Standard Communications mt930b, Service Manual

Page: 39 / 155

Maintenance
MT930B Service Manual Page 6-7
IM3 (–25 dBm Input) Measurement
Measurement Conditions:
• Input: J101, J102, J103, or J104 at –25 dBm (75
Ω
)
•
Output: 70 MHz IF TEST (75
Ω
)
• AFC: OFF
• MGC: OFF (–30 dBm Ref.)
Measurement Procedure:
1. Set the UUT and the signal generator to 950 MHz.
2. Adjust the input level so 70 MHz IF TEST is –30 dBm when the input level is
–25 dBm, and take this value as the reference.
3. Input signals of 990 MHz and 1030 MHz at –25 dBm, and measure the IF
TEST level when the receive frequency is set to 950 and 1070 MHz.
Each IM3 reading is step 2 minus step 3.
4. Use the value obtained when inputting 1500 MHz at –25 dBm as the refer-
ence, and measure the IM3 appearing at 1380 and 1500 MHz when two
signals at 1420 and 1460 MHz are input at –25 dBm.
5. Use the value obtained when inputting 1750 MHz at –25 dBm as the refer-
ence, and measure the IM3 appearing at 1630 and 1750 MHz when two
signals at 1670 and 1710 MHz are input at –25 dBm.
6. Use the value obtained when inputting 2150 MHz at –25 dBm as the refer-
ence, and measure the IM3 appearing at 2030 and 2150 MHz when two
signals at 2070 and 2110 MHz are input at –25 dBm.
7. Take the worst readings obtained in steps 3 through 6 as the measure-
ments.
Measurement Specification:
−−−−
IM3 (–25 dBm Input):
≥≥≥≥
50 dBc