Circuit Description - Kenwood TH-D72A Service Manual

TH-D72A/D72E
1. Outline
The TH-D72A/D72E is an FM Dual Band (A: 144/440MHz/
E: 144/430MHz) handheld transceiver designed to be used
as an Amateur Radio.
2. Frequency Confi guration
This equipment has an individual VCO/PLL and IF circuit
for both Band A and B. Using these circuits, it can receive
2 separate bands and can transmit and receive at the same
time.
4

CIRCUIT DESCRIPTION

Band B
PLL
45.505MHz
MIC
AMP
16.800MHz
Band B
Demodulator
455kHz
Band A
PLL
50.400MHz
x3
16.800MHz
Band A
AF
AMP Demodulator
450kHz
Figure 1 Frequency confi guration
TH-D72A (K-type)
A 144.000 ~ 147.995MHz
B 438.000 ~ 449.995MHz
C 189.050 ~ 193.045MHz
D 392.950 ~ 404.945MHz
E 193.950 ~ 197.945MHz
F 388.050 ~ 400.045MHz
Table 1 Frequency confi guration
The VCO of Band A is used for the fi rst-local oscillator for
VHF/UHF reception of Band A. The VCO of Band B is used
for VHF/UHF transmission with modulator by 2-VCOs and
for the fi rst-local oscillator for VHF/UHF reception of Band B.
The reference oscillator of 16.8MHz connected with
each PLL IC for Band A and B are used as the comparison
frequency at each PLL IC. The reference oscillator of Band
A is generated three times to 50.400MHz and is used for
the second-local oscillator for the reception of Band A. The
second-local oscillator for the reception of Band B uses the
crystal oscillator of 45.505MHz.
A
B
A
C
B
D
45.050MHz
A
E
B
F
49.950MHz
x2
TH-D72E (E-type)
144.000 ~ 145.995MHz
430.000 ~ 439.995MHz
189.050 ~ 191.045MHz
384.950 ~ 394.945MHz
193.950 ~ 195.945MHz
380.050 ~ 390.045MHz
VHF TX
UHF TX
Band B
VHF RX
Band B
UHF RX
Band A
VHF RX
Band A
UHF RX