Harris Platinum HT EL 2000LS, Technical Manual

Page: 68 / 90

A.2.1
Driver Module, Low Band
(Refer to the Low Band Driver Amplifier Schematic 843-4999-638)
The low band driver module consists of a class A stage, driving
a second stage consisting of two parallel class A amplifier blocks.
A pi input attenuator (R4, R5, R6 on the Driver RF input
assembly) is used to set the overall gain of each low band driver
to 35 dB. The input attenuator also serves to improve the mod-
ule’s input return loss.
The attenuator output feeds the first amplifier stage, which
produces about 24 dB gain. The output passes to a 2 dB fixed
attenuator, used to improve the output match seen by the first
stage.
The RF signal then feeds the 2-way Divider assembly. On this
divider assembly there is in the signal path a microstrip direc-
tional coupler (which provides a forward drive power sample for
overdrive protection), a microstrip trombone line section (for
phase adjustment), and a foreshortened Wilkinson 2-way micros-
trip divider. The divider’s two outputs drive two parallel Class A
amplifiers. The outputs are recombined using a foreshortened
Wilkinson microstrip combiner, which passes the signal through
a directional coupler to the module output. The directional cou-
pler provides a reflected power sample to the module’s protec-
tion, control and monitor (PCM) system.
On the input and output Driver RF Intraconnection assemblies
are provided optional capacitors for response correction. On the
input assembly, A5A4, are C1 and C15. On the driver RF
intraconnect assembly is C4. A capacitor may be added where
needed for frequency response correction and or input matching.
The low band driver’s output is rated at 50 Watts peak-of-sync
visual, and 200 Watts CW in aural service.
A.2.2
Driver Module, High Band
(Refer to the High Band Driver Amplifier Schematic 843-4999-639)
The high band driver module consists of two cascaded class A
stages, driving a third stage consisting of two parallel class AB
amplifier blocks.
A pi input attenuator (R4/R5/R6 on the input Driver RF intra-
connection assembly) is used to set the overall gain of each high
band driver to 35 dB. The input attenuator also serves to improve
the module’s input return loss.
The attenuator feeds the first amplifier stage, which produces
about 17 dB gain. Its output passes to a 2 dB fixed attenuator,
used to improve the output match seen by the first stage. The
signal then passes through a L-section matching network to the
second class A stage.
Figure A-1. Low Band Driver Module,
Simplified Block Diagram
Figure A-2. High Band Driver Module,
Simplified Block Diagram
Platinum™ Series
A-2 888-2457-001
WARNING: Disconnect primary power prior to servcing.