Broadcast Electronics FM-5T, User Manual, Page: 164 / 191

2-10
WARNING: DISCONNECT POWER PRIOR TO SERVICING
D. Test load and connecting line (50 Ohm non-inductive, 1 5/8 inch line input, 5 kW
minimum).
E. Calibrated in-line wattmeter with 1 5/8 inch sampling section and cables (Bird
4720 Thruline with 5 kW element or equivalent).
2-107. Procedure. To adjust the controls, proceed as follows.
2-108. Check and adjust output power meter calibration control R113 before proceeding (refer to
OUTPUT POWER METER CALIBRATION in the preceding text).
2-109. Adjust the VSWR null control as follows:
WARNING
WARNING
DISCONNECT ALL TRANSMITTER PRIMARY POWER
BEFORE PROCEEDING.
1. Disconnect the transmitter primary power.
2. Ensure the test load and wattmeter are connected to the transmitter output.
3. Refer to Figure 2-1 and connect the multimeter between TP-6 (signal) and TP-1
(ground) or to the chassis.
4. Apply power and operate the transmitter in the local manual mode ( REMOTE
DISABLE illuminated, APC ON extinguished) at the desired 100% RF power
output as indicated by the in-line wattmeter.
5. Refer to Figure 2-1 and adjust VSWR null control R119 for a 0.0 volt dc indication
on the multimeter.
WARNING
WARNING
DISCONNECT ALL TRANSMITTER PRIMARY POWER
BEFORE PROCEEDING.
2-110. Disconnect the transmitter primary power.
2-111. Disconnect cable 131 from the reflected power directional coupler (
↓
port) on the transmit
ter low-pass filter.
2-112. Using the nut-driver, loosen the clamps securing the reflected power directional coupler to
to the low-pass filter.
2-113. Rotate the reflected power directional coupler 180 degrees so the arrow on the coupler is up
(
↑
). Secure the clamps.
2-114. Connect the 10 dB attenuator to the reflected power directional coupler and connect cable
131 to the attenuator.
2-115. Apply power and operate the transmitter at the normal RF power output as indicated by
the in-line wattmeter.
2-116. Depress the VSWR switch/indicator to illuminate the switch/indicator.
2-117. Refer to Figure 2-1 and adjust reflected power calibrate control R84 until the OUTPUT
POWER meter indicates a VSWR condition of 1.9 : 1.