Measuring Forward Gain; Example - Motorola BLE Series Installation And Operation Manual

4 4 4 4 - - - - 2 2 2 2 B e n c h T e s t i n g

Measuring Forward Gain

This subsection provides instructions for measuring the full gain and the operational gain and
flatness of the BLE*/*.
To measure the full gain of the amplifier:
1
Determine whether the power-supply jumper (J1) is positioned for
2
Remove the input pad (JXP-IN) before you apply power to avoid damage to the hybrids.
3
Connect the BLE*/* to the test equipment as illustrated in Figure 4-1 and apply power.
Verify that the B+ voltage is 24 V ± 0.4 V and re-install the input pad.
4
5
Apply the sweep signal and adjust test equipment as needed.
6
Select manual gain by placing the drive control select jumper in the
the
MANUAL LEVEL
7
Measure the gain at mixed forward frequency using the procedure outlined in the operator
manual provided with the test equipment in use. To correct this number, add the insertion
loss of the SSP-PIN power combiner (0.5 dB at 550 MHz, 0.6 dB at 750 MHz, or 0.7 dB at
870 MHz), the loss of the cable simulator at mixed forward frequency, and the loss of the
cable equalizer (1.0 dB), if it is installed.
E xa m p le
The test equipment indicates a measured gain of 12.5 dB with a BLE75S/* and the cable
simulator is set to 20 dB.
0.8 dB (power combiner)
+ 1.0 dB (cable equalizer)
+ 20.0 dB (cable simulator)
+ 12.5 dB (measured gain).
34.3 dB (unit gain).
The result must meet advertised specifications for the unit.
The operational gain of the BLE*/* provides reduced gain capability. This enables the unit to
operate in the proper region of the Bode board when it is controlled by the ADU or TDU drive
units.
To measure the operational gain and flatness of the amplifier:
1
Perform steps 1 through 6 in Measuring Forward Gain above.
2
Estimate the ambient temperature and find the required gain reserve by referring to
Table 3-3. Reduce the gain at the highest frequency by the amount given in the 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.
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
control (Figure 2-9) fully clockwise.
or operation.
LO HI
position and turn
MAN