Kenwood TM-731A Service Manual page 2

TM-731A/E
CIRCUIT DESCRIPTION
Frequency Configuration
The TM-731A/E uses a synthesized PLL and includes a vari-
ablefrequency oscillator that enables selection of 5 kHz,
10 kHz, 12.5 kHz, 20 kHz, or 25 kHz channel steps. (See Fig.
1.)
Signals received in the 144 MHz band are down-converted to
a first intermediate frequency of 10.7 MHz (M,W) and
16.9 MHz (K,P) by mixing with the first local oscillator frequen-
cy (133.3 MHz to 135.3 MHz (W), 127 MHz to 131.100 MHz
(K,P), 133.3 MHz to 137.30 MHz (M)), and then to the se-
cond intermediate frequency of 455 kHz by mixing with the
second local oscillator frequency of 10.245 MHz (M,W) and
17.355 MHz (K,P).
Signals received in the 430 MHz band are down-converted to
the first intermediate frequency of 30.825 MHz (M,W) and
21.6 MHz (K,P) by mixing with the first local oscillator frequen-
cy (399.175 MHz to 409.175 MHz (M,W), 416.400 MHz to
428.400 MHz (K,P)), and then to the second intermediate fre-
quency of 455 kHz by mixing with the second local oscillator
frequency of 30.37 MHz (M,W) and 21.145 MHz (K,P). Dou-
ble conversion is thus used for both the 144 MHz and 430 MHz
bands.
Unit Model | TM-731A (K.M,P) | TM-731 (W)
Final Unit eee sotoot hy, | %45-3340-61
CFW455F
144~ 147.995 MHz (K,M,P)
_144~145.995 MHz (W) = .
MCF 455 kHz
16.9 MHz {K,P)
ist MIX 10.7 MHz (M,W)
ANT SW
RF AMP
MIX, IF, DET
ca
- . | 10.245 MHz (M,W)
17.355 MHz (K,P}
127.1~ 131.095 MHz (K,M,P)}
133.3~ 137.295 MHz (M) ; ;
133.3~ 135.295 MHz (W) sp
144 MHz STEREO
BAND PLL AF AMP
PA
TX AMP
SYSTEM
anaLocue sw | |oo
144~
.
[oil Lahey JACK
145.998 MFZ (Wr ae in ee eel
4144~ 147.995 MHz (K,M,P} | MAIN
2-S
T {
a Ae
439. "995 MHz (M,W!
438349905 Mie KK, P) reha| SUB
PA
TX AMP
430 MHz
.
BAND
PLL
MIC AMP
438~ SYSTEM
449.995 MHz (K,M,P)
399.175-
MIC
430~ 409.17 MHz (W)
439.995 MHz (W)
416.400 ~ 428.395 MHz (K,M.P)
MCF
21.6 MHz (K,P} CFW455F
30.825 MHz (MW) 455 kHz
ANT SW RF AMP MIX, IF,DET
Ist MIX = 0.370 MHz (MW)
1.145 MHz (K,P)
Fig. 1 Frequency Configuration