Measuring Levels Across A Balanced Lin - Motorola R-2001D Operator's Manual

WIRE LINE REMOTE BASE
PHONE LINE LEVELS
D. MEASURING LEVELS ACROSS A BALANCED LINE
I. Use a BALUN (balanced-to-unbalanced) device because of the unbalanced nature of the DVM/Counter In jack.
The BALUN must be high impedance (6K ohm or more) to make bridging measurements without upsetting levels.
2. Connect the BALUN's balanced side (high impedance) across the phone line. Connect the BALUN's unbalanced
side to the DVM/Counter In jack, as shown in figure 4-18. Set the BALUN switch in the OPEN position.
3. Set DISPLAY to DVM AC mode. Measure the test tone level on the phone line by interpolating the AC VOLTS-
DBM scale on the display.
4.
Set DISPLAY to Scope AC. Analyze waveform and measure AC volts peak-to-peak by interpolating the volts per
division.
5. With the BALUN switch in the OPEN position, the BALUN represents a nominal lOdb insertion loss from the
balanced side to the unbalanced side. For example, an actual line level of Odbm will indicate
-10
dbm at the DVM
input. Characterize your unit before use.
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