TKR-D710
11
1. Outline
The TKR-D710 is a VHF repeater operating in the 136~
174MHz frequency range.
2. TX-RX unit
TX-RX unit (X57-894) consists of the following circuit.
(1) Internal/external reference circuit
(2) Transmitter reference 16.8MHz PLL circuit
(3) Transmitter main PLL circuit
(4) Modulation level adjustment circuit
(5) Front-end circuit
(6) 1st-Mixer circuit
(7) IF circuit
(8) Receiver PLL circuits
(9) AVR circuits
(10) Other circuits
2-1. Internal/External reference circuit
The internal reference circuit consists of X500, Q502,
Q504 and D505. The output of 19.2MHz VCTCXO (X500) is
fed to buffer amplifi er Q502. The higher harmonic wave is
attenuated by the LPF. This reference signal is fed to IF IC
(IC304) as the 2nd Local signal through the Tripler.
The internal reference signal is amplified by Q504 to
achieve the needed level for PLL ICs. That signal is divided
by a Wilkinson divider. The divided signal is fed to the PLL IC
for the receiver. Another signal is fed to the transmitter ref-
erence 16.8MHz PLL IC through PIN diode switch (D505).
CIRCUIT DESCRIPTION
TX REF
19.2MHz
RX VCO
/PLL
1dB
ATT
1dB
ATT
X58-5190-10
2nd Lo
REF
AMP
Q504
AMP
Q502
SW
X3
Q202
LPF
LPF
X500
OSC
19.2MHz
D504,D505
Fig. 1 Internal/external reference circuit
2-2. Transmitter reference 16.8MHz PLL circuit
The transmitter reference 16.8MHz PLL circuit produces
the reference frequency signal for the Transmitter Main PLL
circuit and modulates the low-frequency components.
The circuit consists of IC600, IC601, IC602, IC603,
IC604, Q601, Q602, Q603, and X600.
The VCXO (X600) signal enters the buffer amplifi er Q603
and is amplifi ed by Q602. The higher harmonic wave is at-
tenuated by the LPF and returns to IC602. Its phase is com-
pared with that of the reference frequency 5kHz.
The phase difference signal produced by the comparing
phase is converted to a DC voltage by a lag-lead type loop
fi lter. This DC voltage is input to the IC604 invert amplifi er
and is synthesized with the modulating signal. This DC volt-
age is input to the X600 control voltage terminal for control-
ling the VCXO oscillating frequency 16.8MHz.
The 16.8MHz oscillating signal is fed to the Q603 buffer
amplifi er. The output signal of the buffer amplifi er is used as
the reference frequency signal of the transmitter main PLL
circuit.
Summary of Contents for TKR-D710
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Page 110: ...Printed in Japan No RQ148 Communications Systems Business Operation ...
