Nautel XR6, Operation And Maintenance Manual

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XR6/XR3 Operations and Maintenance Manual Description
Page 1-2 Issue 3.1 2013-03-14
In three-phase transmitters the output of the rectifier is fed through the Hall Effect current sensor,
which supplies a dc current signal to the distribution PWB. The distribution PWB provides a dc
current sample to the control/display PWB. In single-phase transmitters the output of the rectifier/
SCR control assembly is applied to to the SCR control/B+distribution PWB, which supplies the dc
current signal to the distribution PWB.
The rectifier output is also applied to the B+ distribution PWB (three-phase) or the SCR control/B+
distribution PWB (single-phase), which then provides the B+ voltage to the RF power module and
LVPS power supplies, and a B+ sample to the exciter interface PWB. Voltages from the low voltage
power supplies are then supplied throughout the transmitter.
In three-phase XR6 transmitters there are three B+ dc voltage levels that are automatically selected to
provide optimum performance: 312 V, 190 V, and 115 V. In three-phase XR3 transmitters there are
two such levels: 220 V and 115 V. In single-phase XR6 transmitters there are four B+ dc voltage
levels that are automatically selected to provide optimum performance: 315 V, 196 V, 115 V and 69 V.
In single-phase XR3 transmitters there are also four levels: 220 V, 196 V, 115 V and 69 V.
Ac power transformer
The XR6/XR3’s power transformer can be set to use a range of input voltages. See Section 3,
“Installing the power transformer” on page 3-1 in the XR6/XR3 Installation Manual .
Exciter stage
See electrical schematics
SD-1
,
SD-2
and
SD-3
and Figure 1.1 on page 1-3 . The exciter stage consists
of an exciter interface PWB (A2A1), RF synthesizer PWBs A (A2A2) and B (A2A4), interphase PDM
driver PWBs A (A2A3) and B (A2A5), distribution PWB (A11), and RF drive buffer PWB (A15). The
exciter stage contains two independent exciter sections (A and B), which can be selected automatically
or by local or remote control.
Exciter Interface PWB
The exciter interface PWB (A2A1) accepts audio from the remote interface PWB, carrier reference,
exciter selection, reset, and inhibit controls from the control/monitor stage. It also receives low-level,
regulated dc voltages and a B+ sample from the ac/dc power stage, and a sample of the PA volts
from the RF power stage. Each exciter section generates its own RF frequency source, PDM and
digital control signals, for use in the RF power stage. The exciter interface PWB passes signals to the
RF drive buffer PWB, which then outputs the RF drive signals to the RF power module in the RF
power stage
The exciter interface PWB also provides physical interconnection for the RF synthesizer PWBs (A
and B), and interphase PDM driver PWBs (A and B).