“High resolution scans of obsolete technical manuals”
If your looking for a quality scanned technical manual in PDF format please visit
our WEB site at
manuals@artekmedia.com and we will be happy to email you a current list of the
manuals we have available.
If you don’t see the manual you need on the list drop us a line anyway we may
still be able to point you to other sources. If you have an existing manual you
would like scanned please write for details. This can often be done very
reasonably in consideration for adding your manual to our library.
Typically the scans in our manuals are done as follows;
1) Typed text pages are typically scanned in black and white at 300 dpi.
2) Photo pages are typically scanned in gray scale mode at 600 dpi
3) Schematic diagram pages are typically scanned in black and white at 600
dpi unless the original manual had colored high lighting (as is the case for
some 70’s vintage Tektronix manuals).
4) Most manuals are text searchable
5) All manuals are fully bookmarked
All data is guaranteed for life (yours or mine … which ever is shorter). If for ANY
REASON your file becomes corrupted, deleted or lost, Artek Media will replace
the file for the price of shipping, or free via FTP download.
The Modulation Meter, type
a solid-state, line- or battery-operated
precision measuring instrument for ac-
curate measurement of the modu
depth of
ation of
quency range from
Modulation Meter
cepting telemetric signals with a modulation frequency up to 200 kHz, and
stereo signals for which it features an
L/R-separation of
The
flection for
and
kti~
srnall amount of residual modulation
generated in the
er, it
and
F"M
measurer( enfs on distol-ted signuls are
AM
signals and the peak devi-
FM
signals in the carrier fre-
5
to 1002 MHz. The
is
designed for ac-
46
dB.
indicating metel- has fuI I -scale de-
3,
76,
30,
53,
*1C,
t
hl\,
is
possible to measure residual
AM
in
signals, and vice versa. Accilrate
k3C1
peak value. Due to the vely
oscillators, sp~~rious
If;GC,
idiodulation Meter plop-
and
AFM2,
lation
1
0C9h
and
AM
is
AM,
zt2C.C
FM
on
A.
Introduction
rendered easy by a
the positive
ue to be measured separately.
creased resolution
nal indicator, such as a voltmeter,
he
ranges downwards.
The input signal level necessury for
occbracy
cy range
range
the range
mcim operating input
Besidzs a manual level control, the
Modulation Meter features
level control with a regulating range
of
To increase the versatility of the Modulation Meter for
row-band equipment, it
two
kHz, just as three standal-d deen~phasis
networks of
non-standard of
four low-pass filters with frequencies of
2. The above accuracies are valid for modulation
depths up to 90% AM within the carrier frequency
range 15-300 MHz, and up to 30% AM within the
carrier frequency range 300-1 002 MHz.
dB
increase in minimum input level, the
15 kHz
Automatic level setting:
AM
distortion:
Carrier frequencies within
the range
5
-
300 MHz:
The following typical values are to be added to
the above accuracies:
At a modulation frequency of 20 Hz:
At a modulation frequency of 50 Hz:
At modulation frequencies above 100 Hz, the addi-
tional error
Note:
ic level settings) are valid only with the
set to SLOW. In position FAST, the lower frequency
limit
0.2% distortion at 30% AM and at modulation
quencies within 20 Hz - 15 kHz.
1%
cies within
The specified accuracies (manual and automat-
is
distortion at 90% AM and at modulation frequen-
is
160 Hz.
10
negligible.
Hz - 50 kHz.
6%
of reading.
1
%
bf
reading.
METER
1
switch
fre-
Carrier frequencies within
the range 300 - 1002 MHz:
In order to achieve the highest possible sensitivity
of the modulation meter, the frequency of the crystals must be as high as possible. Overtone crystals
-
100
having frequencies within the range 40
are recommended. The crystal frequency f
termined by
f -2
f=
cr 2n
where f indicates the carrier frequency and n the
odd harmonic of the crystal overtone-frequency.
The sensitivity specifications, item
are based on the following combinations of carrier
frequency, order of harmonic, and range of crystal
frequencies.
Carrier frequency
s
f
s
s
Order of harmonic
MHz
n
l
NPUT
Range of crystal
frequencies
MHz
is
cr
LEVEL,
f
cr
de-
Characteristics of the crystals:
Type:
Frequency:
Frequency tolerance:
Frequency tolerance over
operating temperature range:
Condition of resonance:
Mode of operation:
Max. drive level:
Max. equivalent series
diagram shown in
signals to the 50
are fed to a diode mixer via an input
attenuator providing for 10, 20, 30,
and 40 dB attenuation and thus accom-
RF
modating
r.m.s. The mixer, which
highly linear, so that distortion of
and
amplitude-modulated signals
is
coupled to the local tuning oscillator.
RF
For
5 to 200 MHz, mixing
the fundnmental frequency of the local
oscilla:or, whilst it takes place with
the third and fifth harmonics in the
range from 200 to 1002 MHz.
sults in an
mixer can also be coupled to an option-
al Crystal Oscillator Unit,
252, which can accommodate four crystals, thereby enabling measurements at
four predetermined, fixed frequencies.
the signal from the mixer
through an IF filter, which
linear band-pass filter with
of
1400 kHz, a high degree of phase-
linearity being necessary in order to
pass a multiplex stereo signal with min-
imum distortion.
From the
to an
buffer. At the same time, the
IF
signals from 3 mV to 10 V
input signals in the range from
IF
signal of 2 MHz. The
IF
filter, the
preamplifier which acts as a
simplified block-
Fig.
Dl
,
the
Cl
coaxial connector
is
balanced
is
is
realized with
code
is
is
a
bandwidth
IF
signal
RF
input
avoided,
This
re-
900-
passed
a phase-
is
fed
IF
pre-
amplifier provides for
the
IF signal.
gether with ideal coupling to the
filter, keeps the noise level down to
a minimum at all input levels.
The
IF
preamplifier
diode attenuator whose biasing current
can be controlled
LEVEL, accessible on the front panel of
the Modulation Meter. Level control can
be performed within a range of 40 dB.
Alternatively, the
driven by a voltage proportional to the
IF
level amplified in an AGC amplifier.
This
provides for automatic level control
within 40 dB. Fine adjustment
theless also possible by means of the
potentiometer
The
IF
signal from the
then fed to an
sists of two wideband amplifier stages.
The
IF
amplifier brings the
the level required by the
The
amplified
either through
through a phase-compensator, according
to the position of the
.
The band-pass filter has a band-
trol
width of
just as the
use when measuring on weak signals
from narrow-band equipment. The phase
compensator leaves the initial bandwidth
unchanged.
detector and
sists of a unity-gain amplifier with low
output impedance and serves to suppress
any influence from the
is
available for external monitoring from
a coaxial connector on the front panel.
IF
The
is
fed both to the AM detector and to
the
IF
output amplifier. The AM detec-
tor
is
an amplifier with a mean-value
detector in the feedback loop which
also provides for the large amount of
linearity required. The AM detector has
a
dc and an ac output. The first of
these
strument via the FUNCTION selector.
In the corresponding position of the
FUNCTION selector, the meter indicates the value of the AM detector's
dc current
el. The second output of the AM detector
below) via the selector FUNCTION.
As stated above, the
buffer amplifier
output amplifier which provides for amplification so that the level required for
driving a following limiter
The limiter transforms the
a square wave, the zero crossing of
which
peak-to-peak value being compared with
variations in the mean value. Subsequent
limiting action takes place in the following limiter section. The resulting signal
is
detector section which consists of a
monostable multivi
amplifier.
The signal from the last limiter section
is
vibrator which provides for pulses of
constant width. The
tivibrator are amplified in an output amplifier. The output
with a regulating loop consisting of a
peak detector and an amplifier.
regulating loop keeps the value of the
peak-to-peak voltage of the output am-
is
is
coupled to the AF section (described
is
fed via a buffer amplifier to the
used to trigger a monostable multi-
IF
output amplifier. It con-
IF
output which
signal from the buffer amplifier
coupled to the meter of the in-
-
in other words: the IF lev-
IF
signal from the
is
also fed to the
is
obtained.
IF
signal into
controlled by variations in the
IF
FM
brator and an output
pulses from the mul-
amp1 ifier
is
provided
This
pl ifier constant. Hence, as the amplitude
and the width of the pulses are constant,
the mean value of the signal will vary
according to the number of pulses per
second. The mean value
when the
sition IF CHECK for reading the value
of the intermediate frequency. To ensure
a
high degree of accuracy and an extreme-
ly low hum level, both the multivibrator
and the output amplifier are furnished
with their own regulated power supply.
From the AM or
is
fed to a low-pass filter via a relay
controlled by the FUNCTION selector.
The low-pass filter features the
gree of
ing stereo information without any disturbing influence on
The low-pass filter
two-section,
uator which determines the metering
ranges.
providing for amplification
signal to the level required by the next
stages.
The AF amplifier
phasis networks providing for the stan-
dard deemphases of 50, 75, and 750
and the non-standard deemphasis of
dB/oct. The amplified AF signal can
also be passed through one of four
pass filters with frequencies of
75 and 200 kHz, or through a
pass filter with 3 dB points at 50 Hz
and 15
applications.
These networks and filters are followed
by an AF amplifier.
from this amplifier
front panel via the AF OUTPUT connector for distortion measurements or
external monitoring.
OUTPUT does not interfere with the me-
ter indication. The output voltage from
the first AF amplifier
other AF amplifier providing for the
voltage necessary for the AF detector.
The signal from the AF OUTPUT can
either be dc-coupled or ac-coupled to
tions according to the position of the
switch MAN.-AUTO.
The AF detector gives the true peak value of any AF signal. Depending on the
position of the FUNCTION selector, the
positive or the negative modulation peak
can be measured. The AF detector has
two time constants, thereby furnishing
two meter responses.
The AF detector
pedance-matching network providing for
low output impedance to the meter.
CONTROLS,
General
As can be seen in Fig. D2 and
Modulation Meter, type
provided with the following controls,
meter, and terminals:
Controls, Meter, and Front Plate Termin-
als (see Fig. D2)
Power Lamp and
The power switch
monitored
RANGE Selector and Drum Scale (2)
The selector RANGE
tion rotary switch. In the first six po-
sitions, the RANGE selector provides
for selection of the frequency ranges
according to the table printed on the
front plate of the instrument. (Note
that the ranges
frequency bands.) The next position
a rest position. In the last position,
the plug-in Crystal Oscillator Unit (if
any)
is
monitored
ately above.
TUNING Knob (3)
The knob TUNING provides for adjust-
ment of the local oscillator frequency
at
2
is
monitored by a cursor on the drum scale.
LEVEL Potentiometer (4) and MAN.
AUTO. Switch
by
is
connected. The selector
MHz from the signal frequency. It
is
followed
METER,
the lamp POWER.
E
by
AND
ON
switch (1)
OIV
is
is
and F .each cover two
the drum scale immedi-
by
TERMI
D4, the
AFM2,
a toggle switch
an eight-posi-
(5)
an im-
NALS
is
is
RANGE
-
When the switch MAN. -AUTO.
position
ter
instrument manually within a range of
min. 40 dB.
When the switch MAN.-AUTO.
,position AUTO., the LEVEL potentiome-
ter
automatical
i
nstrument.
FUNCTION Selector
The selector FUNCTION
position rotary switch. The position
LEVEL
nal
IF
level. When measuring, the positions
IF
ment to the exact carrier frequency.
(See under "Meter" below) The percentage of amplitude modulation of AM signals can be measured by placing the
selector in position AM
cording to the sign of the modulation
peak to be measured. The frequency
deviation of
sured
FM
the modulation peak to be measured.
METER
'the selector
position rotary switch. Each position
corresponds to the fu
the meter, viz: AM
loo%,
METER
The switch
In position SLOW
meter response
should not be used when measuring on
signals with modulating frequencies
higher than 160 Hz.
mod
fast.
IF
MAN.,
is
used to vary the sensitivity of the
is
used for fine-adjustment of the
ly adjusted sensitivity of the
the LEVEL potentiome-
(6)
is
a
is
used when searcfiing the sig-
(i.e., tuning) and monitoring the
CHECK are used to tune the instru-
+
or AM - ac-
FM
signals can be rhea-
by
placing the selector in position
+
or FM - according to the sign of
RANGE
FM3
Switch
>I60 Hz, the meter response
BANDWIDTH
Selector
METER
-
10
-30
(8)
METER
is
(9)
(7)
RANGE
l
I-scale range of
3
-
10 - 30
-
100
-
is
a sliding switch.
fmod >10 Hz, the
slow. This position
In
position FAST
is
is
seven-
is
a five-
300kHz.
in
in
-
is
The potentiometer LEVEL has two func-
The switch IF BAbIDWIDTH
is
a sliding
Fig.D2. Front plate of the Modulation Meter, type AFM2.
switch. It provides for switching from
the band-pass filter to the phase-comparator and vice versa,
width of k25 kHz to one of k400kHz.
AF
FlLTER/DEEMPHASIS Selector (1 0)
The selector AF
a nine-position rotary switch. In the scales.
first position
a
band-pass filter
used when measuring residual AM and
FM.
kHz
REO),
pass filters are switched in. They are
used when measuring
AM
filters are used for modulation frequencies up to 3 kHz and 15 kHz, respective-
In the next four positions - 200
(L/R
STEREO), 75 kHz
15 kHz, and 3 kHz - four low-
modulation. The 3 kHz and 15 kHz
FI
-
50 Hz- 15 kHz (3 dB)
i
.
e
.,
from a band-
LTER/DEEMPHASIS
is
switched in. It
(A
f,
FM
deviation or
is
-
is
STE-
IY.
is
The 75 kHz filter
tion frequencies up to 75 kHz and for
measurements of
The last filter - 200 kHz
modulation frequencies up to 200 kHz
and for measurements of stereo L/R
separation (bandwidth: 10 Hz (0.1 dB)
-
350 kHz (3 dB)
The last four positions of the AF FILTER/
DEEMPHAS
emphases of 50
IS
selector introduce four de-
p,
used for modula-
FM
stereo deviation.
-
is
).
75p
(European and
used for
American standard for stereo work), 750
ps (narrow-band equipment) and a 6 dB/
oct (non-standard)
Meter
The meter of the Modulation Meter,
type
sion type. It
The upper scale
ing in the AM ranges from
0 to
or
from
viation, according to the positions of
the FUNCTION selector and the
RANGE selector. It
with a LEVEL mark to permit setting of
IF
the
The middle scale (12) provides for read-
ing in the AM ranges from 0 to 3% or
0
to 30%, and in the
0 to 3 kHz, Oto30kHz, or 0 to 300
kHz deviation, according to the position
of the FUNCTION and
I
ec tors.
se
The lower scale (13)
checking the frequency of the converted
signal.
viation around the 2 MHz intermediate
frequency. An
for exact tuning to the intermediate fre-
Before connecting the instrument to the
power line, make sure that the supply
transformer and the line voltage indicator are set to the voltage of the power
l
ine.
To prepare the instrument for
220
V
line voltage operation, refer to
diagram XI and proceed as follows:
1)
If the instrument must be used at a
line voltage of
3
and 5 and lugs 4 and 6 on the sup-
ply transformer.
2)
If the
line voltage of
4
and 5 on the supply transformer.
Then loosen the screws on the voltage
indicator and set the indicator to the
desired voltage.
MEASLIRI
instrument must be used at a
NG
11
0
V,
interconnect lugs
220
V,
interconnect lugs
AMPLITUDE MODULA-
110
E.
V
or
Operating Instructions
3)
Set the switch BANDWIDTH to
kHz when measuring on broad-band
equipment, or to
suring on narrow-band equipment.
4)
Set the switch
the modulation frequency of the signal
is
less than
160
FAST.
5) Set the switch
MA
N
.
6)
Set the drum scale to the desired
frequency range
selector.
7)
Set the selector FUNCTION to LEV-
EL.
8)
Set the tuning knob so that the cur-
sor on the drum scale indicates the signal frequency
so as to obtain maximum meter deflection.
*2
rt400
*25
kHz when mea-
METER
Hz; otherwise set it to
MAN.
by
using the RANGE
MHz, and then tune
to SLOW if
-AUTO. to
Modulation Percentage of AM Signals
1)
Feed the signal to be measured to
RF
the
that the max. applicable signal
r.m.s., and that the input impedance
is
2)
ing to the instructions printed on the
front panel, or refer to Fig.
TION
INPUT connector. Bear in mind
50
R.
Use the RF input attenuator accord-
D
-
GENERAL DESCRIPTION.
D3
is
10
V
in SEC-
9)
Turn the selector FUNCTION to
CHECK.
10)
Make a fine adjustment with the
TUNING knob so that the meter reads
IF
CHECK.
11)
Set FUNCTION to LEVEL. When
using MAN.-AUTO. in position MAN.
readjust to the
sary by means of the LEVEL potentiometer. When using MAN. -AUTO. in position AUTO., fine level-adjustment can
recommended to use the
AUTO. switch in position AUTO. when
performing
evitable level variations of the signal
then are equalized.
12) In order to obtain
select the low-pass filter corresponding
to the modulation frequency of the
Modulation
Frequency
50 kHz
15 kHz
AM
measurements, as the in-
the
MAN.
best accuracy,
-
sig-
El,
nal under test. See Fig.
SECTION
to
der
"AM
13)
Turn FUNCTION to
depending on which peak of modulation
is
to be measured.
14)
Rotate the selector
until a proper deflection
15)
Read the modulation percentage.
Check if the reading
both peaks of modulation: a difference
indicates distortion of the modulation
envelope. See Fig.
SECTION
"AM MODULATION Distortion".
Residual AM on
B
-
SPECIFICA'I'IONS un-
MODULATION Accuracy".
AM
METER
is
E2, and refer to
B
-
SPECIFICATIONS under
FM
Signals
and refer
+
or AM
RANGE
is
obtained.
the same for
-
,
20 Hz
c
-
-
10 Hz
5 MHz
Fig.
percentage measurements.
Modulation
Frequency
50 kHz
15 kHz
20 Hz
10 Hz
5 MHz
Fig.
percentage measurements.
-5%of reading + 1% of f.s.d.-
El
.
Accuracy of modulation
E2.
Distortion for modulation
-
-+
Carrier
300MHz 1002 MHz
300 MHz 1002 MHz
Frequency
Carrier
Frequency
Proceed as described above. If resolu
tion somewhat higher than that corresponding to the 3% AM range
external meter, e. g., an electronic voltmeter, may be connected to the AF OUT-
PUT connector. The external meter will
read
1
volt for full deflection of the in-
ternal meter,
RANGE selector set to
tion percentage read on the voltmeter
is
0.003% per mV.
The minimum residual AM reading for
a given deviation caused by the instrument itself can be estimated as follows:
1)
Apply
to LEVEL.
2)
Rotate the TUNING knob back and
forth so that the intermediate frequency
is
changed over the range 2 MHz - A f
to 2 MHz
viation of the frequency-modu lated sig-
nal whose residual AM
(Check the frequency change with the
IF
CHECK scale.)
3) Read the
change in the LEVEL reading. The minimum residual AM
Switch
to the desired channel by means of the
four-position selector.
8)
Insert a screwdriver in the hole corresponding to the selected channel, and
adjust the corresponding trimmer until
the meter indicates
the
Crystal Oscillator Unit
IF
CHECK.
9)
If
necessary, repeat steps
until all four channels are trimmed.
10)
'the Crystal Oscillator Unit, code
900-252,
Proceed as described above for
FM
measurements, but keep in mind
that certain specifications of the Modulation Meter proper cannot apply, and
refer to SECTION C under "Change in
Specifications of AFM2 Caused by the
Crystal Oscillator Unit", and see Fig.
is
now ready for use.
FREQUENCY RANGE
6
AM
to 9
or
E3.
Fig.
E6.
Attenuation and sensitivity ranges when the Crystal Oscil lator Unit,
The
connector on the front plate of the instrument, then passed through a resistive attenuator
20
which
of the mixer and to adapt the Modula-
tion Meter to
3
mV to 10 V r.m.s.
All
numbered between 1300 and 1399.
TUNER (See diagram No.
The local oscillator consists of (2103 in
a common-base Hart ley
same circuit configuration
ranges. Only the tank circuit
and LA) and the emitter capacitor CA
are exchanged to obtain the different
fundamental ranges from
Up to 200 MHz, the mixing takes place
with the fundamental frequency of the
local oscillator. Mixing with input signals which have a frequency higher than
200 MHz
or 5th harmonics of the local oscillator.
The intermediate frequency
be
used; however, only the lower sideband
can be used at 5 MHz
because the lower frequency limit of
the local oscillator
input signal
dB, 30 dB or
is
inserted to avoid overloading
RF
components of the
is
accomplished with the 3rd
2
MHz, and both sidebands can be
is
fed to the BNC
(~rovidin~ for 10 dB,
40
dB attenuation)
signals in the range
RF
attenuator are
1)
coupl ing . The
is
used in all
(CC, CB,
7
to 200 MHz.
is
chosen to
RF
input signal
is
7
MHz.
With the selector
CRYSTAL OSCILLATOR, the local os-
cillator
lator providing for operation at a fixed
frequency, such as the Crystal Oscil-
lator Unit, code
The signal from the
that from the local oscillator or the
Crystal Oscillator Unit are fed to the
diodes
balanced mixer and provide for good insulation between the input terminals and
the local oscillator or the Crystal
cillator Unit, and thereby reduce the
influence of stray radiation. The resulting 2 MHz signal
via
The tuner lias its own current limiters,
i.e.,
-12
Al l components of the tuner are num-
bered between 100 and 199.
IF
The output impedance of the mixer
matched capacitively to that of the
filter. In this fashion, variations of the
output impedance of the mixer become
uncritical. From
frequency signal of
a band-pass filter which
mixing products.
degree of phase-linearity
essary to achieve measurements on FM
signals with minimum distortion, especial-
ly when the modulation frequency
All
components of the
bered between 200 and 299.
IF
PREAMPLIFIER
(See diaaram No.
The three-stage IF preamp1 ifier consists
Q301,
of
the IF filter against load impedance variations from the
same time, it provides for amplification
before the signal
uator. Amplification alongside with an
glmost ideal connection to the
results in a minimum amount of noise at
all input levels. The ohmic part of the
IF amplifier input
of
R304,
of
C306. The amplified
fed to the
The IF attenuator (see Fig. F1) consists of
R311 and the four diodes
R311 and the four diodes form
divider with one fixed resistance and the
variable resistance resulting from the combination
Combining these four diodes ensures linear
characteristic and thereby minimum distor-
tion. The resistance value resulting from
the above combination depends on the
biasing current of the four diodes.
biasing current
tor of the current generator
sition
the base of
termined by the reference voltage source
Q311.
thereby its collector current,
by means of the potentiometer
EL)
accessible from the front of the instrument.
biasing current of the diode complex
CR301 to CR304, and, therefore, in regulation of the
sitivity of the
RF
input voltage can be adiusted
means of R345.
Q302, and
IF
and the reactive part by means
IF
attenuator via C308.
CR301
MAN.
The emitter current of Q310, and
This
-
is
of the MAN.-AUTO switch,
Q310
results in regulation of the
IF
level. Finally, the sen-
IF
attenuator at a given
IF
filter are num-
AND
Ill)
IF
ATTENUATOR
(2303.
attenuator. At the
is
fed to the
is
matched by means
IF
signal
CR310 to CR304.
CR302
drawn from the collec-
//
CR303 - CR304.
Q310.
is
at a potential de-
is
nec-
is
high.
It protects
IF
atten-
IF
filter
is
then
a voltage
This
In po-
is
control led
RIA
(LEV-
by
When the switch MAN.-AUTO.
position
a voltage delivered
fier. The AGC
differential amplifier Q512 and Q513
followed by a unity-gain amplifier
and Q309. The base of Q513
potential determined by the divider consisting of
R554. The base of Q512 receives a signal proportional to the
AM
any)
Q308) of the unity-gain amplifier driv-
ing the exponential amplifier
The emitter of Q310
provided by the voltage reference source
(3311 . the emitter basis ;oltage of Q310,
and thereby the biasing current of the
diodes
control led by the potentiometer
(LEVEL)
All components of the
and
300 and 399.
IF
AMPLIFIER (See diagram No. ll
The signal from the
then fed to the
sists of the two
stages
'The
a voltage level higher than that required by the
provides for compensation of the attenuation in the following band-pass filter
or phase-compensator
All
numbered between 300 and 399.
PHASE-COMPENSATOR AND
PASS
the amplified
a phase-compensator or to a band-pass
filter, according to the position of the
IF
BANDWIDTH switch. When the
BANDWIDTH
the phase-compensator
It provides for compensation of the
error that arises in the
phase error
the position
WIDTH switch, the band-pass filter
switched on. It
IF
the
but has a bandwidth of h25 kHz, and
is
signals from narrow-band equipment.
BUFFER AMPLIFIER (See diagram N0.V)
The signal from the phase-compensator
or the band-pass filter
fer amplifier which separates filter,
detector, and output amplifier. It consists of a two-stage unity-gain amplifier
(Q501 and Q502) and serves to suppress
any influence from the
signal from the buffer amplifier
both to the
output
filter concerning phase-linearity
intended for use when measuring on
AM
ampi ifier.
IF
filter characteristic
h25 kHz of the
is
of the same type as
is
IF
detector and to the IF
IF
fed to a buf-
output. The
BAND-
is
AM
is
fed
,
first low-pass filter section
C710 and C711 on diagram
the network consisting of
R539, and C530. R539
brate the AM detector.
Note: The low-pass filter and the following AF section are described below.
All
the components of the AM detector
are numbered from
IF
OUTPUT AMPLIFIER (See diagram
500 to 599.
(L701, L702,
VII),
R537, R538,
is
used to cali-
via
N0.W
The signal from the buffer amplifier
also fed to the IF output amplifier which
consists of the four stages
Q505, and (3506, and which provides
for amplification of the
level required by the following limiter
stages. The two diodes
are used to protect the limiter input stage
high
against too
a voltage.
(2503, Q504,
IF
signal to the
CR502 and CR503
is
All
components of the Buffer amplifier
are numbered between 500 and 599.
AM DETECTOR (See diagram N0.V)
The signal from the buffer amplifier
fed to the
a three-stage amplifier
and Q509 with a mean-value detector
CR505 and CR506 in the feedback loop.
The feedback ensures a good linearity.
A pair of output transistors, Q510 and
Q511, provides for two outputs. The
signal on the collector of
portional to the
fed via R546 to the differential amplifi-
er which
setting circuitry (described above), and,
via R543 and
plementary
Q515, forming a dc output amplifier
delivering voltage to the
output. The signal from the collector of
Q511
dicating meter which provides for check-
ing of the IF level.
The signal on the collector
detected signal which
AM
detector. It consists of
Q507, Q508,
Q511
IF
level.
is
part of the automatic level
R555, to a pair of com-
emitter-fol lowers, Q514 and
is
also fed via R544 to the in-
This
IF
LEVEL
Q510
is
fed through a
is
pro-
signal
(DC)
is
is
is
the
All components of the
fier are numbered between 500 and 599.
LIMITER
Genera
The amplified
of three limiters.
All components of the limiter stages are
numbered from 600 to 699.
First limiter stage.
The first limiter stage consists of two
emitter-coupled transistors, Q601 and
Q602. Their working point
by the current delivered
dc current generator
IF
signal from the
fed to the base of Q601, wh t 1st the base
of Q602
a sufficient
and Q602 are cut-off, and the output
voltage of the first limiter (at
a square-wave. The peak-to-peak value
of this square-wave
stant current generator Q607. The first
limiter
circuit which holds the zero-crossing of
the square-wave output voltage. The
regulation circuit consists of a
a differential amplifier, Q603 and
where any signal from the peak-difference
detector
ponent of the square-wave. The output
signal of the differential amplifier (if
any)
Q602 via the two emitter-fol lowers Q605
and
Subsequent l imiter stages
From
fed to two subsequent limiter stages
Q608-(2609 and Q610-Q6ll where it
is
again limited. The resulting signal
then fed to the
FM DETECTOR (See diagram No.VII)
The
mu1 tivibrator and an output stage.
The multivibrator consists of
Q702. It
positive pulses from the last
stage.
base of Q701 via
is
cut-off when no
to its base whilst transistor Q702 conducts, and conversely.
is
compared with the dc com-
is
fed to the bases of Q601 and
Q606.
C605, the square-wave signal
FM
detector via Q612.
FM
detector consists of a monostable
(2701 and
is
triggered by the train of
I
imiter
This
train of pulses
C701. Transistor Q701
IF
is
signal
fed to the
is
Q604,
is
is
applied
is
then passed, via a low-pass filter
consisting of
C711, to the
low.
A positive voltage, varying proportionally to the modulating frequency,
drawn from the collector of (2704 and,
via R726 and
amplifier stage consisting of the double
transistor Q709 and
The amplifier signal present on the
emitter of Q711
IF
FREQ.
part
is
fed via R736 to the meter when
the selector FUNCTION
position. R737 and R739 provide for
fine adjustment of
and gain.
The monostable
'
output
own +10
supplies. 'they consist of
Q615 and Q616 for +10
Q618, Q619 and Q620 for -10
(See diagram
All components of the
numbered between
stage are provided with their
L701, L702, C710 and
AF
section described be-
is
R727, fed to a unity-gain
Q710 and Q711.
is
fed via R734 to the
(DC) output, whilst the other
is
in
IF
CHECK
IF
CHECK position
mu1 tivibrator and the
V
and
-1
0 V regulated power
Q613, Q614,
V,
and Q617,
V.
VI)
FM
detector are
700 and 799.
multivibrator has a time-constant
The
determined by
and it delivers a square-wave signal
across
the output stage which consists of
and
two transistors of the output stage are
determined by the constant dc current
generator
square-wave
amplified in Q705 and
turn drive the constant-current generator
Q708 via Q707, thereby regulating
amplitude variations. As the width of
the pulses and their amplitude are constant, the mean value of the output
voltage of the output stage will vary
according to the number of pulses per
second of the square-wave,
cording to the modulating frequency.
Frequency-modulation of the
will cause a variation of the output
voltage of the output stage.
R702. The positive pulses drive
Q704.
R707, R708 and C703,
Q703
The working points of the
Q708. The peak value of the
is
detected by CR704 and
(2706, which in
i
.
e., ac-
IF
signal
This
signal
AF AMPLIFIERS
(See diagram VI 11)
The signal from the AM detector
to the second low-pass filter, consisting
of
L801, L802, L803, L804, L805, C801,
C802, C803 and C804, when the selector
FUNCTION
AM. The signal from the
is
fed to the second low-pass filter
when the selector FUNCTION
of the positions
is
characterized by its good phase-
linearity and its almost flat frequency
response, which are both required for
passing a stereo signal with minimum
distortion.
The filtered signal
the first section of a two-section resistive AF attenuator (see diagram
and fed fo the first
which consists of
Q803.
Q806.
amplification and for the low output
pedance required for coupling to the
subsequent low-pass filter
All components of the AF AMPLIFIERS
I
AF AMPLIFIERS
The amplified signal from amplifier
fed to the low-pass filter, which con-
sists
C902, and which provides for limitation
of the noise bandwidth in the AF section of the instrument without deterioration of the phase-linearity and
response.
The filtered signal
the third AF amplifier.
amplifier, consisting of Q901 and
which
in when the
is
15
other positions of the
selector. For filter characteristics, see
SECTION
emphasis networks and the
are regular RC networks.
The following AF amplifiers IV and V,
consist respectively of
Q906, Q907, and Q9Q8, Q910, Q911 and
is
passed via the second section
AF
attenuator (see diagram XII)
04,
It
provides for the necessary
'3805 and
.
and
II
are numbered from 800 to 899.
Ill
-
V (See diagram
of L901, L902, L903, C901, and
frequency-
is
then passed through
It
is
a unity-gain
is
part of the active filter switched
FI LTER/DEEMPHASIS selector
in
position 3 kHz, 15 kHz and 50 Hz
kHz
(3
dB).
It
acts as a buffer in the
FILTER/DEEMPHASIS
B
-
SPECIFICATIONS. the de-
6
dB/oct filter
Q903, Q904, Q905,
im-
1X)
II
is
Q902,
-
Q912. They bring the signal up to the
level required by the AF detector.
is
The AF OUTPUT signal
the emitter of
AF
OUTPUT switch
and via R920 and C911 when the AF
OUTPUT switch
All the components of the AF amplifiers
111
-
V
are numbered from 900 to 999.
AF DETECTOR (See diagram X)
The signal from the emitter of
fed to the AF detector which consists of
diodes
is
of modulation, whilst diode
for detection of the positfve modulation
peaks. Selection of the peak of modulation (positive or negative)
means of the FUNCTION selector in
the positions AM or FM.
The detected signal
impedance converter so that
fed to the
and to the meter.
of the fixed contacts and then lift out. Replace the new rotor in the opposite sequence.
Check the orientation of the rotor and take extreme care not to damage the contacts
4)
5)
6)
7)
on the fixed printed circuit board. Before securing the
the rotor does not foul the fixed printed circuit
centred and
To remove the fixed TUNER printed
Remove .the
Turn the TUNING knob fully counterclockwise.
Insert a
plate and loosen the set screw in the coupling of the variable capacitor.
Unsolder the
care not to
heat when
that
the contacts mesh correctly (no overlapping of the contacts).
circuit board, proceed
TUNER
2.5
mrn
10
damage the leods or the cable insulation. Do not use excessive
unsoldering these connections.
printed circuit rotor
hexagonal key through the hole in the bottom chassis support
leads
and
cables soldered to the printed circuit board, taking
as
board.
described in
7
retaining screws, check that
Check that
cis
3)
above.
it
follows:
is
properly
.
8)
9)
10)
11)
12)
13)
Remove the three screws securing the printed circuit board.
Using the blade of a screwdriver
support, hold the coupling in place and carefully pull out the printed circuit
inserted
through the hole in the bottom chassis
board.
To replace the printed circuit board, proceed
Again using the blade of a screwdriver inserted through the hole in the bottom
chassis support, guide the coupling into position over the variable capacitor shaft
and mount the printed circuit
lnsert the three retaining screws, but
Mount the printed circuit rotor as described above in
boad
into place.
do
as
follows:
not tighten them
3).
at
this
point.
14)
15)
Secure the three retaining screws when both the rotor
boarcls are orientated correctly.
Ustng a hexegonal key, loosen the
Turn tho
that the capacitor in
wer the llttle trimmtng miark to the left of the scale and tighten the screws securing
the
Meta I-paper capacitors
Plastic capacitors
Electrolytic capacitors
Variable capacitors
Special tubes
Rectifiers
Diodes
Transistors
Integrated circuits
Lamps, batteries, fuses
Switches
Coils, coil material and transformers
As
we are continually improving our instruments, it
you
parts, that
include the following information*
400- to
500-
to
700-
486-
580-
to
785-
is
important, when ordering spare
The code number and description of 'the part
The circuit reference from the wiring diagram
The complete type designation of your instrument
The serial number of your instrument.
Please note that the position of any part can easily be found by referring to the last
column of the parts
list.
This
indicates on which figure the part can be located.
metal film
metal film
metal film
carbon film
carbon film
carbon film
carbon film
carbon film
carbon film
carbon film
carbon film
carbon film
metal film