Adjusting The Pa; Adjusting The Driver Bias - Codan NGT 2010 RF Technical & Service Manual

NGT—Checks and adjustments

Adjusting the PA

Adjusting the driver bias

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