Kenwood TK-481, TK-480 User Manual

Document Copyrights

form or by any means, electronic, mechanical, photocopying, recording, or otherwise, for any purpose without the prior written permission of Kenwood.

Disclaimer

While every precaution has been taken in the preparation of this manual, Kenwood assumes no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from the use of the information contained herein. Kenwood reserves the right to make changes to any products herein at any time for improvement purposes.

800MHz/900MHz FM TRANSCEIVER

TK-480/48 1

SERVICE MANUAL

REVISED II

This service manual applies to products with 30100001 or subsequent serial numbers.

Whip antenna (T90-0636-25) : TK-480 (T90-0640-25) : TK-481

Knob (ENC) (K29-5232-03)

Knob (VOL) (K29-5231-03)

Panel assy (A62-0981-04)

Badge (B43-1139-04)

Knob (PTT) (K29-5157-03)

Cabinet assy (A02-3659-03) : K2

Packing (G53-0841-02) : K2

CONTENTS

GENERAL ............................................................ 2

SYSTEM SET-UP ................................................ 2

OPERATING FEATURES .................................... 3

REALIGNMENT................................................. 11

CIRCUIT DESCRIPTION.................................... 14

SEMICONDUCTOR DATA................................ 20

DESCRIPTION OF COMPONENTS .................. 23

PARTS LIST ....................................................... 24

EXPLODED VIEW ............................................. 30

PACKING ........................................................... 31

ADJUSTMENT .................................................. 32

TERMINAL FUNCTION .................................... 40

PC BOARD VIEWS

DISPLAY UNIT (X54-3210-XX) .................... 41

TX-RX UNIT (X57-5630-XX) ......................... 47

SCHEMATIC DIAGRAM ................................... 53

BLOCK DIAGRAM............................................. 57

LEVEL DIAGRAM (TK-480) .............................. 59

LEVEL DIAGRAM (TK-481) .............................. 60

KNB-16A/17A (Ni-Cd BATTERY) ..................... 61

KPG-36 (PROGRAMMING INTERFACE CABLE)

KSC-19 (CHARGER) .......................................... 61

SPECIFICATIONS.............................................. 62

.... 61

Photo is TK-480/481 K2 type. (Produced in Singapore)

CAUTION When using an external power connector, please use with maximum final module protection of 9V.

TK-480/481

GENERAL / SYSTEM SET-UP

INTRODUCTION

SCOPE OF THIS MANUAL

This manual is intended for use by experienced technicians familiar with similar types of commercial grade communications equipment. It contains all required service information for the equipment and is current as of this publication date. Changes which may occur after publication are covered by either Service Bulletins or Manual Revisions, which are issued as required.

ORDERING REPLACEMENT PARTS

When ordering replacement parts or equipment information, the full part identification number should be included. This applies to all parts : components, kits, and chassis. If the part number is not known, include the chassis or kit number of which it is a part and a sufficient description of the required component, for proper identification.

PERSONNEL SAFETY

The following precautions are recommended for personnel safety :

• DO NOT transmit until all RF connectors are secure and

any open connectors are properly terminated.

• SHUT OFF this equipment when near electrical blasting caps or while in an explosive atmosphere.

• This equipment should be serviced by only qualified technicians.

SERVICE

This radio is designed for easy servicing. Refer to the

schematic diagrams, printed circuit board views, and alignment procedures contained within.

NOTE

WE CANNOT guarantee oscillator stability when using

channel elements manufactured by companies other than KENWOOD or its authorized agents.

You must use the KPG-49D to program TK-480/481 trans-

ceivers with a serial number of 30100001 or greater. You cannot use the KPG-35D for those radios.

TK-480/481 transceivers with a serial number of

30100001 or greater have a red triangle in the KENWOOD logo label (B43-1139-04) on the front panel. You will also find the model name plate marked as “Ver 2.0” on the rear of the transceiver.

Unit TX-RX unit Display unit

Model &

destination 0-10 0-11 0-10 0-11

TK-480

TK-481

Note X57-5630-XX/X54-3210-XX : Produced in Singapore

X57-5630-XX X54-3210-XX

K ✓✓ K2 ✓✓ LOC : 44.395MHz ✓ K ✓✓ K2 ✓✓ LOC : 44.395MHz ✓

Frequency range Remarks QT/DQT DTMF Charger Battery 16 key

806~870MHz

896~941MHz

SYSTEM SET-UP

Merchandise received

License and frequency allocated by FCC

Choose the type of transceiver

Transceiver programming

IF1 : 44.85MHz

Frequency range (MHz) RF power Type

TX 806~825 2.5W TK-480 K,K2

851~870 RX 851~870 TX 896~902 TK-481 K,K2

935~941

RX 935~941

A personal computer (IBM PC or compatible), programming interface (KPG-36), and programming software (KPG-49D) are required for programming. (The frequency, trunked system features, conventional system features, TX power HI/LOW, and signaling data are programmed for the transceiver.)

✓✓Option ✓

–

Are you using the speaker microphone?

Delivery

YES

KMC-25

Speaker microphone

(Option)

OPERATING FEATURES

TK-480/481

1. Operation Features

The TK-480/481 is an 800/900MHz band EFJ LTR™-compatible trunked radio designed to operate in both trunked and conventional modes. The programmable features are summarized.

Model Trunking mode

Conventional mode

This model can handle up to 32 systems with up to 250 groups in each system. The transceiver can be used in both trunked mode and conventional mode. Systems, groups, and their functions are programmed.

2. Transceiver Controls and Indicators

2-1. Physical Layout

Microphone Speaker

1 2 3

Volume/Power switch

Transceiver Power and Volume switch. Turn clockwise to switch On the transceiver. Turn counterclockwise fully to switch OFF the transceiver. Also adjusts the volume level. When the power is switched off, all the parameters, such as the system and group, are stored in memory. When the power is switched on again, the system returns to the previous conditions.

Auxiliary (orange) key (Programmable)

Battery pack release catch

Push down to release the battery pack. See Installing the Ni-Cd Battery Pack.

MONITOR key* (Programmable)

PTT (Push-To-Talk) key

Press this key, then speak into the microphone to call a station.

LAMP key* (Programmable)

TX/BATT indicator

This red LED lights during transmission (it does not light during busy or when transmit is prohibited). If the battery voltage falls below the programmed voltage during transmission, the brightness of this indicator decreases at intervals of about one second, so it can be used as the battery voltage alert function.

S, A, B, and C key (Programmable)

Note : The transceiver is also available without the DTMF

keypad (

2-2. Panel controls

The key on the top and front panel is momentary-type push buttons. The functions of these keys and knob are explained below.

Antenna connector

Connect the supplied antenna here.

System or Group selector knob (Programmable)

Turning the system (or group) selector knob clockwise

increases the system (or group) number by one. Turning

the knob in the counterclockwise direction decreases the

system (or group) number by one.

After the system number (or group number) reaches the

highest system number (or group number), it goes back

to lowest system number (or group number).

System numbers (or group numbers) not set are skipped.

Caution : The FPU (KPG-49D) allows selecting between

system selector and group selector.

DTMF keypad (keypad model only)

Press the keys on the telephone keypad to send DTMF tones.

Universal connector

Connect the external KMC-25 speaker/ microphone (optional) here. Otherwise, keep the supplied cover in place.

* : MONITOR and LAMP are arbitrary names chosen for these buttons. They can be used for any of the auxiliary functions.

2-3. Programmable keys

The FPU (KPG-49D) enables programmable keys to se-

lect the following functions.

Auto Tel, AUX(only when Voice Scrambler is not selected), DTMF ID (BOT), DTMF ID (EOT), Display Character, Emergency (only AUX key), Function, Group Down, Group Up, Home Group, Key Lock, Lamp, Memory (RCL/STO), Memory (RCL), Memory (STO), Monitor A, Monitor B, Monitor C, Monitor D, Redial, RF Power Lo, Scan, Scan Del/Add, Scan Temporary Delete, Scrambler (Only when Voice Scrambler is selected), SP Attenuation (Only MIC switch), System Down, System Up, TEL Disconnect and none.

These functions the FPU programs to the function keys are described in the following sections.

TK-480/481

OPERATING FEATURES

■ Auto TEL

Automatically connects available repeaters that are connected to telephone circuits when operating as LTR system. The time allocated to search for available repeaters is 60 seconds, after which connection failure occurs, a DTMF tone is output and the function terminates.

If connection to an available circuit is made, only ID 253, EOT or hang-up time-out can terminate the function.

■ AUX

This function can be programmed when the voice scrambler board is not installed.

If this key is pressed, an underscore (“_”) appears at the extreme right of the LCD and AUX port which is inside of the transceiver turns to the active level. If pressed again, the underscore disappears and the AUX ports turns to the deactive level.

■ DTMF ID (BOT)

Pressing this key in Conventional mode, automatically sends the preset Connect ID.

■ DTMF ID (EOT)

Pressing this key in Conventional mode, automatically sends the preset Disconnect ID.

■ Display character

This key switches the LCD display between the system/ group number and system/group name.

■ Emergency

Pressing this key for longer than the programmed “Emergency Key Delay Time” causes the transceiver to enter the emergency mode. The transceiver jumps to the programmed “Emergency System/Group” and transmits for the programmed “Active Time”.

The transceiver disables mic mute while transmitting. After finishing transmission, the transceiver receivers for the programmed “Interval Time”. The transceiver mutes the speaker while receiving. Following the above sequence, the transceiver continues to transmit and receive.

If “Man Down Switch” has been programmed on the radio and the switch is activated, the radio enters Emergency mode after the specified “Man Down Delay Time” expires.

■ Key lock

Pressing this key causes the transceiver to accept entry of only the [Function], [Key Lock], [PTT], [Lamp], [Monitor A], [Monitor B], [Monitor C], [Monitor D], and [Emergency] keys.

The locked keys also include the tuning control.

■ Lamp

This key illuminates the LCD and keys on the front panel. When the key is pressed, the LED lamp goes on.

When it is released, the lamp goes off after about five seconds. If any key is pressed while the LED lamp is on, the lamp is kept on for five seconds.

■ Memory

This key allows DTMF memory data to be recalled; up to 32 memories each with a memory dial of up to 16 digits and an A/N of up to 10 digits per memory.

■ Monitor

Used to release signalling or squelch when operating as a conventional. It is also used to reset option signalling.

■ Redial

Pressing this key when System/Group is shown, displays the previously transmitted DTMF code. Pressing [PTT] at this time, transmits the code that is currently displayed.

■ RF power low

Used to temporarily switch transmission output to low power. Turning the function on enables:

Hi→Low, Low→Low

Key states are backed up, except in the PC mode when they are reset.

■ Scan

Press this key starts scanning. Pressing this key stops scanning.

■ Scan Del/Add

Used to select whether system scan routines are used during system scan. Each pressing of the key (to ON) toggles between lockout and lock. The scan routine is started when on lock. The DEL indicator flashes when the system is on lockout.

■ Function

Pressing this key causes the transceiver to display “FCN”. Then, pressing a DTMF key causes the corresponding programmed function to start. This key may be convenient when using many functions with the 12-key keypad (K2 type).

■ Group up/down

When the key is pressed each time, the group number to be selected is incremented/decremented and repeats if held for one second or longer.

■ Home group

Each pressing of the key selects a preset system/group.

■ Scan temporary delete

This key is temporarily deleted a system being scanned. If you press this key when scan is stopped (when a call is being received from another station), the system is temporarily deleted and scanning restarts.

This key operates even when “Scan Type” is set to “List Type System Scan”.

■ Scrambler

If a scrambler code (1 to 4) has been set in the FPU, an underscore (“_”) appears at the extreme right of the LCD display when scrambler is active. Pressing this key changes ON/OFF of scramble operation.

Holding this key down for 2 seconds sets Scramble Code Select Mode.

OPERATING FEATURES

TK-480/481

■ System up/down

When the key is pressed each time, the system number to be selected is incremented/decremented and repeats if held for one second or longer.

■ Telephone disconnect

Pressing this key ends an RIC connection (disconnects the telephone line).

■ None

Sounds error operation beep, and no action will occur.

Use this function when the transceiver is required to be more simple operated.

2-4. Display

Sub display

Displays the system, channel and group numbers. Also

displays various functions, such as TA.

Alphanumeric display

The twelve-character dot matrix alphanumeric display shows the system and group numbers. You can program system and group names with up to ten characters in place of these numbers. The left display is used as a delete indicator ( call (

) or scrambler ( _ ) function. The delete/add indicator shows the systems locked out of the scanning sequence. Selective call and scrambler are optional functions that can be programmed.

) and the right is used for the selective

3. Scan Operating

3-1. System scan

System scan can be selected with the “Scan” key by pro-

gramming the scan feature. When the “Scan” key is pressed and the “SCN”’ mark appears, scan mode in entered. Scanning starts from the system following the currently displayed system. When a call is received, scanning stops, and the system and group are displayed.

When the system knob or programming key is touched

during scanning, the scan stops and the revert system or group can be changed. Scanning resumes one second after the key is released.

System scan consists of the following 2 types.

■ Fix system scan

All the set systems except locked-out ones are scanned.

If the DEL/ADD feature is assigned to the programmable key, it can be controlled from the front panel.

P (Priority) indicator

The P indicator ( ) appears when a selected channel is programmed as priority, in conventional operation.

MON (Monitor) indicator

The MON indicator appears when the button programmed as MONITOR is pressed.

SVC (Service) indicator

This icon is not used on this transceiver.

SCN (Scan) indicator

The SCN indicator appears when using Scan mode.

LO indicator

Appears when low power is selected.

Handset indicator

The handset indicator ( ) appears when the selected group is programmed as telephone IDs.

MAIL indicator

Flashes when a status message (FleetSync™) is received. Lights when a status message is stored in the stack memory.

■ List type system scan

A scan list can be set for each system. The list to be scanned can be changed by changing the

display system.

If many system have been set, the scan speed can be

increased by narrowing the systems to be scanned with scan lists.

3-2. System lockout

The system lockout feature is used to lock systems out

of the scan sequence, and can be selected by programming in the following two ways:

■ Fixed lockout

The system to be locked out is selected by programming.

When a locked system is selected, the Delete ( appears on the left of the SYSTEM indicator. The revert system is scanned even if it is locked out. If there is a locked system, the Delete ( ning.

) indicator flashes during fixed scan-

) indicator

■ User selectable lockout

If the scan lockout feature is programmed to a key, the

user can lock systems out of the scan sequence with the key. To lock a system out of the scan sequence, press the key when the system is displayed. The Delete ( is displayed on the left of the SYSTEM indicator.

) indicator

TK-480/481

OPERATING FEATURES

To unlock a system, select the system and press the key. The Delete ( tem has returned to the scan sequence. The revert system is scanned even if it is locked out. If there a locked system, the Delete ( systems are locked out, the scan stops and only the revert system is received.

) indicator disappears to indicate that the sys-

) indicator flashes during fixed scanning. If all

3-3. Drop-out delay time (Scan resume time)

If a call is received during scan, the scan stops. The scan resume time can be programmed as 0 to 300 seconds in one-second increments. The default value is 3 seconds.

3-4. Dwell time

The dwell time is the time after transmission ends until the scan resumes in scan mode. It can be set 0 to 300 seconds by programming. The default value is 3 seconds.

3-5. System/Group revert

System/Group revert can be programmed for one of the following;

■ Last called revert

The system or group changes to the revert system or group when a call is received with the system or group being scanned.

■ Last used revert

If a system/group call is received during scanning and the PTT button is pressed for transmission and response within the drop out delay time, the system or group is assigned as the new revert system or group.

■ Selected revert

If the system/group was changed while scanning, the newly selected system/group.

■ Selected + Talkback

If the system/group was changed while scanning, the newly selected system/group. The transceiver “talks back” on the current receive group.

3-6. Scan message wait

The time for staying with the home repeater that receives a signal during system scan and monitoring data messages can be programmed. If there is no signal from the home repeater, the system is scanned for about 50ms. If there is a signal, three data messages are monitored. Normally, three data messages are monitored for each system, and it can be increased in multiples of three data messages per line to up to eight lines.

If the repeater data message indicates that there is no call, data monitoring is terminated and the home repeater of the next system is scanned.

3-7. Group scan operation

Group scan can be programmed for each group. In addition to the ID codes of the selected group, the ID codes of the other groups that are permitted for group scan are decoded. (The two fixed ID and block decode codes are always decoded.)

If, during group scanning, a call is received with one of the selectable group ID codes for which group scan is enabled, the group display indicates the group number that the call came in with. That group then becomes the new selected group. Group scan resumes after the specified dropout delay time or dwell time shared by the system scan elapses.

3-8. In Conventional system.

If QT or DQT is set for the channel, the channels, including signalling, are scanned.

In case of the priority group is set in conventional system, if a group scan (including group scan during a system scan) temporarily stops (receiving) in a group that does not have priority, a look back is performed to the priority group. Look back is performed according to the look back time A and B settings. If a call is received on the priority group, reception immediately switches to the priority group.

4. Details of Features

4-1. Time-out timer

The time-out timer can be programmed in 15 seconds increments from 15 seconds to ten minutes. If the transmitter is keyed continuously for longer than the programmed time, the transmitter is disabled and a warning tone sounds while the PTT button is held down. The alert tone stops when the PTT button is released.

4-2. Sub LCD

You can use 3-digit the display to display the system number, channel number or group number. It is useful when the main (12-digit) display indicates system, group or channel name or other functions.

4-3. Selective Call Alert LED

You can select whether or not the LED on the transceiver flashes in an orange color when selective call was occurred.

4-4. PTT ID

PTT ID provides a DTMF ANI or MSK ID to be sent with every time PTT (connect ID at beginning of transmission, disconnect ID at end of transmission, or both).

You can program PTT ID “on” or “off” for each group channel (DTMF). The contents of ID are programmed for each transceiver.

The transceiver is capable to have ID. The format is DTMF. The timing that the transceiver sends ID is programmable.

BOT : Connect ID is sent on beginning of transmission.

EOT : Disconnect ID is sent on end of transmission.

Both : Connect ID is sent on beginning of transmission and disconnect ID is sent on end of transmission.

There is also “PTT ID” setting for each channel.

OPERATING FEATURES

TK-480/481

4-5. Radio password

When the password is set in the transceiver, user can not

use the transceiver unless enter the correct password.

This code can be up to 6 digits from 0 to 9 and input with

the keypad or selector, and “S” key.

4-6. Battery Warning

This transceiver has battery warning feature. If the low voltage is detected during transmission, the transceiver warns it by flashing red “LED”.

Then more low voltage is detected during transmission, the transceiver stops transmission and warns it by flashing red “LED” and beep.

Please notice “standard” for the battery exchange, charging time by flashing red LED and beep.

4-7. Minimum Volume

The minimum volume is programmable (off (0) to 31). The transceiver remains the minimum volume level however the mechanical volume position is set to zero.

4-8. Call indicator

The call indicator can be programmed for each group. In trunked system, it can be set to respond to a selectable decode ID or one of two fixed IDs, except block IDs. When a call is received with a selectable decode ID, the call indicator flashes. When a call is received with a fixed ID, the call indicator lights continuously.

On a conventional system, the call indicator can be programmed to light for each QT or DQT code. It keeps flashing while a call is being received. It is turned off by pressing any front panel key.

4-9. Free system ringback

This feature is available only when a telephone interconnected ID code is selected. If a busy tone sounds when the PTT button is pressed, the transceiver enters this mode automatically.

When the PTT button is released, a beep sounds for 400ms to indicate that the mode has been entered. If the scan is on, it is resumed (the “SCN” mark goes on). When any repeater becomes available, a ringing tone sounds and this mode ends.

The mode is terminated when the system, group, scan, PTT, key is changed.

4-10. System search

This feature can be programmed to automatically access other programmed systems when the selected system cannot be accessed. If an intercept tone sounds when the PTT button is pressed after setting the mode, the transceiver has entered the mode.

If the group ID is a telephone interconnect ID, the transceiver then attempts to access, in succession, other systems that have a telephone interconnect ID in the revert group location. If the group ID is a dispatch ID, the transceiver attempts to access other systems that have a dispatch ID programmed in the revert group location.

If there is no system to be accessed, an intercept tone sounds, the mode is terminated, and the transceiver returns to the first system. If the access is successful, the mode is terminated, and the searched system becomes the new selected system (If during scanning, the scan stops).

4-11. Transpond

This feature can be programmed to turn on and off for each group. If the ID of the group for which transpond is enabled is received, two data messages (transmit ID and turn-off code) are automatically transmitted if the PTT button is not pressed as a response within the time set (0 to 300 seconds in 1-second increments). If the PTT button is pressed within the time, the transpond is not preformed.

4-12. Transmit inhibit

The transceiver can be programmed with a transmit inhibit block of ID codes. If an ID code within this block is decoded the preset time before the PTT button is pressed, transmission is inhibited. The BUSY indicator lights and a busy tone sounds until the PTT button is released to indicate that transmission is not possible (except clear-to talk mode).

Transmission with the group for which the encode ID is not set is inhibited, and the busy tone is output while the PTT button is held down, regardless of the clear-to -talk setting.

4-13. Auto TEL

A telephone interconnect call can be made by simply pressing the key by assigning this feature to the key. This feature accesses the TEL channel of the available system automatically.

When the key is pressed, a queue tone is output, and the “AUTO TEL” appears on the alphanumeric display along with a flashing handset indicator ( mode has been entered. If the TEL ID is set for the revert system, the TEL channel of that system is accessed. If all TEL channels are busy, an attempt is made to access the TEL channels of another system in which the TEL ID code has been programmed. It is repeated for 60 seconds until the access succeeds. If the access succeeds, a dial tone returns from the repeater. If the key is pressed again when the queue tone is sounding, this mode is canceled.

If the access fails after 60 seconds, a deny tone is output and this mode is terminated. When the talk ends, the revert system/group returns. When the scan mode is effective, the scan resumes. The Auto TEL feature can be programmed to turn on or off for each system.

) to indicate that this

■ ARQ mode

If affects Trunking mode only. Automatic Repeat Request (ARQ) mode is a manner to minimize the air traffic of data communication. Also, it enables to occupy the trunking repeater channel for the data communication period.

■ Data TX with QT/DQT

Whether programmed QT/DQT is modulated or not with a data transmission except for Selcall. A radio unit can receive a data message regardless of QT/DQT if the receiving unit is not scanning.

TK-480/481

OPERATING FEATURES

5. Option Signalling

5-1. DTMF

Built-in DTMF decoder is available for option signalling. It is possible to use individual call, group call, D.B.D.

(Dead Beat Disable). D.B.D. is used with DTMF only.

If the option signalling matches, a predetermined action

will occur.

If option signalling matches on a group which is set up with option signalling, the option signalling indicator ( flash and option signalling will be released. The transpond or alert tone will sound.

If the selective call alert LED is set up, the orange LED will flash.

While option signalling matches (or if option signalling is deactivated when you are transmitting), you can mute or unmute ID/QT/DQT/Carrier.

■ AND/OR

You can select AND or OR for option signalling match conditions.

Alert/Transpond

AND QT/DQT/ID+DTMF; Option matches = Action

OR QT/DQT/ID+DTMF; Option matches = Action

AF mute open

AND QT/DQT/ID+DTMF; Option matches = Action

OR QT/DQT/ID; Signalling only matches = Action

) will

■ AND/OR

AND : QT/DQT/ID + MSK to unmute. MSK matches =

alert tone

OR : QT/DQT/ID to unmute. MSK matches = alert tone

Alphanumeric Two-way Paging Function

(FleetSync™)

6-1. General

The Alphanumeric Two-way Paging Function (FleetSync™) is a Kenwood proprietary protocol. It enables a variety of paging functions.

6-2. ID Construction

A radio unit ID is defined by a combination of 3-digit Fleet and 4-digit ID numbers. Each radio unit must be assigned its own Fleet and ID numbers.

6-3. PTT ID

A pre-programmed unique ID (Own) can be sent at the beginning of transmission and/or the end of transmission to identify which radio unit is on air.

When selecting (Sel) for MSK ID, the radio calls the specific Fleet user the same as selective call.

6-4. Selective Call (SELCALL)

This is a voice call to a particular individual or group of stations.

With OR set up, alert/transpond will not function with

only DTMF.

With OR set up, AF mute will not release when only

DTMF matches.

With a conventional group not set up with QT or DQT,

only the carrier is considered when signalling matches.

■ Auto Reset

If option signalling matches a group set up with option signalling, option signalling is released. After matching option signalling, option signalling will temporarily reset automatically.

■ Dead Beat Disable

If the D.B.D. code matches, a predetermined action will occur. Whether option signalling is activated or not, when D.B.D. matches on any group, the transceiver will become TX inhibited or TX/RX inhibited. While D.B.D. is active, if the D.B.D. code + “#” code is received, D.B.D. will disactivate.

When D.B.D. matches, transpond will function. Alert will not be output, and option signalling match icon will not appear.

5-2. MSK

Built-in MSK (FleetSync™ : Fleet-ID) decoder is available for option signalling. When the group ID matches, squelch remains muted while the station waits for reception of proper MSK signal. When MSK signal matches, squelch unmutes.

■ Example of call types;

[100][ALL ] : <Group Call> All the units whose fleet number is “100” are called. [100][1000] : <Individual Call> The unit, whose the fleet number is “100” and ID number is “1000”, is called. [ALL][ALL ] : <Broadcast Call> All the units are called. [ALL][1000] : <Supervisor Call> All ID “1000” are called regardless of their fleet number.

■ Unit ID Encode Block

Encode ID Block can be set to limit manual dial ID. The radio unit will not accept an ID other than these IDs which are entered from the keypad. If Inter-fleet Call is enabled, block ID setting affects each fleet group.

6-5. Status Message

Using a 2-digit number, you can send and receive a Status message which may be decided in your talk group. Each Status may be displayed with 16 alphanumeric characters if programmed in the radio. A maximum of 9 received messages can be stored in the stack memory, and it can be reviewed after reception. If the message memory becomes full, the oldest one will be erased. The stack memory will be cleared by turning radio power off.

OPERATING FEATURES

TK-480/481

■ Status 80~99 (Special)

Status numbers from 80 to 99 are reserved for special purposes. Entering these statuses from the DTMF keypad can be inhibited.

Please notice that the following status numbers are used for special purposes;

80~87 : Reserved for future use.

88 : Terminates to emergency mode.

89 : Request for hornalert (For Mobile).

90 : Remote stun on. Disable the received radio unit’s

TX.

91 : Remote stun on. Disable the received radio unit’s

TX/RX.

92 : Cancel remote stun. Enable the received radio unit’s

TX/RX.

93 : Acknowledgement status sent when the radio unit is

in stun mode (TX disabled).

94 : Acknowledgement status sent when the radio unit is

in stun mode (TX/RX disabled).

95~97 : Reserved for future use.

98 : Man Down Emergency status.

99 : Emergency Status.

Note : Remote stun works with DTMF D.B.D. function also.

■ Automatic Status Response

If you pre-select a status number and leave the radio in the Status Mode, it can automatically respond with the selected status number upon request from the base station. (The request function is initiated by serial control on the base station (Optional).)

6-6. Short Message (Optional)

A maximum of 48 characters can be sent (External equipment is required). Received Short Messages will be displayed in the same manner as a Status Message. A maximum of 4 received messages can be stored in the stack memory. In the Stack Mode, 3-digit LCD indicates the received Short Message as “M01”~”M04".

6-7. Long Message (Optional)

A maximum of 1024 characters can be sent (External equipment is required). Received Long Message will not be displayed or stacked in the radio memory but is output through the COM (Data) port.

6-8. Emergency Function

Emergency status 99 will be sent at the beginning of each emergency transmission.

■ FleetSync™ Baud Rate

MSK data baud rate setting. The same rate must be set

as a communication partner.

1200bps : Data communication is made in 1200bps. The communication area is much wider than 2400bps. Recommended for repeater operation. 2400bps : Data communication is made in 2400bps. The communication area is narrower than 1200bps, but it will decrease the data traffic. Data rate 2400bps may not work properly depending on the repeater’s characteristic.

■ Message Mode Timer

Message Mode Timer is a delay timer returning from

message/stack mode to Normal mode.

■ Status/Short/Long Message on Data Group

Status/Short/Long Message transmission is made

whether on the Data System/Group.

■ Status/Short/Unit ID Message Serial Output

(Option)

Whether a received Status/Short message or PTT ID is

output or not from serial port.

■ Call Alert (Continuous)

The radio can provide the alert tone repeatedly until next

operation.

■ PTT ID Sidetone

This function allows a single beep sound after the PTT ID

(MSK) for FleetSync singalling is encoded.

■ Caller ID Stack

The radio stores the last 3 received caller IDs to volatile

memory.

■ Caller ID Display

PTT ID is displayed on LCD.

6-10. Parameters

■ GTC Count

Number of Go To data Channel messages to be sent before transmitting a data message if it is being made on Data System/ Group. If a radio unit receives a GTC message, it will move to the Data System/Group of the current system. Increase this item to make sure the called radio unit moves to the Data System/Group.

■ Emergency Status response

“Alert” can be selected for the called radio unit’s response to reception of status 99 which is used as an emergency status.

6-9. Other Functions

■ Manual Dial

Fleet, ID and Status numbers can be entered from DTMF keypad. (DTMF microphopne is required.)

■ Random Access (Contention)

When a channel (or all the repeater channels for Trunking mode) is busy, radio unit will not transmit (depending on its Busy Channel Lockout setting in conventional mode). As soon as a channel is cleared, some transmissions may crash. Random access is used to avoid this by employing a random transmission sequence.

TK-480/481

OPERATING FEATURES

■ Number of Retries

Number of Retries is the maximum number of retry transmission when no acknowledgement is received in the Maximum ACK Wait Time. Increase this item to improve data communication reliability.

■ TX Busy Wait Time

TX Busy Wait Time is the maximum amount of time before giving up the data transmission when the channel (or all the repeater channels for Trunking mode) is busy. Also, this timer affects if it expires during Random Access period.

■ Maximum ACK Wait Time

Maximum ACK Wait Time is the maximum amount of time to wait for an acknowledgement from the called radio unit. It is used as an interval time of retries. It must be set greater than the ACK Delay Time of the called radio unit.

■ ACK Delay Time

ACK Delay Time is the amount of time from the end of receiving a data to the beginning of sending an acknowledgement. It should be adjusted as the repeater’s hang-up delay time. Also, it must be set less than the Maximum ACK Wait Time of the calling radio unit.

■ TX Delay Time (RX Capture)

TX Delay Time is the amount of unmodulated transmission to let the called unit stop scanning or exit its battery save mode. It is used only when starting a data communication sequence.

■ Data TX Modulation Delay Time

Data TX Modulation Delay Time is the amount of time from the beginning of transmission to the beginning of a data modulation. It is used every time data is transmitted. It must be set to more than 300ms if data communication is made in Trunking Mode.

7. Audible User Feedback Tones

The transceiver outputs various combinations of tones to notify the user of the transceiver operating state. The main tones are listed below.

The high tone is 1477Hz, the mid tone is 941Hz, and the low tone is 770Hz.

7-1. Power On Tone

This tone is output when the transceiver is turned on. (The high tone is output for 500ms.)

7-2. Alert Tone

This tone is output when the transceiver is TX inhibition for TOT and PLL unlocked. It is output until the PTT button is released. (The 697Hz tone is output.)

7-3. DBD On Tone

When a D.B.D. code is received, transpond tone sounds.

7-4. DBD Off Tone

When a D.B.D. release code is received, transpond tone

sounds.

7-5. Password Agreement Tone

When the correct password is entered, the tone sounds.

The optional feature's control tone can be set to yes or no.

7-6. PTT Release Tone

When you release the PTT switch, the PTT release tone

sounds.

7-7. Busy Tone

Sounds in LTR mode, when you cannot use a repeater (system busy or TX inhibit). Sounds in conventional mode, when busy channel lockout is functioning. You can select yes or no for the optional feature's warning tone.

7-8. Group Call Tone

Sounds when a group call with the correct DTMF option signalling is received, repeats 7 times. You can select yes or no for the optional feature's warning tone.

7-9. Individual Call Tone

Sounds when an individual call with the correct DTMF option signalling is received. You can select yes or no for the optional feature's warning tone.

7-10. Key Press Tone [A]

Sounds when a key is pressed. For toggle keys, sounds when toggle function is turned on (key press tone [B] sounds when it is turned off). You can select yes or no for the optional feature's control tone.

7-11. Key Press Tone [B]

Sounds when a key is pressed. For toggle keys, sounds when the toggle function is turned off (key press tone [A] sounds when it is turned on). You can select yes or no for the optional feature's control tone.

7-12. Key Press Tone [C]

Sounds when a key is pressed. Also sounds when storing data, adding a DTMF code to memory, and when changing test mode settings. You can select yes or no for the optional feature's control tone.

7-13. Key Input Error Tone

Sounds when a key is pressed but that key cannot be used. You can select yes or no for the optional feature's warning tone.

7-14. Roll Over Tone

Sounds at the smallest system/group. You can select yes or no for the optional feature's control tone.

7-15. Transpond Tone

Sounds when an individual call with the correct LTR/ DTMF option signalling is received. For group calls, only the group tone will sound, not the transpond tone.

TK-480/481

User mode

Panel test mode

PC mode

Firmware programming mode

Panel tuning mode

Data programming mode

PC test mode PC tuning mode

Clone mode

OPERATING FEATURES / REALIGNMENT

7-16. Intercept Tone

This tone indicates that the transceiver is out of range. It indicates that the PTT button is pressed, and transmission has started, but the repeater cannot be connected and talking is not possible. It is output until the PTT button is released. (The mid tone and low tone are output alternately in 200ms intervals.)

7-17. Delay Tone

This tone is output when the PTT button is pressed and the repeater is accessed three times or more to indicate connection with the repeater is delayed. This tone is the same as the busy tone. (It is not output of clear to talk has been set to yes.)

7-18. Proceed Tone

This tone is output when the PTT button is pressed, transmission starts, and the repeater is connected to indicate that the user can talk if the clear to talk function has been set. (The high tone is output for 100ms.)

7-19. Queue Tone

This tone is output until the auto TEL function is set and the TEL channel is accepted successfully. (The mid tone on for 50ms, off for 50ms, and on for 50ms in 1 second intervals.)

7-20. Deny Tone

This tone is output if the auto TEL function is set, the queue tone is output, but the TEL channel cannot be accessed within 60 seconds. It is similar to the intercept tone. (The mid tone and low tone are output alternately in 150ms intervals.)

7-21. Free System Ringback Mode Tone, System

Search Mode Tone

This tone indicates that the transceiver is free system ringback mode or system search mode. (The mid tone is output for 400ms.)

7-22. Ringing Tone

This tone indicates that the transceiver can use the repeater in free system ringback mode. (The mid tone and no tone are output eight cycles alternately in 50ms intervals.)

7-23. System Search Tone

Sounds when the system changes during system search. You can select yes or no for the optional feature's warning tone.

REALIGNMENT

1. Modes

Mode Function

User mode For normal use.

Panel test mode Used by the dealer to check the funda-

mental characteristics.

Panel tuning mode Used by the dealer to tune the radio.

PC mode Used for communication between the

radio and PC (IBM compatible).

Data program- Used to read and write frequency data

ming mode and other features to and from the radio.

PC test mode Used to check the radio using the PC.

This feature is included in the FPU.

See panel tuning.

Firmware program- Used when changing the main program

ming mode of the flash memory.

Clone mode Used to transfer programming data from

one radio to another.

2. How to Enter Each Mode

Mode Operation

User mode Power ON

Panel test mode [A]+Power ON (Two seconds)

PC mode Received commands from PC

Panel tuning mode [Panel test mode]+[S]

Firmware programming mode [S]+Power ON (Two seconds)

Clone mode [C]+Power ON (Two seconds)

3. Panel Test Mode

Setting method refer to ADJUSTMENT.

7-24. System Search End Tone

Sounds when a possible connection to a repeater in system search is not mode. You can select yes or no for the optional feature’s warning tone.

4. Panel Tuning Mode

Setting method refer to ADJUSTMENT.

TK-480/481

REALIGNMENT

5. PC Mode

5-1. Preface

The TK-480/481 transceiver is programmed by using a

personal computer, programming interface (KPG-36) and programming software (KPG-49D).

The programming software can be used with an IBM PC

or compatible. Figure 1 shows the setup of an IBM PC for programming.

5-2. Connection procedure

1. Connect the TK-480/481 to the personal computer with the interface cable.

2. When the POWER switch on, user mode can be entered immediately. When PC sends command the radio enter PC mode, and “PROGRAM” is displayed on the LCD. When data transmitting from transceiver, the red LED is blinking. When data receiving to transceiver, the green LED is blinking.

Notes:

• The data stored in the personal computer must match model type, when it is written into the flash memory.

• Change the TK-480/481 to PC mode, then attach the interface cable.

5-3. KPG-36 description (PC programming interface cable: Option)

The KPG-36 is required to interface the TK-480/481 to the

computer. It has a circuit in its D-subconnector (25-pin) case that converts the RS-232C logic level to the TTL level.

The KPG-36 connects the universal connector of the TK-

480/481 to the computers RS-232C serial port.

5-4. Programming software description

The KPG-49D programming disk is supplied in 3-1/2" disk

format. The software on this disk allows a user to program TK-480/481 radios via programming interface cable (KPG-

36).

5-5. Programming with IBM PC

If data is transferred to the transceiver from an IBM PC

with the KPG-49D, the destination data (basic radio information) for each set can be modified. Normally, it is not necessary to modify the destination data because their values are determined automatically when the frequency range (frequency type) is set.

The values should be modified only if necessary. Data

can be programmed into the flash memory in RS-232C format via the universal connector.

KPG-49D instruction manual parts No. : B62-1096-XX

IBM-PC

KPG-36

KPG-49D

Fig. 1

6. Firmware Programming Mode

6-1. Preface

Flash memory is mounted on the TK-480/481. This allows the TK-480/481 to be upgraded when new features are released in the future. (For details on how to obtain the firmware, contact Customer Service.)

6-2. Connection procedure

Connect the TK-480/481 to the personal computer (IBM PC or compatible) with the interface cable (KPG-36). (Connection is the same as in the PC Mode.)

6-3. Programming

1. Start up the programming software (KPG-49D), select

“firmware program” in the “Program” item, and press

the Return key on the personal computer. This starts up

the firmware programmer.

2. The top screen is displayed. Press any key to advance to

the next screen.

3. Set the communications speed (normally, 57600 bps)

and communications port in the Setup item.

4. Set the firmware to be updated by File select (=F1).

5. Turn the TK-480/481 power ON with the [S] switch held

down. Hold the switch down for two seconds until the

display changes to “PROG 57600”. When “PROG

57600” appears, release your finger from the switch.

6. Check the connection between the TK-480/481 and the

personal computer, and make sure that the TK-480/481 is

in the Program mode.

7. Press F10 on the personal computer. A window opens on

the display to indicate progress of writing. When the TK-

480/481 starts to receive data. the [P] icon is blinking.

8. If writing ends successfully. the LED on the TK-480/481

lights and the checksum is displayed.

9. If you want to continue programming other TK-480/481 s,

repeat steps 5 to 8.

REALIGNMENT

TK-480/481

Notes:

• To start the Firmware Programmer from KPG-49D, the Fpro path must be set up by KPG-49D Setup.

• This mode cannot be entered if the Firmware Programming mode is set to Disable in the Programming software (KPG-49D).

• When programming the firmware, it is recommend to copy the data from the floppy disk to your hard disk before update the radio firmware. Directry copying from the floppy disk to the radio may not work because the access speed is too slow.

6-4. Function

1. If you press the [MON] switch (top of left side) while “PROG 57600” is displayed, the checksum is displayed. If you press the [MON] switch again while the checksum is displayed, “PROG 57600” is redisplayed.

2. If you press the [LAMP] switch (bottom of left side) while “PROG 57600” is displayed, the display changes to “PROG 19200” to indicate that the write speed is low speed (19200 bps). If you press the [LAMP] switch again while “PROG 19200” is displayed, the display changes to “PROG 38400”, and the write speed becomes the middle-speed mode (38400 bps). If you press the [LAMP] switch again while “PROG 38400” is displayed, the display returns to “PROG 57600”.

How to enter the password with the encoder; If the encoder is rotated while “CLONE LOCK” is displayed, numbers (0 to 9) are displayed flashing. When you press the [S] key, the currently selected number is determined. If you press the [S] key after entering the password in this procedure, “CLONE MODE” is displayed if the entered password is correct. If the password is incorrect, “CLONE LOCK” is redisplayed.

4. Power on the slave TK-480/481.

5. Connect the cloning cable (No. E30-3325-05) to the universal connectors on the master and slave.

6. Press the [S] key on the master while the master displays “CLONE MODE”. The data of the master is sent to the slave. While the slave is receiving the data, “PROGRAM” is displayed. When cloning of data is completed, the master displays “END”, and the slave automatically operates in the User mode. The slave can then be operated by the same program as the master.

7. The other slave can be continuously cloned. When the [S] key on the master is pressed while the master displays “END”, the master displays “CLONE MODE”. Carry out the operation in step 4 to 6.

Note:

Only the same models can be cloned together.

Note:

Normally, write in the high-speed mode.

7. Clone Mode

Programming data can be transferred from one radio to another by connecting them via their external universal connectors. The operation is as follows (the transmit radio is the master and the receive radio is a slave).

1. Turn the master TK-480/481 power ON with the [C] key

held down. If the password is set to the TK-480/481, the

TK-480/481 displays “CLONE LOCK”. If the password is

not set, the TK-480/481 displays “CLONE MODE”.

2. When “CLONE LOCK” is displayed, only the knob (en-

coder) and [S], and [0] to [9] keys can be accepted. When

you enter the correct password, and “CLONE MODE” is

displayed, the TK-480/481 can be used as the cloning

master. The following describes how to enter the pass-

word.

3. How to enter the password with the keypad;

If you press a key while “CLONE LOCK” is displayed.

The number that was pressed is displayed on the TK-480/

481. Each press of the key shifts the display in order to

the left. When you enter the password and press the [S]

key, “CLONE MODE” is displayed if the entered pass-

word is correct. If the password is incorrect, “CLONE

LOCK” is redisplayed.

Cloning cable (E30-3325-05)

Fig. 2

TK-480/481

CIRCUIT DESCRIPTION

1. Overview

This transceiver is an 800/900MHz band EFJ LTR™

trunked system compatible FM portable transceiver that can be programmed to operate on both LTR and conventional systems.

2. Circuit Configuration by Frequency

The receiver is a double-conversion superheterodyne

with a first intermediate frequency (IF) of 44.85MHz and a second IF of 455kHz. Incoming signals from the antenna are mixed with the local signal from the PLL to produce the first IF of 44.85MHz.

This is then mixed with the 44.395MHz second local os-

cillator output to produce the 455kHz second IF. This is detected to give the demodulated signal.

The transmit signal frequency is generated by the PLL

VCO, and modulated by the signal from the microphone. It is then amplified and sent to the antenna.

TK-480

TX 806~825MHz

851~870MHz

RX 851~870MHz

ANT

AMP

TK-481

TX 896~902MHz

935~941MHz

RX 935~941MHz

1st MIX

44.85MHz

TK-480 :

806.15~825.15MHz TK-481 :

890.15~896.15MHz

TK-480 806~825MHz 851~870MHz

MCF

TK-481 896~902MHz 935~941MHz

455kHz

IF SYSTEM

44.395 MHz

PLL

VCO

AMP

MIC

AMP

MIC

3. Receiver System

3-1. RF unit

An incoming RF signal from the antenna terminal is passed through the antenna switch (D7, D9, and D10 are off) and then the bandpass filter (L11). The signal is amplified by RF amplifier Q9, and passed through the bandpass filter (L20) to remove the spurious signal again. The resulting signal is applied to the first mixer (Q6), where it is mixed with the first local oscillator signal output from the frequency synthesizer to produce the first IF (44.85MHz).

3-2. IF unit

The first IF signal is passed through a four-pole monolithic crystal filter (XF1) to remove a adjacent channel signal. The filtered first IF signal is amplified by the first IF amplifier (Q5) and then applied to the IF system IC (IC9). The IF system IC provides a second mixer, second local oscillator, limiting amplifier, quadrature detector and RSSI (Received Signal Strength Indicator). The second mixer mixes the first IF signal with the 44.395MHz of second local oscillator output (crystal unit X1) and produces the second IF signal of 455kHz.

The second IF signal is passed through the ceramic filter (CF1,2) to more remove the adjacent channel signal. The filtered second IF signal is amplified by the limiting amplifier and demodulated by the quadrature detector with ceramic discriminator (CD1). The demodulated signal is routed to the audio circuit.

Fig. 1 Frequency configuration

ANT

IC12

L30 D9,D10

HPF

ANT

LPF

L11 BPFQ9RF AMP

HPF BEF

L20 BPFQ61st MIX

1st local OSC (PLL)

DE-

EMP

EXP

XF1

MCFQ51st IF

MUTE

Fig. 2 Receiving system

2nd local OSC

IC3 (2/2)

AF AMP

IC9

MIX,DET,IF

IC4

VOL

IC8 (2/2) AF AMP

AF AF

CF1 CF2

Q310

SSW

VC1

VC2

IC300

AF PA

EXT. SP

INT. SP

CIRCUIT DESCRIPTION

SQ voltage

ANT input level

SQ close

SQ open

RSSI voltage

ANT input level

Preset value

TK-480/481

3-3. Audio amplifier circuit

The demodulated signal from IC9 is amplified by IC8 (2/

2), high-pass filtered, low-pass filtered, high-pass filtered, band-eliminate filtered,and de-emphasized by IC12.

The signal then goes through an AF amplifier IC3 (2/2), an electronic volume control (IC4), and an AF switch (Q310 is on), and is routed to audio power amplifier (IC300), where it is amplified and output to the internal speaker.

The audio mute signal (AM) from the microcomputer becomes Low in the standby and Q304, Q305 which are power supply circuit for IC300 turn off. Also, IC12 is set to the power down mode according to data from microprocessor, and the AF signal is muted. When the audio is output, AM becomes High to turn Q304, Q305 ON, and voltage is supplied to power terminal VP of IC300. Also, IC12 is canceled out of the power down mode.

The speaker is switched by the logic of speaker switching terminal SSW on the universal connector. When SP-MIC is not attached, the logic of SSW becomes High and SW (Q310) is turned ON, and the AF signal is input to both amplifiers of IC300.

When SP-MIC is attached, SSW is connected to GND at inside of SP-MIC. For this reason, Q310 is turned OFF, and the AF signal is input only to amplifier for EXT SP of IC300.

Change of INT/EXT SP refer to Fig. 3.

AM SSW VC1 VC2 SP

H H H L INT

H L L H EXT

L H L L MUTE

L L L L MUTE

3-4. Squelch circuit

The output from IC9 enters FM IC again, then passed through a band-pass filter. The noise component output from IC9 is amplified by Q19 and rectified by D3 to produce a DC voltage corresponding to the noise level. The DC voltage is sent to the analog port of the CPU (IC15). And IC9 outputs a DC voltage (RSSI) corresponding to the input of the IF amplifier. The CPU reads the RSSI signal via pin 24.

IC15 determines whether to output sounds from the speaker by comparing the input voltage of pin 28 and pin 24 with the preset value.

IC9 : FM IF IC

IF AMP

DET

RSSI BPF

AMP

Q19 D3

NOISE

AMP

DET

IC15 CPU

Fig. 4 Squelch circuit

SSW

Q301

Q308

Q305

Q304

VC1

VC2

Fig. 3 Audio amplifier circuit

IC300

Fig. 5

INT. SP

4. Transmitter System

Squelch and RSSI voltage vs ANT input level

4-1. Microphone amplifier

EXT. SP

The signal from the internal microphone goes through the mute switch (Q300).

When the SP-MIC is not attached, the microphone switching terminal (MSW) on the universal connector becomes High, and mute switch (Q300) is turned ON. When the SP-MIC is attached, MSW is connected to GND at inside of SP-MIC. For this reason, Q300 is turned OFF, the internal microphone is muted, and only the input of the external microphone is supplied to the microphone amplifier of the TXRX unit.

TK-480/481

CIRCUIT DESCRIPTION

The signal from microphone passes through the limitter circuit in D11, and through the high-pass filter, the ALC circuit, the low-pass filter, the high-pass filter, and pre-emphasis/IDC circuit in IC12. When encoding DTMF, mute switch (Q7) is turned OFF for muting the microphone input signal.

The signal passes through the D/A converter (IC4) for the maximum deviation adjustment, and enters the summing amplifier consisting of IC3 (2/2), and is mixed with the low speed data from the CPU (IC15).

The output signal from the summing amplifier passes through the D/A converter (IC4) again for the TA maximum deviation adjustment,and the AF switch (Q21 is off in TX), and goes to the VCO modulation input.

The other output signal from the summing amplifier passes through the D/A converter (IC4) again for the BAL adjustment,and the buffer amplifier (IC1 (2/2)), and goes to the VCXO modulation input.

EXT.

MIC

Q300

MIC

D11

LIMIT

HPF ALC

4-2. Drive and Final amplifier

The signal from the T/R switch (D5 is on) is amplified by

the pre-drive (Q11) and drive amplifier (Q12) to 50mW.

The output of the drive amplifier is amplified by the RF power amplifier (IC30) to 2.5W (1W when the power is low). The RF power amplifier consists of two stages MOS FET transistor. The output of the RF power amplifier is then passed through the harmonic filter (LPF) and antenna switch (D7 is on) and applied to the antenna terminal.

4-3. APC circuit

The APC circuit always monitors the current flowing through the RF power amplifier (IC30) and keeps a constant current. The voltage drop at R127, R128 and R129 is caused by the current flowing through the RF power amplifier and this voltage is applied to the differential amplifier (IC21 1/2).

IC21 (2/2) compares the output voltage of IC21 (1/2) with the reference voltage from IC4, and the output of IC21 (2/2) controls the VGG of the RF power amplifier to make the both voltages to same voltage.

The change of power high/low is carried out by the change of the reference voltage. Q14,15 and 18 are turned on in transmit and the APC circuit is active.

DTMF

98IC12

PRE EMP

IDC

COMP LPF HPF

MUTE

MSW

Q301

IC4

D/A

LSD

IC3 (2/2)

SUM AMP

IC4

D/A

IC4

D/A

Fig. 6 Microphone amplifier

From

T/R SW

(D5)

REF

VOL

(IC4)

Q11

Pre-DRIVE

AMP

R127

R128

R129

Q12

DRIVE

AMP

IC21 (1/2)

IC30

POWER AMP

VDD VGG

IC21 (2/2)

LPF

Fig. 7 Drive and final amplifier and APC circuit

Q21

MUTE

IC1

BUFF

AMP

ANT

IC14

VCO

VCXO

ANT

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