Description Of The Oscillator - BRUEL & KJAER 1022 Instructions And Applications

Description of the Oscillator· and Mixer-Section.
Fig. 1.1 shows a block diagram of the complete Oscillator.
The fixed oscillator is tufied to 120 k c/s and can be frequency modulaled. The
reactance tube circuit acts as a variable inductance and the modulation swing
can be varied from 0 to
±
250
c/~y
means of a switch on the front panel
of the apparatus, marked FREQUENCY DEVIATION.
By means of the switch marked MODULATION FREQUENCY the frequency
of the built-in saw-tooth oscillator may be chosen. Frequencies of 1- 1.6--2.5
-4-6.3- 10-16 and 25 c/ s are available. The oscillator is a blocking type,
tuned to approximately 7 Mc/ s, and Lhe frequency of the saw-tooth oscilla-
tions is set by changing the grid resistor.
Fixed Variable
)J
Oscillator Amplifier
Regulating
Amplifier
Mixer
Low Pass
Filter
Variable
Oscillator
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I
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I
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Impedance
Output Matching
Amplifier Circuit
Ref. Sig. Remote
1000c;~l
~
Fontrol
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Magnetic :
Clutch 1
I
Output
Attenuator
Load
Output
Attenuator
Output
Fig. 1.1. Block Diagram of the Beat Frequency Oscillator 1022.
Provision is made for external modulation. The external generator should
then be connected to two terminals of the socket on the front plate marked
REMOTE CONTROL. For external modulation a voltage of approximately
3.5 volts is necessary when a modulation swing of
±
250 c/s is required.
When external modulation is etmployed the switch marked MODULATION
FREQUENCY must be in position "Ext. Mod. " , as in this position of the
switch the reactance tube is on and the saw-tooth oscillator is off.
A variable capacitor inserted in the tuned circuit of the fixed oscillator,
arid operated by the knob marked FREQUENCY INCREMENT, permits
exact frequency selection in the range
.±
50
ci s
for any setting on the main
scale. Thus, using this capacitor, frequencies down to zero may be obtained,
even t!J.ough the main scale is only calibrated from 20 c/s to 20ooo cis:
By means of a noiseless switch on the front panel, marked OSCILLATOR
STOP, the voltage on the anode of the 120 kc/ s oscillator can be disconnected.
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