HP 654A - 5-26. 10 dB-STEP ATTENUATOR CHECK

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