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2-14
INSTALLATION
Orban Model
464A
Matching Output
Level to
Device Being
Driven
When
the
Co-Operator
is
used
to
provide
peak
overload protection
for a
recording
or
transmission
device,
it
is
best
to adjust
the
Co-Operator's output so
that
it
drives
the
device
up
to,
but
no
further than,
its
optimum
operating
level.
The
following procedure
explains
how
to
match
these levels
and
calibrate the
Co-
Operator's
PEAK OUTPUT LEVEL
meters
to
the
overload point
of
the
driven
device.
It
is
only necessary
to
match
levels
once
for
each
protected device.
Level-matching
for
FM
transmitter,
STL, and
subcarrier generator protection
is
covered
in
the
preceding
section, "Installation
—
FM
Transmitter,
STL,
Subcarrier Generator Pro-
tection".
NOTE:
The
Co-Operator's output
impedance
is
30
ohms.
Its
output
level will there-
fore
be 0.4dB lower
with
a
600fl load
than
it
will
with
a a
10KQ
(bridging) load.
Although
this
drop
is
small,
you
may
wish
to recalibrate the
PEAK OUTPUT LEVEL
meters
for
critical
applications
(the
meters
do
not
directly
sense the voltage across
the output
terminals).
(Co-Operators with
serial
numbers below 1306000 had
a
93a
output
impedance.
If
the
load
impedance
of
one
of
these
is
changed from
10RQ
to
600a,
the output
level will
change
by
about
1.2dB.
If
you have
a
93a
unit
and would
like to
convert
it
to
30a
output
impedance,
contact
Orban
Customer
Service
for
instructions.)
Allow
about 15 minutes
for
level-matching.
You
will
need
a
sine
wave
oscillator
and
a calibrated oscilloscope (or
true
peak-
reading
voltmeter).
1)
Set
the
LEVEL
and
COMPR
buttons
to
OFF.
2)
If
you
are
going
to
use
the
high-frequency
limiter, set
the
HF
LIMIT
buttons to
OPERATE.
Otherwise,
set
them
to
DEFEAT.
If
you want
absolute
peak
control at the
output of the high-frequency
limiter,
be
sure
that
the internal clippers are
operational (see step
2
of
the
Installation Instructions in
Section
2).
3)
Connect
a calibrated oscilloscope
or
true
peak-reading voltmeter
to the
LEFT
OUT
terminals
of
the
Co-Operator.
4)
Connect
a sine
wave
oscillator to
the
Co-Operator's
LEFT
IN
terminals.
Set the
oscillator's
frequency
to
100Hz.
5)
Advance
the
Co-Operator's
L INPUT
atten
control
until
you
observe
a noticeably
clipped output
waveform on
the oscilloscope (or
until
the
reading
on
the
peak-
reading
meter
no
longer
increases).
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