FCC ID: K66VX-7R
Circuit Description
VX-7R Circuit Description
VX-7R Circuit Description
VX-7R Circuit DescriptionVX-7R Circuit Description
The VX-7R consists of a RF-UNIT, a CNTL-UNIT and an AF-UNIT. The RF-UNIT
contains the receiver front end, PLL IC, power and switching circuits, and the VCO-UNIT
for transmit and receive local signal oscillation. The CNTL-UNIT contains the CPU, and
audio ICs, and the power circuitry for the LCD. The AF-UNIT contains the IF, and audio
ICs.
Receiver Signal Flow
The VX-7R includes five receiver front ends, each optimized for a particular frequency
range and mode combination.
(1) Triplexer
Signals between 0.5 and 540 MHz received at the antenna terminal pass through a first
low-pass filter composed of L3059, L3060, C3176 and C3175.
Received 430-MHz signals, after passing through a low-pass filter to the UHF T/R
switch circuit composed of diode switch D1048 (RLS135), D1051 (1SV307).
Received 145-MHz signals, after passing through a low-pass filter to the VHF T/R
switch circuit composed of diode switch D1053 (RLS135), D1054 (1SV307).
Received 50-MHz signals, after passing through a low-pass filter to the 50MHz T/R
switch circuit composed of diode switch D1058 (RLS135), D1059 (1SV307).
(2) 145-MHz Band and 76-300MHz Reception
Received signals between 140 and 150 MHz pass through the Triplexer circuit, low-pass
filter/high-pass filter circuit, VHF T/R switch circuit and protector diode D1002 (1SS362)
before additional filtering by a band-pass filter prior to application to RF amplifier Q1004
(2SC5555). The amplified RF signal is pass through the band-pass filter to first mixer
Q1012 (2SC5555). Meanwhile, VHF output from the VCO-UNIT is amplified by Q1017
(2SC5374) and applied through diode T/R switch D1041 (DAN222) to mixer Q1012 as
the first local signal.
The 47.25-MHz intermediate frequency product of the mixer is delivered to the AFUNIT.
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FCC ID: K66VX-7R
Circuit Description
The TUNE voltage from the CPU on the CNTL-UNIT is amplified by DC amplifier
Q3017 (NJU7007F2) and applied to varactors D1020 and D1022 (HVC369B), D1019,
D1021, D1023, D1024, D1033 and D1036 (1SV325) in the variable frequency band-pass
filters. By changing the electrostatic capacitance of the varactors, optimum filter
characteristics are provided for each specific operating frequency.
(3) 435-MHz Band and 222-540MHz Reception
Received signals between 430 and 450 MHz pass through the Triplexer circuit, low-pass
filter/high-pass filter circuit, UHF T/R switch circuit and protector diode D1001 (1SS362)
before additional filtering by a band-pass filter prior to application to RF amplifier Q1003
(2SC5555). The amplified RF signal is pass through the band-pass filter, RF amplifier
Q1006 (2SC5555) and band-pass filter to first mixer Q1011 (2SC5555). Meanwhile,
UHF output from the VCO-UNIT is amplified by Q1016 (2SC5374) and applied through
diode T/R switch D1045 (HN2D01FU) to mixer Q1011 as the first local signal.
The 47.25-MHz intermediate frequency product of the mixer is delivered to the AFUNIT.
The TUNE voltage from the CPU on the CNTL-UNIT is amplified by DC amplifier
Q3017 and applied to varactors D1005, D1018, D1030 and D1031 (HVC358B) in the
variable frequency band-pass filters. By changing the electrostatic capacitance of the
varactors, optimum filter characteristics are provided for each specific operating frequency.
(4) 50-MHz-Band and 30-76 MHz Reception
Received signals between 50 and 54 MHz pass through the Tripl exer circuit, low-pass
filter circuit, 50MHz T/R switch circuit and protector diode D1003 (1SS362) before
additional filtering by a band-pass filter prior to application to RF amplifier Q1005
(2SC5555). The amplified RF signal is pass through the band-pass filter to first mixer
Q1008 (2SC5555). Meanwhile, 50MHz output from the VCO-UNIT is amplified by
Q1018 (2SC5374) and applied through diode T/R switch D1046 (HN2D01FU) to mixer
Q1008 as the first local signal.
The 47.25-MHz intermediate frequency product of the mixer is delivered to the AFUNIT.
The TUNE voltage from the CPU on the CNTL-UNIT is amplified by DC amplifier
Q3017 and applied to varactors D1025 and D1026 (1SV325) in the variable frequency
band-pass filters. By changing the electrostatic capacitance of the varactors, optimum filter
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FCC ID: K66VX-7R
Circuit Description
characteristics are provided for each specific operating frequency.
(5) 0.5 - 30 MHz Reception
Received signals between BC and SW MHz pass through the Triplex er circuit, l ow-pass
filter circuit, 50MHz T/R switch circuit and protector diode D1003 before additional
filtering by a band-pass filter prior to application to RF amplifier Q1009 (2SC4915-0).
The amplified RF signal is pass through the band-pass filter to first mixer Q1013
(2SC4915-0). Meanwhile, 50MHz output from the VCO-UNIT is amplified by Q1018 and
applied through diode T/R switch D1046 to mixer Q1013 as the first local signal.
The 47.25-MHz intermediate frequency product of the mixer is delivered to the AFUNIT.
The TUNE voltage from the CPU on the CNTL-UNIT is amplified by DC amplifier
Q3017 and applied to varactors D1013 (HVR100) in the variable frequency band-pass
filters. By changing the electrostatic capacitance of the varactors, optimum filter
characteristics are provided for each specific operating frequency.
(6) 540 - 999 MHz Reception
Received signals between 540 and 999 MHz pass through the high-pass filter circuit,
T/R switch D1004 (1SV271) to application to RF amplifier Q1002 (2SC5227). The
amplified RF signal is pass through the band-pass filter to first mixer Q1010 (2SC5227).
Meanwhile, UHF output from the VCO-UNIT is amplified by Q1016 and applied through
diode T/R switch D1045 to mixer Q1010 as the first local signal.
The 47.25-MHz intermediate frequency product of the mixer is delivered to the AFUNIT.
The TUNE voltage from the CPU on the CNTL-UNIT is amplified by DC amplifier
Q3017 and applied to varactors D1015 and D1017 (HVC355B) in the variable frequency
band-pass filters. By changing the electrostatic capacitance of the varactors, optimum filter
characteristics are provided for each specific operating frequency.
(7) 47.25-MHz First Intermediate Frequency
The 47.25-MHz first intermediate frequency from first mixers is delivered from the RFUNIT to the AF-UNIT through jacks J1004 and J2001. On the AF-UNIT, the IF for AM
and FM-narrow signals is passed through NAR/WIDE switch D2001 (DAP222) and
47.25-MHz monolithic crystal filter (MCF) XF2001 to narrow IF amplifier Q2002
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