF low noise amp with a NF of 2.5 dB. Without this amplifier, my error vector magnitude or error rate is 2.1%, after an amplifier it goes down to 0.7%.

My question is, the receiving signal will have its own SNR and with that SNR I achieve 2.1%, after amplification of the signal power which is relative to SNR, cause the signal will have the same amount of signal power and noise power and amplification will linearly amplify both of these factor.

With taking this into consideration, how can the error rate improve cause the amplification is with respect to signal power and noise power? I cant figure this out, please advice.

There are two configurations:
1. LNA+ SA, then you can calculate the link NF and gain, you will get low NF
2. Only SA, the SA NF is greater than LNA
So, the sensitivity = -174+logBW+NF+S/N, all params are same except NF, with low NF, you will get low sensitivity, so EVM will improve.