Orban 8182A Operating Manual page 38

Interfacing
A BTSC
Stereo Generator:
The Orban Model 8185A
TV
Stereo Generator
connects
to
the
8182A
through
the
14-pin connector on
the
8182A's
rear
panel.
Appendix
G
of this
manual
contains
a
wiring
diagram
of the interface
and
a short
explanation of
how
it
works. Section
2
of the
8185A
Operating
Manual
explains
how
to
make
the
8182A
work with the
8185A.
You
can
also
connect the
8182A
to
Orban's
older-model
stereo generator, the
8182A/SG.
Part
3
of the
8182A/SG
Operating
Manual
explains
how
to
make
the
8182A work with the
8182A/SG.
To interface another
manufacturer's
stereo
generator
to the
8182
A,
connect the
8182A's
left
and right
main outputs
to
the audio inputs
of
the stereo generator.
(The 8182A's main outputs appear on
its
rear-panel barrier
strip.)
Strap the 8182A's
Card #7 Output Format Jumpers
and
De-Emphasis jumpers
as
required by the stereo
generator.
Most generators
require
L/R format and de-emphasis IN
("flat"
output).
Remote
Gain Reduction Meter:
A
negative
DC
voltage approximately proportional
to the Total
Master Gain Reduction
is
available
between
the
OPTIMOD-TV
rear-
panel
G/R
terminal and
circuit
ground.
The
voltage scale
is
approximately -0.33V
per
dB
of gain reduction,
and
the source
impedance
is
8.87K.
A
standard 0-25dB
Orban
gain reduction
meter can be connected
directly
between
this
terminal
(-)
and
ground
(+).
The Orban
meter
has
a sensitivity of
1mA
f.s.
and
a
DC
resistance of
about 950
ohms.
Full-scale
corresponds
to
30dB
G/R.
Because
only
25dB
G/R
can be
achieved, the
last
5dB
of the scale
is
colored red.
(The purpose
of this
is
to
match
the
scale
to that of
the
BASS G/R
meter,
which
is
capable
of,
and
fully calibrated
to,
30dB
G/R.)
If
an external meter
with
different characteristics
is
used,
it
is
easy to calculate
the
required
additional
multiplier resistor for
a
0-30dB
scale
by the
formula:
M=(9.75/F)-(8870+R),
where
M
is
the required
multiplier resistor
in
ohms,
F
is
the
full
scale
meter
sensitivity in
amps, and
R
is
the internal
DC
resistance
of the
meter
in
ohms.
If
M
is
negative, the
meter you wish
to
use
is
not sensitive enough, or
has too
high an internal resistance.
If
you wish
to
interface the
G/R
output
to a
remote
control for
telemetry, bear
in
mind
that
the input
impedance
of
the
remote
control
will
load
down
the
G/R
output and reduce
the voltage according to the gain factor:
G=X/(X+8870),
where
X
is
the input resistance of the
remote
control
in
ohms.
The
scaling of
the
remote
control should therefore be
-0.33xG
volts
per
dB gain reduction.
3-8