The enterprise ETC "KONTUR" (Novosibirsk) has created a radio communication service tester (tester) RST-430 for measuring, including the sensitivity of a radio station receiver. The device is multifunctional, it performs a number of tasks in the field of monitoring and measuring various parameters of communication facilities. You can find out about all the functions and technical characteristics here
In the PCT-430 tester, the main purpose of the FND meter is to measure the signal-to-noise ratio. That is, the noise in the signal is the main information parameter. If you try to measure harmonic distortion in a noisy signal, the result will be incorrect. To measure harmonic distortion, the signal must have a minimum presence of non-fundamental harmonics.
The measured SINAD signal-to-noise ratio is displayed in decibels (dB) and with a FND measurement in percent.
SINAD signal-to-noise ratio of 12 dB corresponds to 25% when measured through FND. How to measure sensitivity, by SINAD or FND, is a matter of personal preference. A change in SINAD signal-to-noise ratio of 1 dB corresponds to a 3% change in FND. Since the noise level is not uniform, the SINAD measurement is easier, since the value on the indicator fluctuates less, however, the measurement through the FND allows you to catch the pattern of noise change.