ANALOG MODULATION MODE
3-83
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.
These modes are not available in digital and vector modulation since the connector is
redirected for envelope control.
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
List of available soft keys for analog 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/
Φ
M Drive
FM/
Φ
M Drive
- -
FM/
Φ
M Source
FM/
Φ
M 1 Source
- -
FM/
Φ
M 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/
Φ
M drive signal is also fed to the LF OUTPUT socket. The signal is the sum of
both FM/
Φ
M 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/
Φ
M 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.
Wideband FM and pulse modulating signals are not accessible via the monitor mode.
enabled