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NGT—Checks and adjustments
Adjusting high output power
Drawing
ALTERNATIVE TEXT
NOTE
NOTE
Before adjusting the output power, you must check the state of links X2 and X3 on the
Filter and Control PCB in the RF unit:
•
•
To adjust the high output power:
1
1
1
1
1
1
1
1
1
180
08-05416
The transceiver does not have to be in Service mode to make this
adjustment.
The output power is factory-set, so it is not likely to be outside the
specified limits. Check that there are no faults with the transmitter circuits
before attempting to adjust the output power.
X2 and X3 both open—required when setting the output power to 100 W PEP (this
complies with the licensing regulations in Australia)
X2 and X3 joined—required when setting the output power to 125 W PEP at low
frequency, reducing to 100 W PEP at 30 MHz
Select any channel frequency between 4 and 6 MHz.
Connect an average or PEP power meter with a 50 Ω dummy load to the RF
connector ( ).
Connect an oscilloscope via a 47 kΩ resistor to the antenna connector.
Set the oscilloscope timebase to 500 µs per division and the trigger to auto.
Connect a signal generator to provide two-tone audio (700 Hz and 2300 Hz) via the
test unit to:
•
the audio input on the 15-way GPIO connector on the junction box or 2012 RF
Unit (see
Figure 40 on page
•
the 2011 RF Unit via the NGT test handset (see
Hold down PTT, then adjust the two-tone level for compression.
Adjust the Y sensitivity of the oscilloscope for on-screen display and adjust the
trigger for a stationary waveform.
Adjust the two-tone balance control for good crossover display.
Adjust HI PWR (R32) (see
•
for 100 W PEP, X2 and X3 both open
•
for 125 W PEP, X2 and X3 joined
The indicated PEP level with two-tone modulation depends on the type of
measuring instrument, as shown in
170), or
Figure 33 on page
163) for the required output:
Table
48.
NGT Transceiver System Technical Service Manual
Figure 41 on page
170)
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