Icom IC-F7000 User Manual download pdf (Page 12)

4 - 1

SECTION 4 CIRCUIT DESCRIPTION

4-1 RECEIVER CIRCUITS

4-1-1 RF FILTER CIRCUIT (PLL AND MAIN UNITS)

Received signals from the antenna connector are applied to

the transmit/receive switching and protection relay (PLL unit;

RL7301) which is controlled by the CPU via the “TRXS” line.

The signals pass through the 30 MHz cut-off low-pass filter

(PLL unit; L7321, C7321–C7323, C7325), and then applied

to the MAIN unit via the J7321.

The signals pass through the 1.6 MHz cut off high-pass fil-

ter (MAIN unit; L51–L54, L57, C54, C56, C57, C59,

C61–C64, C69) and transmit/receive switch (D54), and are

then applied to one of the bandpass filters (including one

low-pass filter for below 2.0 MHz). These filters are selected

by the filter control signals (B0–B8) as described in the table

below.

The filtered signals are applied to the pre-amplifier (MAIN

unit; Q102, Q103), and then passed through the 33 MHz

cut-off low-pass filter (L202, L203, C202–C206). The filtered

signals pass through the low-pass filter (MAIN unit; L202,

L203, C202–C206), and are then applied to the 1st mixer

circuit (Q201, Q202, Q204, Q205).

4-1-2 1ST MIXER AND IF CIRCUITS (MAIN UNIT)

The 1st mixer circuit converts the received signals into a

fixed frequency, 64.445 kHz 1st IF signal using PLL output

frequency. By changing the PLL frequency, only the desired

frequency is picked up at the 64.445 kHz bandpass filter

(FI201) at the next stage.

The IF amplifier (Q203) and resonator circuits are designed

between the filter pair. The PLL output signal (1LO) enters

the MAIN unit via the J601 and is amplified at the 1st LO

amplifier (Q601). The amplified signal is passed through the

100 MHz cut-off low-pass filter (L602–L604, C602,

C604–C607, C609) to suppress harmonic components, and

then applied to the 1st mixer circuit (Q201, Q202, Q204,

Q205).

4-1-3 2ND MIXER AND IF CIRCUITS (MAIN UNIT)

The 1st IF signal from the bandpass filter (FI201) is convert-

ed again into a 455 kHz 2nd IF signal at the 2nd mixer cir-

cuit (D303, L303, L304). The 2nd LO signal (2LO) from the

PLL unit enters the MAIN unit via the J301 to be applied to

the 2nd mixer circuit.

4-1-4 3RD MIXER AND IF CIRCUITS (MAIN UNIT)

The 2nd IF signal passes through the low-pass filter (L305,

C308, C310, C311, C315), and is then applied to the IF

amplifier (Q401) via the ceramic bandpass filter (FI401). The

amplified signal passes through the other ceramic bandpass

filter (FI402), and then applied to the 3rd mixer circuit via the

IF amplifier (Q501). The 2nd IF signal is converted into a

12 kHz 3rd IF signal at the 3rd mixer circuit (IC501). The 3rd

LO signal (3LO) from the PLL unit enters the MAIN unit via

the J3601 to be applied to the 3rd mixer circuit.

LPF

Antenna

PLL unit

to transmit/receiver switch

LPF

FI201 FI401

FI402

Q401

Q5013rd mixer

IC501

IC1002

1st mixer

Q201

Q202

Q203

Q204

2nd mixer

D303

1st LO

64 94 MHz

BPF

2 30 MHz

0.5 1.9999 MHz

BPF

Crystal

BPF

Crystal

amp.

BPF

Crystal

LPF

amp.

DSP

UNIT

2nd LO

64 MHz

3rd LO

443 kHz

• RECEIVER CONSTRUCTION

Frequency (MHz)

0.5–1.9999

2.0–2.4999

2.5–2.9999

3.0–3.4999

3.5–4.9999

5.0–5.4999

5.5–6.9999

7.0–8.9999

9.0–9.9999

10.0–13.9999

14.0–14.9999

15.0–17.9999

18.0–23.9999

24.0–29.9999

BPF ctrl signal

LPF ctrl signal

L1M

L2M

L4M

L6M

L12M

L22M

1 2 ... 7 8 9 10 11 12 13 14 15 16 17 ... 78 79

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Icom IC-F7000 User Manual Page 12

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