Standard Communications mt930b, Руководство по обслуживанию, Страница: 35 / 155

Maintenance
MT930B Service Manual Page 6-3
MEASUREMENTS
RF MEASUREMENTS
RF Input Level Measurement
Measurement Conditions:
• Set up the equipment as in Figure 1.
• Input: J101, J102, J103, or J104 at 950, 1210, 1700 MHz (75
Ω )
•
Output: Video output
• AFC: ON
• AGC: ON
• RF input level: –20 to –65 dBm
10300
Figure 6-1. Equipment Setup for Measurement
Measurement Procedure:
Vary the received frequency to 950, 1210, and 2150 MHz, lower the signal gen-
erator input level, and measure the input level at each frequency that occurs just
before noise appears on the TV monitor. Take the three worst readings as the
measured values.
Measurement Specification:
−−−− RF Input Level: –20 to –65 dBm
Input Return Loss Measurement
Measurement Conditions:
• Use an Advantest R3762A vector analyzer for this measurement.
• Insert a DC block between the test terminal and the vector analyzer or
make sure the LNB is off, before making connections.
• Input: J101, J102, J103, J104; 950 to 2150 MHz at –10 dBm (75
Ω )
• MGC: MAX
Measurement Procedure:
Set the input switch to 1 through 4 in turn, connect the vector analyzer to the ap-
propriate input pin (J101 through J104), and measure the return loss.
Measurement Specification:
−−−− Input Return Loss: ≥≥≥≥ 12 dB