Kenwood TH-28E - CIRCUIT DESCRIPTION; Frequency Configuration; Receiver System

TH-28A/E
CIRCUIT DESCRIPTION
Frequency Configuration
The frequency configuration is shown in Figure 14
and Table 1.
455kH2
(1)
144.000~147.995MHz
{K,
P,
M,
x)
CF 144,000~145.995MHz_ (T, &)
ANT
/
ma
45.05MHz
(2)
144,000~147.995MHz_
{K,
P,
M,
X)
tstMIX
MCE
SP
444,000~145.995MHz
(T,
&)
ANTSW
RE
AMP
py
MIX.
IF.DET
[mj
AF
AMP
(3)
189.050~193.045MHz
_
{K,
P,
M.
X)
—_ 189.050~191.045MHz (T, E)
C3 45.505MHz
ist MIX “T
438.000~ Left RE AMP
449.995MHz 392.95 ~ MIC
404.945MHz MIG
PA AMP TX AMP . PLLVCO ey ANP (|
(2) a
= 12.6MHz Fig. 1 Frequency configuration
Receiver System Receiving Double superheterodyne system
-
RE
amplifier
system
1st
IF
frequency
45.05MHz
ee . 2nd IF f ne 455kHz
The signal from the antenna is passed through a = . reqveny 1
—- - . Transmitting|—-——-Direct-osceillating—————-—--|---
low-pass filter and transmission/reception. selector cir- system amplification system
cuit, and input to the RF amplifier. “odulation Variable reactance
The input signal is amplified by Q213 and sent-to the .
;
system
phase
modulation
bandpass filter to eliminate the unwanted frequency = - _
band. Table 1 Basic configuration
For sub-UHF reception, the signal from the antenna
passes through the high-pass filter, and is amplified by
RF amplifier Q216. ; Ss
7 ee
pet HPF re)
of
assem
ma
nee
OL
ay
OG
Cement
sr]
seusemsminionsseniectenne
saints
penngeeg
=
gyn
bee] LPF be] ANT [ \ DH>- IF AMP,DET 41
& —L
S CI
| =
2nd Local OSC
BSW)
on
BSW)
(sug
OS
Fig.2
Receiver
section
configuration
°
First-stage
mixer
.
item
Rating
The
input
signal
is
mixed
with
the
first
local
oscilla-
Nominal
center
frequency
(fo)
|
45.05MHz
tor
signal
from
the
PLL
circuit
by
first-stage
mixer
Pass
bandwidth
+7
5kHz2
of
more
at
3dB
0214
(Q217
for
sub-UHF)
and
so
is
converted
into
the
Attenuation
bandwidth
¥29kHz
or
less
at
2508
first
IF
singal.
The
unwanted
frequency
band
of
the
Guaranteed
attenuation
80dB
or
more
at
—910kHz
first IF signal is eliminated by a two-stage monolithic Spurious : 40¢B or more wthin +1MHz
crystal
filter
(MCF).
Ripple
|
1.0dB
or
less
Insertion loss 4.0dB or less
Terminal impedance 8000/2pF
Table
2.
MCF
(L71-0409-05)
(TX-RX
unit
XF1)