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TM
11-5820-919-40-1
selected  antenna  (reactive/resistive).
Tuner DC Source TR1, Q1, Q2, Q3,
Q11.
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,
The  circuit
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.
Tune  Start.
A  Tune  Start
signal
is  generated  whenever  any  of  the
As  temperature  increases,  the  voltage
needed  to  drive  the  antenna  tuner  relays
following  occur:
will  increase.
Conversely,  if  the
temperature  decreases,  the  relay  volt-
1.
The radio is turned on.
age  will  decrease.
The
temperature-
dependent  voltage  range  is  from  about
2.
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-
3.
The frequency is changed by 1 kHz
or more.
tance  decreases.
A Zener diode, VR1,
is connected so that a constant +18v is
applied  to  the  thermistor.
The  Tune  Start  signal  turns  the  +16v
Transistors
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.
DC-DC
Converter.
This  network
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
1.
Switch  Q10  closes.
Current  flows
vswr  condition  (vswr  is  the  detection
through  coil  L2,  storing  energy.
of  swr)  occurs  during  a  normal  transmis-
sion.
The  antenna  tuner  will  perform  a
2.
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).
diode  CR5.
Without  disturbing
Tune-Check.
3.
The  current
flowing
in
C32
charges
the L-C values set into the tuning net-
it to 31v.
work,  the  antenna  tuner  hybrid  closes
transfer  relay  and  measures  the  antenna
4.
The energy stored in L2 (which
tuner  vswr.
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.
through  Q9.
Driver Q7, Q8 pro-
vides  the  base  current  to  drive
Each  induc-
Element
Switching.
switch  Q10.
tive  and  capacitive  element  (L1-L11  and
C1-C8) is switched into and out of the
ANTENNA
TUNER
MODULE
(Figure
rf pathway by a relay (K1-K11 and K1-
2-13).
K8).
The  element  and  relay  are  grouped
together  as  KL1-KL11  and  KC1-KC8.  To
General.
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


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