On-target SNR measurement

I want to measure the performance of a receiver demodulation algorithm, something like Bit Error Rate as a function of the power of the incoming signal (in dBm) and compare it to simulation results.

I first simulate it on the computer and get a result of BER as a function of SNR.

After implementation on target, I measure the BER of my algorithm by changing the power of the incoming signal (in dBm).

My architecture is that I have an RF circuit that drives an ADC.

How can I relate the real measures with the theoretical, knowing the noise figure of my RF circuit part?

By removing the RF signal, I have been able to measure (numerically, after the ADC) the RMS value of the noise in base band (1024 points @240kHz). By applying a RF signal at a good level (-80 dBm), I have measured the RMS value of my baseband signal+noise in the same way as above.

Given these data, I can calculate the (S+N)/N ratio and then the S/N when I apply -80 dBm at the input of my receiver.

My conclusion is that knowing this I can calculate the SNR at every RF level before and after the RF circuit. I can then plot the theorical results, the measurements vs the incoming signal in dBm.

Is it correct? If not why?

Edit: I know the SNR is a ratio of power, but we can do it with voltage (RMS value or amplitude is better?)

Edit2: I just realised that with my method I can only measure a (S+N)/N ratio (as RMS values cannot be added or substracted)...