TK-7360/7360H/7360H
(
V
)
13
1. Frequency Confi guration
The receiver utilizes double conversion. The first IF is
38.85MHz and the second IF is 450kHz. The fi rst local oscil-
lator signal is supplied from the PLL circuit.
The PLL circuit in the transmitter generates the neces-
sary frequencies. Figure 1 shows the frequencies.
ANT
SW
RF
AMP
1st
MIX
AF
PA
TCXO
MIC
AMP
X2
multiply
RF
AMP
POWER
AMP
CF 450kHz
MCF
38.85MHz
IF SYSTEM
PLL/VCO
19.2MHz
38.4MHz
ANT
RX
TX
SP
MIC
Fig. 1 Frequency confi guration
2. Receiver System
The receiver is a double conversion superheterodyne.
The frequency confi guration is shown in Figure 1.
2-1. Front-end RF Amplifi er
An incoming signal from the antenna is applied to an RF
amplifi er (Q511) after passing through the transmit/receive
switch circuit (D303, D304, D307 and D308) and bandpass
fi lter (L518, L519 and varactor diodes: D506, D507).
After the signal is amplifi ed (Q511), the signal is fi ltered
by the bandpass (L513 and varactor diodes: D504, D505) to
eliminate unwanted signals before it is passed to the fi rst
mixer.
The voltage of these diodes are controlled by tracking
the MCU (IC704) center frequency of the bandpass filter.
(See Figure 2)
2-2. First Mixer
The signal from the RF amplifi er is heterodyned with the
fi rst local oscillator signal from the PLL frequency synthe-
sizer circuit at the fi rst mixer (Q507) to create a 38.85MHz
fi rst intermediate frequency (1st IF) signal. The fi rst IF signal
is then fed through one pair of monolithic crystal fi lters (MCF:
XF500) to further remove spurious signals.
Item
Rating
Nominal center frequency
38.85MHz
Pass bandwidth
±6.0kHz or more at 3dB
40dB stop bandwidth
±25.0kHz or less
Ripple
1.0dB or less
Insertion loss
4.0dB or less
Guaranteed attenuation
75dB (–900kHz); 50dB (+900kHz)
Spurious: 40dB or more within fo±1MHz
Terminal impedance
610
Ω
// 3.0pF// Coupling Cap 13.0pF
Table 1 Crystal fi lter (L71-0659-05): XF500
2-3. IF Amplifi er Circuit
The fi rst IF signal is amplifi ed by Q504, and enters IC500
(FM processing IC). The signal is heterodyned again with
a second local oscillator signal within IC500 to create a
450kHz second IF signal. The second IF signal is then fed
through a 450kHz ceramic filter (Wide: CF500, Narrow:
CF501) to further eliminate unwanted signals before it is
amplifi ed and demodulated by the quadrature detector with
the ceramic discriminator (CD500).
Item
Rating
Nominal center frequency
450kHz
6dB bandwidth
±6.0kHz or more
50dB bandwidth
±12.5kHz or less
Ripple
2.0dB or less
Insertion loss
6.0dB or less
Guaranteed attenuation
35.0dB or more within fo±100kHz
Terminal impedance
2.0k
Ω
Table 2 Ceramic fi lter (L72-0993-05): CF500
Item
Rating
Nominal center frequency
450kHz
6dB bandwidth
±4.5kHz or more
50dB bandwidth
±10.0kHz or less
Ripple
2.0dB or less
Insertion loss
6.0dB or less
Guaranteed attenuation
60.0dB or more within fo±100kHz
Terminal impedance
2.0k
Ω
Table 3 Ceramic fi lter (L72-0999-05): CF501
CIRCUIT DESCRIPTION
Fig. 2 Receiver System
ANT
L518,L519
D506,D507
BPF
Q511
RF AMP
Q504
IF AMP
Q507
MIX
XF500
MCF
D303,D304
D307,D308
ANT
SW
IC501
DC OP AMP
Q500
Doubler
X1
TCXO
IC500
FM system IC
IC702
Baseband IC
1st local
OSC (VCO/PLL)
CF500 (Wide)
CF501 (Narrow)
TV
CD500
TVC &
APCC
L513
D504,D505
BPF
