Yamaha T-2 Owner's manual

Yamaha T-2 Owner's manual
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Thank you for your purchase of this new Yamaha T-2 FM Stereo Tuner. You will find it to
be the product of the most sophisticated Yamaha research and technology which continually
attempts to make the best possible audio performance available to the widest range of en-
thusiasts.
encouraged to thoroughly familiarize yourself with the operating instructions in these pages.
To make the most of the outstanding performance features of this tuner, you are
Features
®
Duai Gate MOS FET and FM 7-gang Frequency
Linear Variable Capacitor are used for the
front-end. RF MODE Switching-over Circuit -
provided on the RF stage delivers high sensi-
tivity reception and excellent interference sup-
pression characteristics.
display of the frequency of a station as it is
tuned in.
® AUTO DX Circuit is equipped, which detects
“quality” of received signals and automatically
switches over |F ranges so as to make high
quality reception possible, i.e., it automatically
switches over to LOCAL MODE to deliver
excellent audio characteristics {low distortion,
wide range) in case of reception with com-
8 Signal Meter of the interference wave detection paratively less interference, and to DX MODE
type displays existence of such wave and to efficiently cut interference and perform
multipath. | high sensitivity reception when wave is weak
with strong interference.
8 Timing Circuit is provided to deliver muting e MPX Circuit is exclusively Yamaha's DC NFB
function which eliminates shock noise when SWITCHING circuit depending on High-Siew-
the power switch is turned ON/OFF. Rate DC amplifier. 19 kHz pilot signals are
completely canceled as they become unneces-
® Station Indicator equipped performs digital sary so that high frequency characteristics are
extensively improved (flat at up to 18 kHz or
thereabouts).
Contents
Caution; Read this Before Operating
Your T2....... PS 3
Connection Diagram .... .... ... рев... 4
Connections... ........ oi... 5
The Names and Functions of Components ... 6
Broadcast Reception ........... | Cee 8
IF MODE Switch ..............—e..... 9
REC CAL Switch .............i..... 10
Multipath Detection ................. 10
Circuit Explanation . . ................ 11
Performance Graphs ........... | a
Specifications .......eomeereoeci an re. 16
Bolck Diagram ........ 2... 17
Schematic Diagram . . . ............... 18
Trouble shooting aaa Cee 19
IMPORTANT !
unit in the space below
Please record the serial number of your
Model Name T-2
Serial No.
of the chassis.
Retain this Owners Manual
place for future reference.
The serial number is located on the rear
in a safe
The T-2 is a high performance FM stereo
tuner with excellent selectivity, sensitivity,
and several special features. This manual is
required reading if you are to get the best
from it.
Aen
Do not drop or otherwise jar the T-2 which
Is precision instrument.
Do not place the T-2 where it will be ex-
posed to direct sunlight, excessive heat (for
instance over a radiator or on top of an
amplifier which generates a fair amount of
heat), moisture, or dust.
Do not use chemical solvents (such as
benzene or alcohol) to remove traces of dirt.
Wipe only with a soft, slightly damp cloth.
Do not attempt to carry out internal adjust-
ments or repairs. Leave this to your local
service representative.
Do not assume your T-2 is faulty before
checking the "Trouble Shooting’ list on page
19 for common operating errors.
J
Operate all switches and knobs in accord-
ance with the instructions. Avoid applying
undue force, which should never be neces-
sary, and do not attempt to use intermediate
settings.
№
Keep this manual in a safe place for future
reference, and refer to it frequently until
you are perfectly familiar with all T-2 con-
trols and functions.
Warning — to prevent fire or shock hazard,
do not expose this appliance to rain or
moisture. {
Outdoor FM Antenna
с
-
752
Coaxial
Cable
—
2
—
_—
3009 Feeder Line
T-type Indoor
FM Antenna
Ei o mew =
Tape Deck
0:
To LINE IN R L
Stereo Amplifier
+ @ 1: À
R Ww Е EI §
To TUNER or AUX terminal
АМТЕММА
75 LINEAL
*
© YAMAHA
75 LIMBAL
*
(EU VOTE SO WATTS
LEFT
O FIXED VARIABLE DO ©
Фу
RIGHT ECO
BOTTOM CAUTION.
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This reomver comphes, as of date
manufscturco with FCC Aulés and
19
PouUlstions Part IS. Subpars C
OCOOOO0O0O00090000900000000000006000600060600
WARNING-TO PREVENT FIRE OR SHOCK HAZARD DO AG DUTLET
NOT EXPOSE THIS APPLIANCE TO RAIN OF MOISTURE у в
CAUTION-DO NOT REMOVE THESE SCREWS SEE
LEE ICIEC
lecv él:
Toy MA
Ground (Earth)
Connection
To HORIZ terminal
o
To VERT terminal
AC Outlet
T-TYPE INTERNAL (INDOOR) ANTENNA +1 FM OUTDOOR ANTENNA F TYPE CONNECTOR В
The T-type internal {indoor) antenna, which If reception is unsatisfactory with the T-type e The F type connector facilitates connection
comes with the tuner itself, is for use in areas internal (indoor) antenna, install an outdoor of your T-2 tuner to an outdoor antenna or
close to the broadcasting station where there is FM antenna (good for both FM reception). | other through a coaxial cable. To connect the
a strong signal. » An FM antenna may be connected to the = F type connector with a coaxial cable (3C-2V
First, connect the feeder line of the T-type an- 30082 and 75£2 terminals on the rear panel. or alike), please follow the procedures shown
tenna to the rear panel 300% BAL terminals For an FM antenna, you may use either a - in the diagram below and do it firmly.
(Fig. 1). Extend the two antenna arms horizon- 300 balanced feeder or a 75£2 coaxial cable. :
tally to form a T, then slowly turn the T until However, in areas in which there is much out- Fig. 3 HOW TO CONNECT F TYPE CONNECTOR
you find the position at which reception is best. side static from motorcycle or auto ignition |
Secure the arms in that orientation by attaching noise, a 75 coaxial cable (3C-2V or 5C-2V)
to walls or ceiling. is recommended.
e When connecting up a coaxial cable, be care-
Fig. 1 ful not to let the braiding and inner core con-
Connecting an FM T-type tact one another so as to cause a short (see
internal {indoor} antenna Fig 2)
fy CID
9 Fig. 2
Po ; .. . FM outdoor antenna : i
. ‚ Let the coaxial cable
Fabricate the coaxial through the ring.
cable to the above Fold the mesh wire
FM antenna and coaxial size. [If the core is hd
“cable connection stranded wire, solder end back, and insert
{Connect a 3008 feeder it's end.) the connector between
Direction of 300 BAL termina!.) ` * the coaxial cable coat
Broadcasting and the mesh wire,
station To make this insertion
easier, turn the con-
7592 2 — З лип nector right and left
Coaxial cable during insertion.
— A NTENNA © :
J Crush a portion of
759 UNBAL 3008 BAL я
® e y the ring
NO Screwdriver
Long Nose Plier
Cut off excessive
mesh wire and tighten
ene
io Cia cae serene and connection and the ring. Also cut off Cable
rai n coaxi an
{3C-2V] to expose braid, insert secure cable the core № leave 2mm
(5C-2V) coaxial cable. with screws. or 3mm tength.
\ this completes con-
nection,
Go YAMAHA NATURAL SOUND FM STEREO TUNER T->
FRA se 920 92 94 96 pe 100 102 174 I0S ICS MHz STERED LOOAL DR
ser 1 14 61 — me} ppp a fo er op a a re rpg map grep Emma a pren re ne er par) pp pny [E En
ua an vu
1” ==) |
POWER REC CAL BLEND MODE MUTOTS" IF MODE RFE MODE SIGNAL QUALITY TUNING STATION
OFF à OFF AUTO AUTD STERED AUTO DX HI SENSITIVITY E T
40 60 BD — 200 10D & 100 200+
O 20
| 1 log falda
0 MO DFF/MULTIPATH LOBAL HI SELECTIVITY = a
Taleteta
FM ВИНЕ
Gy Tuning Scale
The FM frequency indication is calibrated in
MHz (megahertz) units.
2 Dial Pointer
Turn the tuning knob so that this pointer
points to a station frequency to tune in.
6 STEREO
(Stereo indicators
This indicator comes on automatically when
FM stereo broadcasting is received and goes out
automatically when there is monaural recep-
tion.
(There is no lighting for monaural reception.)
Oe AL (Local Indicator)
It lights up during LOCAL (general) reception.
When IF MODE SWITCH is in LOCAL (==),
however, it lights up regardiess of remote or
local reception.
3X (DX Indicator)
If the DX indicator light is on when the IF
MODE switch gis in the AUTO ОХ ( JE) posi-
tion, it signifies that the tuner is operating in
the DX MODE. During FM broadcasts in which
there is tuning to a powerful local station, the
LOCAL MODE takes over.
© Tuning Knob
Turn this knob to select a station.
Watch both the SIGNAL QUALITY METER
and TUNING METER to obtain the best pos-
sible reception.
VER Power Switch)
When it is depressed,
i.e. ON (=) position,
power is supplied, and when it is depressed
once more, ie. OFF (Æ) position, power is
turned off. |
* Because of the muting circuit, sounds will not
be produced instantly when the power switch
is turned on. Switch-on of the power can be
known by lighting up of lamps illuminating
the tuning scale, signal meter, and tuning
meter.
ATER
TT
ording Level
Calibration Switch)
When this switch is pressed ON ( == ) the 333Hz
(50% modulation) signal which determines the
recording output level is sent from the OUT-
PUT terminals.
(Refer to p.10 to REC CAL switch.)
O BLEND Switch
In weak reception areas, when a hissing or high-
pitched noise makes for poor FM stereo recep-
tion, press AUTO ( JM ) this switch. The blend
circuit will cut in to eliminate the high-range
noise completely. If the BLEND switch Is set to
the OFF ( = | you can obtain better FM
stereo separation in the higher ranges whenever
there is strong signal. At this time, the stereo
indicator becomes dim in proportion to the
quantity of blending achieved.
I MODE (Mode Switch
When this switch is in AUTO STEREO ( M4),
STEREO (Stereo Indicator) lights up and stereo
reception is achieved, and when monaural
signals are received, it turns out and monaural
reception is achieved.
The switch in MONO (==) position forces the
tuner monaural reception. This position used
for reception of a remote station produces
monaural reception even with stereo broad-
casting for a better signal-to-noise ratio.
Leave the switch in AUTO STEREO (ME ) posi-
tion, normally.
(RAuting / DTS Switch)
With this switch ON (Hl), you can reduce the
background noise that appears when selecting
FM stations. However, in poor reception areas,
the muting circuit activation may eliminate …
the weak station itself, so you are encouraged
to set to the OFF/MULTIPATH position when
tuning in very weak stations. |
(In the OFF/MULTIPATH (==) position, FM
Multipath detection is possible.
(Refer to p. 10 for multipath detection.)
DE UF Mode Switch!
When the switch is AUTO DX ( HA), DX (long
distance) or LOCAL (general) function auto-
matically switches to the other. So, please
leave the switch at this position for normal use.
The switch turned to LOCAL (==) position
compells the tuner to perform the local func-
tion regardless of remote or local reception. Use
this position if it is your choice.
(Refer to p. 9 for IF MODE SWITCH)
RE MODE (BF Mode Switch
The switch turned to HI SENSITIVITY (m)
permits high sensitivity receiving. For normal
use, use this position.
Use HIGH SELECTIVITY (a=) position in
order to keep from distortion or crosstalk
caused by adjacent station's strong interference.
O OUTPUT LEVEL CONTROL
This:-'knob permits you to adjust the output
level of the rear panel OUTPUT VARIABLE ter-
minals from 0.1 to 1 Vr.m.s (100% FM modula-
Ч |
© STATION (Station Indice
tion). At the click stop in the center, the output
tevel is 0.5 Vr.m.s. |
{r.m.s. = root mean square)
SIGNAL QUALITY Meter
This meter indicates the quality (static, inter-
ference level) of the signal being received. When
there is much interference the meter indicator
will waver, the amount of deviation reflecting
the degree of interference.
* During FM reception, when the MUT/OTS
switch is set the OFF/MULTIPATH ( ==)
position, the meter wavering means multipath
detection is in process. When the multipath has
been detected, adjust in accordance with the
multipath detection instructions on p. 10.
® TUNING Meter
This is used when tuning in FM stations: the in-
dicator points to dead center when the tuning
knob is turned and the signal quality meter in-
dicator moves to the right. 8
When a desired station is tuned in, the indicator
displays the station’s frequency In digit. (No
display is available when a station is detuned )
Generally, use the tuning scale to tune in the
desired station's frequency and do micro adjust-
ment by means of SIGNAL QUALITY METER
and TUNING METER. Then, use this indicator
to verify the frequency of the station you are
receiving.
When MUT/OTS SWITCH is in OFF/MULTI-
PATH (a) position, it keeps light up and
keeps displaying the frequency the dial pointer
indicates.
YAMAHA NATURAL SOUND Bh STEREO TUNER T-2
REC CAL BLEND MODE MUT-OTS FF RAODE AF MODE
ALTO STEREO ON AUT DX HI SENS: TIVITY R
459
; 10, A da, de Jos, à 05 MHz STEREO LOCAL DX
SIGNAL QUALITY TURING STATION
L
| NANA HANA
7 ore t T Hi Ч -
qu ЧЕ us
¿
heck the antenna and amp connections, then
switch on the power 8.
3e The REC CAL switch @ is OFF,
e The BLEND switch € is set to AUTO,
e The MODE switch Mis set to AUTO STEREO,
e The MUT/OTS switch $ is ON,
e The IF MODE switch @ is set to AUTO DX,
e The RF MODE switch ® is set to the HI SEN-
SITIVITY position.
*The DX indicator lights up when the tuning is
off at this time.
With the tuning knob @ , turn the tuning indi-
cator $9 approximately to the desired station.
The indicator light grows brighter and displays
station's frequency in digit as you begin catch
ing the station signal. |
8
"When the signal you receive is sufficiently
strong, the LOCAL MODE takes over and the
DX indicator light goes out.
TWhile referring to Fig. 4, tune in FM stations by
turning the TUNING knob ® so that the TUN-
ING meter @ indicator is placed at the center
when the SIGNAL QUALITY meter ® deflects
to the extreme right.
The signal quality meter, however, may happen
to go further to the right when the TUNING
meter is not at the dead center but stays with
an amplitude of variation. Such a case, meter
display indicates the existence of multipath
interference.
Change the orientation or position of the an-
tenna so that there will be maximum indication
on the signal quality meter when the tuning
meter points to dead center (Fig. 4). -
Fig. 4
Reading SIGNAL QUALITY meter and TUNING
meter |
When there is an interference wave, the SIGNAL QUALITY
meter indicator deflects as follows.
SIGNAL QUALITY SIGNAL QUALITY
If the SIGNAL QUALITY meter indicator deflects to larger
degree when the TUNING meter indicator is displaced from
the center position than when it is in the center position,
there is an interference wave. Adjust the direction and height
of antenna so that the SIGNAL QUALITY meter indicator
deflects to the extreme right with the TUNING meter indi-
cator placed in the center.
When there is not interference wave:
SIGNAL QUALITY TURING
Î
E
-200 ¡IO
E The STEREO indicator € lights up when
the station is broadcasting stereo. lt goes out
automatically in the case of monaural.
Adjust the output of the OUTPUT VARIABLE
terminal by means of the OUTPUT LEVEL
control O. (Fig. 5)
Note: For fine adjustments applicable to spe-
cific receiving conditions, please refer to[1 2,
and [3].
Fig. 5
ET TR
| À
= ven
QO
e 3
By pulling the nail of this leg, the front panel can
be turned upward. Do so when necessary.
[1] For reception in the area of weak field
strength remote from a station, where high
sensitivity and remote receiving function are
required, it is recommended to use RF MODE
SWITCH ® in HI SENSITIVITY (B®) and IF
MODE SWITCH @ in AUTO DX (B®). In order
to further secure the tuner's receiving capacity,
use MODE SWITCH Y in MONO (=) position,
and MUT/OTS SWITCH @ in OFF/MULTI-
PATH (=) position, respectively.
This remote reception however presents sound
quality inferior to local reception.
If and when remote reception is subject to
strong interference by an adjacent station (inter-
ference by an adjacent station or intermodula-
tion interference by a powerful station), bring
RF MODE SWITCH® to HI SELECTIVITY ( ==.)
position, whereby the dynamic range of the FR
(front end) section is extended and at the same
time a further increase is achieved in selectability
so as to reduce interference by strong waves.
With a station which imposes no interference, the
switch in this position exhibits about one half
sensitivity of that available in HI SENSITIVITY
position. Please therefore use Hi SENSITIVITY
position when receiving a station free from inter-
ference by strong waves.
STATION indicator € lights up and displays
a tuned freguency when it goes in tune with a
station powerful to some extent as far as MUT/
OTS SWITCH® is ON (ÆL ) position (that is, as
far as muting circuit does not function).
Here, notice that this indicator is not able to
achieve fine adjustment, so do it with TUNING
meter.
This T-2 switch (Fig. 6) enables you to obtain
good reception in remote areas or there is much
interference.
AUTO DX (M) Position
In a poor FM reception area or when there is
interference from a nearby station, setting to the
AUTO DX ( M) position will automatically acti-
vate the DX MODE and its indicator light will
come on. In the AUTO DX ( M) position you
get maximum suppression of interference as well
as excellent sensitivity when listening to weak
signals. |
When the station signal is sufficiently strong, the
T-2 automatically switches to LOCAL MODE for
a wider range of reception with minimal distor-
tion and excellent sound quality. |
LOCAL (æ } Position
Set to this position whenever there is sufficiently
large antenna input and only slight interference
with reception. The low distortion characteristic
takes over and you obtain crystal clear sound
of very high resolution. |
* In remote areas with poor reception, you are en-
couraged to set to the AUTO DX ( m) position.
Fig. © IF MODE
AUTO DX
LOCAL
A suitable sound level is essential if you hope to
obtain good sound quality when recording FM
broadcasts. Press on the REC CAL switch for an
OUTPUT terminal signal of 333 Hz (50% modula-
tion). When the tape deck is connected up, you
can thus obtain a suitable recording level at all
times irrespective of the program (Fig. 7). When
setting for the right recording level, adjust either
the T-2 OUTPUT LEVEL control or the deck
LINE INPUT level control to the values indicated
in the table below.
Tape Used Setting Level By REC CAL
CrO2 tape —6 VU
LH tape —4VU
FeCr type —2VU
“The above values are only a rule of thumb. The
actual value may differ in terms of the tape deck
or FM modulation.
Tape Deck |
EA 0508
10
“If you switch off the power in the REC CAL
(=m) position, a certain amount of signal sound
remains.
FM multipath is somewhat like the TV “ghost”
phenomenon. As shown in Fig. 8, some FM signals
are received directly by the antenna while others
reach it from many directions, bouncing off build-
ings or mountains. The latter are called multipath
waves. These are received only slightly later than
the direct waves, and this causes some sound distor-
tion, separation and deterioration in tonal quality.
This multipath effect can be prevented by using a
tall antenna with good directional characteristics
and by installing it after careful study to obtain
the right orientation so as to eliminate interference.
Fig. 8
Reception Antenna
Reflected Wave
Wave, Recieved
Indicator quivers when Direc
multipath waves are
detected.
SIGNAL QUALITY
EM Antenna
TUNING
Multipath Detection
During FM reception, a delicate quiver of the
signal meter indicator when the MUT/OTS
switch is set to OFF/MULTIPATH (=) indicates
multipath interference. Change ‘your antenna
orientation or position so that the indicator stabi-
lizes. o
e Using Oscilloscope |
Connect VERT and HORIZ terminal i.e. MULT I-
PATH terminals, provided on the T-2' rear panel,
to VERT (vertical) and HORIZ (horizontal) input
terminals on a oscilloscope, and make the T-2
tune in with a station correctly and bring the
Braun tube to display wave form. —
Please refer to the below photographs to adjust
the position and height of an antenna ¡f multi-
path is revealed on the Braun tube. |
Wave forms
on oscilloscope
Photo. 1
No multipath exists
Photo 1
Photo. 2 & 3 Photo. 2
Muitipath exists
Photo. 3
_
Z
1. FRONT END
Three dual-gate MOS FETs are used in the front
end, allowing easy transmission of high-frequency
signal to the rear stage. Further, an RF MODE
switching circuit is provided for the first time in
the world, enabling selection of a sensitivity in
accordance with wave conditions of a station.
The switch provides HI SENSITIVITY and HI SE-
LECTIVITY positions. In the HI SENSITIVITY
position you can receive a station placing emphasis
on the sensitivty, while in the HI SELECTIVITY
position you can reject interference from a near
station to securely obtain a desired wave. All
this insures higher quality reception by match-
ing the nature of radio waves you are receiving.
(The circuit operation is shown in the block dia-
gram below.)
2. DIGITAL READOUT
The T-2 provides a STATION indicator which
digitally indicates the frequency when a station
Is tuned in. The indicator has an OTS (optimum
tuning system), which 1s OFF during tuning but
turns ON to automatically lock the frequency to
the correct tuning point once a station is tuned in.
"Block Diagram of Front End
75 © ©
300 4 |
|
Balun Transformer
* When it is placed in the ON condition by ap- |
plying + bias to the diode #2, the source im-
pedance of 1st RF amplifier becomes almost
zero in high-frequency band, and it operates
completely matching with the antenna tuning
point.
(HI SENSITIVITY reception)
When it is placed in the OFF condition by
applying — bias to the diode #2, a negative
feedback is given to the source of 1st RF.am-
plifier, suppressing the gain and at the same
time improving the linearity. And thus a high-
dynamic range and high-selectivity reception
with lesser intermodulation interference and
blocking is ensured.
{Hl SELECTIVITY reception)
*
Tuning Circuit
| 10
— |
HIGH SENSITIVITY
NOU A A A E A
Connection Circuit
Front End Frequency Linear Wide Air Gap Precise 7-gang Variable Capacitor
and RF MODE Switching Circuit | - - = - - - eu = -
| | AGC
смо © i
F-type 1st RF Amp. 2nd RF Amp.
Connector Antenna и Double Tune oN € Triple Tune
Te Ta
Counter Buffer
Г
A
RF MODE
Connection Circuit
— IF OUTPUT
Ts Ts
LOSC Buffer
- Local Oscitlator
Digital Counter Output OTS
: OUTPUT
HIGH SELECTIVITY
+B -B
11
3. IF {Intermediate Frequency Amplifier)
STAGE |
To ensure high-quality reception under every wave
condition, the T-2 provides an AUTO DX circuit
which automatically switches IF band by checking
the quality of receiving wave. For the LOCAL
position which permits superior audio quality ina
reception with comparatively less interference, are
used two ceramic block filters checked and ad-
justed through differential-gain direct-assessment,
and IF amplifier with a 7-stage differential current
limiter and buffer amplifier is applied. These IF
block filters with superior transmission charac-
teristics realize high audio qualities of 55dB stereo
separation and 0.05% distortion factor {stereo
1kHz) while ensuring a sufficient selectivity of
55dB in a normal area. Further, for the DX posi-
tion which effects good reception in areas with
much interferences, is used a low-spurious ceramic
block filter of which the transmission charcteristic
is also checked through a differential-gain direct-
assessment and which is equivalent to eight ele-
ments, making the effective selectivity 100dB. This
AUTO DX circuit detects interference through the
interference-detector circuit and switches IF band
by operating the transistor switch. For the dis-
criminator, is used a wide-band balanced ratio de-
tector which is also analyzed through the differen-
tial gain direct-assessment, ensuring a detector
output with a very low distortion.
Direct Assessment of Differential Gain
To improve interference-rejection - characteristics
for FM reception a high selectivity is to be ob-
tained. But there is a problem that improving a
selectivity results in an increased distortion and
lowered fidelity. To ensure a lowest possible dis-
tortion and higher separation while improving a
selectivity, Yamaha introduced a direct assessment
of differential gain. This method checks a devia-
tion of amplitude-conversion gain to a faint fre-
quency shift in an FM signal transmission system,
and permits a superior audio quality by reducing
the differential-gain deviation while securing a
required selectivity. |
Block Diagram of AUTO DX Circuit
iF CIRCLHT
Ceramic Block
Filter Unit #1
Buffer Amp st 1F Amp €: Buffer
IF INPUT LOCAL
il System
> od 2 1
Current Limiter
Type Differential IC | mx System
LED
OX Indicator ®
AUTO DX Circuit
RECEIVING MODE
a Flip
Select Circuit Flo
|
A
DX +4 LOCAL
Switch Trigger | -
TRI IL
Low Г]
4-element |oss-
spurious type
ceramic filter
Wide Range
LoCALpDX
Switch Trigger
Tuning Detection Signal
Sth-7th Balanced Type
2nd-4th Ceramic Block IF Amp & - Petio Detector
IF Amp & Limiter Filter Unit #2 Limiter a
li í MPX-COMPOSIT INPUT
— i NJ
Current Limiter Current Limiter L — ——d
Ty Е Type 3-Stagé
Differential IC Differential IC
TR
-5W
Interference MPX-PLL INPUT
Detecting ————
AGC Amp
Interference .
Detecting DC Wide Band
Filter Operational Amp
Muting Level
Detection
Interference
DX Levet Level Signat Muting Out AS
Detection Schmitt utof Tunejs
& Driver Detection
| | Г MPX Stereo Mone Switch
Le Muting Gale
MULTE PATH INDSW
ma
TUNING METER
| Le
+ e
SIGNAL QUALITY METER
AUTO DX OPERATION
e At time of station selection . . . Normally
in DX MODE (High sensitivity, selectivity)
e After station selection :
When there is no interference and sufficient antenna input . | . Switches
When there is much interference or insufficient antenna input . . . Switches
‚When Intermittences ... Keep to DX MODE.
automatically to LOCAL MODE (Low distortion reception)
to DX MODE for high interference suppression characteristics.
(High sensitivity, selectivity)
12
4, DC-NFB-PLL-MPX CIRCUIT
As the MPX circuit demodulates a stereo com-
posite signal through switching it by 38 kHz sub-
carrier, the intermodulation distortion in the
circuit needs to be extremely reduced. This is
because the composite signal thus switched con-
tains frequency response of DC to over 1MHz.
The MPX circuit of the T-2 makes up a unique DC-
NFB-SWITCHING circuit on the foundation of a
high slew rate DC amplifier. The PLL section
for subcarrier generation provides an interference
filter, forming an anti-interference PLL system
which is hardly affected by a stereo signal. Further,
utilizing 19k Hz signal generated in the PLL sec-
tion, 19kHz signal with the level and phase equiva-
lent to those of the input pilot signal is reproduced,
and, passing through the waveform converter cir-
cuit, it becomes almost completely equivalent to
the pilot signal in the waveform, level and phase
to cancel the pilot signal in the input section of
switching circuit. This tracking-type pilot pure
cancel circuit permits demodulation of only pure
composite signal without 19kHz pilot signal which
is unnecessary for the muitiplex stereo decoder.
All this result in the MPX demodulation system
with extremely low intermodulation distortion,
and at the same time enable the cutoff frequency
of low-pass filter at the rear stage to be set to
over 19kHz for a stable reproduction frequency
response — almost flat at up to 18kHz.
5 METER & MUTING SYSTEM |
The signal meter indicates a signal quality based
on interference detection (indicates SN ratio in
the stereo mode). It permits quick setting of time
constant with the MUT/OTS switch placed in the
OFF/MULTIPATH position, and eases interference
detection in multipath phasing, etc. With the mut-
ing system a de-tuning detector signal and an inter-
ference detector signal are applied to the Schmitt
circuit, forming a powerful detector system against
erroneous operation. And the driven gate section
is provided in two stages after and active-load
emitter-follower buffer amplifier (2-stage sym-
metrical gate muting circuit). Also, a timing circuit
is put against power ON-OFF to effect muting.
Block Diagram of DC-NFB Switching PLL MPX Circuit
From Detector > o A
Filter
PLL Anti-interference
Pilot Signal >
Composite Signal
Driver
To DC NFB
From Muting © ad INDICATOR
__ Pilot Signal Cancel {in terms of level, phase)
High Slew
НО! Rate DC Amp Low-Pass Filter
Y YY
Вы
ARA
High Slew Rate DC Amp |
SW ;
> TAS # Separation
> Decader Control
19kHz Z 90
‚ Rectangular Wave
Pilot
Signal PLL 38KHz J
Regeneration Buffer Amp DC Level
Circuit & Phase Shifter Regeneration
}
|
MONO/
STEREO
SWITCH Level
19kHz Sine Wave — Detector
—Ple
DRIVER
OC active load
EF Buffer
Integrator
J IAN Triangular Wave
19kHz £ 180°
SWITCHING CIRCUIT
Sine Change Filter
TO FM BLEND SW
Stereo Indicator
13
= Output/Noise Level vs, Antenna Input Level
9
+
o
Muting
1
ro
о
ë
¿
-ю
Signal/Noise Level (dB)
о 10 20
20 30 an BO 60 70 80 90 100 110 +4
ANTENNA INPUT LEVEL (dBu)
# Modulation Frequency vs. Distortion
Distortion (9%)
907
50 100 200 300 IK
5K 10K 15K 20K
Modulation Frequency (Hz)
14
Distortion (%)
a Antenna Input Level vs. Distortion
2.0
0.5
22
O
205
ANTENNA INPUT LEVEL (dB)
® Frequency Characteristic and Separation Characteristic
Response (dB) Separation (dB)
20 50 100 206 50D IK 2K GK 10K 15K 20K
Modulation Frequency (Hz)
a Distortion, Mistuning OTS Effect
©
2
©
Distortion (%)
"©
of Ci
- 100 -80 =60 -40 - 20 a 40
Mistuning Frequency (kHz)
mn Effective Selectivity Characteristic a Capture Ratio a Comparison of MPX Circuit Characteristics
GI
0.2
3 — O.
m
2 © 0.05
= o _
5 = =
& © 5 0.02
+ © +
a = o to
2 ä $
_— Сл 9.005
= ©
с
2
nN 0.00%
о
v D 10 20 30 40 50 80 70 80 90 150 0.00! В
= Antenna Input Level (dBu} | |
+ | Modulation Frequency (
{=
=
Undesired Carrier Frequency's
eviatio . . I . . ла
Deviation From Desired Carrier m RF Intermodulation Characteristics » Signal Quality Meter Indication
Frequency (kHz)
BO
100
40
RF Intermodulation Ratio (dB)
2 2 ! o | 2 3
Signa! Quality Meter Indication (dB)
Interference Frequency Difference (MHz)
0 10 20
119 120
30 50 60 70 80 20 104
Antenna Input Level (dB u)
13
|
FM SECTION
Tuning Range
50 dB Quieting Sensitivity
Mono (HI SENS., AUTO DX MODE)
Stereo (HI SENS., AUTO DX MODE) o
Ш 28 uV 34.2 dBf
87.6 to 108 MHz
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