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CIRCUIT DESCRIPTION
Model
2001
Section D. Amplified triggers are routed into the hysteresis
switch independently of the internal routing transistor,
providing additional (redundant) line rate reliability.
4.5 SWEEP DRIVE (MODULE M2H)
The M2H module provides the correct sweep drive voltage
required by each oscillator as programmed by the Front
Panel Tuning controls, Sweep Width controls, and the Mode
switch.
These programs are summed to a standard voltage level and
then feed shaping circuits for each band which are en-
abled by the B - I and 6-2 voltages and by a synthezied 8-3
voltage.
The shaping diodes conduct at levels determined by a resis-
tor network driven by a constant current source, 07.
Aseach diode conducts, an additional current is fed into the
summing junction of the output amplifier consisting of
Q12, 013, and Q14.
The output waveform amplitude is controlled by R72, R76,
and R80 which are connected by switch transistors Q15,
Q16, and Q17 into the feedback path t o the summing junc-
tion.
This module also provides two regulated voltages for use
primarily a s programming voltages and an inverting ampli-
fier t o furnish an inverted triangle wave for use in the start-
stop mode of programming.
4.6 SWEEP OSCI LLATOR, BAND 1
(MODULE M9H)
The RF sweep signal for band 1 is developed b y the hetro-
dyne method which utilizes two UHF sweep oscillators, a
diode mixer, and a wide-band RF amplifier.
Sweep oscillator, Q2, sweeps from approximately 1.4 to
1.65 GHz. The average frequency is adjusted by R2 which
controls the average bias on the varactor diodes, CRI, CR2,
and CR3. The sweep drive voltage from pin 9 of the module
i s connected to the opposite side of these diodes causing
the frequency to vary above and below this average fre-
quency in a low-to-high frequency direction.
Sweep oscillator, Q5, is similar to the 0 2 circuit, however,
the varactor diodes have been reversed, and the polarity of
the bias voltage supplied by R12, course adjustment, and
R13, CENT FINE adjustment, has been changed. These
changes cause the oscillator frequency to vary from a high
to low frequency.
The approximate output frequency is
1.4 and 1 . I 5 GHz. This out of phase sweep technique has
several advantages. First, larger sweep widths are obtainable
and second, the nonlinearity (FREQ versus TIME) of one
oscillator is cancelled by the nonlinearity of the second
oscillator.
R9, which is a linearity adjustment, optimizes
this cancelling process by controlling the sweep drive ratio
between the oscillators.
The two sweep signals are combined in a single balance
diode mixer comprised of L4, L5, CR8 and CR9. The
resultant, difference frequency, of 0 t o 500 MHz, is then
amplified in the wide band amplifier consisting of transis-
tor stages Q11, Q12, and (313.
Transistor stages 0 6 and 0 7 supply the blanking voltage to
the wide band amplifier and causes it t o be shut off during
the sweep retrace time. The output from the wide band
amplifier is connected to J1, which in turn is connected to
the output wide band amplifier located in module MIOH.
A second output is also obtained from this amplifier and is
coupled,via R45, to a similar wide band amplifier consisting
of transistor stages Q14, 015, and Q16. The output from
this amplifier is connected to J2 which in turn is connected
to the marker generating circuits.
Transistors 0 8 , 09, and 0 1 0 provide a -15 volt supply to
operate the sweep oscillators. This improves stability and
provides isolation between the oscillators and the -18 volt
supply.
4.7 OUTPUT AMPLIFIER, BAND 1
(MODULE MIOH)
The MlOH module contains a wide band amplifier, an
electronic attenuator, and a leveler amplifier.
WIDE BAND AMPLIFIER
This amplifier provides 2 stages of RF amplification to in-
crease the RF input level present at 0 1 by about 40dB.
The frequency response o f this amplifier i s reduced for fre-
quencies near 0.5 MHz or lower and above 500 MHz.
The input amplifier stage consisting of 01, Q2, and 0 3 is
enabled by the B+1 switching voltage, and the output stage,
consisting of 0 4 , 05, and 0 6 by the -20 voltage, when the
Front Panel band switch is in the Band 1 position. The -20
voltage also provides current through R30 and the
R F
out-
CIRCUIT DESCRIPTION
Section D. Amplified triggers are routed into the hysteresis
switch independently of the internal routing transistor,
providing additional (redundant) line rate reliability.
4.5 SWEEP DRIVE (MODULE M2H)
The M2H module provides the correct sweep drive voltage
required by each oscillator as programmed by the Front
Panel Tuning controls, Sweep Width controls, and the Mode
switch.
These programs are summed to a standard voltage level and
then feed shaping circuits for each band which are en-
abled by the B-1 and B-2 voltages and by a synthezied B-3
voltage.
The shaping diodes conduct at levels determ ined by a resis-
tor network driven by a constant current source, 07.
Aseach diode conducts, an additional current is fed into the
summing junction of the output amplifier consisting of
012, 013, and 014.
The output waveform amplitude is controlled by R72, R76,
and R80 which are connected by switch transistors 015,
016, and 017 into the feedback path to the summing junc-
tion.
This module also provides two regulated voltages for use
primarily as programming voltages and an inverting ampli-
fier to furnish an inverted triangle wave for use in the start-
stop mode of programming.
4.6 SWEEP OSCILLATOR, BAND 1
(MODULE M9H)
The R F sweep signal for band 1 is developed by the hetro-
dyne method which utilizes two UHF sweep oscillators, a
diode mixer, and a wide-band RF amplifier.
Sweep oscillator, 02, sweeps from approx imately 1.4 to
1.65 GHz. The average frequency is adjusted by R2 which
controls the average bias on the varactor diodes, CR 1, CR2,
and CR3. The sweep drive voltage from pin 9 of the module
is connected to the opposite side of these diodes causing
the frequency to vary above and below this average fre-
quency in a low-to-high frequency direction.
Sweep oscillator, 05, is similar to the 02 circuit, however,
the varactor diodes have been reversed, and the polarity of
the bias voltage supplied by R 12, course adjustment, and
R13, CENT FINE adjustment, has been changed.
These
4-6
Model 2001
changes cause the oscillator frequency to vary from a high
to low frequency.
The approximate output frequency is
1.4 and 1.15 GHz. Th is out of phase sweep technique has
several advantages. First, larger sweep widths are obtainable
and second, the nonlinearity (FREO versus TIME) of one
oscillator is cancelled by the nonlinearity of the second
oscillator.
R9, which is a linearity adjustment, optimizes
this cancelling process by controlling the sweep drive ratio
between the oscillators.
The two sweep signals are combined in a single balance
diode mixer comprised of L4, L5, CR8 and CR9.
The
resultant, difference frequency, of 0 to 500 MHz, is then
amplified in the wide band amplifier consisting of transis-
tor stages 011,012, and 013.
Transistor stages 06 and 07 supply the blanking volfage to
the wide band amplifier and causes it to be shut off during
the sweep retrace time.
The output from the wide band
amplifier is connected to Jl, which in turn is connected to
the output wide band amplifier located in module M 1OH.
A second output is also obtained from this amplifier and is
coupled, via R45, to a similar wide band amplifier consisting
of transistor stages 014, 015, and 016. The outpu t from
this amplifier is connected to J2 which in turn is connected
to the marker generating circuits.
Transistors 08, 09, and 010 provide a -15 volt supply to
operate the sweep oscillators. This improves stability and
provides isolation between the oscillators and the -18 volt
supply.
4.7 OUTPUT AMPLIFIER, BAND 1
(MODULE M10H)
The M 1 OH module contains a wide band amplifier, an
electronic attenuator, and a leveler amplifier.
WIDE BAND AMPLIFIER
This amplifier provides 2 stages of R F amplification to in-
crease the RF input level present at 01 by about 4OdB.
The frequency response of this amplifier is reduced for fre-
quencies near 0.5 MHz or lower and above 500 MHz.
The input amplifier stage consisting of 01,02, and 03 is
enabled by the B+l switching voltage, and the output stage,
consisting of 04, 05, and 06 by the -20 voltage, when the
Front Panel band switch is in the Band 1 position. The -20
voltage also provides current through R30 and the
RF
out-
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