Operating Instructions
1–16
1503C MTDR User Manual
would absorb most of the pulse, so its return loss would be large. An open or short
would reflect all the energy, so its return loss would be zero.
The 1503C can be made to display in m /div instead of dB through MENU.
1. Press MENU.
2. Select Setup Menu.
3. Press MENU.
4. Select Vertical Scale is: Decibels.
5. Press MENU. This changes the selection to Vertical Scale is: Millirho.
6. Press MENU again to exit from the Setup Menu.
7. Press MENU again to return to normal operation.
The reflection coefficient is a measure of the impedance change at a point in the
cable. It is the ratio of the signal reflected back from a point divided by the signal
going into that point. It is designated by the Greek letter , and is written in this
manual as Rho. The 1503C measures reflection coefficient in millirho (thousandths
of a rho).
To measure a reflection, adjust VERT SCALE to make the reflection one division
high. Read the reflection coefficient directly off the display above the VERT
SCALE control. For reflections that are greater than 500 m /div, adjust VERT
SCALE for a reflection that is two divisions high and multiply the VERT SCALE
reading by two.
O
F
F
O
F
F
O
F
F
O
N
ac
455.00 ft
Figure 1–14: Reflection Adjusted to One Division in Height
In an ideal transmission system with no changes in impedance, there will be no
reflections, so rho is equal to zero. A good cable that is terminated in its
characteristic impedance is close to ideal and will appear as a flat line on the 1503C
display.
Reflection Coefficient
Measurements
Summary of Contents for 1503C
Page 4: ......
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...
Page 127: ......
Page 128: ......