Residual Fm Check - Racal Instruments 9081 Maintenance Manual

(3)
For close-in noise tune the
analyser
to
400MHz
and
set
the controls
thus
:-
Input attenuator
Scanwidth
Bandwidth
Video
filter
Log.
ref.
1
OdB
10kHz/div.
1
kHz
10Hz
+1
OdB
(4)
Adjust
the
analyser vernier control
to
bring the carrier
to
the top
graticule line.
Verify that the noise at
20kHz
off carrier
is
on
or
below
the
70dB graticule
line
and
that
no spurious frequencies
are visible.
(5)
Disconnect
the
spectrum analyser.
RESIDUAL
FM CHECK
5.25
Test
Equipment Required
Page 5-2
Table 5
Modulation Meter
(9009)
Item 3
Millivol tmeter (True
RMS)
Item 7
Cable
with
N-N
connectors
5
.
26
Procedure
(1)
Check
that all
UUT
modulation control
switches are at
OFF.
(2)
Connect
the
UUT 50Q
output socket
to
the
modulation meter
input.
(3)
Connect a True
RMS
Mi
I
li
voltmeter
to
the
audio output of
the
modulation meter.
(4)
Select
the
1
.5kHz
f.s.d.
range
and
FM
mode
on
the
modulation meter
(9009).
(5)
Refer
to
Table 10 and
verify that the
modulation meter
(9009)
and
millivol
tmeter readings are within
the limits
given
at
several points
in
the
range
360MHz
to
420MHz
and
at
520MHz.
9081
&
9082
Vo
1.2.
5-20