User's Manual

2650 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions
435B, Rev. 0 4-26
4.2.5 (A3-A2) High Band VHF
Amplifier Pallet (P200-VHF-H;
Appendix D)
The RF Output of the Overdrive
Protection Board at J5 connects to J1 on
(A3-A2) the High Band VHF Amplifier
Pallet (P200-VHF-H) made by Delta RF
Technology. The pallet amplifies the RF
to approximately +45 dBm pk-sync +
aural.
The output of the high band VHF
amplifier pallet at J2 connects to J1 on
(A3-A3) the 3 Way Splitter Board
(1301161).
4.2.6 (A3-A3) 3 Way Splitter Board
(1301161; Appendix D)
The Splitter Board takes the +45 dBm
and provides three +40 dBm outputs that
connect to J1, J2 and J3 of (A4) the final
Amplifier Enclosure.
4.2.7 (A4-A1 thru A3) VHF Output
Amplifier Pallets (P400-VHF-H;
Appendix D)
The three RF outputs connect to (A4) the
Final Amplifier Enclosure, which contains
three (A4-A1, A4-A2 & A4-A3) High Band
Output Amplifier Pallets (P400-VHF-H)
made by Delta RF Technology. The RF
Signals connect to J1 on each of the High
Band Output Amplifier Pallets. Each
amplifier pallet provides approximately
13 dB gain.
The RF signal inputs to the Output
Amplifier Boards (+40 dBm) are
amplified to +53.3 dBm pk-sync + aural
outputs at J2 of each board. The outputs
are connected to J1, J2 and J3 on (A5-
A1) a 3 Way Combiner Board (1301157).
4.2.8 (A5-A1) 3 Way Combiner
Board (1301157; Appendix D)
The 3 Way Combiner takes the three
+53.3 dBm pk-sync + aural inputs and
combines them to form the approximate
750-Watt RF Output at J5 of the
Combiner which connects to J2, the RF
Output Jack of the Tray.
The 3 Way Combiner Board provides a
Forward Power Sample at J6 and a
Reflected Output Power Sample at J7.
The Forward Output Power Sample
connects to J4 on (A13) the AGC Control
Board. The Reflected Output Power
Sample connects to J5 on (A13) the AGC
Control Board.
4.2.9 (A13) AGC Control Board
(1142-1601; Appendix D)
The AGC Control Board contains two
peak detector networks which provide
detected outputs that are used for Front
Panel and Remote Meter Indications of
Forward and Reflected Output Power
Levels, AGC Detector Voltage Level and
also the VSWR Cutback protection if the
Reflected Power level increases above
the preset level.
The AGC Control Board provides AGC,
VSWR Cutback and Module Fault
operations for the VHF amplifier tray in
which it is mounted.
4.2.9.1 LED Status Indicators
A -12 VDC Enable from the Exciter tray is
applied to J10 Pin 10. This Negative
Enable causes the J-FET Q9 to be Biased
OFF and a High to be applied to Q4 that
is Biased On that lights the front panel
Enable Indicator. The High is also
applied to J10 Pin 6 that is a High Enable
to the Switching Power Supply, only if
there is no Overtemperature Fault, which
is a Low applied to J10 Pin 5. The High
also connects to the Base of Q8 that
forward Biases it and connects a Low to
Q7 which Biases it Off. If the Output
Power Level of the Tray is above the
preset level and Q7 is biased Off, Q6 and
Q5 will be Biased On and the Module
Status Indicator LED will be illuminated.
If the Enable is removed from J10 Pin 10,
Q9 will turn On applying a Low to Q4 and
to Q8. The Low to Q4 turns it Off which