Yaesu Mark-V FT-1000MP, Техническое дополнение

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Circuit Description
4-1
Main Receive Signal Circuitry
High-Frequency Circuit
The receive signal enters from ANT connector A or B, selected
by relays RL6452/RL6453 on the TUNER-MAIN Unit, and it then
passes through t/r relay RL6451 and is fed to connector J1003 on
the RF Unit from connector J6454.
The receive signal then passes through the “RX Antenna” an-
tenna switching relay RL1003 and an attenuator (-6 dB, -12 dB; -
18 dB when combined) which consists of resistors R1051-R1054
and relays RL1003 and RL1004.
If the VRF feature is engaged (available on 160-20 meters),
the signal then enters a narrow band-pass “preselector” filter which
consists of relays RL1006-RL1015, coils T1026-T1036, and ca-
pacitors C1253-C1264 and C1282-C1285. The preselector, which
provides high-Q filtering ahead of any active devices in the re-
ceiver circuitry, protects the components in the front end from strong
out-of-band energy.
The receive signal then enters a 5th-order Chebyshev low-pass
filter (LPF) which consists of coils L1087 and L1088 and capaci-
tors C1035-C1039. After the signal is removed of frequency com-
ponents of 30 MHz and above, it is fed to one of the band-pass
filter (BPF) networks.
The BPF is a 5th-order Chebyshev type filter; a total of 11
different bandpass filters are provided, covering the frequency range
100 kHz ~ 30 MHz in segments of different widths. Depending on
the receiver frequency, the appropriate band is selected by diodes
D1008 - D1017 (all
1SV271
), D1018 - D1026 (all
1SS356
), D1027 -
D1031 (all 1SV271 ), and D1032 - D1036 (all 1SS356 ). After re-
moval of unwanted frequency components, the incoming RF en-
ergy is applied to the high-frequency amplifier circuit.
The RF amplifier consists of a low-band amplifier circuit FET
Q1018 (
3SK131
), a mid-band amplifier circuit FETs Q1019 -
Q1022 (all SST310 ), and a high-band amplifier circuit Q1028
(
SST310
). The appropriate amplifier circuit is selected* by D1037 -
D1041 and D1045 (all 1SS356 ). After amplification, the signal is
applied to the 1st mixer circuit and/or the sub-receive circuit (RX2
Unit).
* Note - If “Flat” is selected in Menu Program 8-4, RF signal
input is sent to the mid- band amplifier circuit.
Diodes D1046 and D1047 (both
1SS356
), which are connected
to the RF amplifier input and output, turn on (off) the amplifier
circuit via the front-panel IPO switch.
1st Mixer Circuit/1st IF Circuit
The 1st mixer of the RF Unit consists of junction FETs Q1010 -
Q1013 (all
SST310
). The 1st local signal (70.555 ~ 100.455 MHz)
from the LOCAL Unit is amplified by Q1014 ( 2SC2053 ) and
applied to the gates of each FET in the 1st mixer.
The resulting output signal (the difference between the local
signal and receive signal) passes through dual monolithic crystal
filters (MCF)
XF1001 / 1002 (
70R12BUF
, BW: ±6 kHz) to obtain
the 1st IF signal having a center frequency of 70.455 MHz. The
signal is fed to the 2nd mixer circuit of the IF Unit after it is ampli-
fied by FET
Q1009 ( 2SK131 ).
2nd Mixer Circuit/2nd IF Circuit
The 2nd mixer consists of FETs Q2020 and Q2024 (both
2SK302GR
) on the IF Unit. The 2nd local signal (62.24 MHz)
from the LOCAL Unit is amplified by Q2027 ( 2SC2812 ) and is
applied to each FET’s gate in the 2nd mixer.
The output from the 2nd mixer passes through monolithic crystal
filter XF2001 , where it is stripped of unwanted signal components
to become the 2nd IF signal (8.215 MHz). A portion of the 2nd IF
signal from the mixer output is fed to the FM IF circuit through a
noise blanker circuit and buffer-amplifier FET
Q2003
( 2SK302GR ).
The 2nd IF signal that has passed through the MCF enters the
noise blanker gate, D2014 (
1SS226
). It is then routed through
either a crystal filter ( XF2002 , XF2003 , U2002 , U2005 ) or an
attenuator (R2174, R2175, R2183), according to the receiving
mode (CW, SSB, or AM), and then it passes onward to the 3rd
mixer circuit.
Noise Blanker Circuit
A sample of the 2nd IF circuit is amplified by FETs Q2009 and
Q2010 (both
3SK131
) on the IF Unit, and then undergoes detec-
tion by D2006 (
1SS226
). This output passes through R2017 and
R2027, C2006, and Q2001 ( 2SC2812 ) to yield an average AGC
voltage for controlling the degree of amplification of the above
FETs. Noise pulses contained in the output from
D2026 are de-
tected by D2009 (
1SS270
) and Q2012 (
2SC2812
) and are used
to control the NB Gate.
3rd Mixer Circuit/3rd IF Circuit (IF Notch Circuit)
The 3rd mixer uses double-balanced mixer (DBM) IC Q2021
( µPC1037H ) on the IF Unit. The 3rd local signal (8.67 MHz)
from the LOCAL Unit is applied to the DBM IC local port after it
is buffer-amplified by
Q2028 ( 2SC2812 ). The signal output from
the 3rd mixer passes through a ceramic filter, crystal filter, or me-
chanical filter (
U2001 , U2003 , U2004 , U2006 , CF2002 ), to be-
come the 455-kHz 3rd IF signal.
The 3rd IF signal, buffer-amplified by Q2022 (
2SC2812
),
passes through a notch frequency control circuit which consists of
L2004, C2063, C2064, and
D2020 (
HVU306A
). Attenuation in
the IF notch circuit is controlled by VR2005. The 3rd IF is then
buffer-amplified by
Q2023 (
2SC2812
) and further amplified in
two stages by FETs Q2026 and Q2029 (both 3SK131 ).
The IF signal is then buffer-amplified by Q2004 and Q2017
(both
2SC2812
), respectively. The output of Q2004 is applied to
the AF Unit through connector J2002, and the output from Q2017
is sent to the AGC circuit.
AGC Circuit
The AGC circuit consists of D2012 and D2013 (both
1SS198
),
transistor Q2018 ( 2SC2812 ), etc. on the IF Unit. Output from the