Testing VF-PCM Multiplexers
LT51 User Manual
14
Variation of Gain with input level
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 button, then the [f2] soft-key to set
Input
to ‘Term’. The
LT51 RTX (input) impedance is now 600
terminated.
4. Press the key followed by the [f2] soft-key to set the TX Level to
–10.00 dBm using the Knob or Keypad, and press the button to clear
the Dialog box, or appropriate [fx] soft-key if using keypad.
Press the [f4] soft-key to set the TX Freq to 1014 Hz using the Knob or
Keypad, and press the button to clear the Dialog box, or appropriate
[fx] soft-key if using keypad.
5. 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.
Press the [f2] soft-key to set
Centre Frq
to 1014 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
–10 dBm.
7. Repeat for all levels at the steps in the Specification template. Note that a
correction for the input level (relative to
–10 dBm) must be applied to the
result. E.g., for an input level of +3 dBm, you must subtract 13 dB from the
result, ie. +3dBm
– (-10dBm) = 13dB, to get the gain variation.
8. The display will show the received level at 1014 Hz at the RTXa-b input
terminals.
Summary of Contents for UMDT51A
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