Kenwood Th-f6a User manual

144/220/440MHz FM TRIBANDER / 144/430MHz FM DUAL BANDER

TH-F6A/F7E

B51-8580-00 (S) 798

SERVICEMANUAL

DISASSEMBLY FOR REPAIR.................................................. 2

CIRCUIT DESCRIPTION .......................................................... 4

DESCRIPTION OF COMPONENTS....................................... 14

PARTS LIST............................................................................ 19

EXPLODED VIEW .................................................................. 32

PACKING ................................................................................ 33

ADJUSTMENT ........................................................................ 34

PC BOARD VIEWS

TX-RX UNIT (CONTROL SECTION) ...................................... 59

TX-RX UNIT ............................................................................ 65

TX-RX UNIT (VCO SECTION)................................................ 71

SCHEMATIC DIAGRAM ......................................................... 73

BLOCK DIAGRAM .................................................................. 81

LEVEL DIAGRAM ................................................................... 83

OPTIONS ................................................................................ 85

SPECIFICATIONS .................................................................. 86

CONTENTS

KNOB(ENC)

(K29-5159-03)

WHIP ANTENNA

(T90-0781-05):K

(T90-0789-05):T,E

KNOB(VOL)

(K29-5150-03)

CABINET ASSY

(A02-3620-13):T,E

(A02-3719-13):K

CAP

(B09-0615-23)

FRONT GLASS

(B10-2685-13):T,E

(B10-2723-13):K

KEY TOP

(K29-9107-12)

KNOB(PTT/MONI)

(K29-9108-13)

TH-F6A/F7E

DISASSEMBLY FOR REPAIR

1. How to remove the case assembly from

the chassis:

1. Remove 2 screws (1).

2. Remove 2 knobs (2) and 2 round nuts (3).

3. Remove the SP/MIC jack cover (4).

4. Open the bottom part of case assembly and lift the front

panel from the chassis (5).

2. How to remove the main PCB:

2-1. Control section

1. Remove the SP/MIC jack cover (6).

2. Remove 5 screws (7) and lift and remove the control PCB

(TX-RX A/3).

3. Extract the encoder flat cable from the connector.

2-2. RF section

4. Remove 8 screws (8), and 1 round screw (9), then remove

the RF shield cover. Remove the soldering that connects

the whip antenna and bar-antenna (3 locations).

5. Remove the battery terminal screw (0).

6. Lift and remove the RF PCB (TX-RX B/3).

2-3. PLL/VCO section

7. Remove the soldering (8 locations) that holds the PLL/VCO

shield cover (!) then lift the shield cover.

8. Lift the PLL/VCO PCB upward to seperate it from the main

PCB.

Fig. 1

TH-F6A/F7E

DISASSEMBLY FOR REPAIR

3. Soldering the Bar antenna wires

Before solding the bar antenna wires, form the wires as

shown in the figure 2.

Then solder the wires to lands on the PCB.

Fig. 2

4. Removing a relay terminal

Insert a screw driver between the relay terminal and its

holder.

Then pull the relay terminal as shown in the figure 3.

5. Assembling a release latch

Place a coil spring(1) on the release latch(2) as shown in

the figure 4.

Then insert a shaft(3) into the release latch.

Push the above assembly into the rear panel while the

end of coil spring is hooked to the “A” tab.

Fig. 4

Notch Notch

6. Caution at the time of reassembling

While you are reassembling the battery terminal holder

(J19-5428) and the packing (G53-1532), confirm that the

packing is reassembled at the condition that any swell is

not occurred on it. If the packing is assembled with any

swell, width of body also becomes expansive.

J19-5428G53-1532

Swell not

allowed

Fig. 3

Fig. 5

TH-F6A/F7E

CIRCUIT DESCRIPTION

1. A band receiver system

1-1. Receiver circuit

The A band can receive signals in two bands: VHF (220 MHz

band <K type only>) and UHF (K type: three bands). It uses

FM receive mode only, and uses double conversion with the

first IF of 59.85 MHz and the second IF of 450 kHz.

The first amplifier is divided into two bands: 137 MHz -

173.995 MHz (216 MHz - 260 MHz <K type only>) and 410 MHz

- 470 MHz. The incoming signal from the antenna passes

through a low-pass filter and a duplexer, and goes to an

independent amplifier (Q63, Q62) for each band.

1-1-1. VHF band frontend

The incoming signal from the antenna passes through a

VHF band low-pass filter and a duplexer, passes through a

band-pass filter where it is tuned with varicaps (D76, D77),

and goes to the first amplifier (Q63). Unwanted signal

components are eliminated by a two-pole band-pass filter

where it is tuned by varicaps (D72, D75, D81, D83), and the

signal goes to the common mixer (Q45) for the A band. (K

type only: For 200MHz band reception, D74 is turned off with

a control signal to improve band-pass filter coupling and

ensure pass bandwidth.)

ANT

Q45

MT6C

04AE

BPF

APC&VTUNEA

MIX

Q63

3SK320

RFAMP BPFBPF

MPU

D76

D77

D72,D75

D81,D83

LPF

1st IF

59.85MHz

Fig.1

1-1-2. UHF band frontend

The incoming signal from the antenna passes through a

UHF band low-pass filter and enters the first amplifier (Q62)

common to both A and B bands. The amplified signal is

distributed by L distributors (L95, L96) and goes to the LC filter

module (L92). Unwanted signal components are eliminated

by the filter, and the resulting signal passes through another

band-pass filter and enters the mixer (Q45).

ANT

BPF

Q62

3SK320

RFAMP

L95

L96

HPF

LPF

L92

Q45

MT6C

04AE

MIX

1st IF

59.85MHz

BPF

LC FILTER

MODULE

1-1-3. Circuits following IF

The signal heterodowned to the first IF of 59.85 MHz by the

mixer (Q45) passes through a 15kHz MCF (XF2) and unwanted

signal components are eliminated. The resulting signal is

amplified by the IF amplifier (Q43) and goes to the FM IC (IC7).

The FM IC heterodowns it to the second IF of 450 kHz. Then,

the signal passes through a 15kHz external ceramic filter (CF4)

and goes to the FM IC again. The signal amplified by the IF

amplifier built into the IC is demodulated by the quadrature

FM demodulation circuit using a discriminator (CD1) and

converted into an audio signal and output.

The FM modulation signal output from the FM IC passes

through a low-pass filter consisting of a resistor and a capacitor

and is output to the control section. The demodulation signal

input to the control section goes to the electronic volume

(IC706, pin 13) to adjust the audio balance with the B band.

The output signal is amplified by the operational amplifier

(IC717), passes through an active filter consisting of Q719 and

Q717, and goes to the audio amplifier (IC707). The signal

amplified to a higher power by the audio amplifier becomes

the final output signal from the set and output through the

internal speaker or speaker output pin (J701).

Q45

MT6C

04AE

MIX

LO X3

IC7

XF2

TCXO

Q44

2SC

4915

IFAMPMCF

Q43

2SC

5108(Y)

19.8MHZ CF4

4.50KHz

LPF

IC700

BAF

IC707

Q719

Q717

AUDIO

AMP

DE EMPHASIS

IC717

AMP

J701

Fig.3

Fig.2

1-2. Mixer local oscillator

1-2-1. First mixer

The local oscillator signal for the first mixer is supplied from

the VCO-PLL circuit.

1-2-2. Second mixer

The local oscillator signal for the second mixer is a 59.4

MHz signal that is produced by multiplying the 19.8MHz TCXO

(X1) oscillator output with a multiplier (Q44).

2. B band receiver system

2-1. Receiver circuit

The B band has a broadband receiver circuit configuration

and implements broadband reception of 100 kHz to 1.3 GHz.

FM/AM/SSB/CW reception is possible in the range 100 kHz to

29.7 MHz, and FM/wide FM/AM/SSB/CW reception is possible

in the range 29.7 MHz to 1.3 GHz. The FM/AM receiver circuit

uses double conversion with the first IF of 57.6 MHz and the

second IF of 450 kHz. The SSB/CW receiver circuit uses triple

conversion with the first IF of 57.6 MHz and the second IF of

450 kHz. The wide FM receiver circuit uses single conversion

with the IF of 10.8 MHz.

TH-F6A/F7E

CIRCUIT DESCRIPTION

Fig.4

The first amplifier is divided into four bands: 100 kHz - 50

MHz, 50MHz - 108MHz, 108 MHz - 265 MHz, 265 MHz - 600

MHz, and 600 MHz - 1.3 GHz. The incoming signal from the

antenna passes through a low-pass filter and a duplexer, and

goes to an independent amplifier for each band. Then, the

signal goes to the second common broadband amplifier (IC10)

and its output is fed to the mixer (Q28) and heterodowned to

the first IF.

2-1-1. FM/AM receiver circuit

The signal heterodowned to the first IF of 57.6MHz passes

through a 15kHz MCF (XF1), and unwanted signal components

are eliminated. The resulting signal is amplified by the IF

amplifier (Q26) and goes to the FM IC (IC5). The FM IC

heterodowns it to the second IF of 450 kHz. In FM mode, the

signal passes through a 12.0kHz external ceramic filter (CF3)

and goes to the FM IC. The signal amplified by the internal IF

amplifier is demodulated by the quadrature FM demodulation

circuit using a coil (L19) and converted into an audio signal

and output. In AM mode, the signal passes through a 4kHz

external ceramic filter CF1 and goes back to the FM IC. It is

amplified by the AM AGC amplifier built in the FM IC, an audio

output from the FM IC as an audio signal.

2-1-4. AM bar antenna receiver circuit

This unit incorporates an AM bar antenna, and either the

bar antenna or the supplied antenna can be selected in the

520kHz-1.8MHz (SW) and 3.5MHz-10.1MHz (MW) bands (the

initial value: bar antenna). The bar antenna has two kinds of

tuners for SW and MW tuning, one of which is selected with a

switching FET (Q32, Q48, Q52). The antenna is tuned with a

varicap (D60) for AM tuning to select a desired signal. The

signal from the bar antenna is amplified by and its impedance

is converted by the buffer amplifier (Q59), and the resulting

signal goes to the common mixer (Q28) for the B band. The

signal is routed over the same path for AM demodulation as

for the supplied antenna after leaving the mixer.

19.05MHZ

FINE2

D20,24

KV1566J

TUNE

IC4

TA4101F

SSB DET

SSB/CW

Q22,29

UPA672T

IC5

TK10931V

SMB

SQB

Q23

LMX

OSCILLATOR

453KHz

CF1

450KHz

CF3

CF2

10.8MHz

D25

DAN

235E

TUNE

D29

HVC

376B

Q27

2SC

4915

OSCILLATOR

Q26

2SC

4915

IF AMP

Q28

MT6C

03AE

MIX

FINE1

UHF(600~1300)

UHF(265~600)

VHF(108~265)

IC10

MPC2746TB

AMP

57.6MHz

XF1

10.8MHz

MCF

Q24

2SC

4915

CF5

Q28

MT6C

03AE

IC10

MPC2746TB

AMP

D57

HSC277

TUNE

D60

KV1566J

BAR

ANT

Q6,Q4

Q48,52

2SK1824

Q32

2SK1830

MIX

Q59

3SK320

RF AMP

Fig.5

2-1-5. Audio signal

The FM and AM demodulation signals output from the FM

IC (IC5) pass through a low-pass filter consisting of a resistor

and a capacitor, and goes to the switching FET (Q29), from

which a switched signal is output to the control unit. The

SSB/CW demodulation signal passes through an RC LPF,

connects to the Q29 output section, and output to the control

unit through a line common to all modes. The demodulation

signal input to the control unit goes to the electronic volume

(IC706, pin 16), the audio balance output with the A band is

restricted, then the signal is output. It joins the A band

demodulation signal and is processed in the same manner

for both A and B bands.

signal demodulated by the diode detection circuit is output.

2-1-2. SSB/CW receiver circuit

In SSB/CW mode reception, the signal takes the same path

to CF1 as in AM mode. The signal input to the FM IC again is

amplified by the AM AGC amplifier in the FM IC, then output

from the AM IF output pin. The signal is fed to the third mixer

(IC4) and converted to an audio signal and output.

2-1-3. Wide FM receiver circuit

The signal converted to the first IF of 10.8 MHz passes

through a ceramic filter CF5 for wide FM, and is amplified by

the IF amplifier (Q24). The signal passes through ceramic filter

CF2 again to eliminate unwanted signal components, and goes

to the FM IF input (pin 7) of the FM IC. The input signal is

amplified by the IF amplifier in the IC, demodulated by the

quadrature FM demodulation circuit using an L18 coil, and

TH-F6A/F7E

CIRCUIT DESCRIPTION

FINE2 D20,24

KV1566J

IC706

M62364

TUNE IC4

TA4101F

SSB DET

SSB/CW

Q22,29

UPA672T IC5

TK10931V

SW FM

SMB

SQB

Q23

LMX

OSCILLATOR

453KHz

CF1

450KHz

CF3

CF2

10.8MHz

D25

DAN

235E

2-2. Mixer local oscillator

2-2-1. First mixer

The local oscillator signal for the first mixer is supplied from

the VCO-PLL circuit. To offset according to modes, the PLL

switching frequency changes in FM/AM/CW, USB, LSB.

1st LOCAL (PLL Switching Frequency)

Fig.6

FM/AM CW USB LSB

UPPER Per 5kHz FM-2.5kHz FM-4.5kHz FM-0.5kHz

LOWER Per 5kHz FM-2.5kHz FM-4.5kHz FM-0.5kHz

2-2-2. Second mixer

The local oscillator signal of the second mixer uses

57.15MHz which is three times as high as the 19.05MHz crystal

oscillator (X3) output. This local oscillator signal is used to (i)

implement fine steps during fine tuning and (ii) offset during

SSB/CW reception.

2rd LOCAL (Oscillator Frequency)

(i) Fine tuning function

When the fine tuning function is ON, the PLL comparison

frequency is 5 kHz (5kHz step). The "receive frequency of

10Hz steps as a set" is implemented by operating the local

oscillator signal of the second mixer in 33.3Hz steps in the

5kHz frequency range. The frequency is varied by 57.15

MHz +/- 2.5 kHz by changing the voltage applied to the

varicap (D29) installed in the local oscillator circuit.

(ii) Mode offset

The IF frequency is adjusted by 2 Hz in SSB mode so that

the demodulated signal passes through the center of the

4kHz ceramic filter (CF1). The frequency is adjusted by

varying the local oscillator frequency.

FM/AM

CW(Fine Tuning)

USB(Fine Tuning) LSB(Fine Tuning)

UPPER 57.15MHz

57.15MHz+2.5kHz

57.15MHz-2.5kHz

LOWER 57.15MHz

57.15MHz+2.5kHz

57.15MHz-2.5kHz

2-2-3. Third mixer

The third mixer (IC4) works in SSB/CW mode only. The

local oscillator signal of 450 kHz +/- 2 kHz is produced in SSB

mode to restore 2kHz correction (offset), and the signal of 450

kHz - 800 Hz is produced to generate an 800Hz beat frequency

in CW mode. A demodulation signal is produced in SSB, and

a 800Hz beat signal is produced in CW.

3rd LOCAL (Oscillator Frequency)

FM/AM CW USB LSB

UPPER 450kHz

450kHz+800Hz 450kHz+2kHz 450kHz-2kHz

LOWER 450kHz

450kHz+800Hz 450kHz-2kHz 450kHz+2kHz

2-3. AGC circuit

The AGC is controlled by using the output from the RF AGC

built into the FM IC (IC5). The AGC is controlled by controlling

the bias current of the IF amplifier (Q26) and the forward

current of the pin diode (D32) for the attenuater. In non-FM

mode, the AM AGC circuit built-into the FM IC is also used.

3. Control

3-1. Reset and backup circuits

The CPU reset signal is generated with the CR time constant

by detecting a rising edge of the M4 line voltage with the

voltage detection IC (IC709). If the voltage supplied to the TH-

F6/TH-F7 decreases and the M4 line voltage falls below the

detection voltage of the voltage detection IC (IC710), the CPU

(IC705) detects it through the interrupt pin, backs up data in

the EEPROM (IC704), and shuts the power off.

3-2. Voltage detection processing

The voltages are measured through the A/D port of the CPU

(IC705) for processing. The battery voltage is supplied through

a resistor, and a warning sound is produced when an abnormal

power supply voltage (17.5 to 22.0 V) is applied to the battery

meter during transmission. The squelch voltage is input from

the IF IC, and a change in the noise voltage is detected to

control squelch. The S meter voltage is input from the IF IC to

control the S meter display. Thermistor voltage (temperature)

detection, remote control microphone key operation, VOX

voltage monitoring, and TONE/DCS decoding are performed

through the A/D port.

3-3. VOX

The signal output from the microphone amplifier (IC702) is

amplified by Q701, rectified/integrated by D709 to convert to

DC voltage, and monitored through the A/D port of the CPU

(IC705) to perform VOX processing.

3-4. Battery save

The CPU (IC705) controls Q728 through the SAVE port to

save battery power.

3-5. LED drive circuit

The CPU (IC705) controls Q709 to turn LEDs on to illuminate

the LCD and keys. The ON AIR/BUSY LED is directly controlled

through the open drain port of the CPU (IC705).

* During fine tuning, it changes with 33.3 Hz step from PLL

Switching Frequency to the next Switching Frequency.

PLL Switching Frequency

* Perform Mode OFFSET

Oscillator Frequency

Table.2

Table.1

Table.3

* PLL Switching Frequency changes with the modes.

TH-F6A/F7E

CIRCUIT DESCRIPTION

3-6. Key/encoder input circuit

The PWR key is assigned to an interrupt port. The PTT key

is assigned to another interrupt port. The other keys and

destination diodes form a 5x6 matrix and pressing a key is

detected by scanning the matrix by software. The encoder

reads data through the interrupt port.

3-7. CTCSS/DCS

The encode signal is output from the D/A port of the CPU

(IC705) by software. The signal level is adjusted with an

electronic VR (IC706) and the signal is divided into VCO and

TCXO and modulated like a 9600bps packet signal.

The audio signal from the IF IC passes through the IC712/

IC711 waveform rectification circuit and enters the A/D port

of the CPU (IC705). The CPU detects that the specified CTCSS

tone frequency and DCS code are detected and controls

muting.

TH-F6A Frequency Construction

A band RX Double Super Heterodyne

3-8. DTMF

The DTMF signal is output from the D/A port of the CPU

(IC705) by software means. The signal is mixed with a signal

at the input side of the audio amplifier (IC707) and output as a

monitor tone. It is mixed with a modulation signal at the input

side of the preemphasis (IC701) and used to as a transmit

signal.

3-9. Serial control

The REM/PTT terminal of the speaker mic jack (J701) is

switched by the CPU (IC705) and functions as TXT/RXD to

communicate with a personal computer.

4. PLL • VCO

The TH-F6/TH-F7 has two PLL loops and a total of four VCOs,

two for each PLL loop. The PLL is divided for A band reception,

B band reception and transmission. Each VCO has oscillator

frequency shift control. For relationships between VCO

oscillator frequencies and shifts, see Table 4-11.

TH-F6A Frequency Construction

2nd

Mixer 1st IF Amplifier1st Mixer2nd IF

VCO2nd LO

Audio

VCO Devider Amplifier

Fig.7

1st Mix.

1st IF

[MHz]

2nd LO

[MHz]

2nd

Mix.

2nd IF

[kHz]

137.000 173.995 196.850 233.845 Upper 59.85 59.4 Lower 450

216.000 259.995 275.850 319.845 Upper 59.85 59.4 Lower 450

410.000 469.995 350.150 410.145 Lower 59.85 59.4 Lower 450

RX Freq. Range

[MHz]

VCO Oscillation

[MHz]

Table.4

Band

[MHz] Devide

144 144.000 147.995 576.000 591.980 4

220 222.000 224.995 444.000 449.990 2

440 438.000 449.995 438.000 449.995 1

Transmission

Frequency Range

[MHz]

VCO Oscillation

[MHz]

Fig.8

Table.5

TH-F6A/F7E

* TH-F6A Frequency Construction

B band RX FM mode Double Super Heterodyne

2nd

Mixer 1st IF Amplifier

1st

Mixer

2nd IF

Devider

Multiplyer

2nd LO VCO

Audio

B band RX WFM mode Single Super Heterodyne

1st IF 1st

Mixer

Devider

Multiplyer

VCO

Audio Amplifier

CIRCUIT DESCRIPTION

Multiply Devide 1st Mix.

1st IF

[MHz]

2nd LO

[MHz] 2nd Mix.

2nd IF

[kHz]

0.100 22.995 461.600 644.760 1 8 57.700 80.595 Upper 57.6 57.15 Lower 450

23.000 103.995 322.400 646.380 1 4 80.600 161.595 Upper 57.6 57.15 Lower 450

104.000 266.995 323.200 649.190 1 2 161.600 324.595 Upper 57.6 57.15 Lower 450

267.000 409.995 324.600 467.595 1 1 324.600 467.595 Upper 57.6 57.15 Lower 450

410.000 469.995 352.400 412.395 1 1 352.400 412.395 Lower 57.6 57.15 Lower 450

470.000 591.995 527.600 649.595 1 1 527.600 649.595 Upper 57.6 57.15 Lower 450

592.000 706.995 534.400 649.395 1 1 534.400 649.395 Lower 57.6 57.15 Lower 450

707.000 707.995 382.300 382.798 2 1 764.600 765.595 Upper 57.6 57.15 Lower 450

708.000 851.995 325.200 397.198 2 1 650.400 794.395 Lower 57.6 57.15 Lower 450

852.000 868.995 454.800 463.298 2 1 909.600 926.595 Upper 57.6 57.15 Lower 450

869.000 896.995 405.700 419.698 2 1 811.400 839.395 Lower 57.6 57.15 Lower 450

897.000 922.995 477.300 490.298 2 1 954.600 980.595 Upper 57.6 57.15 Lower 450

923.000 938.995 432.700 440.698 2 1 865.400 881.395 Lower 57.6 57.15 Lower 450

939.000 1009.995 498.300 533.798 2 1 996.600 1067.595 Upper 57.6 57.15 Lower 450

1010.000 1299.995 476.200 621.198 2 1 952.400 1242.395 Lower 57.6 57.15 Lower 450

RX Freq. Range [MHz] VCO Oscillation [MHz] 1st LO

Fig.9

Table.6

Multiply Devide 1st Mix.

1st IF

[MHz]

29.700 54.995 324.000 526.360 1 8 40.500 65.795 Upper 10.8

55.000 91.995 353.600 649.560 1 8 44.200 81.195 Lower 10.8

92.000 130.795 324.800 479.980 1 4 81.200 119.995 Lower 10.8

130.800 150.995 566.400 647.180 1 4 141.600 161.795 Upper 10.8

151.000 309.995 323.600 641.590 1 2 161.800 320.795 Upper 10.8

310.000 449.995 320.800 460.795 1 1 320.800 460.795 Upper 10.8

450.000 659.995 439.200 649.195 1 1 439.200 649.195 Lower 10.8

660.000 1299.995 324.600 644.598 2 1 649.200 1289.195 Lower 10.8

RX Freq. Range [MHz] VCO Oscillation [MHz] 1st LO

Table.7

Fig.10

TH-F6A/F7E

CIRCUIT DESCRIPTION

* TH-F7 Frequency Construction

A band RX Double Super Heterodyne

2nd

Mixer 1st IF Amplifier1st Mixer2nd IF

VCO2nd LO

Audio

Fig.11

Table.8

1st Mix.

1st IF

[MHz]

2nd LO

[MHz]

2nd

Mix.

2nd IF

[kHz]

144.000 145.995 203.850 205.845 Upper 59.85 59.4 Lower 450

430.000 439.995 370.150 380.145 Lower 59.85 59.4 Lower 450

RX Freq. Range

[MHz]

VCO Oscillation

[MHz]

Band

[MHz] Devide

144 144.000 145.995 576.000 583.980 4

440 430.000 439.995 430.000 439.995 1

Transmission

Frequency Range

[MHz]

VCO Oscillation

[MHz]

Fig.12

Table.9

TH-F7 Frequency Construction

TH-F6A/F7E

CIRCUIT DESCRIPTION

* TH-F7 Frequency Construction

B band RX FM mode Double Super Heterodyne

2nd

Mixer 1st IF 1st

Mixer

2nd IF

Devider

Multiplyer

2nd LO VCO

Audio Amplifier

B band RX WFM mode Single Super Heterodyne

1st IF Amplifier