The Bessel Null or Carrier Null method is the most accurate way to measure the frequency response of frequency-modulated sources. It is used to control deviation since frequency deviation is independent of the modulating frequency. The actual method of finding a null appears to be accurate and easy. The first null can be observed at the modulation index of 2.4. By numerical solving the Bessel Function and employing the spectrum analyzer, a simplified approach is ideal for accurately determining the frequency deviation. In this paper, we would analyze the results by solving the Bessel functions in determining the accuracy of the frequency deviation and subsequently its measurement uncertaint.
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