Ten-Tec JUPITER - Page 83

Reed relay, Кб, switches the 100-watt RF
amplifier cutput to the antenna at CW-
keying speed. Transmitter RF feeds a
voltage-doubler (D4 through D6, C12 and
С46) to develop cut-off bias for the series
diode switch (D7 and D8) to protect the
receiver. Оп receive, the В control
voltage (from the Logic board) turns on
О1, thereby biasing D7 and 08 on and
restoring the RF path from the antenna to
Ше receiver input. The directional
coupler, ТІ, ІМ, and D2, supplies low-
voltage DC signals proportional to forward
and reflected power for metering and
control by the processor. L31 establishes
a static-electricity drain at the antenna
jack, while САРІ provides a protective-
shunt path to transient energy pulses that
might otherwise damage receiver
components. J3 carries T control voltage
to control the PA.
5.4.4. Keypad - P/N 81887
JUPITER's operator controls, rotary
encoders and key-switches, connect via
digital logic on the 81887 KEYPAD board
(Figure 4-18). Located immediately
behind the molded front panel, this board
also carries the L.E.D. indicators for ALC,
TX, RX, and LOCK. The KEYPAD board
is a mechanical host for the 28154
GRAPHICS DISPLAY, the МІС
connector, and for the 81899 board which
mounts the KEY and PHONES jacks.
5.4.5. Rear connectors ~ P/N 81888
Figure 4-20 shows the REAR
CONNECTOR board, a simple mounting
means and junction site for rear panel
connectors and several cables.
5.4.0. DCIN — P/N 81895
The external DC power supply connects to
JUPITER via the 81895 circuit board
which controls, апа filters it for
distribution throughout the transceiver. It
hosts circuitry at Q1 and Q2 for the master
power control, and PÀ protection circuitry.
74269 Second Pprinting
JUPITER Model 538
30 August 2001
Cable 4 carries keying control signals via
J3 and the Q3, Q4 switch circuit. Ul and
Q5 condition the PA current signal,
developed across the R7 shunt and fed
back to the RF board via J6 and Cable 18.
5.4.7. 100 watt Amplifier — P/N 81897
Refer ю Figure 4-21, the schematic of
JUPITER's 100-watt Power Amplifier.
The amplifier comprises two transformer-
coupled broadband push-pull bipolar
transistor stages of amplification that are
effective from 1.8 to 30 MHz. P5, a hard-
wired terminal carries supply current to
the PA from the current-sensing circuitry
on the DCIN board. T control voltage,
hardwired to P6 from El on the Lowpass
Filter board, activates the bias circuits for
driver and final stages during transmit
periods and shuts down the stages during
receive periods. R17 and DI stabilize the
control voltage, which provides a fixed
reference to bias setting controls R19
(Driver Bias) and RIS (Final Bias).
Diodes D2 and D3, coupled to the driver
and final transistors reduce the set-point as
device temperature rises. This is а
precaution against thermal runaway.
Collector-to-Base networks at each device
provide increasing negative feedback with
rising frequency to partially offset the
inherent response of the transistors.
Solder terminals, P3 and P4 at the output
transformer, connect the coax output cable
leading to the Lowpass Filter board.
5-5