In this setup, the SINAD value changes in real time as the signal level is adjusted.

I measured the receiving sensitivity at 27MHz (AM 80% Mod) with the ATX-mini HF/FM receiver using the Si4732. The value was -104dBm. To set it to 12dB SINAD, the volume adjustment had to be maximized and a step-up using a transformer was necessary.

ATX-mini 27MHz 1000Hz 80% AM -104dBm 12dB SINAD

SINAD measurement in progress　　　FFT view of the test signal

In JH1LHV-OM's measurement example, the reading was -100dBm at 26MHz (AM 30% Mod), so the difference is likely due to the modulation depth setting. At 30% modulation, the SINAD did not rise above 12dB at my case. 

I also checked the R80 Chinese-made airband receiver. This receiver has a configuration of NE602-MC3361-TA7640-LM386. A problem arose. Even with volume adjustment, the SINAD did not rise above 8dB. When using a deeper modulation of 80% at 1000Hz and examining the FFT, a component was found at 500Hz. Could this be due to the MC3361 chip being an FM chipset?

Therefore, the sensitivity of the R80 airband receiver is equivalent to a SINAD of 8dB.

R80 118.1MHz 1000Hz 80% AM -105dBm 9.1dB SINAD

SINAD measurement in progress

The FFT display helps visualize noise and distortion components.

Note: When measuring C401, the measurement was smooth.