TM 11-6625-586-45
reading is +1 db greater 10KUV, then (27
Table 5-2. Voltage/dbm Convection
+ + 1) = 26. Record26 dbm as reference
dbm
Voltage
C.
-27
10KUV
-37.4
(21) Disconnect RF voltmeter and reconnect
3KUV
-47
lKUV
circuit as shown in figure 51B.
-57.4
300KUV
(22) Recheck that reference A attenuator
-67
100KUV
reading is the same as in step (18) above. Null
-77.4
30KUV
-81
10KUV
indication should be within .1 db of reference
-97.4
3KUV
A.
-107
lKUV
117.4
.3KUV
300 UV is under indicator line. Turn RF SET TO
LINE control for "red line" indication on RM me-
Table 5-3. Determining Gain or Loss from db Readings
ter.
Multiplier
Multiplier
u. On attenuator calibrator, turn reference at-
Loss
Loss
db
Gain
Gain
db
tenuator until NULL meter reads zero. Check
.832
1.20
1.6
1.01
.989
.1
that AFC DEV meter reads zero and VIDEO LE-
.822
1.22
1.7
.977
1.02
.2
.813
1.23
1.8
1.03
.966
.3
VEL is at set point. Adjust if required.
.803
1.24
1.9
1.05
.955
.4
.794
1.26
2.0
.944
1.06
.5
and record as L1.
.776
2.2
1.29
1.07
.933
.6
.759
2.4
1.32
1.08
.923
.7
w. Perform the following calculation for the
.741
2.6
1.35
1.10
.912
.8
measured value of attenuation, L (in dbm).
.724
1.38
2.8
1.11
.902
.9
L1 Reference A +
Reference C =
.708
1.41
3.0
1.12
.891
1.0
.692
L (where L1, and Reference A are in
3.2
1.44
1.13
.881
1.1
.676
1.48
3.4
.871
1.15
1.2
db; L and Reference C are dbm).
.661
3.6
1.51
1.16
.861
1.3
Example:
L1 = 47.3 db
.646
1.55
3.8
1.17
.851
1.4
reference A = 16.2 db
.631
4.0
1.58
1.19
.841
1.5
reference C = 27.0 dbm
then
This is the absolute output voltage with LO RF
47.3 16.2 + 27.0 = L
UV dial at 300 UV and RF meter at red line.
31.1 + 27 = L
L = -58.1 dbm
y. Repeat steps t through x for values on the
x. Convert the value of L above into an abso-
LO RF UV dial of 100, 30, 10, 3, and 1UV and
lute voltage as follows:
record.
(1) Refer to table 5-2 for dbm value corre-
sponding to voltage indicated on LO RF UV dial
such that 3KUV is under indicator line check that
of signal generator. Let dbm value from table 52
RF meter is set to "red line."
be M.
aa. Disconnect attenuator calibrator from test
set-up and connect RF voltmeter to output of
Then
dbm where
Z105.
dbm = dbm deviation from indicated
dial reading.
record as VH.
If
db is positive and represents
a gain, and if
db is negative and
ac. Disconnect RF voltmeter and reconnect at-
represents a loss.
tenuator calibrator as shown in figure 51B.
(2) From table 5-3 find multiplying factor
for value of
dbm.
maximum clockwise. RF meter should peg.
(3) Multiply voltage on LO RF UV dial by
ae. On attenuator calibrator, turn reference
multiplying factor and record.
attenuator knob until null meter reads zero. Check
Example. Let L = 58.1 dbm
that AFC DEV meter reads zero and VIDEO
from table 3-3 300KUV = 57.4 dbm = M
LEVEL meter is at set point. Make adjustments
then
dbm
if needed.
57.4 58.1 = -.7 db (a loss) or .923 (from
table 34
counters and record as LH.
then V = 300 UV x (.923) =
such that .3UV is under indicator line.
276.900UV
5-4
