Icom IC2820H User Manual

DUAL BAND FM TRANSCEVER

S-14325XZ-C1
Mar. 2007

INTRODUCTION CAUTION

This service manual describes the latest service information
for the IC-2820H DUAL BAND FM TRANSCEVER at the
time of publication.

MODEL VERSION

USA-01
AUS-01

IC-2820H

To upgrade quality, any electrical or mechanical parts and
internal circuits are subject to change without notice or
obligation.

KOR-01
TPE-01
EXP-01

NEVER connect the transceiver to an AC outlet or to a DC
power supply that uses more than 15 V. This will ruin the
transceiver.

DO NOT expose the transceiver to rain, snow or any liquids.

DO NOT reverse the polarities of the power supply when

connecting the transceiver.

DO NOT apply an RF signal of more than 20 dBm (100 mW)
to the antenna connector (J1). This could damage the
transceiver’s front end.

ORDERING PARTS

Be sure to include the following four points when ordering
replacement parts:

1. 10-digit order numbers

2. Component part number and name

3. Equipment model name and unit name

4. Quantity required

<SAMPLE ORDER>

1110003491 S.IC TA31136FNG IC-2820H MAIN UNIT 5 pieces

8820001210 Screw 2438 screw IC-2820H Top cover 10 pieces

Addresses are provided on the inside back cover for your
convenience.

Icom, Icom Inc. and
Kingdom, Germany, France, Spain, Russia and/or other countries.

logo are registered trademarks of Icom Incorporated (Japan) in the United States, the United

REPAIR NOTES

1. Make sure a problem is internal before disassembling
the transceiver.

2. DO NOT open the transceiver until the transceiver is
disconnected from its power source.

3. DO NOT force any of the variable components. Turn
them slowly and smoothly.

4. DO NOT short any circuits or electronic parts. An
insulated tuning tool MUST be used for all adjustments.

5. DO NOT keep power ON for a long time when the
transceiver is defective.

6. DO NOT transmit power into a signal generator or a
sweep generator.

7. ALWAYS connect a 50 dB to 60 dB attenuator between
the transceiver and a Modulation Analyzer or spectrum
analyzer when using such test equipment.

8. READ the instructions of test equipment thoroughly
before connecting equipment to the transceiver.

CONTENTS

SECTION 1 SPECIFICATIONS

SECTION 2 INSIDE VIEWS

SECTION 3 DISASSEMBLY INSTRUCTIONS

SECTION 4 CIRCUIT DESCRIPITON

4-1 RECEIVER CIRCUITS ............................................................................................................... 4-1

4-2 TRANSMITTER CIRCUITS ....................................................................................................... 4-4

4-3 FREQUENCY SYNTHESIZER .................................................................................................. 4-6

4-4 POWER SUPPLY CIRCUITS ..................................................................................................... 4-8

4-5 PORT ALLOCATIONS ............................................................................................................... 4-9

SECTION 5 ADJUSTMENT PROCEDURES

5-1 PREPARATION .......................................................................................................................... 5-1

5-2 FREQUENCY ADJUSTMENT ................................................................................................... 5-2

5-3 TRANSMIT ADJUSTMENT ....................................................................................................... 5-3

5-4 RECEIVE ADJUSTMENT .......................................................................................................... 5-4

SECTION 6 PARTS LIST

SECTION 7 MECHANICAL PARTS

SECTION 8 BOARD LAYOUTS

SECTION 9 BLOCK DIAGRAM

SECTION 10 VOLTAGE DIAGRAM

SECTION 11 HM-133

SECTION 12 UT-123 (Optional product)

SECTION 1 SPECIFICATIONS

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1 - 1

SECTION 2 INSIDE VIEWS

• TOP VIEW

D/A converter
(IC1: M62364FP)

1st IF Mixer for UHF bands
(IC20: SPM5001)

LO filter
(763.650−953.640 MHz)

Frequency synthesizer
(Right band)

AF switch
(IC30: CD4066BPWR)

• BOTTOM VIEW

D/A converter
(IC8: M62364FP)

Electric volume
(IC33: SM6451B)

D/A converter
(IC54: M62364FP)

1st IF Mixer for VHF bands
(IC19: SPM5001)

LO divider
(79.150−121.150 MHz)

Frequency synthesizer
(Left band)

AF filter

(IC48: LM2902PWR)
Level converter
(IC46: MAX3221IPWR)

AF switch
(IC31: CD4066BPWR)

VHF PA module
(IC3: S-AV32)

AF power amplifier
(IC38: LA4445)

EEPROM
(IC22: 24LC512)

CPU
(IC25: HD64F2506FC26)

IF IC (Left band RX)
(IC15: TA31136FNG)

DTMF decoder
(IC56: BU8872FS)

Reference frequency oscillator
(Left band)

2 - 1

UHF PA module
(IC2: S-AU82L)

IF IC (Right band)
(IC18: TA31136FNG)

Reference frequency oscillator
(Right band)

SECTION 3 DISASSEMBLY INSTRUCTION

1. Removing the top cover

q Unscrew 10 screws, then remove the top cover.

10 screws

Top cover

w Disconnect the speaker cable.

Speaker cable

3. Removing the MAIN UNIT

q Unscrew 11 screws from the MAIN UNIT.

w Disconnect the cooling fan cable, and unsolder 6 points at

the antenna connectors (grey colored).

6 unsoldering points

Cooling fan cable

2. Removing the bottom cover

q Unscrew 7 screws, then remove the bottom cover.

7 screws

Bottom cover

e Remove the MAIN UNIT in the direction of the arrow.

MAIN UNIT

3 - 1

SECTION 4 CIRCUIT DESCRIPTION

4-1 RECEIVER CIRCUITS

RF CIRCUITS

<Left band>

• 118−174 MHz

The received signals from the antenna connector ANT-1
(J1) are passed through two LPFs (L101, 104, 108, C342,
346; L88, 92, 96, C318, 326, 330), then applied to the RF
amplifi er (Q37) via TX/RX switch (D75). The amplifi ed signals
are passed through the RX switch (RL2), attenuator (D68)
and tuned BPF (D55, 66), before being applied to another
RF amplifi er (Q33). The amplifi ed signals are applied to the
1st mixer (IC19) via the another tuned BPF (D41, 44) and
RX switch (D38).

While the diversity operation is activated, the received
signals are also input from ANT-2 (J2). The received signals
are passed through two LPFs (L103, 106, 109, C344, 348;
L90, 93, 98, C319, 327, 348), antenna switch (D65, 72) and
limitter (D64, 67), then applied to the RF amplifi er (Q39).

The amplified signals are applied to the RX switch (RL2),
and gone through the same process as the received signals
from ANT-1 (J1).

• 174−260 MHz

The received signals from the antenna connector (J1) are
passed through two RX switches (RL3 and D56) and the
tuned BPF (D51), then applied to the RF amplifier (Q34).
The amplified signals are passed through the BPF (D45),
attenuator (R139, 144, 147) and RX switch (D36) before
being applied to the 1st mixer (IC19).

• 260−375 MHz

The received signals from the antenna connector (J1) are
passed through two RX switches (RL3 and D57) and the
tuned BPF (D50), then applied to the RF amplifi er (Q35).

The amplifi ed signals are passed through the BPF (D465),
attenuator (R142, 143, 150) and RX switch (D37) before
being applied to the 1st mixer (IC19).

• 375−550 MHz

The received signals from the antenna connector (J1) are
passed through the LPF (L101, 104, 108, C342, 346) and
HPF (L77, 80, C296, 297, 303, 308), then applied to the
RF amplifier (Q28) via TX/RX switch (D53, 61, 62). The
amplifi ed signals are passed through the RX switch (RL1),
attenuator (D28) and tuned BPF (D19, 21, 24, 27), before
being applied to another RF amplifi er (Q20). The amplifi ed
signals are applied to the 1st mixer (IC19) via the another
tuned BPF (D11, 13, 15, 17) and RX switch (D8).

While the diversity operation is activated, the received
signals are also input from antenna connector ANT-2 (J2).
The received signals are passed through the LPF (L103,
106, 109, C344, 348), HPF (L95, 99, C329, 333, 338),
antenna switch (D69, 73, 74) and limitter (D63, 66), then
applied to the RF amplifi er (Q29).

The amplified signals are applied to the RX switch (RL1),
and gone through the same process as the received signals
from ANT-1 (J1).

• RF CIRCUITS

Left band

ight band

D38

RX
SW

D35

RX
SW

D7

RX
SW

D8

RX
SW

D44

D41,

BPF

D40,

D43

BPF

D10,

D12,

D14,

D16

BPF

,D13,

D11

D17

D15,

BPF

D36

RX
SW

D37

RX
SW

118−174 MHz

Q33

RF

AMP

Q32

RF

AMP

118−174 MHz

375−550 MHz

Q19

RF

AMP

375−550 MHz

Q20

RF

AMP

ATT

ATT

D55,

D60

BPF

D54,

D58

BPF

D20,

D18,
D23,

D26

BPF

D21,

D19,
D24,

D27

BPF ATT

D45

BPF

D46

BPF

D68

ATT

D70

ATT

Q39

Q29

D30

ATT

RL1
Q30
D32

D28

174−260 MHz

Q34

260−375 MHz

Q35

RF
AMP

RF
AMP

RF
AMP

RF
AMP

RX
SW

RL2
Q38
D76

RX
SW

D64,D67

LIMIT

LIMIT

D63,D66

D51

BPF

D50

BPF

Q37

D65,D71,D72

D69,D73,D74

Q28

RF
AMP

RF
AMP

ANT

ANT

SW

SW

D48,D49

LIMIT

D56

D57

RX
SW

RX
SW

D78,

LIMIT

D79

LPF

HPF

TX/RX

D53
D61
D62

TX/RX

SW

RL3
Q40
D80

D59
D75
D77

SW

RX
SW

LPF

LPF

ANTENNA

HPF

ANTENNA

LPF

HPF

810−1000 MHz

ATT

Q23

RF
AMP

D9

RX
SW

ATT

Q18

RF

AMP

D22

RX
SW

HPF

4 - 1

1ST IF CIRCUITS

DEMODULATOR CIRCUITS (Left band)

RX signals from the RF circuits are converted into the 38.85
MHz 1st IF signal by being mixed with LO signals from the
left band VCO (Q111, D145−147).

The converted IF signal from the 1st mixer is passed through
the IF fi lter (FI5) to be fi ltered. The fi ltered IF signal is applied
to the 1st IF amplifi er (Q66) via the limiter (D88). The amplifi ed
1st IF signal is applied to the IF IC (IC15, pin 16)

SQUELCH CIRCUITS

• NOISE SQUELCH

A portion of FM-demodulated AF signals from the IF IC
(IC15, pin 9) are level-adjusted by D/A converter (IC8), and
passed throuhgh the noise fl tier (IC15 and some R and C) to
be fi ltered noise components (30 kHz and above signals) in
the AF signals. The fi ltered noise components aree detected
in the IC15 and output from pin 13, then applied to the CPU
(IC25, pin 100) as “L_SQL” signal.

2ND IF AND DEMODULATOR CIRCUITS (Fig. 2)

IC15 is an IF IC which contains 2nd mixer, limiter amplifi er,
noise amplifi er, quadrature detector and RSSI circuit, etc. in
its package.

The 1st IF signal from the 1st IF amplifi er (Q66) is converted
into the 450 kHz 2nd IF signal by being mixed with tripled
reference frequency signal (38.4 MHz) from the PLL IC (IC41)
via the tripler (Q105). The converted 2nd IF signal is output
from pin 3, and passed through the ceramic filter (FI1 for
narrow mode, FI2 for wide mode) to remove sideband noise,
then applied to the IF IC from pin 5 again.

• FM DEMODULATOR

The fi ltered 2nd IF signal from pin 5 is amplifi ed at the limiter
amplifier, and FM-demodulated at the quadrature detector
circuit. The demodulated AF signals are output from pin 9
and routed to the AF circuits via two AF switches (IC11 and
IC13).

• AM DEMODULATOR CIRCUITS

In the AM mode, the 2nd IF signal from the FI2 is applied to
the AM-demodulator circuit (Q55, Q57). The demodulated
AF signals are routed to the AF circuits via two AF switches
(IC11 and IC13).

Then the CPU outputs “L_AF_MUTE” signal from pin 82 to the
speaker mute switch (Q102), according to the

“L_SQL” signal
level. Thus the AF line is connected to the GND to turn the AF
output OFF.

• CTCSS/DTCS

CTCSS/DTCS signals in the demodulated AF signals from
the AF switch (IC13) are passed through the tone fi lter (Q41)
. The fi ltered CTCSS/DTCS signals are applied to the CPU
IC25, pin 70) as “L_DTCSIN” signal.

The CPU (IC25) com­pares the applied signal and the set CTCSS/DTCS, then out­puts control signal as same as “NOISE SQUELCH.”

• DTMF

DTMF signals

in the demodulated AF signals from the AF
switch (IC13) are passed through two AF switches (IC57
and IC58), then applied to the

DTMF decoder (IC56) to be

decoded.

AF CIRCUITS

The AM/FM-demodulated AF signals from the AF switch
(IC11) are passed through the AF filter (Q47). The filtered
AF signals are applied to the electric volume (IC33) to be
adjusted its level. The level-adjusted AF signals are applied
to the dual AF power amplifiier (IC38) to
power level, then applied to the internal (CHASSIS; SP1)
or an external speaker via external speaker jack (J7).

obtain AF output

• 2ND IF AND DEMODULATOR CIRCUITS (LEFT BAND)

AM DEMODULATOR CIRCUITS

L_R5

R306

to the AF circuits

AM-demodulated AF signals

FM-demodulatedAF signals
from the D/A converter (IC8)

C407

AGC voltage to the 1st IF amplifier (Q66)

4

5

6

Q55

1

2

3

R310

C417

R319

R311

R884

R317

R314

C418

C419

R321

R307

NOISE FILTER

R327
R328

C423

6

1

R324

C425

5

2

C422

If an external speaker is connected to the J8, the level­adjusted AF signals from the electric volume (IC33) are
applied to the connected speaker.

2nd IF FILTERS

C427

4

3

C426

R335

Q57

C429

R332

8

FILIN

R316

C428

7

DEC

FILOUT

D82

D83

C933

I O

FI2

I O

38.4 MHz 2nd LO signal
from the PLL IC (IC41)

FI1

C932

QUADRATURE DETECTOR

X2

R341

1

2

3

4

5

6

VCC

IFIN

OSCIN

OSCOUT

MIXOUT

IF IC (IC15)

R346

C930

C931

D84

D85

C437

R334

FM-demodulated AF signals
to the AF circuits

L_SQL
L_RSSI

C404

R308

R315

4 - 2

C416

AFOUT

QUAD

9

10

C435

IFO UT

11

RSSI

12

N-REC

N-DET

14

13

GND

MIXIN

16

15

1st IF signal from
the 1st IF amplifier(Q66)

RF CIRCUITS

<Right band>

• 118−174 MHz

The received signals from the antenna connector ANT-1
(J1) are passed through two LPFs (L101, 104, 108, C342,
346; L88, 92, 96, C318, 326, 330), then applied to the
RF amplifier (Q37) via TX/RX switch (D59). The amplified
signals are passed through the attenuator (D70) and tuned
BPF (D54, 58), before being applied to another RF amplifi er
(Q32). The amplified signals are applied to the 1st mixer
(IC20) via the another tuned BPF (D40, 43) and RX switch
(D35).

• 375−550 MHz

The received signals from the antenna connector (J1) are
passed through the LPF (L101, 104, 108, C342, 346) and
HPF (L77, 80, C296, 297, 303, 308), then applied to the
RF amplifier (Q28) via TX/RX switch (D53, 61, 62). The
amplified signals are passed through the attenuator (D30)
and tuned BPF (D18, 20, 23, 26), before being applied
to another RF amplifier (Q19). The amplified signals are
applied to the 1st mixer (IC20) via the another tuned BPF
(D10, 12, 14, 16) and RX switch (D7).

• 810−1000 MHz

The received signals from the ANT-1 (J1) are passed
through the HPF (L102, 105, 107, 110, C337, 339, 340,
343, 347, 349) and RX switch (D22), then applied to the RF
amplifier (Q23). The amplified signals are passed through
the attenuator (R39, 40, 51), and applied to the another RF
amplifi er (Q18) to be amplifi ed again. The amplifi ed signals
are then passed through another attenuator (R14) and RX
switch (D9) before being applied to the 1st mixer (IC20).

1ST IF CIRCUITS

RX signals from the RF circuits are converted into the 46.35
MHz 1st IF signal by being mixed with LO signals from the
right band VCO (Q72, D89, 90; Q73, D87, 91, 92).

The converted IF signal from the 1st mixer (IC20) is passed
through the IF fi lter (IF6) to be fi ltered. The fi ltered IF signal is
applied to the 1st IF amplifi er (Q75) via the limiter (D100). The
amplifi ed 1st IF signal is applied to the IF IC (IC18, pin 16)

2ND IF AND DEMODULATOR CIRCUITS

IC15 is an IF IC which contains 2nd mixer, limiter amplifi er,
noise amplifi er, quadrature detector and RSSI circuit, etc. in
its package.

The 1st IF signal from the 1st IF amplifi er (Q75) is converted
into the 450 kHz 2nd IF signal by being mixed with tripled
reference frequency signal (45.9 MHz) from the PLL IC (IC14)
via the tripler (Q52). The converted 2nd IF signal is output
from pin 3, and passed through the ceramic filter (FI3 for
narrow mode, FI4 for wide mode) to remove sideband noise,
then applied to the IF IC from pin 5 again.

• FM DEMODULATOR

The fi ltered 2nd IF signal from pin 5 is amplifi ed at the limiter
amplifier, and FM-demodulated at the quadrature detector
circuit (X3). The demodulated AF signals are output from pin
9 and routed to the AF circuits via two AF switches (IC12
and IC16).

• AM DEMODULATOR CIRCUITS

In the AM mode, the 2nd IF signal from the FI3 is applied to
the AM-demodulator circuit (Q63, Q67). The demodulated
AF signals are routed to the AF circuits via two AF switches
(IC12 and IC16).

• DEMODULATOR CIRCUITS (Right band)

R_R5

R351

4

5

6

Q63

1

2

R352

to the AF circuits

AM-demodulated AF signals

FM-demodulatedAF signals
from the D/A converter (IC8)

C450

AGC voltage to the 1st IF amplifier (Q75)

3

R358

R359

FM-demodulated AF signals
to the AF circuits

C458

R366

C454

AM DEMODULATOR CIRCUITS

R374

R376

180K

Q67

R372

R885

NOISE FILTER

C471

0.01

6

1

R388

R383

R_SQL
R_RSSI

C470

5

2

C460

R374

4

3

R385

C475

C476

R397

R375

C477

R402

R389

R400

C480

2nd IF FILTERS

C486

D93

D94

C487

C478

7

8

FILIN

FILOUT

AFOUT

QUAD

9

10

C927

C929

DEC

IFOUT

11

5

6

IFIN

RSSI

12

C491

R_R5

VCC

N-DET

D95

C926

FI3

C928

FI4

C495

R414

45.9 MHz 2nd LO signal
from the PLL IC (IC14)

1

2

3

4

OSCIN

OSCOUT

MIXOUT

IF IC (IC18)

N-REC

GND

MIXIN

16

15

14

13

X3

R415

D96

1st IF signal from
the 1st IF amplifier(Q75)

R_R5

QUADRATURE DETECTOR

4 - 3

SQUELCH CIRCUITS

• NOISE SQUELCH

A portion of FM-demodulated AF signals from the IF IC
(IC18, pin 9) are level-adjusted by D/A converter (IC8), and
passed throuhgh the noise fl tier (IC18 and some R and C) to
be fi ltered noise components (30 kHz and above signals) in
the AF signals. The fi ltered noise components are detected
in the IC18 and output from pin 13, then applied to the CPU
as “R_SQL” signal.

Then the CPU outputs “R_AF_MUTE” signal from pin 51 to the
speaker mute switch (Q102), according to the

“R_SQL” signal
level. Thus the AF line is connected to the GND to turn the AF
output OFF.

• CTCSS/DTCS

CTCSS/DTCS signals in the demodulated AF signals from
the AF switch (IC16) are passed through the tone fi lter (Q42)
. The fi ltered CTCSS/DTCS signals are applied to the CPU
IC12) as “R_DTCS” signal.

The CPU (IC25) compares the applied signal and the set
CTCSS/DTCS, then outputs control signal as same as “NOISE
SQUELCH.”

• DTMF

DTMF signals

in the demodulated AF signals from the AF
switch (IC16) are passed through two AF switches (IC57
and IC58), then applied to the

DTMF decoder (IC56) to be

decoded.

AF CIRCUITS

The AM/FM-demodulated AF signals from the AF switch
(IC12) are passed through the AF filter (Q48). The filtered
AF signals are applied to the electric volume (IC33) to be
adjusted its level. The level-adjusted AF signals are applied
to the dual AF power amplifiier (IC38) to
power level, then applied to the an external speaker via
external speaker jack (J8).

obtain AF output

4-2 TRANSMITTER CIRCUITS

MICROPHONE AMPLIFIER CIRCUITS

The audio signals from the microphone (MIC signals) are
applied to the microphone amplifi er (IC28) via J2 and HPF
(Q87). The amplified MIC signals are passed through the
microphone gain switch (Q88) and MIC mute switch (IC30),
then passed through or by-passed ALC amplifi er (IC32) via
AF switches (IC29 and IC52).

The MIC signals from the AF switch (IC52) are passed
though the HPF (IC48), LPF (IC48) and AF switch (IC51),
and then applied to the AF amplifier (IC48). The amplified
MIC signals are applied to the D/A converter (IC8) for level
(deviation) adjustment. The level adjusted MIC signals are
applied to the VCO as the modulation signals via modulation
signal selector.

<OPERATION ON THE LEFT BAND>

The modulation signals are applied to the variable capacitor
D147 of the left band VCO (Q111, D145–147) via the
modulation selector (IC9) and modulation mute switch
(Q109), and modulated. The modulated VCO output are
amplifi ed by the buffer (Q113) and LO amplifi er (IC44), and
applied to the transmit amplifi ers as the TX signal, via the LO
switches (D155, 157), LPF(L157, C818, 820) and attenuator
(R33, 37, 46).

TRANSMIT POWER AMPLIFIERS

TX signal from the attenuator (R33, 37, 46) is amplifi ed by
pre-drive (Q25) and drive (Q27) amplifi ers to obtain RF level
for power module (IC3). The amplifi ed TX signal is applied
to the power amplifier which is a VHF band PA module
composed by two power MOS-FETs. The power-amplified
TX signal is passed through the LPF, power detector,
antenna switch (D59) and LPF, before being applied to the
antenna connector (CHASSIS; J1).

• MICROPHONE AMPLIFIER CIRCUITS

5VS

MIC signals from
the microphone

C619

C620

R527

R532

R533

HPF

R537

33K

Q87

C624

C623

R541

R538

C625

R547

R545

R560

R549

Microphone

R562

5

3

1

2

IC28

amplifier

4

C635

C636

MIC_SENC

IC29

1

AF

switch

R566

APC CIRCUITS

A portion of the TX signal from IC3 is rectifi ed at the power
detector (D39, D47), and converted into the DC voltage
which is in proportion to the RF power, and applied to the
operational amplifier (IC4, pin 6). IC4 is an APC amplifier
for both of V/UHF bands. The TX power setting voltage
“PCON_V” from the D/A converter (IC1, pin 7) is applied
to the pin 5 as a reference. IC4 is rolled as a differential
amplifier which outputs voltage in inverse proportion to
rectified one. When the TX power increased, the rectified
voltage also increased, that causes the decrease of output
voltage of differential amplifier. The decrease of output
voltage of differential amplifi er causes the drop of the gate
voltage of IC3, Thus the TX power maintained to keep stable
level.

TX muting is carried out by TX mute SW (Q36) controlled
by “TX_mute” signal. Applying “TX_mute” signal to the base
terminal of Q36 to turn it ON, 8 V DC appears on the pin 6 of
IC4 and its output voltage downs to 0 V DC to inactivate IC3.

HPF

IC30

C637

1

MIC

2

R577

C649

R802

AN6123MS

INPUT

3

GND

4

OUTPUT

5

mute
switch

C648

R578

DET

VCC

IC32

7

6

switch

R550

Q88

7

6

C644

R801

C645

R574

R575

R804

IC52

C862

1

AF

2

R589

1

C656

R628

R784

C861

R774

C857

R775

C687

R766

C858

HPF

R640

R771

R765

IC48

1
2
3

5
6

7 8

Amplifier

ALC

LPF

R660

R664

C856
14
13
12

10
9

R763

C855

R764

R785

C866

IC51

7

1

6

R767

AF switch

R762

Modulation signals
to the modulation circuits

4 - 4

<OPERATION ON THE RIGHT BAND>

The modulation signals are applied to the variable capacitor
D87 of the left band VCO (Q73, D87, 91, 92) via the
modulation selector (IC63) and modulation mute switch
(Q64), and modulated. The modulated VCO output are
amplifi ed by the buffer (Q76) and LO amplifi er (IC45), and
applied to the transmit amplifi ers as the TX signal, via the
VCO switch (D102). The amplifi ed LO signals are applied to
the transmit amplifi ers via the LO switch (D103), two HPFs
(L124, C527, 532; L159, C533, 535) and attenuator (R43,
47, 57).

TRANSMIT POWER AMPLIFIERS

TX signal from the attenuator (R43, 47, 57) is amplifi ed by
pre-drive (Q22) and drive (Q26) amplifi ers to obtain RF level
for power module (IC2). The amplifi ed TX signal is applied
to the power amplifier which is a UHF band PA module
composed by two power MOS-FETs. The power-amplified
TX signal is passed through the LPF, power detector,
antenna switch (D62) and LPF, before being applied to the
antenna connector (CHASSIS; J1).

• APC CIRCUITS

Q25

PRE PWR

DRIVE

TX signal from
LO switch (D155, D157)

D29

LIMIT

VT8VT8

Q27

DRIVE

AMP

IC3

AMP

HV

RF POWER DETECTOR (VHF)

C155

L46

C157

C161

C162

C164

L56

D39

APC CIRCUITS

A portion of the TX signal from IC2 is rectifi ed at the power
detector (D42, 52), and converted into the DC voltage
which is in proportion to the RF power, and applied to the
operational amplifier (IC4, pin 2). IC4 is an APC amplifier
for both of V/UHF bands. The TX power setting voltage
“PCON_U” from the D/A converter (IC1, pin 6) is applied
to the pin 3 as a reference. IC4 is rolled as a differential
amplifier which outputs voltage in inverse proportion to
rectified one. When the TX power increased, the rectified
voltage also increased, that causes the decrease of output
voltage of differential amplifier. The decrease of output
voltage of differential amplifi er causes the drop of the gate
voltage of IC2, Thus the TX power maintained to keep stable
level.

TX muting is carried out by TX mute SW (Q36) controlled
by “TX_mute” signal. Applying “TX_mute” signal to the base
terminal of Q36 to turn it ON, 8 V DC appears on the pin 6 of
IC4 and its output voltage downs to 0 V DC to inactivate IC3.

C314

C318

L88

LPFLPF

C326

L92

L96

C330

C186

R154

C198

C202

C203

C212

D47

C227

C226

R201

D59,D75,D77

TX/RX

SW

TX signal from
LO switch (D103)

Q22

PRE PWR

DRIVE

D25

LIMIT

UT8UT8

Q26

DRIVE

AMP

IC2

AMP

HV

TX_MUTE

IC4,Q31,Q36

APC

CTRL

PCON_U PCON_V

L50

C173

C166

C176

C174

TX_MUTE

D53,D61,D62

D42

R166

C199

C221

C214

R176

L61

R178

C224

C231

D52

C265

C275

C273

C272

TX/RX

SW

C296

C303

L77

C297

RF POWER DETECTOR (UHF)LPF HPF

L80

C308

L101

LPF

C342

L104

L108

C346

4 - 5

4-3 FREQUENCY SYNTHESIZER

VCOs

This transceiver has 3 VCOs; Left band VCO, Right band RX
VCO and Right band TX/RX VCO.

LEFT BAND VCO (Q111, D145–147)

This VCO oscillates 1st LO signals for Left band RX and TX
signal for VHF band.

<While receiving>

The VCO output signal is amplifi ed by buffer (Q113) and LO
amplifier (IC44), and applied to the LO filters according to
the RX frequency.

• While Receiving 118–174 MHz signals

LO signals 135.575−255.575 MHz are applied to the divider
(IC43) via LO switch (D150) and attenuator (R706, 710,

711), and divided into 271.15−511.15 MHz signals. The
divided LO signals are buffer-amplified by Q116, and applied
to the left band 1st mixer (IC19) via the LPF (L115, 156,
C809, 812, 816) and another LO switch (D156).

RIGHT BAND RX VCO (Q72, D89, 90)

This VCO oscillates 1st LO signals for right band RX (118–
174 MHz and 810–1000 MHz).

The VCO output signal is amplified by buffer (Q74) and
applied to the LO amplifier (IC45) via VCO switch (D160),
and applied to the LO fi lters according to the RX frequency.

• While Receiving 118–174 MHz signals

LO signals 164.35−220.35 MHz are passed through the LPF
(L123, 125, C529, 534, 539) via LO switches (D107, 159),
and applied to the right band 1st mixer (IC20).

• While Receiving 810–1000 MHz signals

LO signals 381.825−476.82 MHz*
amplifier (IC62) via LO switch (D101). The amplified LO
signals are doubled to 763.65−953.64 MHz*

1

are applied to the LO

2

signals by
being passed through the HPF (L130, 133, C554, 558, 560),
LPF (L151, C794, 796, 799) and HPF (L135, C563, 568).

The doubled LO signals are applied to the right band 1st
mixer (IC20).

• While Receiving 174–260 MHz signals

LO signals 141.15−221.145 MHz are passed through the
LPF (L148, 152, C785, 789, 795, 804) via LO switches (D151,

153), and applied to the left band 1st mixer (IC19).

• While Receiving 375–550 MHz signals

LO signals 135.575−255.575 MHz are doubled to 271.15−

511.15 MHz signals, by being passed through the HPF (L149,
C787, 790, 791), LPF (L151, C794, 796, 799) and HPF
(L153, C800, 807) via LO switches (D152, 154). The doubled
LO signals are applied to the left band 1st mixer (IC19).

<While transmitting>

The VCO output signal is amplifi ed by buffer (Q113) and LO
amplifier (IC44), and applied to the transmit amplifiers via
the LO switches (D155, 157), LPF(L157, C818, 820) and
attenuator (R33, 37, 46).

• VCO CONFIGULATION BY FREQUENCY

LEFT BAND VCO RIGHT BAND RX VCO RIGHT BAND TX/RX VCO

(Q111, D145–147) (Q72, D89, 90) (Q73, D87, 91, 92)

136–174 MHz – 400–470 MHz

Oscillating
Frequency

VCO

Components

(118–174 MHz) 135.575−255.575 MHz 164.35−220.35 MHz –

(174–260 MHz) 141.15−221.145 MHz 381.825−476.82 MHz*

RX

(375–550 MHz) 135.575−255.575 MHz – 353.65−523.17 MHz

TX

RIGHT BAND TX/RX VCO (Q73, D87, 91, 92)

This VCO oscillates 1st LO signals for right band RX (375–
550 MHz).

<While receiving>

LO signals 353.65−523.17 MHz are passed through the
RF mute switch (Q79) and LPF (L131, 134, C562) via LO
switches (D104, 108), and applied to the right band 1st
mixer (IC20).

<While transmitting>

The VCO output signal is amplified by buffer (Q76), and
applied to the LO amplifier (IC45) via the VCO switch
(D102). The amplifi ed LO signals are applied to the transmit
amplifi ers via the LO switch (D103), two HPFs (L124, C527,
532; L159, C533, 535) and attenuator (R43, 47, 57).

1

–

4 - 6

1

*

: 810–1000 MHz for USA

2

*

: 856.35−1046.34 MHz for USA

PLL CIRCUITS

The PLL circuit provides stable oscillation of the transmit
frequency and receive 1st LO frequency. The PLL output
frequency is controlled by the divided ratio (N-data) from the
CPU.

LEFT BAND VCO LOOP

A portion of VCO output signals from the buffer (Q113)
are applied to the PLL IC (IC41) via another buffer (Q112).
The applied signals are
programmable counter according to the control signals
(“L_PLLSTB,” “PLLDATA” and "PLLCK”) from the CPU.
The divided signal is phase-compared with the 12. 8 MHz
reference frequency signal from the reference frequency
oscillator (X5), at the phase detector.

LEFT BAND VCO LOOP

•

PLLCK
PLLDATA
L_PLLSTB

X5

12.8MHz

TCXO

divided at the prescaler and

IC41

PLL

IC

135.575 −255.575 MHz

LOOP

FIL

BUFF

Q112

Q111

D145
D146
D147

BUFF

The phase difference is output from pin 5 as a pulse type
signal after being passed through the internal charge pump.
The output signal is converted into the DC voltage (lock
voltage) by passing through the loop filter (R694, 696–
698, C760–762). The lock voltage is applied to the variable
capacitors (D145 and D146), and locked to keep the VCO
frequency constant.

If the oscillated signal drifts, its phase changes from that of
the reference frequency, causing a lock voltage change to
compensate for the drift in the VCO oscillating frequency.

To the TX amplifiers

Q113

AMP

IC44

or
LO filters

RIGHT BAND RX VCO LOOP

A portion of VCO output signals from the buffer (Q74) are
applied to the PLL IC (IC14) via the VCO switch (D160) and
another buffer (Q112). The applied signals are

divided at
the prescaler and programmable counter according to the
control signals (“R_PLLSTB,” “PLLDATA” and "PLLCK”) from
the CPU. The divided signal is phase-compared with the 15.3
MHz reference frequency signal from the reference frequency
oscillator (X1), at the phase detector.

The phase difference is output from pin 5 as a pulse type
signal after being passed through the internal charge pump.
The output signal is converted into the DC voltage (lock
voltage) by passing through the loop filter (Q61, 62, D86).
The lock voltage is applied to the variable capacitors (D91,

92), and locked to keep the VCO frequency constant.

RIGHT BAND RX AND TX/RX VCO LOOP

•

PLLCK
PLLDATA
R_PLLSTB

TCXO

IC14

15.3MHz

X1

PLL

IC

Q61
Q62
D86

LOOP

FIL

164.350−220.350 MHz

BUFF

−

523.170 MHz

BUFF

Q76

353.65

Q72
D89
D90

Q73
D91
D92
D87

RIGHT BAND TX/RX VCO

A portion of VCO output signals from the buffer (Q76) are
applied to the PLL IC (IC14) via the VCO switch (D102)
and another buffer (Q60). The applied signals are
at the prescaler and programmable counter according to the
control signals (“R_PLLSTB,” “PLLDATA” and "PLLCK”) from
the CPU. The divided signal is phase-compared with the 15.3
MHz reference frequency signal from the reference frequency
oscillator (X1), at the phase detector.

The phase difference is output from pin 5 as a pulse type
signal after being passed through the internal charge pump.
The output signal is converted into the DC voltage (lock
voltage) by passing through the loop filter (Q61, 62, D86).
The lock voltage is applied to the variable capacitors (D91,

92), and locked to keep the VCO frequency constant.

D160

To the TX amplifiers
or
LO filters

Q74

Q60

VCO

SW

D102

VCO

SW

BUFF

AMP

IC45

divided

4 - 7

4-4 POWER SUPPLY CIRCUITS

Voltage from the power supply is routed to whole of the circuit in the transceiver via switches and regulators.

MAIN UNIT

NOISE

FILTER

IC21

5V
REG

IC55,

D164

CURRENT
DETECT

NOISE

FIL

Q83,

D119

5VS
REG

D120

Q84,

5VS
REG

HVHVTX power

amplifiers (IC2, IC3)

IDET

CPU5V

CPU (IC25)
(for current monitoring)

PLL ICs (IC14, IC41),

5VS

D/A converter (IC8),
ALC IC (IC32), etc.

DTMF decoder (IC56),

L5V

Electric volume (IC33),
AF mixer (IC59), etc.

CPU (IC25),
EEPROM (IC22),
Reset IC (IC23), etc.

IC3

+5

REG

+3

REG

+3.2V

5V

CONTROL UNIT

CPU (IC13),
Regulator (Q14, Q15),
Protector/Buffer (IC12), etc.

Reset IC (IC9),
LCD module, etc.

PWR

Q82

PWR

CTRL

Q81

VCC
REG

IC24

+8

REG

5V

Limitter (D165−D168), etc.

AF filter (Q47, Q50),

8V

MIC amplifier (IC28),
APC controller (IC4), etc.

VCC

AF power amplifier (IC38)

4 - 8

4-5 CPU PORT ALLOCATION

PIN

PORT NAME

No.

3

4

MM_MUTE

5

6

R_WN_SEL

7

11

MIC_SENC

17

18

21

R_PLLSTB

L_PLLSTB

22

23

DTCS_SEL

24

25

L_WN_SEL

26

27

28

L_VCO_SHIFT

29

R_PLLSW

30

31

R_UNLOCK

32

33

L_UNLOCK

34

35

36

L_PLLSW

37

AN

DA_SEL

DCONT

MOD_DA

MODSEL

L_AMC

L_R5C

UMMUTE

UTX_C

PLLCK

PLLDATA

VMMUTE

VTX_C

Cut-off frequency shifting signal to the HPF
(IC48).

Cut-off frequency shifting signal to the HPF
(IC48).

MIC mute signal to the MIC mute switch (IC30).
“H”=MIC mute.

ALC amplifier control signal tot the AF
switches (IC29 and IC52).
“H”=ALC amplifi er ON.

2nd IF filter (Right band; Wide/Narrow)
toggling signal.
“H”=Narrow. "L”=Wide.

Microphone sensitivity select signal.
“H”=High sensitivity.

Modulation line switching signal to
the MOD selector (Left band; IC9).
“H”=Modulation enable.

Modulation line switching signal to
the MOD selector (Right band; IC63).
“H”=Modulation enable.

Strobe signal to the PLL IC (Right band;
IC14).

Strobe signal to the PLL IC (Left band;
IC41).

AM-demodulator circuit (Left band) control
signal.
“H”=AM mode (AM-modulator circuit is
activated).

Tone filter switching signal to the LPF
(Q100).
“H”=DTCS mode. “L"=CTCSS mode.

RX circuits (Left band) control signal.
“H”=RX circuits (Left band) is activated.

2nd IF filter (Wide/Narrow) toggling
signal.(Left band)
“H”=Narrow. “L”=Wide."

Modulation mute signal to the MOD
mute switch (Right band; Q64).
“H”=Modulation muted.

Transmitting control signal to the VT8
regulator (Q12, 15).

VCO oscillating frequency shift signal to
the Left band VCO.

Lock-up time control signal to the loop fi lter
(Right band).
“H”=Fast lock-up time.

PLL unlock signal from the PLL IC (Right
band; IC14).

Clock signal to the PLL ICs (Right band;
IC14, Left band; IC41).
(Commonly used for both of the Left and
Right bands.)

Data to the PLL ICs (Right band; IC14, Left
band; IC41).
(Commonly used for both of Left and Right
bands.)

PLL unlock signal from the PLL IC (Left
band; IC41).

Modulation mute signal to the MOD
mute switch (Left band; Q109).
“H”=Modulation muted.

Transmitting control signal to the UT8 regulator
(Q13, 17).
“H”=While transmitting.

Lock-up time control signal to the loop fi lter
(left band).
“H”=Fast lock-up time.

DESCRIPTION I/O

PIN

PORT NAME

No.

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

38

R_UVCO_SEL

R_VVCO_SEL

39

40

L_LO_SW

R_DA_SEL

42

R_AFFIL_SEL

42

R_DET_MUTE

43

L_DA_SEL

44

L_DET_MUTE

45

48

51

52

53

53

55

56

57

61

62

63

64

65

66

68

I

69

70

71

76

I

77

78

79

80

80

82

D5VC

R_AF_MUTE

L_AFFIL_SEL

DA3STB

DA2_STB

DTCS

DTMF

MIC_SEL

DTMSTB

MICUD

R_RSLV

L_RSLV

IDET

R_WXALT

R_DTCS_IN

L_WXALT

L_DTCS_IN

TEMP

SCL

AF_VOL_CK

AF_VOL_DATA

AF_VOL_STB

AF_VOL_RES

PWR

SDA

VCO power control signal to the VCO
select switch (Right band UHF; Q65, 68).
“L”=Right band TX/RX VCO is activated.

VCO power control signal to the VCO
select switch (Right band VHF; Q65, 68).
“L”=Right band RX VCO is activated.

LO filter switching signal to the LO
regulator (Q106).

AF line switching signal to the AF switch
(IC12).

Switching signal to the AF filter (Right
band; Q48).

AF line switching signal to the AF switch (IC16).
“H”=AF mute.

AF line switching signal to the AF switch
(IC11).

AF line switching signal to the AF switch (IC13).
“H”=AF mute.

Power control signal for the optional unit. O

AF mute signal to the SP mute switch (Right
band; Q101).
“H”=AF mute.

Switching signal to the AF fi lter (Left band;
Q47).

Strobe signal to the D/A converter. O

Strobe signal to the electric volume. O

DTCS signal. O

DTMF signal. O

Connected microphone detect signal. I

Strobe signal to the DTMF decoder (IC56). -

[UP]/[DWN] key input. I

While receiving; inputs RSSI
signal (IC18; Right band).
While transmitting; inputs Lock Voltage
from the PLL IC (IC14).

While receiving; inputs RSSI signal
from IF ICl (IC15; Left band).
While transmitting; inputs Lock Voltage
from the PLL IC (IC41).

Current level from the current detector
(IC55, Q164).

Demodulated Weather alert signal from the
WX fi lter (Q47). [USA] only

Demodulated DTCS signals from the
CTCSS fi lter (Q42).

Demodulated Weather alert signal from the
WX fi lter (Q48). [USA] only

Demodulated DTCS signals from the
CTCSS fi lter (Q41).

Transceiver's internal temparature from the
thermal detector circuit (R509).

I/O port for clock signal to the EEPROM
(IC22).

Serial clock signal to the electric volume
IC.

Data signal to the electric volume IC. O

Latch enable signal to the electric volume
IC.

Reset signal to the electric volume IC. O

Power control signal to the PWR controller
(Q82).
“H”=While the power is ON.

Data signal to the EEPROM (IC22). I/O

DESCRIPTION I/O

O

O

O

O

O

O

O

O

O

O

I

I

I

I

I

I

I

I

I/O

O

O

O

4 - 9

PIN
No.

83

85

100

101

102

105

122

123

127

128

129

130

134

135

136

137

138

143

144

PORT NAME

L_AF_MUTE

MIC_PTT

RESET

L_SQL

CL_SFT2

R_SQL

R_DATA

TX_DATA

TX232

RX232

DA_CK

DA_DATA

DA_STB

R_R5C

R400_S

R_RX800

R_AMC

DTMSD

DTMCK

DESCRIPTION I/O

AF mute signal to the SP mute switch
(Q102).

Input port for [PTT] key on the connected
microphone.

Reset enable signal input. I

Noise signal from the IF IC (Left band;
IC15).

Clock frequency shifting signal. O

Noise signal from the IF IC (Right band;
IC18).

Data lines for the control unit. I

Data lines for the control unit. O

Data bus for RS-232C communication. O

Data bus for RS-232C communication. I

Serial clock signal to the D/A converter. O

Serial data to the D/A converter. O

Strobe signal to the D/A converter. O

RX circuits (Right band) control signal. O

Power line control signal to the 375−550 MHz
band RF circuit (Right band).

Power line control signal to the 810−1000
MHz band RF circuit (Right band).

AM-demodulator circuit (Right band)
control signal.

Data to the DTMF decoder (IC56). -

Clock signal to the DTMF decoder (IC56). -

O

I

I

I

O

O

O

4 - 10

SECTION 5 ADJUSTMENT PROCEDURE

5-1 PREPARATION

¤ REQUIRED TEST EQUIPMENTS

When adjusting IC-2820H, following test equipments and JIG cable (modified 8-pin modular jack; see the illust below) are required.

EQUIPMENT GRADE AND RANGE EQUIPMENT GRADE AND RANGE

DC power supply

RF power meter
(terminated type)

Frequency counter

Modulation
Analyzer

JIG CABLE

¤

Controller

Output voltage : 13.8 V DC
Current capacity : More than 20 A
Measuring range : 1–100 W
Frequency range : 100–600 MHz
Impedance : 50

Ω

SWR : Less than 1.2 : 1

Frequency range : 0.1–600 MHz
Frequency accuracy : ±1 ppm or better
Sensitivity : 100 mV or better

Frequency range : 30–600 MHz
Measuring range : DC to ±10 kHz

8-pin modular jack

ytre

i

u

q

w

Audio generator

Standard signal
generator (SSG)

AC millivoltmeter Measuring range : 10 mV to 10 V

Terminator

Attenuator

AUDIO GENERATOR

(300–3000 Hz/1–500 mV)

Frequency range : 300–3000 Hz
Output level : 1–500 mV

Frequency range : 0.1–1 GHz
Output level : 0.1 µV to 32 mV
(–127 to –17 dBm)

Impedance : 50

Ω

Capacity : More than 100 W

Power attenuation : 40 dB
Capacity : More than 100 W

AC MILLIVOLT METER

<SETTING>

Frequency
Level : 20 mV rms*

+−

80 mV rms*

: 1 kHz

1
2

(10 mV to 10 V)

+−

Main unit

JIG cable

To the MICROPHONE CONNECTOR

ENTERING ADJUSTMENT MODE

¤

q
w
e
r
t
y
u
i

8V
MICU/D
EXTMIC
PTT

MICE
MIC

GND
MICIN

y (MIC)

t (MICE)

w (MICU/D)
u (GND)

r (PTT)
u (GND)

22 kΩ

33 kΩ

[PTT]

*
*

q Connect the JIG cable to the MICROPHONE CONNECTOR (see the illust above).
w Push and hold the both of [MAIN•BAND] keys, then turn power ON.

KEY ASSIGNMENTS IN THE ADJUSTMENT MODE

¤

Entering adjustment mode, the function display shows adjustment item and conditions as below.

DUAL BAND TRANSCEIVER

REF

[PWR]

[DIAL] (Right band)

Adjusts the value
for the item manually.

D

N

A

B

N

I

A

M

V/MHz
SCAN

M/CALL

MW

DUP

MONI

NOTE: This display is example only.

TONE
DTMF

LOW
PRIO

M/CALL

MW

V/MHz
SCAN

D

N

A

[MAIN•BAND] (Right band)

B

N

I

A

M

• Stores the set value

• Adjusts the value
for the item automatically.

[V/MHz•SCAN]

[MAIN•BAND] (Left band)

Selects the next adjustment item.

[M/Call•MW]

Selects the previous adjustment item.

1

; except [USA-01]

2

; [USA-01] only

5 - 1