TFT 763 User manual
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TFT
OPE
RJ:
.T
ION
MANUAL
ADDENDUM
M
ODEL
7
63
.
11\ANUAL
REVISION
LE
VEL
EFFECTIVITY S/N
-----
-----
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AN
T
MANUAL
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noe
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an
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l .
763
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m
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Schematic
f.
.ssy
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.
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SECTION
1
1.1
1.2
1.3
1.4
1
.5
SECTION
2
2.1
2.2
2.3
2.4
2.5
2.6
SECTION
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.
9 .
3.10
3.11
3.12
SECTION
4
4.1
4.2
4.3
4.4
f,()OEL
763
FM
MlDULATION
MONITOR
TABLE
OF
CONTENTS
GENERAL
INFORMATION
Page
General Description.
...
....
.............
...
1-1
Specifications..................
.
..
......
..
1-1
Accessory Equipment......
....
......
........
1-3
Warranty.....
...
......
.......
....
..
........
1-4
Claim
for
Damage
in
Shipment...
......
..
...
. 1-4
INSTALLATION
Unpacking
and
Installation.......
.....
...
..
2-1
Power
Requirements......
.....
....
.........
.
2-1
Installation
and
Connections.
......
.
.......
2-1
t-t>del
704F
Connections
....
........
...
......
2-2
Composit
Output
Connections.......
....
.....
2-2
Field
Installation
of
Options.
...
..
.......
. 2-3
OPERATION
General
_.........................
.......
....
3-1
Turn-On
and
Wann-Up........................
3-1
Front
and
rear
panel controls
and
connections
••••••••••••••••••••••
;....
3-1
Setting the Carrier
Level
into the rt>nitor. 3-5
Measurement
of
FM
f.t>dulation using
tt>dulation
Meter............
..
........
3-5
t<l!asurement
of
AM
f.t>dulation using
f.t>dulation
Meter........
.....
...
..
....
3-6
Measurement
of
FM
t-bdulation
Peak
Flashers..
......
........
........
. 3-6
Measuring
Residual
Noise........
...........
3-6
Distortion
Measurements...........
.........
3-6
Use
of
the
f.t>del
704F
Remote
Meter
and
Flasher Panel.
.......
.................
3-6
Carrier
Power
alanns (optional)
••••
•
~......
3-7
tt>dulation
Alann
_
(optional)....
.....
.......
3-7
THEORY
OF
OPERATION
Block
Diagram
•••••
~........................
4-1
AM
Detector
and
Carrier
Level
Circuits.....
4-2
Local
Oscillator....
.
..............
........
4-2
First
Mixer.........
............
.....
...
...
4-2
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...
SECTION
4
TABLE
OF
CONTENTS
(Continued).
(Continued)
4.5
4.6
4. 7
4.7.1
4.8
4.9
Limiting Amplifier
and
Discriminator••
4-3
Baseband
Lowpass
and
amplifier
••••
••••
4-3
Calibration Signal Generator
and
Lowpass
••••••••••••••••••••••••••
4~3
Peak
Flasher
Lowpass
Filter
•••••••••••
4-3
Inverting Amplifier
•••••••••••••••••••
4-3
Thumbwheel
Current Source
and
Peak
Detectors
••••••••••••••••••••••••
4-4
4.10
Audio
.Ar.lplifiers
••••.
•••
••••.•••••••..
4-4
4.
11
Meter Amplifiers,
Peak
Meter
Detector
and
Averaging
Meter
Detector•• •••
4-4
4.12
Power
Supplies
••••••••••••••••••••••••
4-5
SECTION
5
MAINTENANCE
General
Access
SECTION
5.
1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.8.1
5.8.2
5.
8.3
5.8.4
6
6.1
6.2
6.3
6.4
6.5
6.6
6.7
Periodic Maintenance
Modulation
Accuracy
Check
Calibration
Circuit
Adjustment
Modulation Attenuator
Check
RF
Level
and
AM
Modulation Circuitry
Checks
Trouble Shooting
Guide
Meter
and
Flashers Inoperative
Modulation
Meter
Inoperative
Peak
Flashers Inoperative
RF
Level
and
AM
Modulation Circuitry Inoperative
SCHEMATIC
DIAGRAMS
Block
Diagram
Wiring
Diagram
Moni
-
tor
Schematic
Carrier
Fail
Alann
Carrier
Power
Alarms
(Optional)
Modulation
Alann
(Optional)
Remote
Meter
and
Peak
Flashers (Accessory)
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1.1
SECTION
1
GENERAL
INFORMATION
General Description.
The
Model
763
FM
Modulation
Monitor
is
designed for
continuous monitoring of
an
FM
broadcast
transmitter
operating in the
frequency range
of
88 to
108
MHz.
The
monitor
is
factory-adjusted for
the customer's assigned
transmitter
frequency. Features include:
1.2
RF
Input
Flashers
to
indicate
when
a
preset
modulation
percentage
is
exceeded
on
either
positive
or
negative peaks.
Adjustab
le
attenuator
for reading residual
AM,
noise
and
low
percentage modulation
on
the modulation
meter.
Wide
audio bandwidth.
Internal
calibration
circuit
to check
the
modulation
meter
and
peak
flashers.
Carrier-fail
alarm to
indicate
loss
of
RF
input to
the Monitor.
Low-level audio output
for
aural
program
monitoring•
Three options,
all
field
installable:
Carrier
Power
Alann
Modulation
Alann
Balanced
Audio
Output
S
pecifications
.
Frequency
Range
RF
Input Voltage
Range
Input
Impedance
88
to
108
MHz
l to
7
volts
nns
50
ol'lns
nominal
Modulation Meter
Deviation
for
100
%indication
Meter
Range
Attenuator
Range
Accuracy
(5-kHz
modulation)
Frequency
Response
Characteristics
Remote
Output
1-1
+75
kHz
Oto
133%
Oto
-50dB
in 10-
dB
steps
+2'.t
at
all
iiiodul
ati
on
percentages
+0.1
dB
from
100
Hz
to
75
kHz
+0.25
dB
from
50
Hz
to
100
kHz
Peak-reading
circuit.
Scale
and
ballistics
confonn to
FCC
re
qui
remen
ts
Suitable for
driving
two
Model
704F
Remote
Readout
Panel
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1.2
(Continued)
Peak
Modulation
Indicators
Deviation for
100%
Indication
Peak
Level
Accuracy (5-kHz modulation)
Frequency Response
Response
Time
Accuracy
(1
cycle
of
50
kHz)
Remote
Output
Modulation
Calibrator
Measurement of Residual
AM
Range
Accuracy
(at
-30
dB)
Audio
Outputs
(at
100%
modulation)
Composite Outputs (with
or
without 75-us
deempha-
sis)
Signal-to-Noise Ratio
(400
Hz
with
deempha-
sis)
Hannonic
Distortion
Intennodul
ati
on
Frequency Response
(
W/0
deemphasis)
Audio
Monitor Output
Stereo Monitor Output
SCA
Monitor Output
+75
kHz
Set
by
a front-panel
three-digit
thurnbwheel
switch
in
1%
steps
from
soi
to
129i
on
both
positive
and
negative peaks.
+2%
at
100%
modulation
+2%
from
400
Hz
to
50
kHz,
+4%
from
50
Hz
to
75
kHz
+2i
Suitable
for driving
two
Mode
1
704F
Remote
Readout Panels.
Built
in,
for
calibration
of
modulation meter
and
peak
flashers
from
the
front
panel .
0
to
-70
dB
+1
dB
5
volts
nns
into
5000
otwns
75
dB
o.a
max
•
o.
1i
max.
per
SMPTE
standard
+0.25
dB
from
50
Hz
to
i s
kHz
0
dBm
into
600
ohns
1
volt
nns
into
600
ohms
1
volt
nns
into
600
ohms
Carrier-Fail
Alarm
-Relay
drive
output capable
of
sinking
50
mA
at
30V
DC
when
RF
carrier
drops
below
50%
of
nominal.
Preselector
Input -
Direct
input to discriminator
for
use with
FM
presel
ector
Frequency
Input Level
1-2
700
kHz
100
mV
rms
for fu
11
limiting
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1.2
(Continued}
Optional Features
Carrier
Power
Alarm
--,.
Modulation
Alarm
Balanced
Audio
Output
Level
Frequency
Response
Power
Requirements
Operating
TemperatuFe
Dimensions
1
.3
Accessory Equipment.
1.3.l
Model
704F
Remote
Readout Panels.
Two
relay
drive outputs,
one
for
carrier
level changes
of
+5%
and
the other for
+10%.
Each
output
is
capable
of
sinking
50
mA
at
30V
DC.
An
output capable of sinking
50
mA
at
30
V
DC
when
modulation drops
below
30%
for a period of time
between
2 seconds
and
1 minute,
internally
adjustable.
0
dBm
into
600
otllls
+1
dB
from
50
Hz
to
50
kHz
117/230V
AC
+10'1,
58
to
400
"z-
o C
to
50
C
19"
WX5-1/2" HX
14"
D
Rack
Mount
These
remote
modulation meter
and
peak
flasher
panels duplicate
the corresponding front-panel indications.
They
connect to terminals
on
rear-
panel
strips
Jl
and
J2
of
the
Model
763
through 5-conductor cables.
Power
for
_operating the
two
remote panels
and
drive for the
remote
me~er
and
·
peak
flashers
are supplied
by
the
Model
763.
,.
.
l
.3.
2
Model
724A
Stereo Monitor.
This instrument
is
for
use
by
stereo
FM
stations
to
meet
all
FCC
stereo monitoring requirements. Acomposite input
is
furnished
by
the
Model
763
.
1.3.3
Model
730A
SCA
Monitor.
The
Model
730A
enables
FM
stations
broadcasting
SCA
information
on
the
carrier
to meet
all
FCC
SCA
monitoring requirements.
The
Model
763
provides a composite input
to
the
Model
730A.
l
.3.
4
Model
764A/765A
FM
RF
Preselectors•
Either the
Model
764A
or
765A
allows the user to monitor the
transmitter
at
a remote
location.
Both
models
are
digitally
tunable
to
any
channel in the
FM
band
.
The
Model
764
has a
digital
frequency
error
readout,
the
765
does
not.
..
1-3
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1.4
Warranty.
TIME
&
FREQUENCY
TECHNOLOGY,
INC
. , warrants each of the
' instruments
of
its
manufacture to
be
produced
to
meet the specifications
delivered to the
BUYER
;
and
to
be
free
from
defects
in
material
and
workmanship
and
will
repair
or
replace,
at
its
expense,
for
a period of
one
year
from
the date
of
delivery
of
equipment, any
parts
which
are
defective
from
faulty material or poor
workmanship
.
Instruments
found
to
be
defective during the warranty
period shall
be
returned to the factory with transportation charges
prepaid
by
the
BUYER
.
It
is
expressly agreed
that
replacement
and
repair
shall
be
the sole
remedy
of
BUYER
with respect to
any
nonconfonning equipment
and
parts
-thereof
and
shall
be
in
lieu
of
any
other
remedy
available
by
applicable
law
. All returns to the factory
must
be
authorized
by
the
SELLER,
prior
to
such
returns.
Upon
examination
by
the
factory,
if
any
instrument
is
found
to
be
defective,
the
unit
will
be
repaired
and
returned
to
the
BUYER,
with transportation
charges prepaid
by
SELLER.
Transportation charges for instruments
found
to
be
defective within the
first
thirty
(30)
-days
of
the warranty period will
be
paid both
ways
·
by
the
BUYER.
'""
NO
OTHER
WARRANTY
IS
EXPRESSED
OR
IMPLIED.
TFT
IS
NOT
LIABLE
FOR
CONSEQUENTIAL
DAMAGES
.
LS
Claim
for
Damage
in
Shipment.
Your
instrument should
be
inspected
and
tested
as
soon
as
it
is
received.
The
instrument
is
insured for safe delivery.
If
the
instrument
is
damaged
in
any
way
or
fails
to
operate properly,
file
a
claim with the
carrier,
or
if
insured separately, with the insurance
company.
WE
SINCERELY
PLEDGE
OUR
IMMEDIATE
AND
FULLEST
COOPERATION
TO
ALL
USERS
OF
.
OUR
PRECISION
ELECTRONICS
INSTRUMENTS.
PLEASE
ADVISE
US
IF
WE
CAN
ASSIST
YOU
IN
ANY
MANNER
TIME
&
FREQUENCY
TECHNOLOGY,
INC
.
.
3090
OAKMEAO
VILLAGE
OR
.
P. 0.
BOX
58088
SANTA
CLARA,
CA
95052
(408) 727-7272
TWX
910-338-0584
1-4
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2.1
SECTION
2
INSTALLATION
Unpacking
and
Inspection.
Upon
receiving the instrument,
inspect
the packing
box
and
instrument
for
signs
of
possible shipping
damage.
After
installation,
operate the instrument in accordance with
the
procedures
of
Section 3 of
this
manual.
If
the instrument
is
damaged
or
fails
to
operate properly,
file
a claim
wi
_th the transportation
company,
or with
the
insurance
company
if
insured separately•
2.2
Power
Requirements.
The
Model
763
is
factory wired to operate
from
either
a
117-volt or a 230-volt source. Amarking
on
the
rear
panel
of the
instrument
indicates
whi.ch
voltage
is
to
be
used.
The
line
frequency
must
be
between
50
and
400
Hz.
Maximum
power
required
is
35
watts.
2.3
Installation
and
Connections.
The
Model
763
must
be
installed
at
the
transmitter
site
unless a
Model
764A
or
Model
765A
FM
RF
Preselector
is
used.
Connections
to
the Preselector
are
described in
its
instruction
manual.
For
installation
at
the
transmitter
site
without a
preselector,
proceed as follows:
a.
Mount
the
Monitor in the equipment rack.
b~
Connect external equipment to the rear-panel
5%
CARRIER
ALARM
and
.
AUDIO
MONITOR
OUTPUT
tenninals as
desired. Refer to the
Model
763
specifications,
Section
1.2,
for
characteristics
of
these outputs.
c.
Plug the
line
cord into
an
appropriate
power
receptable (see Section 2.2 above). There
is
·
no
·
power
switch
--the
Monitor
is
energized
whenever
it
is
plugged
into
an
AC
outlet.
·
d.
Make
sure
the
rear-panel
RF
INPUT/PRESELECTOR
INPUT
switch
is
in
the
RF
INPUT
position.
e.
Turn
the front-panel
RF
LEVEL
SET
control
fully
counterclockwise.
CAUTION
The
RF
· input to the Monitor must
not exceed 7 V rms,
and
should
not
be
applied to the Monitor unless
the
RF
LEVEL
SET
control
is
fully
counterclockwise.
2-1
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• - 1
·..2.3
2.
3.
1
2.3.2
2.4
(Continued)
f.
Connect
a
coax
cable
from
rear-panel
RF
INPUT
connector J3
to
the modulated
RF
sampling point
on
the
transmitter.
The
level of
this
input
must
be
at
1
east
1 V
rms
and
not
more
than 7 V
rms.
g. Depress the front-panel
RF
LEVEL
button
and
adjust
, the
RF
LEVEL
SET
control for a reading of
100%
on
the
MODULATION
meter.
Then
release the
RF
LEVEL
button.
The
Monitor
is
now
ready for use.
Connection
to
Model
724A
Stereo Monitor.
When
a
Model
724A
is
to
be
used
with the
Model
763,
proceed as follows: ·
a.
Connect
a
coax
cable
from
rear-panel connector
JS
on
the
Model
763
to
the rear-panel
C(J,IPQSITE
iNPUT
connector
on
the
Model
724A.
b.
If
the
Model
724A
is
not
mounted
on
a
common
rack
with the
Model
763
, connect a
ground
strap
from
the
chassis
of
the
Model
763
to
the chassis
of
the
Model
724A,
using
No.16
AWG
or
larger wire.
Connection
to
Model
730A
SCA
Monitor.
When
a
Model
730A
is
to
be
used
with the
Model
763,
proceed
as
follows;
a.
Connect
a
coax
cable
from
rear-panel connector
J6
on
the
Model
763
to
the rear-panel
COMPOSITE
INPUT
connector
on
the
Model
730A
.
b.
If
the
Model
730A
is
not
mounted
on
a
common
rack
with the
Model
763,
connect a
ground
strap
between
the
two
chassis using
No.16
AWG
or
larger
wire.
Model
704F
Connections•
A
Model
704F
Remote
Meter
and
Peak
Flasher
can
be
..
connected to the five
REMOTE
METER
OUTPUTS
terminals
on
strip
Jl,
and
an
additional
Model
704F can
be
connected
to
similar
tenninals
on
J2,
Refer
to
Figure 6.6, the
Model
704F
schematic
and
wiring diagram, for
wire color
code
.
2.5
Composite
Output Connections.
Rear-panel
banana
jacks
J7
, J8,
and
J9 provide high-
impedance
composite outputs for
such
loads
as
distortion
analyzers
and
voltmeters.
The
J9/J8 output
is
the
same
as
the J7/J8 output, except
hat the
J9
audio has
been
passed through
an
internal
75
microsecond
deemphasis network.
2- 2
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2.6
2.
6.
l
Field
Installation
of
Options.
Carrier
Power
Alarm.
When
this
option
is
used, the Carrier-Fail
Alann
(Section
2.3.b)
is
not used.
2.6.2
2.6.3
a.
Plug the
Carrier
Power
Alann
board
into
its
socket
on
the
Model
763
chassis
(see Figure
2-1).
b. Connect a wire
from
either
the
+5%
or
the
+10%
CARRIER
ALARM
tenninal
on
rear-panel
strip-Jl
of
the
Model
763
to
the appropriate terminal
on
the
external alarm device.
The
terminals
on
the
Model
763
can
sink a
maximum
of
50
mA
at
30
V
DC.
c.
Connect a wire
from
the
GND
terminal
of
Jl
on
the
Model
763
to
the ground terminal
on
the external
device.
Modulation Alarm.
a.
Plug the Modulation
Alarm
board
into
its
socket
on
the
Model
763
chassis
(see Figure
2-l).
b. Connect a wire
from
the
MODULATION
ALARM
tenninal
of
rear-panel tenninal
strip
Jl
on
the
Model
763
to
the
appropriate terminal
on
the external alarm device.
The
MODULATION
ALARM
terminal
on
the
Model
763
can
sink a
maximum
of
50
mA
at
30
V
DC.
c.
Connect a wire
from
the
GND
terminal
of
Jl
on
the
Model
763
to
the ground terminal
on
the external
device.
Balanced
Audio
Output.
a.
Solder the transformer into the
Model
763
motherboard (see Figure 2-1).
b.
Wire
the
BALANCED
AUDIO
terminals
on
rear-panel
terminal
strip
J2
to
the appropriate connectors
on
the
Mother
board•.
c. Connect the desired load to the
BALANCED
AUDIO
terminals
on
rear-panel terminal
strip.
2-3
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3.1
General.
SECTION
3
OPERATION
The
Model
76
.3
FM
Modulation Monitor enables
FM
station
personnel
to
monitor
FM
transmts~iortsto
comply
with
FCC
rules.
The
Monitor provides
all
the
test
functions
required for modulation proof-of-
performance
tests.
When
the
Model
763
is
used with the
Model
724A
Stereo Monitor
or
the
Model
730A
SCA
Monitor, stereo
or
SCA
proof..,of-
. p~rformance
tests
can
also
be
made.
The
Monitor displays the modulation percentage
of
the
carrier
being monitored. Either
positive
or
negative modulation can
be
selected for monitoring
on
tbe m~ter.
Two
front-panel
LED's
provide a
flashing indication
when
the modulation percentage exceeds a
preset
limit
on
either
positive
or
negative peaks•
The
Model
763
displays modulation only.
When
used with
the
Model
764A
Preselector,
carrier
frequency
error
measurements can
also
be
made;
and
when
used with
the
Model
764A,
the
Model
724A,
the
Model
724A
Stereo Monitor,
and
the
Model
730A
SCA
Monitor,
stereo
pilot
frequency
and
SCA
subcarrier
frequency can
also
be
measured.
Turn-On
and
Warm-Up.
The
Monitor contains
no
on-off switch,
and
is
on
whenever
it
is
plugged
into
an
appropriate
power
source.
When
the Monitor
is
on,
the front-panel
OPERATE
light
should be
lit,
regardless
of
whether
an
RF
input
is
present
or
not,
to
indicate
that
the
power
supplies are on.
If
the
OPERATE
lamp
does not
light,
check the fuse
on
the
rear
panel.
3.3
Fig.
3-1
Ref.
No.
1
2
3
4
Controls, Connectors, and Indicators.
Name
FM
Switch
AM
Switch
De-emph
Switch
PEAKS
1
amps
and
thumbwheel
switches
3-1
Function
Selects
the
FM
mode
of
operation
Depressed
for
nonnal
FM
monitoring.
Selects
AM
mode.
Used
for
making
residual
AM
measurements
on
the monitored
carrier.
Introduces a
75
us deemphasis
network
into
meter
circuit.
Can
be used in both the
FM
and
AM
models.
The
PEAKS
11
+
11
lamp
fl
ashes
whenever the
positive
modulation
peaks exceed the percentage for
which
the
thumbwheel
switches
have
been
set;
the
PEAKS"-"
lamp
www.SteamPoweredRadio.Com
3.3
Fi-g. 3-1
Ref.
No.
5
6
7
8
(Continued)
Name
RF
LEVEL
switch
and
SET
control
MODULATION
meter
OPERA
TE
1
amp
FLA
S
HER
and
METER
controls
3-2
Function
does the
same
thing
on
negative peaks.
Operation
of
these flashers
is
independent
of
all
switch
settings
except the
MODULATION
CAL
switch.
Used
to
adjust the
carrier
input level
from
the
transmitter
as described in
Section 2.3.
Indicates modulation percentage
of
carrier
being monitored, as described
in
Sections
3.5
and
3.6.
The
scale to
be read depends
on
which
MODULATION
METER
attenuation switch
is
depressed,
as
follows:
MODULATION
METER
Switch
100%
30%
10
%
0.3%
Applicable
Meter Scale
Top
seal
e.
Middle
scale.
Top
scale
divided
by
10.
Middle scale
divided
by
10.
Top
scale
divided
by
100.
Middle scale
divided
by
100.
The
MODULATION
meter
is
also used to
indicate
residual noise, as described
in Section
3.8.
Residual noise in
dB
referred
to
100%
modulation
is
the
sum
of
the reading
on
the lower meter scale
and
the
dB
label
on
the
MODULATION
METER
switch depressed.
When
lit
,
indicates
that
the
AC
power
is
on.
Used
in
calibrating
the
MOD
U
LATION
meter
and
PEAKS
lamps
as described in
Sections 3.5
and
3.7.
www.SteamPoweredRadio.Com
--'-- .
J7
.
1
3.3
Fig.
3-1
Ref.
No
9
10
11
Fig. 3-2
Ref.
No.
1
2
3
4
(Continued)
Name
MODULATION
METER
attenuation
MODULATION
11
-
11
and
11
+
11
switches
MODULATION
CAL
switch
Tenninal
Strip
J2
TO
STEREO
MONITOR
connector
JS
RF
INPUT
connector J3
INPUT
FRO,,
PRESELEC-
TOR
connector J4
!
3-3
Function
Used
with the
MODULATION
meter to
measure percentage modulation
and
residual noise as described under
reference
No.6
on
opposite page.
Select
negative
or
positive
modulation
peaks,
respectively,
to
operate the
MODULATION
meter.
Switches in the
built-in
modulation
calibrator
to
c.al
ibrate
the
MODULATION
meter
and
the
PEAKS
flashers
as
described in Section 3.5
and
3.7.
Provides the following outputs:
BALANCED
AUDIO
--
When
this
option
is
installed,
a O
dBm,
600
otm, balanced
audio output
is
delivered
to
these
two
tenninal
s.
ALTERNATE
REMOTE
METER
--
These
five
tenninals
supply power,
peak
flasher
drive,
and
modulation meter drive to a
Model
704F
Remote
Meter
and
Peak
Fl
asher.
Provides a 1
volt
nns,
600
ohm
composite output
to
drive a
Model
724A
Stereo Monitor.
Accepts the modulated
carrier
from
the
transmitter
being monitored. Input
level
must
be
in
the range
of
l
to
7
volts
rms.
Input impedance
is
50
ollns.
Accepts
700
kHz
input
from
a
Model
764
or
Model
765
Preselector,
when
used.
Input level
is
100
mV
rms
at
50
otlns.
www.SteamPoweredRadio.Com
.
-
..
3.3
.Fi.
g.
3-2
Ref.
No.
5
6
7-
8
(Continued)
Name
TO
SCA
MONITOR
connector J4
Composite
output con-
..
ectors
J7,
J8,
and
J9
RF
INPUT/PRESELECTOR
INPUT
switch
Terminal
strip
Jl
3-4
Function
Provide
al
volt
rms,
600
olln
composite
output
to
drive a
Model
730A
SCA
Monitor.
J7 provides the
same
composite output
as
JS
and
J6,
but
at
a level
of
5 volts
rms
into
5000
ohms.
J9 provides the
same
output as J7,
but
through a 75us
deemphasis network. J8·
is
a ground for
use with
either
J7 or
J9.
Both
the J7
and
J9
outputs are for driving high-
impedance
devices such as
distortion
meters
and
oscilloscopes.
Selects
either
the
RF
input
at
J3 or
the input
from
the
preselector
at
J4 as
the
signal
to
drive the Monitor.
When
the
Model
763
is
used without a
preselector,
this
switch must be in
RF
INPUT
position.
Provides the following outputs:
5%
CARRIER
ALARM
--
This terminal sinks
a
maximum
of
50
mA
at
30
V
DC
when
the
RF
input drops
below
the
level
necessary
to
operate the Monitor.
It
is
also used
for
the Carrier
Power
Alann
when
that
option
is
installed.
CARRIER
ALARM
--
When
the Carrier
Power
Alann
option
is
installed,
one
of
these
two
terminals sinks a
maximum
of
50
mA
at
30
V
DC
when
the
carrier
power
level
changes
by
more
than
5%
of
nominal,
and
the other terminal does the
same
when
the
power
changes
by
more
than
10%.
MODULATION
ALARM
--
When
this
option
is
installed,
this
tenninal sinks a
maximum
of
50
mA
at
30
V
DC
when
the
modulation drops
below
30%
for a period
of
time
between
2 seconds
and
l minute,
internally
adjustable.
