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Intgrated noise measurements cont'd |
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|  MIL-T-48621A (AR)
Adjust the GAIN AM control for a center line meter
u.
reading.
Set MODE switch to INTL OPER with the external noise
v.
source (item 26, Table III) connected to the 0 MOD INPUT
port of the microwave power source (item 18, Table XII).
Adjust the attenuator (Item 17, Table III) to obtain a
center line meter reading, i.e., a reading within the
limits defined by the black band.
w.
Set the MODE switch to
EXT OPER.
x.
Disconnect the external noise source (item 26, Table
III and its variable attenuator (item 17,1 Table III)
and connect the audio oscillator (item 27, Table 111) in
Its place, at the 0 MOD INPUT port of the microwave
power source (item 18, Table 111). Do not disturb the
level settings of the noise ,source or its attenuator.
Using Column 1 of Data Sheet (Table VII) as a frequency
Y"
guide, inject a sine wave calibration signal and
observing the RF spectrum analyzer (item 31, Table III)
at the RF OUT port, adjust the oscillator output level
so that its FM sideband is 36 DB below the microwave
power source (item 18, Table III carrier.
..
-z.' with the base band spectrum analyzer (item 30, Table
III) connected to the" NOISE OUT port, observe the Signal
level (in DB below 1 volt) of the externally injected
sine wave calibration signal. Enter this value in the
DBVC side of Column 3 of the Data Table. Note: The
base band spectrum analyzer has an u
r bandwidth limit
of 60 KHz. For higher frequency cal ration signals,
b
therefore, it is necessary to use a frequency slectlve
voltmeter at the NOTICE OUT Port. Set freq sel Voltmeter
INPUT control to 600 ohms. Perform the same operations
as for the base band spe ctrum analyzer and enter results
in DB in column 3 of the
Data Table. Note: The freq
sel voltmeter reading exhibits slight fluctuation - use
average reading and enter value In Column 4F (Avg) of
Data Sheet.
aa.
Disconnect the audio oscillator (item 27, Table III)
from the 0 MOD INPUT port of the microwave power source
(item 18, Table III) and reconnect the external noise
source (item 26. Table III) and its attenuator (it-
17, Table 111).
Ensure that the level is the same as
recorded on the true RMS voltmeter (item 28, Table 111)
in 1.
43
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