CIRCUIT DESCRIPTION
Model
2001
Transistors 015 and Q16 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 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.
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
~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 (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
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
to 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
at
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.
In 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
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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