NV30/NV40 Operations and Maintenance Manual Description
Page 1-8 Issue 3.3 2014-12-10
modulation monitor or spectrum analyzer. RF sample PWBs A4 and A5 provide similar samples at
A4J1 and A5J1. These samples are applied to exciters A and B (if used) for use by the exciters'
adaptive pre-correction circuitry [for all-digital (HD) or hybrid (FM+HD) modes of operation] and
also by the AUI’s spectrum analyzer display.
Reject load assemblies
See Figure SD-9. Reject load assemblies provide a means to dissipate reject power from the outputs
of the combiner/filter's 3 dB hybrid couplers. Reject load assemblies contain power resistors to
dissipate reject power and cooling fans to regulate temperature. There are three different reject load
assemblies (A, B and C) used in the transmitter.
8-input reject load assembly ‘A’
Reject power generated by the 5 kW combining stage of any of the four 10 kW combiner/filter
assemblies is dissipated by resistors in 8-input reject load assembly ‘A’ (A14). Micro-strip transmission
lines (on 8-input reject load PWB A14A1) in close proximity to the reject load signals induce eight
true RF sample voltages of the associated reject power. These samples are peak detected and applied
to the control/monitor stage via reject load interface PWB ‘A’ (A15). The reject load interface PWB
provides an interface between the ac-dc power stage’s Fan Volts supply and the reject load assembly’s
cooling fans. It also acts as the interface between the cooling fans’ Rej Fan Tach signals and the
control/monitor stage.
4-input reject load assembly ‘B’
Reject power generated by the output combining stage of any of the four 10 kW combiner/filter
assemblies is dissipated by resistors in 4-input reject load assembly ‘B’ (A45). Micro-strip
transmission lines (on 4-input reject load PWB A45A1) in close proximity to the reject load signals
induce four true RF sample voltages of the associated reject power. These samples are peak detected
and applied to the control/monitor stage via reject load interface PWB ‘B’ (A47). The reject load
interface PWB provides an interface between the ac-dc power stage’s Fan Volts supply and the reject
load assembly’s cooling fans. It also acts as the interface between the cooling fans’ Rej Fan Tach signals
and the control/monitor stage.
4-input reject load assembly ‘C’
Reject power generated by the output combining stage of either of the two 20 kW combiners or the
40 kW combiner is dissipated by resistors in 4-input reject load assembly ‘C’ (A46). Micro-strip
transmission lines (on 4-input reject load PWB A46A1) in close proximity to the reject load signals
induce three true RF sample voltages of the associated reject power. These samples are peak detected
and applied to the control/monitor stage via reject load interface PWB ‘B’ (A47). The reject load
interface PWB provides an interface between the ac-dc power stage’s Fan Volts supply and the reject
load assembly’s cooling fans. It also acts as the interface between the cooling fans’ Rej Fan Tach signals
and the control/monitor stage.
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