Bird Technologies 8730 Series - Manual (Page 26)

Maintenance
14
DC Resistance
Measuring the dc resistance between the inner and outer conductors of the RF
connector shows changes in the load over time, a good check of the resistor’s
condition. Under normal operating conditions, the resistor should provide at
least 5,000 hours of operation before requiring any additional service. DC
resistance tracking must start before the load is put into service, and should
be measured annually.
Perform the following steps and record the value for future comparison. Make
sure that there is an ohmmeter with an accuracy of ±1% at 50 ohms and that
the load temperature is between 20 and 25 °C (68 to 77 °F) before starting.
Figure 6 Measuring Resistance
1. Turn off the RF power and interlock circuitry.
2. Disconnect the RF line.
3. Connect the multimeter test leads to the center and outer conductor of the
load. Refer to Figure 6.
4. Compare the measured value with the previous measurement and with
the baseline resistance, measured when the load was put into service.
Note: If the new value differs from either of these by more than 2
ohms this could indicate a failing resistor.
Repair
WARNING
Never attempt to connect or disconnect RF equipment from the
transmission line while RF power is being applied.
Leaking RF energy is a potential health hazard.
WARNING
Never attempt to connect or disconnect RF equipment from the
transmission line while RF power is being applied.
Leaking RF energy is a potential health hazard.
WARNING
Disconnect the unit from all power sources before servicing.
The unit may be energized from multiple sources.
The potential for electric shock exists.