Digital Equipment ChannelWorks DECTV-AA, Руководство по установке, Страница: 38 / 106

3-4 ChannelWorks Cable TV Installer’s Guide
Verifying The TransMaster’s Output Signal Level
Verify the TransMaster’s output signal level and the forward and return center frequen-
cies by performing the following procedure:
1. Using an RF Combination Meter or similar combination signal generator/RF sig-
nal level meter, set the RF Combination Meter’s RF OUT frequency to the Trans-
Master’s input center frequency.
Use a 50 dB attenuator to allow the RF Combination Meter to generate a +5 dBmV
signal.
2. With the RF Combination Meter’s RF Switch off, attach a test cable from the RF
Combination Meter’s RF OUT port to the TransMaster’s RF IN connector.
This simulates a cable TV network’s return signal at the required level.
3. Set the RF Combination Meter’s RF IN frequency for the same frequency as was
selected for the TransMaster’s RF Output.
4. Attach another test cable from the RF Combination Meter’s RF IN port to the
TransMaster’s RF OUT connector. This simulates a cable TV network’s forward
signal at the required level.
5. Turn the RF Combination Meter’s RF Switch to ON.
The RF Combination Meter should read b35 and +55 dBmV. You may
have to adjust the meter’s attenuator for a meter reading nearest the center of the
scale.
6. Record the reading.
Adjusting The TransMaster Gain
Once you know the input and output levels of the TransMaster, you can set the gain.
Perform the following procedure to set up and align the TransMaster:
1. With the TransMaster’s input and output frequencies set, use a small flat screw-
driver to rotate the IF Gain and RF Output controls (front panel, see Figure 3-3)
full clockwise.
Ensure that the Input Frequency Select DIP switches are set correctly for the
required input (return) channel. Refer to the “Return (Input) Channel Frequency
Selection” section.
2. Using the same setup as in the previous section (“Verifying the TransMaster’s Out-
put Signal Level”), inject a Continuous Wave (CW) signal in the TransMaster’s RF
IN port at the required input level.
Adjust the IF Gain control fully counterclockwise. Adjust the RF Gain control
fully counterclockwise..