5-16.
LEVELED RF OUTPUT ADJUSTMENTS (Cont’d)
Equipment
Oscilloscope
HP 1741A
10:1
Divider Probe, 2 Required
HP 100040
Detector
HP 8473C
Digital Voltmeter (DVM)
HP 3456A
Adapters:
APC 3.5 (f) to APC 3.5 (f) (HP 8340B only)
HP P/N 5061-5311
APC 3.5 (f)
—
Type N
(in)
(HP 8341B only)
HP P/N 1250-1744
Dual Banana to BNC (f)
HP P/N 1251 -2277
BNC (f)
—
Clip Lead
HP P/N 81 20-1292
Procedure
MODULATOR OFFSET
1. Connect the OVM to A26TP3 (MOO LVL). Preset A26R88 (MO) fully clockwise (Figure 5-53). Turn
the OUT’s LINE switch ON and allow 30 minutes warm up.
2. Press [INSTRPRESET] on the OUT. Press [CW] [8] [GHz].Press [SHIFT] [METER]to bypass
the ALC circuit and allow direct control of the linear modulator circuit.
3. Adjust the front panel rotary knob (RPG) for a DVM indication of 0.00 V + 3 mV, then note the
indication in the POWER dBin display. Adjust A26R88 (MO) counter-clockwise to decrease the
POWER dBin indication by 0.2 dB.
LEVELED BIAS
4. Disconnect the DVM and connect the oscilloscope as shown in Figure 5-52.
5. Set the oscilloscope as follows:
DISPLAY
CHANNEL A
CHAN
A
0.02 V/Div
DC
COUPLED
TRIGGER
EXT. POS.
TIME/Div
SinS
6. On the OUT, press [INSTRPRESET] [STARTFREQ] [7] [GHz] [STOPFREQ] [1] [3]
[.]
[5] [GHz].
Press [SHIFT][PWR SWP]
[-]
[2] [0] [dBm]. Press [SWEEPTIME] [5] [0] [msec].
Save this instrument state by pressing [SAVE][2].
7. The oscilloscope display should be similar to Figure 5-54. Adjust A24R12 (MIN) so that all points
on the trace are reduced to the lowest possible voltage level (i.e., maximum negative voltage).
5-102
Adjustments
HP 8340B/41B