I have created a software (gnuradio) that performs modulation/demodulation and supports a number of modulation schemes and error correcting codes. I'm in the process of evaluating the BER vs SNR for this software by using a secondary industrial-grade hardware. This device can measure the BER. Unfortunately, the device does not have the capability of measuring the input signal SNR, which means I have to measure it manually. At the moment, I'm thinking of using a spectrum analyzer. Basically, I will compare the signal level relative to the noise floor and derive the SNR (simple subtraction since everything is in dBs). However, I was looking for suggestions on more elegant methods of doing this and what type of hardware would be required.
2$\begingroup$ Is this some kind of lab setup with a known message and a simulated AWGN channel? In that case it's not usually necessary to measure the SNR since the signal and noise powers can be read right off the test equipment. $\endgroup$– Phil Frost - W8IIAug 8, 2018 at 0:57
$\begingroup$ The message is known. The RF signal is transmitted through an SMA cable so the noise is a physical one. $\endgroup$– Moses Browne MwakyanjalaAug 8, 2018 at 14:57
FLDigi will calculate the SNR for a PSK31 signal based on the spectrum scope.