Bird Technologies 8251D208 User Manual

Page 25

3. Replace vent plug. If coolant needs to be added,

refer to the RF Load Resistor section.

DC Resistance Measurement

Preparation

and Tools

Required

Be sure that the vent plug is installed.

Preparation:

Tools: Common hand tools

Ohmmeter with an accuracy of ± 1% at 50

ohms.

Temperature of the load between 20°C to 25°C

(68°F to 77°F)

Accurate measurement of the dc resistance between the in-

ner and outer conductors of the RF input connector will pro-

vide a good check of the condition of the load resistor.

Checking the dc resistance is simply used to measure a

change in the condition of the resistor over time. The track-

ing of the dc resistance must start before the resistor is first

put into service. Perform the following steps and record the

value for future comparison. Check and record the resis-

tance of the load periodically according to use.

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.

Checking the

DC Resistance

Measure the dc resistance. Follow the instructions below.

1. Turn off RF power and interlock circuitry before

any electrical disconnection’s are made.

2. Disconnect the RF coaxial line.

3. Connect the multimeter test leads across the cen-

ter and outer conductor of the load resistor. Refer

to figure 4 for placement of the leads.

4. Record the value of the resistance before the load

is put into service. Compare subsequent values

with the latest reading. If the values vary more

than 2 ohms this could be an indication of a fail-

ing resistive element.

Maintenance