Testing VF-PCM Multiplexers
LT51 User Manual
13
Frequency Response
1. Make the connections between the Test circuit and the LT51 as in Fig. 3.1.
2. Turn the LT51 ON. [after Reset: Ztx = 600
, Zrtx = HiZ 600
, TX Source =
OFF, TX Freq =10 kHz, Mode = TX-RX (4W)]
3. Press the [f5] soft-
key to select the ‘NEXT Loss’ measurement. This will
enable the SINE Transmitter at 10 kHz, 0 dBm on the LT51 TX terminals
and set the LT51 RTX (input) impedance to 600
terminated.
4. Press the key, followed by the [f1] soft-key to set the frequency
Span
.
Use the knob to set the span to 4.5 kHz.
5. Press the key followed by the [f4] soft-key to set the TX Freq to 1000
Hz, using the Knob or Keypad, and press the button to clear the Dialog
box, or appropriate [fx] soft-key if using keypad.
6. Press the key, followed the [f4] soft-key to set the
Zero Offset
for the
level measured at 1000 Hz.
7. Press the key followed by the [f4] soft-key to set the next TX Freq
using the Knob or Keypad, and press the button to clear the Dialog
box, or appropriate [fx] soft-key if using keypad. Repeat for all frequencies in
the Specification template.
8. Press the [f5] soft-key, to set
Sweeping
to ‘ON’. This will automatically
sweep across the 4.5 kHz BW to show a graph of the Frequency Response
in the spectral display. Use the Marker to read the frequency response at
each frequency.
9. The display will show the received level and frequency over the 4.5 kHz BW
at the RTXab input terminals. Press (Spectral) or (Numerical)
to toggle between displays of the signal.
Summary of Contents for UMDT51A
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