Kenwood TM 221 E Service Manual

Page 2

TM-221A/ E/ ES

CIRCUIT DESCRIPTION

ODEL TM-221A145W) TM-zzie (1M) TM-221ES (45W)
uurr K I M1 [ T1 I W1 12 [ W2
Final unit X45436002 x45-1330-03 54360.02
Control unit x53-3040-1i 1x53304021 1x53304022 x53-3040-51 lX53-3040-61 x53.3oao«51 1x53304061
TX-HX unit x57.3oso-11 X57-3060-51 x57-3oeo-52

Table 1 Comparison of TM-221A, TM-221E and TM-221ES

Frequeny configuration

The TM-ZZlA/E/ES utilize a PLL synthesizer system
incorporating a digital VFO. (See Fig. 1.) The channel
step can be selected as 5, 10, 12,5 (T,Wl, 15. 20, or ZBkHz.

The receiver operates as a double conversion system. He-
ceived signals are mixed with the first local oscillator
(133.305~137.300MH2 (KM), 133.300~135,295MH2
(T,W)) to produce the first intermediate frequency of
10.695MHZ (K,M), 10.7MHZ (T,W). The first intermediate
frequency is mixed with the second local oscillator (10.24
MHz (KM), 10.245MH2 (T,Wl) to produce the second
intermediate frequency of 455kH2.

The transmitter system consists of a PLL circuit in-
corporating a direct oscillator and direct divider. The
output is amplified by a linear amplifier prior to being
transmission.

144~148MH2 (KM)
1M~146MH1 iT,Wl
7

in MlX

ANT SW

RF AMP

Receiver system

0 General

Incoming signals from the antenna pass through a low-
pass filter in the Transmitter Final unit and a diode trans-
mit/receive switch, then enter the receiver front end.

After passing through two antenna coils the signals are
amplified by a GaAs igalium arsenide) FET (Oi
33K184fS)l Undesired signals are removed by 3 tuning
coils (L19~L21 : K,M) or a 3pole helical resonator (L3 :
T,W). The resulting signal is applied to the first mixer
02: 35Kl3l(v12), which employs an N channel MOS FET
to obtain good 2~signal characteristics. In the first mixer
(02) the signal is mixed with the first local oscillator
from the PLL system to produce the first lF signal of
10.695MH2 (K,M), 10.7MHz (T,W). Interfering Adjacent
channel interference is removed from the first IF signal
by a twostage monolithic crystal filter (MCF) (L6),

455k H:
C FW455F

ll 3..

1 33305-
137.300MH2 (Km
i 33.300~

135.295MH: mm

1M.000~

147.995an (KM)

144,000-

145.995MH! (T.W)

10,595MH2 (KMlI
uo_7MHx (UM m 1o_24MHx IKM)

MIX.IE.DET -' AF AMP -'[I I

T 10.245MH2 (T,Wl

[- - _ l

PLL I
SVSTEM

PA AMP .- TX AMP n-L I

-4 MIC

Mic AMP -<[G

Fig. 1 Frequency configuration