Service manual

10 8495D/K Attenuators Operating And Service Manual
Operator’s Check
Operator’s Check
The Operator's Check is supplied to allow the operator to make a quick
check of the instrument prior to use or if a failure is suspected.
Description The attenuator is driven from a 50-ohm signal source at 1 kHz. The output
level from the attenuator is detected by a narrow-bandwidth voltmeter. The
attenuator and detector range switches are stepped together and the
variations in level noted. This verifies that each attenuator section is being
properly switched and checks the low-frequency accuracy of the attenuator.
NOTE The SWR meter used in this check is calibrated for a square-law detector
and therefore the range changes and errors (read in dB) are twice that
indicated by the meter.
Figure 4 Operator’s Check Setup
Procedure 1. Connect equipment as shown in Figure 4 with the attenuator set to 0 dB.
2. Set the test oscillator to 0.3 Vrms at 1 kHz.
3. Set SWR meter range to 2 dB (expanded) and adjust its bandwidth to
center of adjustment range. Fine tune oscillator frequency to obtain
maximum meter indication.
4. Set attenuator and SWR meter range switch as shown in Table 4 and
verify that SWR meter indicates within the limits shown.