Nautel GV3.5, Operation & Maintenance Manual, Page: 15 / 251

GV5/GV3.5 OPERATIONS & MAINTENANCE MANUAL DESCRIPTION
VERSION 0.2 2014-07-23 PAGE 3.1.7
Reject Load Assembly
The reject load assemby (A13) provides a means to dissipate reject power from the outputs of the
combiner/filter's 3 dB hybrid couplers. The reject load assembly contains power resistors to dissipate
reject power. Cooling air for the reject load assembly is provided by fans in the fan tray assembly (A14).
The module control/interface PWB (A3) monitors the speed of the cooling fans and regulates the
voltage being applied to them accordingly.
Reject power generated by the combining stage of the combiner/filter is dissipated by resistors in the
1-input reject load assembly. Micro-strip transmission lines (on 2-input reject load PWB A13A1) in close
proximity to the reject load signals induce one true RF sample voltage of the associated reject power.
This sample is peak detected and applied to the control/monitor stage via the module control/interface
PWB (A3). The module control/interface PWB provides an interface between the ac-dc power stage’s
Rej Fan Volts supply and the fan tray assembly’s cooling fans. It also acts as the interface between the
cooling fans’ Rej Fan Tach signals and the control/monitor stage.
Output Power Probe
See electrical schematic Figure SD-36. The output power probe (A15) monitors the transmitter's forward
and reflected power and generates the Fwd Pwr Sample (A1J1) and Refld Pwr Sample (A2J1) signals
applied to the control/monitor stage for protection and monitoring. RF monitor PWB A3 provides a
nominal 1.6 V (GV5) or 1.3 V (GV3.5) rms [at 5 kW (GV5) or 3.75 kW (GV3.5)] signal at A3J1, which is
applied to the panel mount connector (W8J1) behind the front door. This can be used with a modulation
monitor or spectrum analyzer. RF sample PWBs A4 and A5 provide similar samples at A4J1 and A5J1.
These samples are applied to exciter B (if used) for use by the remote AUI’s spectrum analyzer display.