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WJ-8718-19/FE HF RECEIVER
GENERAL DESCRIPTION
SECTION I
GENERAL DESCRIPTION
1.1
ELECTRICAL CHARACTERISTICS
The WJ-8718-19/FE HF Receiver (Figure 1-1) operates over the frequency
range of 5 kHz to 99.99999 MHz.
The receiver can demodulate AM, FM, Ctf, USB and
LSB signals.
Receiver functions may be controlled manually through the front panel,
or remotely through the rear panel remote input connectors.
In the manual mode,
operating parameters are selected through momentary-contact, push-button switches
with LED indicators.
Pushbutton access to 100 programmable memory channels is
provided.
RF frequency, BFO frequency and memory/scan operation parameters are
entered via a keypad on the front panel.
RF and BFO frequencies may alternately
entered via a large tune wheel.
Seven segment LED displays are used to display RF
and BFO offset frequencies. The front panel functions are implemented through an 8-
bit microprocessor, and the address, storage and memory devices required to interface
the front panel components with the signal processing circuits in the reaceiver.
Remote control of receiver parameters and Master/Slave operation is
possible via the Asynchronous I/O port.Control format is EIA Standard RS-232.
In addition, remote control can be accomplished via the Serial Synchronous I/O port.
Selectable IF bandwidths of 0.3, 1.0, 3.2, 6 and 50 kHz operate in
conjunction with the AM, FM, or CW detection modes.
When the LSB, or USB
detection modes are chosen, the normal IF filters are disabled and a special 2.2 kHz
BW SSB filter is enabled.
RF gain is controlled manually or by Fast or Slow AGC.
A
dual-purpose meter indicates Signal Strength or Line Audio level.
Internal frequency tuning circuitry of the receiver includes the 1st, 2nd,
and 3rd LO and BFO Synthesizers.
The phase lock loop frequency synthesizers
determine tuned frequency to a resolution of 10 Hz.
The synthesized BFO tunes +/-
8.00 kHz from 455 kHz in 10 Hz,100 Hz and 1 kHz steps.
A non-volatile memory
stores the tuned frequency for a minimum of 48 hours after power interruption (i.e.,
power failure or manually turning power off).
Rear panel features include BNC connectors for a 50 ohm RF input,
a
455 kHz IF output and a 1 MHz reference input/output selected by a related slide
switch.
Two circular connectors provide audio outputs that include:
a 600 ohm
balanced line audio output and an unbalanced phone output.
Line voltage selection
for high and low voltage conditions may be accomplished in a few seconds by
inserting the printed circuit (PC) wafer in one of four positions in the line cord
assembly.
Maintenance operations are straightforward due to
clean mechanical
packaging and placement of nearly all components on plug-in circuit boards.
These
circuit boards mount on motherboards which have all pins accessible from the bottom
of the receiver.
Removing the top cover exposes the assemblies, which may be
unplugged from their sockets or freed from the main chassis by quick disconnect
plugs.
The dc power supplies are thermal and short circuit protected, requiring no
adjustments, and are easily replaced.
A printed circuit wafer, accessible on the rear
panel, enables matching the power transformer to line voltages of 110 Vac (+/-15%)
and 220 Vac (+/-155S).
1-1
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