Axcera-430B FCC Type Acceptance Report Parts List/Tune-up Info
February 2004
7-8
The idling current, no RF drive applied, of the device Q1 is set for 250 mA. To set the
current, remove the RF drive, measure the voltage across R20 (two 1
Ω
resistors in
parallel on the filter/amplifier board) and adjust R13 for .125 volts (using Ohms’ Law: [E=I
x R] : [E=250 mA x .5
Ω
] : E=125 mV).
7.2.11.4 High-Band VHF Driver Pallet
This board is supplied by Delta RF Technology, Inc. Refer to the data sheets in the
subassembly section of this manual for more information. The board has approximately 19
dB of gain and the output is typ31 dBm.
7.2.11.5 Overdrive Protection Board
The level of the RF input and output of (A3-A1) the overdrive protection board (1198-
1601) should be +31 dBm during normal operation.
To set up the overdrive circuit, check that the output power level of the transmitter is at
100% and adjust R11 on the board for a reading of .4 VDC at TP1. Increase the output
power level of the transmitter to 110%, sync only, and adjust R12 until the output power
begins to drop off. Return the output power level of the transmitter to 100%.
7.2.11.6 High-Band VHF Amplifier Pallet
This board is supplied by Delta RF Technology, Inc. Refer to the data sheets in the
subassembly section of this manual for more information. The board has approximately 14
dB of gain and the output is typ45 dBm.
7.2.11.7 3-Way Splitter Board
This board contains no tuning adjustments. The board takes the +45 dBm input and
splits it into three equal +40 dBm outputs.
7.2.11.8 VHF Amplifier Pallets
These boards are supplied by Delta RF Technology, Inc. Refer to the data sheets in the
subassembly section of this manual for more information. Each board has approximately
13 dB of gain and the output is typically
+53.3 dBm.
7.2.11.9 3-Way Combiner Board
There are no adjustments to the (A5-A1) 3 way combiner assembly. The three +53.3 dBm
inputs are combined to produce the 600 watts peak of sync + aural output (+57.8 dBm)
at the RF output jack J5 of the combiner.
J5 of the combiner connects to J2 the RF Output Jack of the VHF Amplifier Tray.
7.2.11.10 Calibration of the Visual Plus Aural Output Power and VSWR Cutback
Check that a dummy load of at least 600 watts is connected to the output of the tray
that is to be calibrated. Place switch S1 on the AGC control board in the Manual position
before beginning the setup.
To adjust the visual output power levels:
1. Remove the J16 cable from (A5) the sync tip clamp/modulator board (1265-1302) in
the exciter tray. Set Manual AGC switch S1, on (A13) the AGC control board (1142-
1601) in the 600-watt amplifier, to the Manual position. Turn the transmitter to the
Operate position.
