Operation; Signal Termination; Voltage Controlled Function Generator Operation - Wavetek 143 Instruction Manual

The upper and lower limits are defined by the
maximum and minimum dial
®
settings multi-
plied by
@ .
VCG input will not drive the gen-
erator beyond the normal dial limits of a range.
FREQUENCY MUL T Switch
The outer knob selects one of ten frequency
multipliers for the d;•I
@
setting.
VERNIER Control
A fine adjustment of the frequency dial
®
setting.
Not GCV OUT Connector (Rear Panel)
in parallel with a higher impedance matches the receiving
instrument input impedance to the generator output im-
pedance, thereby minimizing signal reflection or power loss
on the line due to impedance mismatch.
3.2.2
Voltage Controlled Function Generator Operation
Operation as a voltage controlled function generator (VCG)
is as for a manually controlled function generator, only the
frequency within particular ranges is additionally controlled
with de levels (±2V excursions) injected at the VCG IN con-
nector. Set the frequency dial to a reference from which
the frequency is to be voltage controlled.
1.
For frequency control with positive de inputs at VCG
IN, set the dial for a lower frequency limit.
Shown 2. For frequency control with negative de inputs at VCG
IN, set the dial for an upper frequency limit. This connector gives a 0 to +2V signal propor-
tional to the frequency of the generator within
any given range. The signal can be used as the
X drive for X-Y recorders.
Not EXT DC OFFSET IN Connector (Rear Panel)
Shown
Applied voltage offsets the selected waveform lin-
early. Offset is 1 V for each -1 V applied with out-
put connected into an open circuit. Maximum input
is ±15V. Offset is affected by the attenuator
@
3.2 OPERATION
Perform the initial checkout in Section 2 for the feel of the
instrument. Any questions concerning individual controls
and connectors may be answered in paragraph 3.1.
3.2.1 Signal Termination
Proper signal termination, or loading, of the generator con-
nectors is necessary for its specified operation. For example,
the proper termination of the main output is shown in
figure 3-3. Placing the 50fl terminator, or 50Q resistance,
MODEL 143
RG58 OR
EFFECTIVE
RECEIVING
INSTRUMENT
Figure 3-3. Signal Termination
3.
For modulation with an ac input at VCG IN, set the
dial at the desired center frequency. Do not exceed
the maximum dial range of the selected frequency
range.
Figure 3-4 is a nomograph with examples of dial and voltage
effects. Example 1 shows that with OV VCG input, fre-
quency is as determined by the main dial setting, 1.0 in this
MAIN DIAL VCGIN
OUTPUT
SETTING VOLTAGE
FREQUENCY
FACTOR
2.0 -2.0
.002
1.8
-1-6
.2
1.6 -1-2
.4
1.4 - .8
,,_v'-~~
.6
~"'J.~
_..
1.2
- .4_. .8
1.0
-
- 0
E~~L~1
1.0
'
'
.8
'
+ .4
1.2
'
.6
'
+ .8
1.4
'
.4 +1.2
'<"+
1.6
,.,~
~
.2
+1.6
~.,>
1.8
'
'
.002
+2.0
2.0
Figure 3-4. VCG Voltage-to-Frequency Nomograph
3-3