Transmit Signal Circuitry; Fm If Circuit/Fm Demodulator Circuit; Ssb/Cw Demodulator Circuit; Am Demodulator Circuit - Yaesu Mark-V FT-1000MP Field Technical Supplement

Circuit Description
AGC circuit is fed back to the RF AGC circuit that consists of
FETs and PIN diodes of the IF amplifier stages, by which the out-
put is controlled.

FM IF Circuit/FM Demodulator Circuit

The 2nd IF signal that has passed through buffer-amplifier FET
Q2003 on the IF Unit, and the 3rd local signal (8.67 MHz) that has
been buffer-amplified by Q2028, are fed to IC Q2015
(MC3372ML) for FM demodulation.
The FM demodulator IC contains a mixer, limiter amplifier,
filter amplifier, squelch trigger, and demodulator. The IF input sig-
nal is mixed with the 3rd local signal, band-limited by ceramic
filter CF2001 (CFWS455G, BW: ±4 kHz), amplified by the lim-
iter amplifier, and demodulated into an audio signal by the de-
modulator. It then passes through a filter (R2028, C2021) and con-
nector J2004 en route to the AF Unit. The signal then enters ana-
log switch IC Q3001-3 (BU4066BF) through a de-emphasis cir-
cuit which consists of R3060 and C3052.
The squelch circuit selectively amplifies the noise component
of the demodulator output by the filter amplifier inside the FM IC
and the active band-pass filter consisting of an externally attached
resistor and capacitor. This circuit uses a signal detected by D2001
(1SS270).

SSB/CW Demodulator Circuit

The 3rd IF signal from the IF Unit is applied to the SSB de-
modulator of Q3007 (µPC1037H) on the AF Unit, which pro-
duces audio by applying the carrier signal from the DDS-CAR
Unit to Q3007 after buffering by Q3020 (2SC2812). Similarly,
the CW signal is demodulated by a carrier signal which is offset by
the "Pitch" frequency.
The demodulated SSB and CW signals are each stripped of
high-frequency components by an active low-pass filter consisting
of op-amp IC Q3008-2 and IC Q3008-1 (M5218AFP). Then, they
enter analog switch IC Q3001-2 and IC Q3001-4 (BU4066BF).

AM Demodulator Circuit

The 3rd IF signal from the IF Unit is applied to I-DET Unit
U3003 on the AF Unit, from which it enters IC Q3703
(MC13020M) for AM demodulation.
The IC for AM demodulation consists mainly of an envelope
detector, VCO, phase shifter, synchronous detector, and DC/AC
detector. From the IF signal that is fed to the IC, the envelope
detector output and synchronous detector output are picked up.
The output from the demodulator circuit passes through ana-
log switches Q3701-1 and Q3701-2 for switching between the syn-
chronous detector output and envelope detector output. It then
enters analog switch IC Q3001-1 (BU4066BF) after removal of
the high-frequency components by an active low-pass filter which
consists of op-amp IC Q3013-1 (M5218AFP) on the AF Unit.
4-2
Low-Frequency Amplifier Circuit
The demodulated signal that is selected by one of analog
switches IC Q3001-1 to IC Q3001-4 on the AF Unit (according to
the receiving mode) passes through the squelch switch, audio mut-
ing FET Q3002 (2SK160), low-frequency amplifier transistor
Q3006 (2SC2812), electronic volume IC Q3005 (M51131L), op-
amp IC Q3014-1 (M5218AFP) for buffer-amplification, and IC
Q3022 (TDA2003V) for low-frequency power to drive the inter-
nal or external speaker with a maximum output of approximately
1.5 W. The signal that passes through electronic volume IC Q3005
is also sent to the headphone terminals after it is amplified by head-
phone amplifier IC Q3015-1 (M5218AFP).

Transmit Signal Circuitry

Microphone Amplifier Circuit
The audio signal from microphone jack J9421 on the MIC Unit
is passed through connector JP9421 and the DISPLAY Unit's con-
nectors (J5528 and J5529), is amplified by transistor Q3048
(2SC2812) on the AF Unit, and then is applied to electronic vol-
ume IC Q3044 (M51131L), which is controlled by the MIC knob
on the panel.
The output (audio signal) from the electronic volume control
is amplified by Q3045 (2SC2812) and fed to balanced modulator
IC Q3046 (µPC1037H) through the buffer-amplifier transistor
Q3043 (2SC2812).
During FM transmission, the audio signal is routed to connec-
tor J2011 inside the IF Unit after its volume is adjusted by VR6814
on the ALC Unit. The audio signal that has passed through the pre-
emphasis circuit consisting of C2201 and R2228 on the IF Unit is
mixed with a tone signal from the CNTL Unit, and is amplified
and limited by op-amp IC Q2049-2 (M5223AFP) of the IDC cir-
cuit. The audio then passes through the splatter filter (secondary
active low-pass filter) formed by op-amp IC Q2049-1, R2229, and
R2230, plus C2119 and C2206, and is then fed to the frequency-
modulator circuit inside the IF Unit through VR2008 and VR2009
for setting of the frequency deviation.
SSB Modulator Circuit
The carrier signal appropriate to the transmitting mode (LSB
or USB) is applied from the CAR-DDS Unit to balanced modula-
tor IC Q3046 on the AF Unit, and is modulated by microphone
audio.
The balanced modulator produces the upper and lower side
bands and carrier signal. The carrier and audio signal are suppressed
and the carrier balance is adjusted by VR3012. As a result, the
output signal obtained is a DSB signal with a carrier suppression
ratio of 35 dB or more.
The DSB modulated signal (1st IF signal: 455 kHz) then passes
through mechanical filter XF9801 inside the SSB-FIL Unit on the
IF Unit, stripping residual carrier and the undesired sideband; the
signal then passes as an SSB signal through buffer-amplifier Q3049
(2SC2812), connector J3026, and the IF Unit's connector J2009.