INDIVIDUAL SOURCE OPERATION
3-21
Modulation ON/OFF
[Mod ON/OFF]
switches all modulation ON or OFF and the condition is indicated in the centre of
the Signal Generator menu:
Modulation DISABLED
Modulation is also controlled by the individual modulation ON/OFF keys. For modulation to
appear on the carrier, modulation must be both enabled with the
[Mod ON/OFF]
key and the
individual
[AM ON/OFF], [FM ON/OFF],
[
ϕ
M ON/OFF]
and
[Pulse ON/OFF]
keys. The
individual modulation ON/OFF keys only reduce the modulation to zero, whereas the
[Mod
ON/OFF]
key completely disables the modulation system so that the instrument reverts to a carrier
frequency generator.
Amplitude modulation selection
Select amplitude modulation as follows:
(1) Press [SIG GEN] to show the Signal Generator menu with the current modulation displayed
in the bottom half of the screen.
(2) Press
the
[AM]
soft key if displayed (otherwise the instrument is already in the AM mode).
(3) Press
[AM Depth]
. Enter the modulation depth using the numerical key pad and terminate
with any [ENTER] key. If you exceed the 99.9% modulation limit it is automatically reset to
the maximum allowed value.
(4) If the internal modulation is to be the sum of two internal signals, select
AM1 + AM2 internal
from the utilities (see ‘Mode selection’ on page 3-17). A typical display is shown in Fig. 3-16
below. Press the
[AM2]
key to select the second signal. Press the
[AM2 Depth]
key and
enter the required modulation depth for the second signal. If you exceed the (99.9%
−
AM1)
modulation depth limit, it is automatically reset to the maximum allowed value.
B3907
Fig. 3-16 Signal Generator menu with two modulation channels
(5) Select
[AM Mod Freq],
enter the modulation frequency and terminate with the [Hz] or [kHz]
key
.
If you exceed the 20 kHz modulation limit it is automatically reset to the maximum
allowed value.
(6) If required, change the waveform from that shown on the display (see ‘Internal waveform
selection’ on page 3-19).
(7) Press
[AM ON/OFF]
to toggle between the on and off states as shown by the display.
