LOW FREQUENCY OPERATION
The instrument has
two
modes of LF operation. The LF output can be
used
either
as a
modulation signal monitor or as an independent low
frequency
generator.
Pressing [LF] displays
either the LF Monitor
Menu or the LF Generator Menu
,
depending on which mode was last
selected.
LF monitor
The left-hand side of the LF Monitor Menu, varies
according to the modulation mode;
single,
composite, dual or dual composite. In each case the right-hand side is occupied
by a
single soft key, [LF Gen.].
TABLE
3-1-1
LIST OF AVAILABLE
SOFTKEYS FOR
DIFFERENT
MODULATION MODES
Single Composite Dual
Dual Composite
Mod. Drive
Mod. Source
Mod.
Drive
Mod. 1 Source
Mod. 2 Source
AM
Drive
AM Source
FM/OM Drive
FM/OM Source
AM Drive
AM 1 Source
AM 2 Source
FM/OM Drive
FM/OM 1 Source
FM/OM 2 Source
Modulation source monitoring
Internal sources only may be monitored.
To monitor a
modulating
signal source, press the
appropriate
key. The
source monitor level
and the source information appeal' on the display. The
modulating signal output
is
fed to the LF OUTPUT
socket at a
fixed level
of 1 V.
Modulation drive monitoring
Modulation drive
monitoring is intended for the user to monitor complex modulating
signals from both internal and external sources.
To monitor a
modulation drive,
press the
appropriate key. The LF
monitor level and the selected drive are displayed.
When the summed
AM drive signal is selected, a signal which is the sum of both AM
channels is fed to the LF OUTPUT socket, if in
a
composite or dual
composite mode. The LF
level function controls the
output
level
at 100% depth, therefore the actual output voltage
depends on the modulation depth. If AM is turned off, the associated LF output is removed.
The
summed FM/OM drive signal is also fed to the LF OUTPUT socket. The signal
is
the sum of both FM/OM channels. The FM drive signal
at
the monitored
point is nominally 1 V
but varies over
a
range
of
approximately
3 dB (except at
deviation
values below about 1 kHz)
depending on the set modulation and the carrier frequency selected. If FM/OM is
turned off, the
LF signal is removed. If one component of
a composite modulation setting is turned off, the
component
which is left on remains at its original level.
Note...
Wideband FM and pulse modulating signals are not accessible via
the monitor mode.
46882-074C
3-1-45
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