selected antenna (reactive/resistive).
Tuner DC Source TR1, Q1, Q2, Q3,
This circuit provides a regulated
The module systematically switches
inductors and capacitors into the L-C
power supply (+16v) for the relays in
the antenna tuner module.
coupling network KL1-KL11, KC1-KC8,
compensates for changes in temperature
until the resulting impedance matches
the impedance of the radio set.
and battery voltage; it is activated by
grounds from Tune In Progress or Tune
Start lines which turn on switch Q11.
A Tune Start
is generated whenever any of the
As temperature increases, the voltage
needed to drive the antenna tuner relays
Conversely, if the
temperature decreases, the relay volt-
The radio is turned on.
age will decrease.
dependent voltage range is from about
The mode switch is changed from
+12v to +18v.
V/RCV or D/RCV to V/TR or D/TR.
The mechanism of tempera-
ture regulation is thermistor TR1; as
the temperature increases, its resis-
The frequency is changed by 1 kHz
A Zener diode, VR1,
is connected so that a constant +18v is
applied to the thermistor.
The Tune Start signal turns the +16v
relay supply (located at the power
Q1, Q2, Q3 buffer the thermistor output
amplifier module) on momentarily, and
to provide a low impedance dc source.
causes removal of the impedance-matching
elements from the rf pathway.
converts +28v to +31v which is used in
Tune-Check Enable. A Tune-Check
the output stage (T3, Q10, Q11, T4, T5).
Enable signal is sent from the PA module
It works in the following way:
to the antenna tuner hybrid if a high
Switch Q10 closes.
vswr condition (vswr is the detection
through coil L2, storing energy.
of swr) occurs during a normal transmis-
The antenna tuner will perform a
When Q10 opens, the energy stored
tune-check the next time Keyline goes
in L2 is transferred to C32 via
low (PTT or CW Key).
the L-C values set into the tuning net-
it to 31v.
work, the antenna tuner hybrid closes
transfer relay and measures the antenna
The energy stored in L2 (which
If the vswr is less than
determines the charge of C32) is
1.6:1, transfer relay opens and normal
proportional to the on and off
operation is resumed.
If the vswr is
time of switch Q10.
greater than 1.6:1, the impedance-
U1 sets the frequency to 50 kHz.
matching elements are removed from the
Differential amplifier Q5, Q6
rf pathway when the Keyline goes low
determines the on to off ratio
(PTT or CW Key). At this time, the
(duty cycle) via feedback applied
module begins the tuning cycle.
Driver Q7, Q8 pro-
vides the base current to drive
tive and capacitive element (L1-L11 and
C1-C8) is switched into and out of the
rf pathway by a relay (K1-K11 and K1-
The element and relay are grouped
together as KL1-KL11 and KC1-KC8. To
The antenna tuner auto-
switch an inductive element out of the
matically matches impedances between the
rf pathway, the following must happen.
radio set (50 ohms resistive) and the