WJ-8611 DIGITAL VHF/UHF RECEIVER
CIRCUIT DESCRIPTIONS
5-3
The power for all of the assemblies in the WJ-8611 Receiver is provided
by the Type 766032-1 Switching Power Supply (PS1). It accepts an input
voltage ranging from 90 to 264 Vac, with line frequencies ranging from 47
to 63 Hz. The +13.5 Vdc, -13.5 Vdc, and +5.5 Vdc outputs are supplied
directly to the Digital Control PC Assembly (A2). They are then
distributed to each of the assemblies in the receiver.
5.2 TYPE 797228-1 RF TUNER ASSEMBLY (A3) CIRCUIT DESCRIPTION
The RF Tuner Assembly (A3) functions as the analog tuner for the
WJ-8611 VHF/UHF Digital Receiver. It selects a specific signal of
interest from the RF spectrum, and down-converts the selected signal to an
intermediate frequency suitable for digitization. It also provides the
Digital Control PC Assembly (A2) with a highly stable 100 MHz reference
signal that is used to generate the various clock signals required by the
Digital Control PC Assembly (A2). The RF Tuner Assembly (A3) consists
of the Part 482902-1 1st LO/1st Converter PC Assembly (A3A1) and the
Part 482903-1 2nd LO/2nd Converter PC Assembly (A3A2). These
assemblies are mechanically and electrically interconnected and function
as an analog tuner. Operating power and control of this analog section is
provided by the Digital Control Assembly (A2) . Refer to the schematic
diagram in
as a reference for the RF Tuner Assembly (A3)
The RF input enters the RF Tuner Assembly (A3) at connector J1 of the
1st LO/1st Converter PC Assembly (A3A1). This input spectrum ranges
from 0 to 1000 MHz. In this assembly, the signal is passed through a
5-band preselector or a preselector bypass path and is converted to a 1350
MHz 1st IF signal. The 1st IF output is the result of mixing the RF input
with the 1st LO synthesizer signal. The 1st LO signal ranges from 1370 to
2350 MHz, and has a tuning resolution of 2.5 MHz. The conversion
process, and IF filtering provides the 1350 MHz IF output with a 3 dB
bandwidth of approximately 14 MHz. The 10 MHz reference for the 1st
LO synthesizer is provided from the 2nd LO/2nd Converter PC Assembly
(A3A2) and is accepted at the 10 MHz REF Input (E2).
The IF Output from the 1st LO/1st Converter PC Assembly (A3A1) is
supplied to the 2nd LO/2nd Converter PC Assembly (A3A2) where the
2nd and 3rd conversion stages produce the 21.4 MHz Signal Monitor
Output (A3A2J1) and 250 kHz IF output (A3A2P1). The 10 MHz internal
reference generator produces two additional outputs. It provides the 10
MHz reference at terminal E4 that is used by the 1st LO synthesizer. It
also produces the 100 MHz REF output at connector A3A2P2. This
reference output is used by the Digital Control PC Assembly (A2) to
produce all of the digital clock frequencies required by the various digital
circuits. This signal is produced by phase locking a 100 MHz VCO to the
10 MHz reference standard.
Courtesy of http://BlackRadios.terryo.org
Summary of Contents for WJ-8611
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