NGT—Checks and adjustments
176 NGT Transceiver System Technical Service Manual
Adjusting the PA
Adjusting the driver bias
To adjust the driver bias:
1 Ensure the transceiver is switched off and the DC supply is disconnected.
1 Disconnect the exciter output from the PA by removing the connector from J2 (Tx
coaxial) on the RF/IF PCB in the RF unit (drawing 08-05261 (sheet 1) or 08-05889
(sheet 1)).
1 Unsolder the link next to the DR (driver) BIAS control (DC supply to the driver
transistors V207 to V212) (see Figure 30 on page 161).
1 Set a multimeter to DC 10 mA range and connect it in place of the removed link.
1 Connect the DC supply, then switch on the transceiver.
1 Select any transmit channel, then hold down PTT.
1 Check that the driver current measures 4 mA ±1mA.
1 If the current is out of the specified limit stated above, change it by adjusting DR
BIAS (R222) (see Figure 30 on page 161).
1 Release PTT.
1 Switch off the transceiver, disconnect the multimeter, then replace the link with a
length of tinned copper wire.
ALTERNATIVE TEXT
Drawing 08-05415 or 08-05511 (sheet 1)
NOTE
The transceiver must be in Service mode to make this adjustment (see
page 154, Accessing Service mode).
To Next Page
Loading...
Need help?
General
