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CIRCUIT DESCRIPTION
Model
2001
Transistors 0 1 5 and Q16 are switching transistors which
connect the output o f the leveling amplifier to the voltage
variable attenuator associated with the operating band.
4.9 MARKER ADDER (MODULE M5H)
The main function of this module is adding together and
amplifying the individual marker signals from the M6 marker
modules. It also contains the external marker mixer circuit
and the sweep sample selection and leveling circuits.
The desired sweep sample signal (band 1 or band 2 and
band 3) is selected by the PIN diode switch CR4 and CR5.
The sweep sample signal i s then leveled in the same manner
as the main RF output signal. The voltage from the moni-
tor, CR7, and the reference voltage from R46 is fed to the
levelingamplifier consisting of transistor stages012 and 013.
0 1 1 provides blanking of the leveling amplifier. Any error
between the two input signals is amplified and fed to the
voltage variable attenuator CR6. The operation of this cir-
cuit produces a constant amplitude signal at the monitor
point.
The leveled sweep sample signal is connected to the external
marker mixer, CR
1
and CR2, and to the sweep sample out-
put connector, J4. A
47
ohm resistor, which is connected
between J4 and the monitor point, establishes the source
~mpedance at approx~mately 50 ohm. The signal is then
routed to each M6 marker module.
The marker output signals from the individual M6 marker
modules are connected to the input pins
I ,
2, 3, and 4 of
the M5H module. One or two M6 outputs are connected to
each input.
The signals are then amplified in the input
stages ( 0 2 , 0 3 , 0 4 , and 0 5 ) and combined in the common
collector load.
The collector load is an external 10mH
choke when the Front Panel MARKER WIDTH Selector
is set t o "WIDE", or a 3.3k ohm resistor, R21, when the
Width Selector is set t o "NARROW." The combined mark-
er signals are then amplified in transistor stages 06, 0 7 and
Q8.
The Front Panel Marker WIDTH Selecter also varies
the high frequency gain of the amplifier by connecting
capacitance across R27, the feedback resistor. The amplified
signal is then fed to the complimentary output stage, Q9
and 010, which is biased so that input signals less than 0.5
voltsare not amplified. This eliminates most spurious mark-
ers and noise from the output. The output is then connect-
ed to the Front Panel MARKER SlZE Control and finally
t o the Front Panel SCOPE VERT. connector.
4.10 MARKERS (MODULE M6's)
Each marker module contains a crystal oscillator, a tuned
or untuned mixer and a marker amplifier. Harmonic genera-
tor marker modules also include one or more harmonic
generating stages.
Several types of marker modules are required to cover the
wide frequency range and to produce both single frequency
and harmonic type markers. A single frequency marker
generator produces a marker at a single frequency while the
harmonic marker generator produces markers at harmoni-
cally related frequencies of the crystal oscillator.
The model number for single frequency markers is M6S
followed by the marker frequency. The model number for
harmonic markers is M6H followed by the harinonic marker
frequency.
The Crystal Oscillator operates between the frequencies of
100 kHz and 55 MHz. Several different types of oscillators
are required to cover this range of frequencies. The 100
kHz oscillators use a tuned oscillator with the crystal operat-
ing at its fundamental frequency in
a
serles resonant mode.
The 1 to
17
MHz crvstal oscillators are either tuned series
resonant mode oscillators or untuned pierce type oscillators.
The 17 to 55 MHz oscillators use a tuned Colpits oscillator
with the crystal operating
a t
its third overtone frequency in
a series resonant mode. The tuning supresses the crystal
fundamental and higher order resonant frequencies. The
crystal and marker frequency are the same for frequencies
between 100 kHz and 55 MHz.
The markers above 55
MHz use harmonic generating techniques.
The output from the crystal oscillator (or harmonic genera-
tor) is combined with the sweep sample in the mixer stage.
I n the case of single frequency markers, the mixer includes
a tuned circuit which selects the desired crystal or crystal-
harmonic frequency and the sweep sample frequency. I n
the case of a harmonic marker, the mixer is untuned. The
mixer circuit is generally a diode mixer, although transistor
mixers are sometimes used. The fundamental and product
signals are filtered from the mixer output, leaving the
"difference signal" which is applied to the marker amplifier
stage.
The marker amplifier is a single stage amplifier having a fre-
quency response of several kHz t o approximately 500 kHz.
The output of the marker amplifier i s connected through
the SlZE Control to the output pin of the module.
CIRCUIT DESCRIPTION
Transistors 015 and 016 are switching transistors which
connect the output of the leveling amplifier to the voltage
variable attenuator associated with the operating band.
4.9 MARKER ADDER (MODULE M5H)
The main function of this module is adding together and
amplifying the individual marker signals from the M6 marker
modules. It also contains the external marker mixer circuit
and
the sweep sample selection and leveling circuits.
The desired sweep sample signal (band 1 or band 2 and
band 3) is selected by the PIN diode switch CR4 and CR5.
The sweep sample signal is then leveled in the same manner
as the main R F output signal. The voltage from the moni-
tor, CR 7, and the reference voltage from R46 is fed to the
leveling amplifier consisting of transistor stages 0 12 and 013.
011 provides blanking of the leveling amplifier. Any error
between the two input signals is amplified and fed to the
voltage variable attenuator CR6. The operation of this cir-
cuit produces a constant amplitude signal at the monitor
point.
The leveled sweep sample signal is connected to the external
marker mixer, CR
1 and CR2, and to the sweep sample out-
put connector, J4. A 47 ohm resistor, which is connected
between J4 and the monitor point, establishes the source
impedance at approximately 50 ohm.
The signal is then
routed to each M6 marker module.
The marker output signals from the individual M6 marker
modules are connected to the input pins 1, 2, 3, and 4 of
the M5H module. One or two M6 outputs are connected to
each input.
The signals are then amplified in the input
stages (02, 03, 04, and 05) and combined in the common
collector load.
The collector load is an external 10mH
choke when the Front Panel MARKER WIDTH Selector
is set to "WIDE", or a 3.3k ohm resistor, R21, when the
Width Selector is set to "NARROW." The combined mark-
er signals are then amplified in transistor stages 06, 07 and
08.
The Front Panel Marker WIDTH Selecter also varies
the high frequency gain of the amplifier by connecting
capacitance across R27, the feedback resistor. The amplified
signal is then fed to the complimentary output stage, 09
and 010, which is biased so that input signals less than 0.5
volts are not amplified. This eliminates most spurious mark-
ers and noise from the output. The output is then connect-
ed to the Front Panel MARKER SIZE Control and finally
to the Front Panel SCOPE VERT. connector.
4-8
Model 2001
4.10 MARKERS (MODULE M6's)
Each marker module contains a crystal oscillator, a tuned
or untuned mixer and a marker amplifier. Harmonic genera-
tor marker modules also include one or more harmonic
generating stages.
Several types of marker modules are required to cover the
wide frequency range and to produce both single frequency
and harmonic type markers.
A single frequency marker
generator produces a marker at a single frequency wh ile the
harmonic marker generator produces markers at harmoni-
cally related frequencies of the crystal oscillator.
The model number for single frequency markers is M6S
followed by the marker frequency. The model number for
harmonic markers is M6H followed by the harmonic marker
frequency.
The Crystal Oscillator operates between the frequencies of
100 kHz and 55 MHz. Several different types of oscillators
are required to cover this range of frequencies.
The 100
kHz oscillators use a tuned oscillator with the crystal operat·
ing at its fundamental frequency in a series resonant mode.
The 1 to 17 MHz crystal oscillators are either tuned series
resonant mode oscillators or untuned pierce type oscillators.
The 17 to 55 MHz oscillators use a tuned Colpits oscillator
with the crystal operating at its third overtone frequency in
a series resonant mode.
The tu ning supresses the crystal
fundamental and higher order resonant frequencies.
The
crystal and marker frequency are the same for frequencies
between 100 kHz and 55 MHz.
The markers above 55
MHz use harmonic generating techniques.
The output from the crystal oscillator (or harmonic genera·
tor) is combined with the sweep sample in the mixer stage.
I n the case of single frequency markers, the mixer includes
a tuned circuit which selects the desired crystal or crystal-
harmonic frequency and the sweep sample frequency.
In
the case of a harmonic marker, the mixer is untuned. The
mixer circuit is generally a diode mixer, although transistor
mixers are sometimes used. The fundamental and product
signals are filtered from the mixer output, leaving the
"difference signal" which is applied to the marker amplifier
stage.
The marker amplifier is a single stage amplifier having a fre-
quency response of several kHz to approximately 500 kHz.
The output of the marker amplifier is connected through
the SI ZE Control to the output pin of the modu Ie.
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