H Heuer Instruments UMDT51A, Руководство пользователя

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Testing PLC Systems
LT51 User Manual 23
Measuring the Return Loss of Line Matching Units (LMU)
WARNING: Ensure that the LMU interface is free of all carrier
signals before connecting the LT51 in RTX mode (eg. Return
Loss). Permanent damage to the LT51 will result otherwise.
1. Insert the Double Plug to BNC Adaptor into the LT51 RTXa-b terminals
2. Connect a cable between the BNC Adaptor and the LMU coaxial interface
3. Turn the LT51 ON.[ after reset: Ztx = 600
Ω, Zrtx = HiZ 600Ω, TX Source =
OFF, TX Freq =10 kHz, Mode = TX-RX (4W)].
4. Press the [f3] key to select the Return Loss measurement.
5. Press the button, then the [f1] soft-key to set ZRTX
to ’75 Ω’, to make
the return loss measurement against a 75 reference.
6. Press the key followed by the [f4] soft-key to set the desired TX
Frequency using the Knob or Keypad, and then press the button to
clear the Dialog box, or appropriate [fx] soft-key if using the keypad.
7. To set the frequency span manually, press the key, followed by the [f1]
soft-key. Or to make the measurement around a particular centre frequency,
press the [f2] soft-key, and set the span using the [f1] soft key [the 25 Hz
selective BW is chosen by default].
8. To make a swept Return Loss measurement over the frequency span
selected above, press the key, and toggle the [f5] soft-key to enable
sweeping. When making swept measurements, Level auto-ranging should
be disabled, i.e. OFF).