Filter
Top Products
TS-440S
CIRCUIT DESCRIPTIO
N
waves changing from continuous waves to relatively low dut
y
pulses
. Q1 is driven by this voltage waveform to control Q2
,
which is connected to the collector of Q4 in series and mo-
tor drive voltage is generated
.
If the motor turns too fast, the SWR value will be smalle
r
than the motor stop value because of the inertia of the mo-
tor
. As a result, the motor will continue to operate even if
the motor stop signal is sent and the SWR value will con-
tinue to be greater than the motor stop value, causing th
e
motor stop signal to turn off. That is, the motor will not sto
p
and it will be difficult to obtain a match
. If the motor spee
d
is too slow, it will take a long time to satisfy a matching con
-
dition
. The TS-440 therefore controls the motor speed ac
-
cording to changes in SWR
.
TUNE STO
P
ADJ
IC8
c/4
Q
5
Triangular
wov
e
generator
Fig
. 7 Antenna
tuner circui
t
The antenna coupler is a T type. Six relays RL100 to RL10
5
are used to change taps within the range 3.5 MHz to 30 MHz
.
2) Cooling fan circui
t
The final unit contains the temperature-sensitive thermisto
r
TH1 thermally coupled with final transistor Q4
. When tem-
perature on the surface of Q4 reaches approx
. 50°C, the fa
n
start comparator Q9B operates (H level), causing Q8 to tur
n
on to operate the fan
. During operation of the fan, tempera
-
ture protection comparator Q9A is at a L level, so the tem-
perature protection circuit does not operate
.
When temperature on the surface of Q4 goes down to 45°C
,
the cooling fan turns off
.
•
Final temperature protection
circui
t
When the temperature of the final transistor Q4 rises u
p
to approx
. 80°C, the temperature protection comparato
r
Q9A turns on (H level), Q1 in the filter unit also turns on
,
and a minus DC voltage is supplied to the ALC line, reduc
-
ing the transmitter output to zero
. (The TS-440 does no
t
return to a receive state
.) When the temperature of th
e
final transistor Q4 falls to approx
. 70°C, the protectio
n
circuits turns off allowing the transmitter to operate again
.
•
SWR protection circui
t
When antenna VSWR is bad, or the reflected wave is to
o
large, because the auto antenna is tuning for example, L4
2
and L43 detect the state and its output is rectified
. Th
e
rectified signal is then amplified by Q2 to control the AL
C
voltage so that drive power is reduced. As a result, loa
d
on the final unit is reduced
.
•
SWR automatic arithmetic circui
t
The TS-440 uses the automatic arithmetic circuit in th
e
AT-250
. The forward wave voltage
VSF
and reflecte
d
wave voltage
VSR
from the filter unit are fed into the ana
-
log arithmetic circuit of the switch unit, and used to se
t
the voltage level of IC8 pin 2 (5 V
+VsR/VSF)
.
Output vol-
tage from the pin 2 is shifted by IC5 to move the needl
e
in the SWR meter
.
IC5 contains a level shift/meter amplifier and an auto tune
r
V-I convertor
. IC7 contains a square wave generator an
d
a voltage comparator
. IC8 contains an integration circuit
.
Q3 and Q4 are used to switch forward and reflected wav
e
input signals alternately
.
Comparato
r
output
Q9
B
/45°
/50°
0° Bo°
Temperature °
C
FAN
OFF FAN
ON
Thermal
Therma
l
protection OFF protection O
N
Fig
. 8 temperature protection operatio
n
V
12