Key Points Behind the Measurement Setup

While the SINAD measurement procedure may look simple, two parameters have a significant impact on the result.

1. Modulation Depth (Why 60%?)

In this setup, a 1 kHz tone with approximately 60% AM modulation is used.

This is not arbitrary.
If the modulation depth is too low, the recovered audio signal becomes weak, and the SINAD reading becomes unstable.
If it is too high, distortion increases and affects the measurement.

Around 50–60% provides a good balance, where:

The audio signal is strong enough
Distortion remains moderate
Measurements become stable and repeatable
2. Audio Output Level (Half of Rated Output)

Another important condition is adjusting the receiver audio output to about half of its rated level.

This avoids two common problems:

Too low → noise dominates the measurement
Too high → amplifier distortion affects SINAD

By setting the output to a moderate level, the measurement reflects the true performance of the receiver rather than the limitations of the audio stage.

Why These Matter

These parameters may seem minor, but they strongly influence the result.

Even with the same receiver, different settings can produce significantly different SINAD values.
Careful setup is essential for meaningful and repeatable measurements.