SECTION III
OPERATING INSTRUCTIONS
3-1. INTRODUCTION.
e. Connect load to output connector having an
3-2. The Model 652A Test Oscillator generates a stable sine
wave output that is available at output impedance levels of
600 ohms and 50 ohms. The frequency of the output is
variable from 10 Hz to 10 MHz. The output power level can
be varied from
10
microvolts to 3.16 volts into 600 or 50
ohm loads. The output monitor may be used as a voltmeter
to monitor the amplitude of the output, or it may be used to
establish a reference level for the output.
3-3. CONTROLS AND INDICATORS .
34. Figure 3-1 identifies and describes the function of all
the front and rear panel controls, connectors, and indicators
on the Model 652A.
3-5. AOJUSTMENT OF MECHANICAL ZERO.
3-6. The output monitor is properly zero.,;et when the meter
pointer rests over the zero mark, and the Test Oscillator is in
normal operating position at normal operating temperature,
and is turned off. Zero.,;et the output monitor as follows to
obtain maximum accuracy and mechanical stability.
a. Turn Test Oscillator on and allow it to operate for
at least 20 minutes, to let the meter movement
reach normal operating temperature.
b. Turn Test Oscillator off, and allow 30 seconds for
all capacitors to discharge.
c. Insert pointed object (such as tip of ball·point pen)
into recess on adjustment wheel, and rotate wheel
until meter pointer is exactly over zero.
3-7. OPERATION.
3-8. To operate the 652A Test Oscillator, proceed as
follows:
a. Set the slide switch (S5) to the proper line voltage
(l IS V or 230 V at 48 - 66 Hz), and connect the
selected primary power to the Test Oscillator.
b. Turn LINE ON switch to On position. Indicator
lamp will glow, verifying application of primary
power.
c. S e t F REQUENCY R A N G E switch a nd
FREQUENCY Dial to desired output frequency.
d. Set OUTPUT ATTENUATOR switch to desired
voltage range.
impedance whlch matches impedance of load.
f. Place MONITOR switch in NORMAL position, and
adjust AMPLITUDE controls for desired output
voltage, as indicated on the output monitor.
g. The output monitor, M l , indicates the
ffiS
value of
the output voltage, and the power level in dBm for
resistive loads of 50 ohms. The output voltage level
is obtained by multiplying the monitor scale reading
by the monitor scale multiplier which appears on
the OUTPUT ATTENUATOR switch. Use the
following equation and the impedance correction
graph of Figure 3 -2 to obtain the Model 652A
output power level in dBm, for loads other than
those marked on the output connectors.
R L
Output Voltage
�
RL + RS X 2V m
Where,
RL
�
Load Resistance (Terminating
Resistance)
RS
�
Source Resistance (Output
Impedance of Oscillator)
V m
�
Model 652A Output Monitor
voltage indication multiplied
by the output at(enuator vol·
tage setting.
Problem: A 600 ohm load is placed on the 50 ohm output
connector. The Model 652A output monitor indicates an
output of 0.9 volts, with the OUTPUT ATTENUATOR set
on the 1.0 volt (+10 dBm) range. Find the actual output
voltage and power level (in dBm) of the Model 652A.
Solution: TI,e actual output voltage is calculated as follows:.
Output Voltage
�
600
X2 (0.9)
�
1.66 volts
600 + 50
If the monitor were to indicate this 1.66 volts, then the
power level indicated would be +17.3 dBm (on the +20 dBm
range). The actual power level, however, in the 600 ohm load
is the algebraic sum of this theoretically indicated power
(+ 17.3 dBm) and a correction factor. The correetion factor is
obtained from the impedance graph of Figure 3-2; for this
example, using a 600 ohm load, it would be -10.8 dBm. The
actual power level in the 600 ohm load, then, is +6.5
dBm[17.3 dBm + (-10.8 dBm)]
3-1