Testing Return Gain And Response; Completing The Test Procedures - Motorola BLE Series Installation And Operation Manual

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 low-end
frequencies.
3
Measure the gain excursions from an average value within the bandpass. The result is the
peak-to-valley flatness. Some improvement is possible by adjusting the flatness controls on
the *LDR/*/II board as described in Section 3, "Amplifier Setup," Flatness Control.
Figure 3-3 illustrates the location of these controls on the *LDR/*/II board.

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 amplifier, remember that it is a flat amplifier. Therefore,
the cable simulator must remain in the test set-up and must remain set to the same cable
equivalent as in the forward sweep test. This provides an approximate indication of the
frequency response, which you can achieve in the field.
To test for return gain and response:
1
Reconnect the test equipment and switch the sweep input and sweep output leads of the
BLE*/* under test to be opposite of the connection shown in Figure 4-1.
2
Remove the power block and replace the 20 A fuse (both illustrated in Figure 2-9) before you
apply power.
3
Re-adjust the test equipment to sweep from 4 MHz through the maximum return band
frequency plus 10 MHz.
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.
4
Measure the gain at the maximum return band frequency (e.g. 40 MHz for S-split). 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 measured gain must meet advertised
specifications for the return amplifier.
Example
14.0 dB (measured gain)
+ 1.0 dB (equalizer insertion loss)
+ 0.8 dB (power combiner)
+ 0.0 dB (pads)
+ 4.6 dB (cable simulator at 40 MHz)
20.4 dB (unit gain)

Completing the Test Procedures

The amplifier is now approximately tailored for a specific field location. Additional adjustments
after installation are minor in nature. Re-install the fuse removed during testing.
B e n c h T e s t i n g
B L E * / * I n s t a l l a t i o n a n d O p e r a t i o n M a n u a l
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