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Model 654A
Section V
Table 5-3. Thermal Converters for Level Flatness Checks.
(See Paragraph 5-16 for explanation)
INPUT
IMPEDANCE
-hp- Part No.
Input Level
Output Voltage
(dc)
+/-0.5% deviation
50 UNBAL
11050A
+10dBm
mV
+/-
uV
OdBm
mV
+1-
uV
75 UNBAL
HOI - 11050A
+10dBm
mV
+/-
uV
OdBm
mV
+/-
uV
135 BAL
H 1 1-11050A
+10dBm
mV
+1-
uV
OdBm
mV
+/-
uV
150 BAL
H12- 11050A
+10dBm
mV
+/-
uV
OdBm
mV
+/-
uV
600 BAL
H10- 11050A
+10dBm
mV
+/-
uV
OdBm
mV
+/-
uV
c. Set the reference supply for minimum output
voltage and record, in Table 5-3, the thermal
converter output voltage indicated on the dc null
voltmeter.
d. Using the formula given below, calculate the
voltage deviation which represents a change of
+/-0.5%; record this in the last column of Table
5-3.
2E (% change)
100
AE = maximum allowable deviation from E
E = thermal converter output voltage
% change = (+/-) 0.5%
Example:
If E = 7mV
2 x 7 x 10
-3
x (+/-)0.5
Then +/- AE
=
+/- 70uV.
10
2
NOTE
The factor 2 is included in the formula as
the thermal converter is a square law
device.
e. Adjust the reference supply for null indication on
the dc null meter.
f. Sweep the 654A slowly over the frequency range
of 10Hz to 10MHz; the dc null meter indication
should not vary more than +/-AE (calculated in
step d of this Paragraph) from null. This verifies a
level flatness, referenced to lkHz, of +/-0.5% at an
output level of + 10dBm.
g. Reset
the 654A frequency to 1 kHz and the
10dBm step attenuator to 0 position and repeat
steps c through f of this paragraph to verify a
flatness of +/-0.5% at an output level of OdBm.
h. If the tolerances are not met, first check the 75
UNBAL
flatness (Paragraph
5-17)
before
performing the calibration of Paragraph 5-67.
5-17. 75 UNBAL FLATNESS CHECK.
a. Perform the procedure of Paragraph 5-16 steps a
through g with the following changes:
in step a. Set IMPEDANCE to 75 UNBAL;
in step b. Use the 75 ohm thermal converter
(Table 5-3).
b. If the tolerances are
not met, perform the
calibration of Paragraph 5-66.
REFERENCE SUPPLY
r
-
RI
6500
BTI
I.34V
Parts list:
R1: R fxd met flm 6500 ohms +/- 1%
-hp- 0811-0392
R2: R var 500 ohms +/-5%
-hp- 2100-0324
R3: R var 50 ohms +/-5%
-hp- 2100-1481
BT1: 1.34V Mallory RM-42R
Figure 5-4. Reference Supply
5-5
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