TB 9-4931-538-40
b. Using necessary adapters and connectors, connect the 50 termination to
multimeter. Record the dc resistance of 50 termination. _____________ .
c. Remove 50 termination and connect APC 3.5 short. Record the dc resistance of
APC 3.5 short. ____________.
d. Subtract dc resistance recorded in c above from dc resistance recorded in b above.
Example:
Step (2)_________ - Step (3)__________ = ZL _________ .
e. Using this formula, solve for ER (ER may be a negative number).
ER = 200 ((ZL - 50) (ZL + 50)) (rounded to nearest 0.01 mV).
f. Add 200 mV to the value obtained in e above rounded to the nearest 0.01 mV.
Example:
ER (Step (5) + 200 mV = ______________mV
g. Connect 50 termination to Channel 1 input.
h. Adjust timebase delay until the rising edge is approximately 2 divisions from the left
side of the display (fig. 18).
i. Adjust TDR DRIVE on horizontal assembly A1 (fig. 11) fully cw. Position the delay
setting to place the edge 2 divisions from the left side of display.
j. Adjust TDR BIAS on horizontal assembly A1 (fig. 11) fully ccw, then slowly adjust
until overshoot appears.
k. Press Delta t key and set MARKERS ON.
l. Set the START MARKER to the leading edge of the step, and set the STOP
MARKER 500 ps to the right of START MARKER (fig. 18).
m. Adjust TDR BIAS on horizontal assembly A1 (fig. 11) until the rising edge of the
step coincides with the STOP MARKER (fig. 19). If this adjustment does not line up with
the STOP MARKER, return to j above and adjust TDR DRIVE (fig. 11) slightly more cw.
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