Modulation
Source
4.
1
kHz
+
EXT
DC
Press
[I
kHz
+
EXT
DC)
to configure the
MOD
INPUT/OUTPUT port
as
a
DC
coupled input for modulating the carrier along with the internal
1
kHz source.
(Refer also to
“3.
EXT
AC
EXT
DC”
for further information about
operation and acceptable ranges.)
Note
1
kHz
+
EXT
AC,
400
Hz
+
EXT
DC,
and
400
Hz
+
EXT
AC
are
available only via HP-IB.
Setting
the
Modulation
Level
When modulating with both an internal and external source, the
level
of
the external source should not exceed 0.5
V
peak or
0.5
Vdc.
This level will provide one half of the displayed modulation.
To
set
modulation to the level you desire, set the displayed modulation to
two-thirds of the desired setting. The external source,
set
to
0.5
V
peak or
0.5
Vdc,
will
provide the additional one-third of the desired
setting (one-half
of
the instrument’s setting).
For example, to set up the modulation for
3
kHz
of
FM deviation, set
the instrument for
2
kHz of
FM.
The external source, set to
0.5
V
peak,
will
provide another
1
kHz of deviation.
If
the external source is set to less than
0.5
V
peak, the modulation
level provided by the source will be less than one-half
of
the
displayed resolution. The following equation may be helpful for
determining the appropriate modulation level setting for the
instrument when the level of the external source is less than
0.5
V.
-=
AD
l+E
A
=
Actual modulation level
E
=
External source level
D
=
Displayed modulation level
Where:
For example, to set up for
3
kHz of FM deviation with an external
source set to
0.3
V
peak, the instrument’s displayed modulation level
would be:
3kHz
=
2.3kHz
1
+
0.3V
5.
MOD
IN~UT/OU~~
This port outputs a
1
Vpk (into
6000)
audio tone when an internal
modulation source is selected
(400
Hz or
1
kHz). When external
coupling is selected
(c-1,
[ETET]
or
[I
kHz
+
EXT
DC)), it provides
the input for a
1
Vpk (into
600Q)
audio source. (Refer to the
preceding table for acceptable audio ranges.)
Operation
Reference
lb-17
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