If pulse
modulation (Option
002)
is fitted proceed as
follows:
(
1 )
Press the [
Pulse
Mod
]
key.
(2)
This causes the message PULSE ON to be displayed.
(3)
Press the [Pulse ON/OFF] key.
(4)
This causes PULSE OFF to be displayed
together with Low Intermodulation
Disabled or Low Intermodulation Enabled shown in the
lower panel.
(5)
Press the [MOD ON-OFF] key to toggle between the enabled and
disabled states.
(6)
If an attempt is made to [Set Steps] from the A menu, the
message PULSE : No
Steps Allowed
will
be
displayed.
Note...
AM is not
available in the Pulse Modulation or Low Intermodulation modes of operation.
Selecting pulse modulation (applies if Option 002 is fitted)
(1)
At the Sig Gen menu, press [Pulse Mod],
when
the
Pulse Mod box on the display
will
be
highlighted.
(2)
Selecting and enabling pulse
mod changes
the RF level control loop to
the Direct
Level Control mode,
which
can take up to
100
ms
to action. For best accuracy,
this process
should be repeated before measurements are taken if
neither
the
carrier
frequency
or RF
level
have been changed
recently. When pulse mod is
disabled
the
RF level is controlled
in
the normal way.
(3)
Switch pulse mod on or off with the [Pulse
On/Off]
key.
When
'On', the
carrier
is
controlled by the logic
level
applied to the PULSE
INPUT socket mounted on the
front panel. A logical T (a voltage between 3.5 and 5
V) allows
carrier output, a
logical 'O' (a voltage
between
0 and 1.0 V)
suppresses it. Turning pulse mod off
effectively applies a logical T allowing carrier output.
MODULATION ALC
The
automatic levelling
control (ALC) is used
in conjunction with an external source and
can
be
disabled when not required. To enable the ALC, proceed as follows:
(1)
At the Sig Gen menu, press [Select Source]. The display will
show the Internal or
External Source
Selection
Menu (Fig.
3-1-8
or Fig.
3-1-10).
(2)
If necessary press [Select External] to obtain the External Source Selection Menu
(Fig.
3-1-10).
(3)
Select the required external source from the
options shown, e.g. [Ext l ALC
Coupling] or [Ext 2 ALC Coupling]. The pictogram at the end of each
line will
change from a
horizontal line
to an
arbitrary waveform symbol when the source is
selected.
(4)
Return to the Sig Gen menu
by
pressing [SIG GEN]. The legend Ext
Mod
1
(or
2)
ALC
coupled
appears at the
bottom of
the display.
3-1-18
46882-074C
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