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MIL-T-48621A (AR)
On the base band spectrum analyzer (item 30, Table
bb .
III)
or frequency selective voltmeter (item 29, Table III)
for frequencies above 50 KHz, observe the signal level
of the external noise source (item 26, Table III) at
the same frequency injected in y.  Enter this value in
Column 4A of the table.
cc
Set OPER/TEST switch to CAV TUNE and MODE switch to
q
INTL TEST.  Repeak cavity.  Set OPER/TEST switch to BAL
position, and adjust BAL ADJ control for center meter
reading, if required.  Set OPEr/TEST to phase shift
position, and adjust PHASE ADJ control for center meter
indication, if required.  Reset MODE switch to EXT OPER
and OPER/TESt switch to OPERATE BAND 2 or 3 as
required.  For base band analyzer, clear screen and
retrigger sweep, and for frequency selective voltmeter,
read average signal level of external noise source at
the calibration signal frequency injected in y. Enter
this value in COlumn 4B of Data Sheet.  Repeat this
entire step for the remaining three DBVN columns.
Average these five values and enter result in COlumn 4EI
of Data Sheet.  Repeat s. through bb. for all
frequencies listed In Column 1 of Data Sheet (Table
VIII ) .  These readings contain the data necessary for
complete integrated noise power (DBCI) measurement t for
.
the band tested.
q
dd .
Set noise tester MODE switch to INTL TEST and the
OPER/TEST switch to CAV TUNE.  Repeat e. through f.
Set OPER/TEST switch to OPERATE BAND 3.  Repeat t.
through dd.
ee.
Using the data tabulated in COlumns 3 and 4 of each
Data-Sheet, calculate COlumn 6 for each Table using the
following three formulas where applicable.
BAND 1 EQUATION:
Using base band spectrum analyzer (item 30,
Table III), with FC = 2000 HZ, BW (bandwidth) = 30 HZ and reference
sidebands = -30 DB:
1.
DBVN - DBVC + 20 log FN - 50.79 + ADBF
DBW
=
Level of noise below the carrier at FC.
Where:
DBCN
=
Level of calibration signal below 1 volt.
DBVC
=
Level of noise at FC below 1 volt.
DBVN
=
Frequency of noise In Hz.
FN
=
@ BF  = Filter attenuation characteristics (in
DB)
at
.
Fc.
45

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