(3)
Pressing
[AC/DC Coupling] changes the coupling from AC to DC
and
vice versa.
When
the input is DC coupled,
small
frequency
offsets can be reduced by using
the nulling facility. Nulling
can be effected by pressing [DCFM Nulling]. The
legend:
***
DCFM NULLING
***
appears briefly
on the display.
Note...
The [IT] and
[•!!•] keys and the control knob do not operate for wideband FM.
CAUTION
The WBFM socket
input impedance is 50 Q. The DC component of of any applied
voltage
must not exceed 5 V.
Modulation
source frequency
(1
)
At the Sig Gen menu press [Source
Freq.J.
(2)
Enter the required source frequency and terminate the
entry with [Hz], [kHz] or
[MHz].
Note...
When
the
modulation
source is operating as
a
continuous signalling
tone
the [Source
Freq
.]
legend is replaced with
the [Tone Number]. Pressing
the
key
allows
a new tone
number
to be
entered.
Source selection
-
internal
The modulation source
may be selected by pressing
[
Select Source]. Sources may
be
internal
or external. If the currently selected
source is
internal, the Internal
Source Selection
Menu is displayed, giving
a choice of six frequencies, F1-F6, see Fig.
3-1-8.
The frequency
assigned
to
die highlighted
F number may
be
changed
by the
numerical key
pad and terminated
with [Hz], [kHz], [MHz] or
[GHz]. Soft keys allow the selection of either a sine or triangular
waveform. The
selection of sub-audible continuous tones can
be
achieved
by
pressing
[CTCSS],
see 'SIGNALLING'. Pressing
[Mod. Src Phase
]
displays the LF Source Phase Control menu, see
Fig.
3-1-9.
The
LF source phase angle can be varied from
-180°
to
+180°.
The
pictograms at the
end
of each line
show
a symbolic sine wave when
a source is selected. This changes to a
triangular wave if [Triangle
Wave] is selected. These symbols also appear- on the main menu.
A
horizontal
bar is shown when a source is not selected or is
not
available.
46882-074C
3-1-15
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