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3.2.6 FM Operation
In FM operation, the instantaneous frequency of the
output Signal varies with the instantaneous amplitude
of the modulating signal (Figure 3-7). Both main and
auxiliary generators may be frequency modulated by
external signals at their VCG inputs (ref: paragraphs
3.2.3 and 3.2.5): Internal operation is the main
generator modulated by the auxiliary generator.
Internal FM operation is the same as a manually
controlled main generator operation (ref: paragraph
3.2.2) except that, in addition, the main generator is
frequency modulated by the auxiliary generator. The
following steps demonstrate setting up the unique
controls for FM modulation. (Bold numbers are keyed
to figure 3-1. Refer to paragraph 3.1 for further
explanations of controls and connectors.)
Step Control/Connector
Setting
AUX GEN Mode 20
Select SET FREQ/AUX
GEN OFF.
As an actual exercise in operation, perform steps 14
through 17 of table
2-1.
3.2.5 Voltage Controlled Auxiliary Generator
Operation
Operation of the auxiliary generator in Voltage Con-
trolled Generator (VCG) mode is very similar to VCG
operation of the main generator (paragraph 3.2.3)
except there is a maximum of 33:1 frequency change
with a 0 to
±
5V change at the AUX VCG input BNC (a
1000:1 change is maximum for the main generator).
AUX SYNC OUT Connector-
This rear panel
BNC provides
a
TTLlevel pulse which lags the
AUX OUT
3
triangle signal by
90°.
5
FUNC 21
4
VERNIER22
3
FREQ 22
Select
desi red
fre-
quency
range.
Set
to
desired
fre-
quency
within
the
range.
Select
desired
wave-
form.
6
WIDTH/aF/aM 20
Select desired ampli-
tude at AUX OUT.
NOTE
Step Control/Connector
Setting
1
AUX GEN MODE 20 Set to AUX OUT only.
2
AUX OUT 3
Connect to circuit under
test,
source impedance
is 600f2.
3-6
The up to 1000:1 VCG sweep of the generator fre-
quencies available in each range results from a 5Vex-
cursion at the VCG IN connector. With the frequency
dial set to 2.0 and the main generator VERNIERfully
ccw, excursion between - 5V and OVat VCG IN pro-
vide the up to 1000:1 sweep within the set frequency
range.
3.2.4 Manual Auxiliary Generator Operation
The auxiliary generator, when used as a separate
function generator, provides frequency and function
selection in a continuous mode. (Bold numbers are
keyed to figure 3-1. Refer to paragraph 3.1 for further
explanations of controls and connectors.) The follow-
ing steps demonstrate setting up of the auxiliary
generator for continuous operation.
*Must be multiplied by FREQ MULT switch setting
Figure 3·6. VCG Voltage·to·Frequency
Nomograph
FREQ/
VCG
OUTPUT
START FREQ
IN
FREQUENCY
DIAL
(VOLTS)
FACTOR*
2.0'
-5
T
.002
1.8
-4
~~
/
/
.2
e-
->
1.6
-3
~~~//
.4
~
.:
"",
1.4
-"...2/
.....
.6
/
,.
1.2
..... .....
-1
.8
.....
..... .....
EXAMPLE 1
.....
1.0 ,--------0
----------
1.0
......
......
.......
.8
.......
+1
1.2
<,
<,
-,
.6
+2
1.4
<,
<,
~4'--i
.4
+3
..............
41,0<::
1.6
.2
+4
""",,~<
1.8
<,
<,
......
.002
+5
2.0
NOTE
Nonlinear operation may result when the
VCG
input voltage is excessive;
that is
when the attempted generator
frequency
exceeds the range limits. The upper limit is
2 times the multiplier
setting,
and the lower
limit is 111 OOOthof the upper
limit.
VCG
input,
output
frequency
is
increased.
Example 3 shows that with a negative VCG input, out-
put frequency is decreased. (Note that the Output Fre-
quency Factor column value must be multiplied by a
frequency
range multiplier to give the actual output
frequency.)
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