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Performance Verification
1780R-Series Service Manual
4–67
Figure 4–14: Measuring return loss of 1780R-Series CH A INPUT
f. Check that the return loss of the CH A INPUT is better than 40 dB for a
frequency range from 50 kHz (reference) to 5 MHz. Make this check,
within this frequency range, with instrument power on and off. (40 dB
converts to 5 mV on the test oscilloscope CRT display.) Check return
loss of CH B1, CH B2, and CH B3 using the same technique as
checking the CH A INPUT.
g. Check return loss of the AUX IN, AUX OUT, and PIX MON OUT
connectors in that sequence. Do not terminate. Leave the instrument
power On. 34 dB converts to 10 mV on the test oscilloscope CRT
display.
h. Check return loss of the EXT REF connector with the terminator
connected. The instrument can be On or Off. 46 dB converts to 2.5 mV
as displayed on the test oscilloscope CRT.
i. Disconnect the Return Loss Bridge from the instrument and the test
oscilloscope.
This completes the Performance Check Procedure.