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Operator Troubleshooting
1503C MTDR User Manual
D–5
SOURCE
IMPULSE
GENERATOR
INCIDENT
VOLTAGE
REFLECTED
VOLTAGE
2E
PEAK
R
S
75W
Z
O
75W
LINE
–0dB
=
–6dB =
–6dB =
–0dB =
+100%
+50%
0%
-50%
-100%
W
225W
75W
25W
0
W
LOAD
R
L
%
/ DIV
%
/ DIV
%
/ DIV
%
/ DIV
OHMS
OHMS
OHMS
20
10
5
2
1
.5
75W
SOURCE
75W
SOURCE
75W
SOURCE
75W
dB =
E
PEAK
100
60
50
40
30
20
15
10
5
0
90
60
50
45
40
35
30
25
20
15
10
5
75W
80
70
65
60
55
50
45
40
35
30
70
65
60
55
76
74
73
72
70
69
68
67
66
65
64
63
71
75W
74
73
72
71
70
69
34
40
46
46
40
34
RETURN LOSS (–dB)
(20% / division, downward 5 major divisions)
–1
00%
=
0
W
Figure D–4: Slide Rule 75
W
Source
If the line impedance and the source resistance are known, the expected amplitude
of a reflection can be approximated. First, select the side of the slide rule having the
correct source impedance. For cables having a higher impedance than the selected
source resistance, put the sliding reference level even with the bottom stationary
scale markings. For cables having a lower impedance than the selected source
resistance, move the reference level even with the top of the scale markings. For best
accuracy, select the scale farthest to your right in which the impedance level of
interest is in view. Read from the adjacent stationary scale the reflection coefficient
or percent reflected voltage that corresponds to the Ohms selected.
Percent Reflected Voltage vs. Load Resistance
To find the terminating load resistance (R
L
) of a line, knowing the percent reflected
voltage or reflection coefficient, use the preceding instructions.
If the load resistance is known, the previous procedures can be used to approximate
the size of the return reflection. An error might be introduced if the impedance of
the connecting cable does not match the source resistance of the pulse generator.
Summary of Contents for 1503C
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Page 92: ...Appendix A Specifications A 6 1503C MTDR User Manual...
Page 104: ...Appendis B Operator Performance Checks B 12 1503C MTDR User Manual...
Page 122: ...Glossary Glossary 6 1503C MTDR User Manual...
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