R3267 Series Spectrum Analyzer Operation Manual (Vol.1)
2.3.12 Measuring Frequency deviation of FM Signals
2-122
Calculating the frequency deviation
13. Read the frequency of the delta marker displayed on the screen.
Calculate the frequency deviation
∆
fpeak from the delta marker frequency
∆
freq
using the formula shown below.
Calculating modulation index
14. Press SPAN, 1, 0 and kHz.
The frequency span is changed to 10 kHz.
15. Press SRCH.
The normal marker is moved to the peak on the trace.
16. Press Next Peak Right.
The normal marker moves to the right-hand peak on the trace.
Figure 2-138 Modulation Frequency of the FM Signal
17. Read the frequency of the delta marker.
The modulation index fm is calculated from the delta marker frequency fm and
frequency deviation Dfpeak, using the following formula.
∆
fpeak =
2
1
× ∆
freq
m =
fm
∆
f
peak