Transmitter Construction - Icom IC-7000 Service Manual

3-2-5 2ND MIXER CIRCUIT (MAIN UNIT)
The 2nd mixer circuit mixes the 2nd IF signal with the 2nd
LO signal to convert into the 1st IF frequency.
The filtered signal from the bandpass filter (FI901) is applied
to the 2nd mixer circuit (D801) and mixed with 2nd LO sig-
nal (124.032 MHz) to convert into the 1st IF signal.
The 2nd LO signal is generated in the DDS unit, and applied
to the 2nd mixer circuit (D801) after being filtered and
attenuated at the low-pass filter (L808, C816, C817) and the
attenuators (R801, R805, R806, R809–R811), respectively.
The converted 1st IF signal is applied to the 1st IF circuit.
3-2-6 1ST IF CIRCUIT (MAIN UNIT)
The 1st IF circuit amplifies and filters the 1st IF signal.
The converted 1st IF signal is applied to the IF amplifier
(Q701) via the TX switch (D703) and then passed through
the bandpass filter (FI601) to suppress unwanted signals via
the filter switches (D601, D602).
The filtered signals are applied to the 1st mixer circuit.
3-2-7 1ST MIXER CIRCUIT (MAIN UNIT)
The 1st mixer circuit mixes the 1st IF signal with the 1st LO
signal to convert into the RF frequency.
The filtered signal is applied to the 1st mixer circuit (IC401)
via the TX switches (D501, D504) and mixed with the 1st LO
signal (124.517–594.487 MHz) to convert into the RF signal.
The 1st LO signal is generated in the DDS unit, and applied
to the 1st mixer circuit (IC401, pins 1, 6) after being ampli-
fied and attenuated at the 1st LO amplifier (IC421, pins 1, 4)
and the attenuators (R416–R418, R421–R423), respectively.
The converted RF signal is applied to the RF circuit.

• TRANSMITTER CONSTRUCTION

MIC
Controller
IC551
FI601
Q801
Crystal
AMP.
BPF
MAIN UNIT
LOGIC UNIT (DSP circuit)
DSP
A/D
D/A
ICs
IC301
IC551
IC2201
1st mixer
IC401
HPFs
1st LO
BPF
(124.517−
594.487 MHz)
3-2-8 RF CIRCUIT (MAIN UNIT)
The RF circuit amplifies and filters the RF signal from the
1st mixer circuit.
The HF/50 MHz bands signal from the 1st mixer circuit
(IC401) is passed through the low-pass filter (L310, L312,
C314, C316, C318, C320, C322) via the band switch (D305).
The HF band signal is passed through one of 5 high-pass
(Refer to 3-1 for used RF high-pass filter) and low-pass
(L205, L207, C209–C213) filters.
The 50 MHz band signal is passed through the bandpass
filter (L219, L220, L246–L248, C240–C242, C282, C285–
C291).
The filtered HF/50 MHz bands signal is amplified at the YGR
amplifier (IC1) after passed through the high-pass filter (L109,
L110, L116, L117, C109, C114–C116) and attenuator (R5–
R7).
The amplified HF/50 MHz bands signal is applied to the
drive and power amplifier circuits (PA unit) via J1.
The VHF/UHF bands signal from the 1st mixer circuit (IC401)
is passed through the low-pass filter (L309, L311, L313,
C313, C315, C317, C319, C321, C323, C325) via the band
switch (D306).
The VHF band signal is passed through the bandpass filter
(L8, L10–L13, C18, C25, C26, C28, C29, C31–C33) via
the band switches (D3, D10) and then amplified at the RF
amplifier (IC2, pins 1, 3). The amplified signal is passed
through the band switch (D1) and attenuator (R5–R7), and
then applied to the YGR amplifier (IC1, pins 1, 4).
The amplified signal is passed through the high pass filter
(L21, C50–C52) via the filter switches (D6, D8) and then
applied to the drive and power amplifier circuits (PA unit) via
J1.
The UHF band signal is amplified at the RF amplifier (IC3,
pins 1, 3) via the band switch (D4) and passed through the
bandpass filters (FI2, FI3). The filtered signal is amplified at
the YGR amplifier (IC1, pins 1, 4) after passed through the
band switch (D2), attenuator (R5–R7) and bypass switches
(D7, D9).
The amplified signal is applied to the drive and power ampli-
fier circuits (PA unit) via J1.
3rd LO
(438.85 kHz)
Q901
455 kHz
AMP.
124.487 MHz
PA UNIT
HF/50 MHz
AMP.
IC504
145 MHz
DRIVER
UNIT
430 MHz
3 - 5
2nd LO
(124.032 MHz)
FI901
Ceramic
BPF
2nd mixer
D801
ANT1
Q301
ANT2
Q302
PA LPFs
Q501
PA
Q401
PA