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(26)
Set the
UUT VERNIER
to
give
-9dBm
on
the
meter.
(27)
Adjust
R143 on
the
p.c.b.
until
the
modulation meter
reads
80%,
and
adjust
R109
for
minimum
distortion
on
the distortion
analyser.
(28)
Repeat
adjustments
(24) to (27)
until
the
modulation depth
is
80%
at
the
+3dBm
and
-9dBm
output
levels.
(29)
Tune
UUT
to
520MHz
and check
that
modulation depth
is
80%
at
+3dBm
and -9dBm.
(30)
D
isconnect the
modulation meter
from
the
UUT
output
and re-connect
the millivoltmeter.
Re-check
operations
(14) to (17).
(31)
Tune
the
UUT
to
50MHz.
Set the
UUT VERNIER
control
to
read
+3dBm
on
the
UUT
meter.
(32)
Set the
OUTPUT
switch
to
X2.
Verify
that the
millivoltmeter reading
is
-f9dBm
±
0.3dB, and
that the
UUT
meter reading
is
within
±0.2dB
of the
|
millivoltmeter reading.
If
necessary
change
the
value
of
R42 on
the
output switch
to
achieve
this.
(33)
Operate
the
UUT VERNIER
control
and
verify that
readings
of at
least
+3dB and
—
1
OdB can be obtained on
the
UUT
meter.
(34)
Tune
the
UUT
to
1
.5MHz (5MHz
for
9081) on range
1
.
(35)
Set the
multimeter
to
the
10V
d.c. range.
Connect
the positive
lead
to
link
LK1 on
the
p.c.b.
(ALC
loop)
and
the
negative lead
to
chassis.
(36)
With
OUTPUT
switch
on
X2
adjust
R19 on
the
p.c.b. (Range
1
mixer
input)
to
give a reading of
2.0V
on
the
multimeter.
(2.8V
for
9081).
(37)
Tune
the
UUT
through
the
frequency range
5MHz
to
36MHz
and
verify
that the
multimeter reading does
not
exceed 2.8V. Tune
the
UUT
through
the
remaining frequency ranges
using
60kHz
step size
and
verify that the
multimeter reading does
not
exceed +6V.
(38)
Disconnect
the
multimeter
and connect
the
UUT
5CD
output socket
to
a
spectrum analyser
which
has
30dB
of input
attenuation selected.
(39)
On
the
UUT
set:-
The
AM
switch
to
OFF
The
OUTPUT
switch
to
X2
(40)
Tune
the
UUT
across the
full
frequency range and
adjust
R94 on
the
p.c.b.
(output amplifier
bias) for
minimum
2nd and
3rd
harmonic
distortion
on
the analyser display
which
must
be
at
least
30dB below
carrier level
.
5-12
9081
&
9082 Vol.2.
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