Table of Contents
Advertisement
Making Measurements
Example 3: Modulation
4. Knowing that the desired deviation is 25 kHz, and choosing the
5. Set the modulation rate on the signal generator to 10.412 kHz. If the
Table 2-3
a.
Press
FREQ COUNT
COUNTER RES
b.
Press
COUNTER ON OFF
count mode to read the difference between two sideband peaks (see
Figure 2-11).
c.
Now adjust the frequency deviation for a maximum null of the carrier.
d.
Calculate the FM deviation by multiplying the modulation index
(from Table 2-10) by the modulation rate:
FM Deviation = 10.39 kHz × 2.401
e.
f.
FM Deviation = 24.95 kHz
Figure 2-11
Markers Show Modulating Frequency
64
modulation index of the first carrier null, calculate the modulating
frequency as follows:
signal source doesn't have an accurate internal modulation source,
use an external source. You can use the delta count mode of the
analyzer to accurately set the audio source frequency as follows:
to activate the counter function, then press
and set the counter resolution.
so that ON is underlined, and use the delta
25kHz
Modulating Frequency
=
--------------- -
Modulating Frequency
=
10.412kHz
2.401
Chapter 2
Advertisement
Table of Contents
