Am Modulator Circuit; Frequency Modulation Circuit; Cw (A1) Signal Generator Circuit; 2Nd If Circuit/2Nd Mixer Circuit - Yaesu Mark-V FT-1000MP Field Technical Supplement

AM Modulator Circuit

As in the SSB modulator circuit, a carrier signal appropriate to
the transmitting mode (AM) from the CAR-DDS Unit and an au-
dio signal from the microphone are applied to balanced modulator
IC Q3046 on the AF Unit.
The control signal from CPU IC Q5008 (M37702M) in the
CNTL Unit causes a voltage of AM 9 V to be sent from transistor
array IC Q5025 (TD62793F). This voltage is applied via VR3011
and D3018 (DAN202K) to IC Q3046, causing the balanced modu-
lator to lose balance. The restored carrier signal and modulated
signal are then fed to the Tx mixer via ceramic filter CF2002
(CFWS455HT) inside the IF Unit.

Frequency Modulation Circuit

The FM circuit uses a voltage controlled crystal oscillator
(VCXO) consisting mainly of IF Unit oscillator Q2044
(2SC2812), X2001, varactor D2049 (HVU306A), and L2026.
The VCXO has a center frequency of 8.215 MHz.
The FM signal is produced by applying a signal from the FM
microphone amplifier circuit to varactor D2049 and varying the
crystal oscillator load capacity in proportion to the signal voltage.
The FM signal is fed to gate 1 of 2nd IF circuit FET Q2036
(3SK131) via Q2043 (2SC2812) for buffer amplification.

CW (A1) Signal Generator Circuit

When the transmitting mode is CW (A1), the control signal
from CPU IC Q5008 in the CNTL Unit causes a CW 9 V voltage
to be sent from transistor array IC Q5025. While microphone au-
dio is cut off by Q3050 (2SC4047), the voltage is applied to bal-
anced modulator IC Q3046 via D3018, providing a carrier from
the balanced modulator for input to the transmit signal circuit of
the IF Unit.
1st IF Circuit/1st Mixer Circuit
The 455 kHz 1st IF signal from the modulator circuit is band-
limited by the IF Unit's ceramic or mechanical filter CF2002,
U2001 (XF9801) according to the selected mode (CW, SSB, or
AM). It is then buffer-amplified by FET Q2037 (2SK160) and
fed to 1st mixer IC Q2030 (µPC1037H).
The IF Unit's double balanced mixer IC Q2030 (DBM) is used
as the 1st mixer. A local signal (8.67 MHz) from the LOCAL Unit
which is buffer-amplified by transistor Q2028 (3SK131) and fed
to the local port of DBM IC is mixed with the 455 kHz 1st IF
signal to produce an 8.215 MHz 2nd IF signal.

2nd IF Circuit/2nd Mixer Circuit

The 2nd IF signal passes through either the IF Unit's crystal
filter XF2002 or attenuator (R2174, R2175, R2183), whichever is
appropriate to the selected mode (CW, SSB, or AM). It is then
amplified by FET Q2036 (3SK131) and fed to the 2nd mixer cir-
cuit.
The 2nd mixer consists of the IF Unit's FETs Q2033 and Q2038
(both 2SK302GR). A 2nd local signal (62.24 MHz) from the LO-
CAL Unit is amplified by Q2027 (2SC2812) and fed to each FET's
Circuit Description
gate. The signal that is produced by the 2nd mixer is removed of
unwanted signal components as it passes through a filter, formed by
T2014/T2017 and C2227, to obtain a 70.455 MHz 3rd IF signal.
3rd IF Circuit/3rd Mixer Circuit
The 3rd IF signal passes through T1001, is amplified by FET
Q1001 (SST310), then is fed to the 3rd mixer circuit D1001
(HSB88WSTR) via T1002. There it mixes with a local signal
(72.255 ~100.455 MHz) generated by the LOCAL Unit to pro-
duce a transmit signal (1.8 MHz to 30 MHz) at the desired operat-
ing frequency.
High-Frequency Transmit Preamplifier Circuit
The transmit signal is passed through a low-pass filter which
consists of L1002/L1003 and C1008-C1012, is amplified by Q1002
(2SC3356), and is passed onward to the PA Unit via buffer am-
plifiers Q1022 (2SC3356) and Q1023 (2SC2954), exiting via
connector J1005.
Power Amplifier Circuit
The transmit signal from the RF Unit arrives at connector J6101
of the PA Unit.
The transmit signal (1.8 MHz to 30 MHz) delivered to the PA
Unit is amplified by pre-driver Q6101 (2SC2166), driver Q6102/
Q6103 (2SC3133) and final amplifiers Q6104/Q6105
(2SC2879), and exits from connector J6102 then route to the LPF-
1 Unit.
Low-Pass Filter (LPF) Circuit
The transmit signal from the power amplifier circuit is sent to
connector J6001 of the LPF-1 Unit and passed through a low-pass
filter consisting mainly of RL6001-RL6014, L6001-L6014, and
various capacitors. The LPF is a 5th-order Chebyshev type filter,
utilizing seven different sections for the various amateur bands at
1.8 ~ 30 MHz.
The low-pass filtered transmit signal is fed to the ANT Unit
through directional coupler L6015 and connector J6005.
The directional coupler, which consists mainly of L6015,
TC6001, and C6061, samples a part of the transmission power to
detect forward power and reflected power. A DC voltage corre-
sponding to the relative forward/reflected power is produced by
D6001-D6004 (all HRF32), and is used for automatic level con-
trol (ALC).
ALC Circuit
The output from the directional coupler is routed from connec-
tor J6003 through connectors J6810/J6814 in the ALC Unit and
applied to the ALC circuit via connector J3018 in the AF Unit.
The ALC circuit consists of an op-amplifier circuit for ampli-
fying the forward and reflected voltage, a time-constant ALC am-
plifier, and a transmit signal control circuit on the IF Unit.
The forward voltage from connector J3018 in the AF Unit is
added with a DC control voltage which passes through the output
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