3-7
3.9
TRANSMITTER POWER ADJUSTMENTS
The transmitter power is adjusted to a maximum of 10 watts in high power mode and 1 watt
in low power mode over the transceiver operating bandwith at the factory. If transmitter RF
power re-adjustment is required, perform as follows:
1.
Remove bottom cover as described in the previous paragraph (3.8). Access to the
two adjustment potentiometers on the Microprocessor Control Unit (MCU) PCB
Module is provided by two access holes located at the back of the chassis tray.
2.
Connect an RF through-line wattmeter to the antenna connector. Set the operating
frequency to 156.000 MHz and key the transmitter.
3.
In low power mode, set the low power adjustment potentiometer R24 to produce 1.0
watt of RF output power (See Figure 3-3).
4.
In high power mode, set high power adjustment potentiometer R23 to produce 9.5
watts of RF output power.
5.
Verify that the RF output power is between 8 and 10 watts on 138.000 MHz,
156.000 MHz and 174.000 MHz.
6.
Replace bottom cover as described in the previous paragraph (3.8).
3.10
TRANSMITTER MICROPHONE LEVEL ADJUSTMENT
1.
Set the transceiver operating frequency to 156.000 MHz and connect an appropriate
test receiver to the RF output connector. Ensure that the output of the transceiver is
terminated into a proper dummy load.
2.
Key the transmitter and input a -10 dBm (0.25 VRMS), 1 kHz audio signal into the
microphone input.
3.
Adjust the microphone level potentiometer (R8 on MCU module) through the access
hole located on the right side of the chassis (see Figure 3-4) to produce a 3.5 kHz
deviation.
4.
Verify that the deviation is at least 3 kHz on the following frequencies: 138.000
MHz, 156.000 MHz and 174.000 MHz.
3.11
TRANSMITTER SIDETONE LEVEL ADJUSTMENT
1.
Set the transceiver operating frequency to 156.000 MHz and connect an appropriate
test receiver to the RF output connector. Ensure that the output of the transceiver is
terminated into a proper dummy load.
2.
Key the transmitter and input a -10 dBm (0.25 VRMS), 1 kHz audio signal into the
microphone input.
3.
Adjust the sidetone level potentiometer (R37 on MCU module) through the access
hole located on the left side of the chassis (see Figure 3-4) to produce a +3.0 dBm
(1.0 VRMS) 600 ohm audio output.
Содержание TFM-138
Страница 13: ...2 2 FIGURE 2 1 Operator s Switches and Controls TFM 138 F10 B software...
Страница 24: ...3 2 FIGURE 3 1 Outline Drawing for Model TFM 138 Transceiver...
Страница 26: ...3 4 Figure 3 2 Wiring Connections for TFM 138 Transceiver...
Страница 30: ...3 8 FIGURE 3 4 Microphone and Sidetone Level Main and Guard Squelch Adjustment Access Holes...
Страница 42: ...STEP SYSTEM PASS FAIL NOTES A 11...
Страница 43: ...STEP SYSTEM PASS FAIL NOTES A 12...
Страница 44: ...STEP SYSTEM PASS FAIL NOTES A 13 NOTES...
