3-50
Analog modulation mode
Analog modulation
The carrier can be frequency, amplitude, or phase modulated, with pulse modulation as an option.
The internal modulation oscillator has a frequency range of 0.1 Hz to 500 kHz, with a resolution
of 0.1 Hz.
To select the Analog control function press one of the
[Single]
,
[Dual], [Comp] or [Dual Comp]
keys on the
Modulation Mode Selecton Menu
(see Fig. 3-6), followed by [SIG GEN]. This causes
the
Sig Gen
menu similar to that shown in Fig. 3-50 to be displayed.
RF
Level
Carrier
Freq.
LOCAL
FM
ON/OFF
FM
Devn.
Source
Freq: F4
Low
Intermod.
Select
Source
Wideband
FM
AM
Carrier :
Freq.
RF Level :
dBm
Single Modulation Mode
Modulation ENABLED
MHz
Int Std: 10 MHz
FM
Int F4 : 1.0000 kHz
Hz
ON
2 700.000 0000
-144.0
ON
0
C0482
Φ
M
Fig. 3-50 Sig Gen menu - default display for 2051T
Selecting the modulation
The type of analog modulation required, AM, FM,
Φ
M, wideband and optional pulse modulation
can be selected by soft keys at the
Sig Gen
menu. Four analog modulation modes are available, see
'Modulation mode selection' above.
Modulation ON/OFF
[MOD ON-OFF] switches all modulation
ON
or
OFF
and the condition is indicated in the centre
of the main display, e.g:
Modulation DISABLED
Modulation is also controlled by a soft key which turns the selected modulation on and off. For
modulation to appear on the carrier, modulation must be both enabled with the [MOD ON-OFF]
hard key and turned on via the soft key. In single modulation modes the [MOD ON-OFF] key and
the
[FM ON/OFF]
,
[AM ON/OFF]
,
[
Φ
M ON/OFF]
keys appear to carry out the same function,
but the action is different, particularly in the FM mode. The
[FM ON/OFF]
etc. soft 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.