The FDR measurement mode is based on the theory of Frequency Domain Reflectometry. Frequency domain reflectometry is a method of determining transmission characteristics by analyzing the reflections in a sweep response. An FFT (Fast Fourier Transform) is performed on the response to determine the frequencies of reflection components. This analysis provides a display of reflection components in an amplitude vs. distance graph that is displayed on your DSAM FDR screen. The highest reflections will emanate from the points in the transmission medium that have the worst impedance match relative to the source. For instance, if the cable is broken or unterminated a large reflection will occur.

The FDR mode continuously updates the graphic depiction of the signal along with the Frequency Domain Reflection data.

D
ISTANCE MARKER

You can position the distance marker over a reflection so that you can pinpoint its distance and amplitude. You can see the marker information directly beneath the graph.

Use the left or right arrows to adjust the distance marker.

Softkeys

Three softkeys on the FDR screen provide the following options:

VIEW

Use the arrow keys to choose the menu item you prefer and press ENTER to make your selection.

Select Auto Reference to automatically view measurement results in the best reference setting on the graph (Keystroke shortcut: SHIFT 9). NOTE: For best reference setting results you may have to select the Auto Reference button more than once (up to three times).

Select 5 dBRL/div, 10 dBRL/div or 15 dBRL/div to adjust the vertical resolution of the graph for the best viewing.

Select Pause to suspend measurement updates (Keystroke shortcut: SHIFT 8).

ZOOM

Select a graph magnification by using the arrow keys to highlight the zoom setting you prefer - 1x, 2x, 3x, 4x, 5x, 6x, 7x, or 8x. Press ENTER to make your selection.

SETTINGS

Select Settings to access the FDR settings screen.