Bird Technologies SCC8 Series-Manual - Manual (Page 26)

Maintenance
12
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 resis-
tor’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 you have 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 8 Measuring Resistance
1. Turn off the RF power.
2. Disconnect the RF cables from the RF connectors on the load.
3. Check the load’s center and outer conductors for visible damage or exces-
sive wear.
4. Connect the multimeter test leads to the center and outer conductors.
Refer to Figure 8.
5. 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.
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
Ethylene glycol is toxic. Do not take internally. Avoid contact with eyes, skin,
and clothing. Avoid breathing vapor. Wash thoroughly after handling.
CAUTION
Use only distilled water or the supplied mixture of distilled water and
ethylene glycol (with a maximum of 35% ethylene glycol) as coolant. Do not
use tap water, automotive antifreeze, sealants, or leak stopping material.
Use of these materials will damage the instrument and void all warranties.
CAUTION
Operation without sufficient coolant can damage the unit.