OPERATION
3-1-52
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 soft keys for different modulation modes
Single Composite Dual Dual Composite
Mod. Drive Mod. Drive AM Drive AM Drive
Mod. Source Mod. 1 Source AM Source AM 1 Source
- Mod. 2 Source - AM 2 Source
- - FM/ΦM Drive FM/ΦM Drive
- - FM/ΦM Source FM/ΦM 1 Source
- - FM/ΦM 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 appear 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/ΦM drive signal is also fed to the LF OUTPUT socket. The signal is
the sum of both FM/ΦM 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/ΦM 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.
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