Bench Testing |
1Perform steps 1 through 6 in Measuring Forward Gain above.
2Estimate the ambient temperature and find the required gain reserve by referring to Table
Example:
The ambient temperature is 70°F. The table indicates that the required gain reserve is 4 dB. Reduce the gain by 4 dB.
The operational gain is the sum of the measured gain after performing Step 2, plus all losses, such as power combiner, cable loss, equalizer, and cable simulator.
The sweep response is essentially flat at this point. If the response exhibits tilt, the cable equalizer must be changed. Install a higher equalizer value if the gain is greater at the low frequencies; install the next lower equalizer value if the gain is less at the
3Measure the gain excursions from an average value within the bandpass.
The result is the
Testing Return Gain and Response
After configuring the return path, you can test the return bandpass to ensure compliance with specifications. When testing the return path, remember that it is a flat response. Therefore, the cable simulator must remain in the test
To test for return gain and response:
1Reconnect the test equipment and switch the sweep input and sweep output leads of the BT100 under test to be opposite of the connection shown in Figure
2Remove the 20 A fuse (F1) at the input port and replace the 20 A fuse (F2, F3, F4, or F5) at the output port (Figure
3
The expected response is flat. Any tilt, which is due to the return equalizer, must average out to a flat response in a cascade of amplifiers. A slope adjustment is not available in the return bandpass.
4Measure the gain at the maximum return band frequency (example 40 MHz for
The amplifier gain is the sum of: the measured gain, the insertion loss of the return cable equalizer at the maximum return band frequency, the insertion loss of the power combiner, any pads installed in either the input or output pad locations, plus the cable simulator loss at the maximum return band frequency. The amplifier gain must meet advertised specifications for the return path.
BT100 Installation and Operation Manual