Ten-Tec JUPITER - Page 80

time functions. The display screen
provides the operator with status and
feedback for the principal and subsidiary
controls, and a selectable menu screen
displays the set-and-forget controls.
The 81895 DC & МО board primarily
distributes DC power to the other boards
and to rear panel receptacles.
5.3. Overall Schematic
Figure 4-1 shows the interconnection of
JUPITER’s 9 printed wiring board
subassemblies. The five principal boards,
Power Amplifier, Lowpass Filter, RF,
Logic, and DC&IO, evolved from the
Ten-Tec Pegasus design. The Graphic
Display, Keypad, Front Connectors, and
Rear Connectors are entirely new.
There are 18 numbered cables and 2
soldered wires interconnecting the boards.
Board-to-board header plugs in a manner
similar to Pegasus couple the Lowpass
Filter, RF, and Logic boards.
5.4. КЕ Board — P/N 81889
For the following, refer to Figures 4-2
through 4-8 in the Schematics chapter.
The RF board schematic comprises an
overall diagram, Figure 4-2, and five detail
parts — Figures 4-3 through 4-7.
5.4.1.1. Local Oscillator Section
Jupiter’s receiver and transmitter are
triple-conversion superheterodyne designs
sharing three local oscillators — Figure 4-3.
The following description of the frequency
plan takes the receiver point-of-view, but
applies in reverse order to the transmitter.
The first local oscillator is a phase-locked
loop that tunes 45.1 – 75 MHz to convert
the signal frequency to Ше 45 MHz first
IF. Tuning data comes from the Logic
board via CLK, serial DATA, and EN_2
lines. The МСО SEL line switches from
the 04 VCO to the Q2 VCO at a
5-2
transceiver frequency of 13.03 MHz. 1710
processes the control signals, the reference
signal from TCXO 14, and the VCO
samples from the loop buffer, Q1. The
circuit surrounding 054-048 is the
charge-pump and loop filter, while Q7
buffers the 15% LO output to the receiver
and transmitter first mixers.
The 14.8475 MHz TCXO reference also
feeds the Q8 frequency tripler to develop
the 44.5425 MHz 2nd_LO for the second
mixers.
Crystal, X1, at 4.76 MHz drives a divide-
by-ten counter at U2 to develop the 476
kHz 3rd_LO.
5.4.1.2. Receiver Section
Figures 4-4 and 4-5 show Jupiter's
receiver schematic. The antenna signal
from the Lowpass board encounters а
common-mode choke at T13 followed by
a PIN diode switched attenuator, К152,
R201 and R202. 043, 052, and 053
condition the attenuator control signal
from the Logic board to levels suited to
switches, D41 and D47. Common control
signals, DATA and CLK, plus EN 1
control driver, U17, which sources the
band-select lines to PIN diode switched
sub-octave filters between C181 and
С148.
045, 054, and 055, form а parallel-
connected high dynamic range КЕ
amplifier with D21 as a gain control
element. 0935 and 040, with associated
parts, comprise the balanced first mixer,
fed by the first LO to develop a 45 MHz
first IF. Monolithic crystal filter, PLA
feeds
the
dual-gate
MOSFET
(038)
first
IF amplifier. Тһе 2"%_LO signal drives
the double-balanced mixer formed by T8,
T10, and the diode pairs. The 279 IF
centered at approximately 454 kilohertz
results.
74269 Second Printing
JUPITER Model 538
30 August 2001