HP TM 11-6625-2779-14&P - Manual (Page 43)

Model 3555B Section V
c. Adjust A3R15 for 0dBm indication on the
3555B meter.
d. Change the 654A frequency to 1kHz.
Change the 3555B FUNCTION switch to
VF/Nm, 600 BAL. Compare the 3555B
meter indication with the indication in step
c. If any difference exists, adjust A3R15 to
split the difference between these two
indications.
NOTE
If the set is being operated from the
ac line ground currents may be
encountered on the low ranges,
particularly if other instruments are
connected in any way to the 3555B.
In order to eliminate this problem,
operate the set from its own internal
battery or use the C MSG filter. If the
C MSG filter is used, perform the
filter calibration described in
Paragraph 5-24 and then perform the
following step.
e.
Change the 654A to -80dBm output .level
at 1.00kHz. Change the 3555B RANGE
switch to -80dBm. Adjust A3R26 for 0dBm
indication on the 3555B meter.
f. Change the 654A to 135 BAL (150 BAL)
and change the 3555B FUNCTION to 135
BAL (I50 BAL). Adjust A3R24 for 0dBm
indication on the 3555B meter.
g. Change the 3555B RANGE switch to -
5OdBm, INPUT switch to TMS TERM, and
the FUNCTION switch to VF/Nm 600 BAL.
Change the 654A to 1kHz at an output
level of -50dBm, 600 BAL. Adjust the
AMPLITUDE control for exactly 0dBm
indication on the 3555B meter.
h. Change the 3555B FUNCTION switch to
900 BAL without changing anything else.
Adjust A3R20 for -0.15dBm indication on
the 3555B meter.
5-21. FREQUENCY RESPONSE ADJUSTMENT.
a.
The following adjustment consists of
selecting fixed values for frequency
compensation at 20Hz, 600 BAL, -70dBm
and 20kHz, 600 BAL, -70dBm.
b. Connect the 654A 600 BAL output to the
3555B input. Set the 3555B controls as
follows:
FUNCTION ............... VF/Nm 900 BAL
INPUT............................. TMS, TERM
RANGE ..................................... 0dBm
RESPONSE ............................. DAMP
c. Set the 654A (600 BAL) output level to
0dBm at a frequency of 20Hz. The 3555B
meter should Section V indicate -0.1SdBm
+0.3dBm. Note this indication.
d. Change the 654A output level to -70dBm at
a frequency of 20Hz. Change the 3555B
RANGE switch to -70dBm and change the
FUNCTION to VF/Nm 600 BAL. The
3555B meter should indicate 0dBm
+0.3dBm. Note the exact indication.
e. Compensation should be made between
the 900 BAL, 0dBm check (step c) and the
600 BAL, -70dBm check (step d). To raise
the level, increase the value of A3R72 until
the 900 BAL 0dBm check indicates high by
the same amount that the 600 BAL, -
70dBm check indicates low. The total
difference should not exceed +0.3dBm.
5-22. COMMON MODE ADJUSTMENT.
a.
Connect the equipment as shown in Figure
5-5 and set the 3555B controls as follows:
FUNCTION ................VF/Nm, 600 BAL
INPUT...............................TMS, TERM
RANGE ....................................... 0dBm
b. Set the 654A frequency to 20kHz and
adjust the output level of the 654A for
0dBm indication on the 3555B meter.
c. Disconnect the left output terminal on the
654A and short the tip and ring together on
the cable. Down range the 3555B RANGE
switch for an on-scale indication.
d. Adjust A1C7 for minimum indication on the
3555B meter. This indication must be
down at least 60 dB.
e. Change the 3555B FUNCTION switch to
CARRIER, 600 BAL and change the 654A
frequency to 100kHz.
f. Use the procedure described above and
adjust A1C4 for minimum indication on the
3555B meter. This indication must be
down at least 40dB.
5-23. BALANCE CHECK.
a.
First check the balance as described in
paragraph 5-13 to be sure that the balance
does not meet specifications. If it does,
disregard this step. If it does not perform
the following procedure.
b. Since there are no adjustments for balance
it will be necessary to change the value of
a fixed factory selected capacitor. To
adjust the balance on the
5-9