Kenwood TKR-751 Owner's manual

Version: 1.02 USA
Last Updated: Sep, 2005
Language: English
Type: K
Modification Information (MOD)
For
T
TK KR R- -7 75 50 0/ /8 85 50 0 V Ve er rs si io on n2 2
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TK KR R- -7 75 51 1/ /8 85 51 1

About Copyright
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the software described in this technical document, relevant in-depth manuals, and help texts and manuals attached to the
software are owned by Kenwood Corporation.
A right to use the software described in this technical document and relevant in-depth manuals is granted to a licensee by
Kenwood Corporation; however, the title to and ownership of the software shall be owned by Kenwood Corporation. Refer
to the help texts attached to this software for details.
Kenwood Corporation does not warrant quality and performance of the software described in this technical document and
relevant in-depth manuals to conform to the applicability of any use, and Kenwood Corporation shall be free from liability
for any defects, damage or loss, or from any warranty to anything other than expressly described in this technical
document and relevant in-depth manuals.
Revision history
Date Description
Sep. 2005 Add Terminal description
Sep. 2005 K-USA R&D modify

Version: 1.02 USA Modification Information (MOD) 1
CONTENTS
1 TERMINAL FUNCTION .............................1
1.1 8-pin Connector ..............................................1
1.2 15-pin Connector ............................................2
1.3 25-pin Connector (D-SUB)..............................3
1.4 14-pin Connector (CN601)..............................4
2 MODIFICATION OF THE ANTENNA ........5
3 INSTALLING THE VOICE SCRAMBLER
BOARD ..........................................................7
3.1 Configuring and Modifying
the SC20-460 Board.......................................7
3.2 Installing the SC20-460................................... 9
3.3 Configuration with the Software....................10
4 MODIFYING THE DC POWER ................12
5 EXTRACTING RSSI SIGNAL FROM THE
ACC 25-PIN D-SUB CONNECTOR .............13

Version: 1.02 USA Modification Information (MOD) 1
1 TERMINAL FUNCTION
This section describes Input/Output terminals of the TKR-
750/850/751/851.
1.1 8-pin Connector
The 8-pin connector is located on the front panel of the
TKR-750/850/751/851. It can use as the microphone
connector for a base station usage and maintenance. You
can write the configuration data into the TKR-750/850/
751/851 by connecting it to the PC with the KPG-91D.
Figure 1-1 8-pin connector
Table 1-1 Assigning signals to 8-pin connector
12345678
No. Pin name Input/Output Description
1 NC --- No connection
2 SB Output Switched Battery Power Output/10.8 - 15.6 V/ 200m A max.,
3 GND Ground
4PTT Output PTT signal Input/ H=more than 4.0V/ L=less than 1.0V/Active L
TXD1 Output PC serial data from radio (COM 1)/ CMOS level/ H=more than 4.0V/ L=less than 1.0V
FPU read, PC Tuning, Firmware Programing
5 MIG --- Microphone Ground
6 MIC Input Microphone Signal Input/ 60% [email protected]+/-2mV 1kHz input/ 600ohm Road/ 10uF AC
coupled/ 300-3kHz +6dB/Oct. (EIA curve)
7HOOK Input Hook Signal Input/ H=more than 4.0V/ L=less than 1.0V/ 5V pull up/ Active L
RXD1 Input PC serial data to radio (COM 1)/ CMOS level/ H=more than 4.0V/ L=less than 1.0V
FPU read, PC Tuning, Firmware Programing
8 NC --- No connection

1 TERMINAL FUNCTION
2Modification Information (MOD) Version: 1.02 USA
1.2 15-pin Connector
The 15-pin connector is located on the rear panel of the
TKR-750/850/751/851 and you can connect external
devices, such as an external speaker.
Figure 1-2 15-pin connector
Table 1-2 Assigning signals to 15-pin connector
!Connecting the external speaker
Figure 1-3 Connecting the external speaker
Disconnect the Jumper Lead and insert the external
speaker's cable to the 12-pin and 6-pin of the 15-pin
connector. It needs to reconnect the Jumper Lead
when using the internal speaker.
123
456
789
1011
12
1314
15
No. Pin name Input/Output Description
1 SB Output Output the voltage between 10.8 to 15.6 V: 1 A max.
2 SB Output Output the voltage between 10.8 to 15.6 V: 1 A max.
3 NC --- No connection
4 GND --- Ground
5 GND --- Ground
6 SPG --- Speaker ground
7 RD Output Received Data output/ 1kohm Road, 10uF AC coupling, 80mVrms@1kHz 60% Dev.
8 RSSI Output RSSI output; 0.2 to 2.5V
9 SPI Input Internal Speaker input (short with SPO)
10 Auxiliary Output 1 Output Open Collector Output; 16V /150 mA max.
11 Auxiliary Output 2 Output Open Collector Output; 16V /150 mA max.
12 SPO Output External Speaker output; 4 W @less than 5% distortion/ 4ohm Road
13 Auxiliary Output 3 Output CMOS Level Output/ H=more than 4V/ L=less than 1V/ 0.2mAmax/ 5V pull-up
14 Auxiliary Output 4 Output CMOS Level Output/ H=more than 4V/ L=less than 1V/ 0.2mAmax/ 5V pull-up
15 Auxiliary Output 5 Output CMOS Level Output/ H=more than 4V/ L=less than 1V/ 0.2mAmax/ 5V pull-up
123
456
789
1011
12
1314
15
Ext.
SP

Version: 1.02 USA Modification Information (MOD) 3
1 TERMINAL FUNCTION
1.3 25-pin Connector (D-SUB)
The 25-pin connector is located on the rear panel of the
TKR-750/850/751/851 and you can connect external
devices, such as a trunking controller.
Figure 1-4 25-pin connector (D-SUB)
Table 1-3 Assigning signals to 25-pin connector
Note: Refer to the “Function Reference” for functions that you can
assign to the Auxiliary Input/Output terminal.
No. Pin name Input/Output Description
1 NC --- No connection (RSSI output after modification; 0.2 to 2.5V)
2 RXD2 Input PC serial data input (COM 2); TTL/RS-232C level
H=more than +2.4V/ L=less than +0.4V/ 5ohm Road/ for FPU read, PC Tuning
3 TXD2 Output PC serial data output (COM 2); TTL/RS-232C level
H=more than +5V/ L=less than -5.0V/ for FPU write, PC Tuning
4 AUXI 1 Input H=more than 4.0V/ L= less than 1.0V/ 5V pull-up
5 AUXI 2 Input H=more than 4.0V/ L= less than 1.0V/ 5V pull-up
6 AUXI 3 Input H=more than 4.0V/ L= less than 1.0V/ 5V pull-up
7 DG --- Control line Ground (TXD/RXD/AUX, etc.)
8 TD Input Transmission Data input; Deviation=15% [email protected] 100Hz (Adjustable)
600ohm Road, 50uF AC coupled, Non Pre-emphasis (+1/-3dB@0-10kHz)
9 TA Input
Transmitted Audio signal input; Deviation=60% STD@280mVrms 1kHz (Adjustable)
600ohm Road, 1uF AC coupled
300-3kHz +6dB/Oct. (EIA curve)@TA line pre emphasis off=Enable
300-3kHz +/-3dB@TA line pre emphasis off=Disable
10 RD Output Received Data output; 80mVrms@1kHz STD/ 1kohm Road/ 10uF AC coupled/
Response +/-2.5dB@0 - 5kHz/ Non-squelched
11 RA Output Received audio signal output; 400mVrms@1kHz STD/ 1kohm Road/ 1uF AC coupled/
Response -6dB/oct@300-3kHz/ Squelched
12 RXG --- Ground for RA/RD
13 SPM Input Speaker Mute input; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ Active L
14 NC --- No connection
15 EMON Input External Monitor Switch input; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ Active L
16 EPTT Input External PTT Switch input; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ Active L
17 SC Output Squelch Control output; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ L=Busy
18 NC --- No connection
19 TXG --- Ground for TA/TD
20 AUXIO 1 Input/Output CMOS Level Input/Output; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ 0.2mA max
21 AUXIO 2 Input/Output CMOS Level Input/Output; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ 0.2mA max
22 AUXIO 3 Input/Output CMOS Level Input/Output; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ 0.2mA max
23 AUXIO 4 Input/Output CMOS Level Input/Output; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ 0.2mA max
24 AUXIO 5 Input/Output CMOS Level Input/Output; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ 0.2mA max
25 AUXIO 6 Input/Output CMOS Level Input/Output; H=more than 4.0V/ L=less than 1.0V/ 5V pull-up/ 0.2mA max

1.4 14-pin Connector (CN601)
The 14-pin connector for installing an additional Voice
Scrambler board is located in the internal board of the
TKR-750/850/751/851, and it can be connected cables of
Voice Scrambler board (SC20-460/480, etc.). (Refer to
3.2 Installing the SC20-460.)
Figure 1-5 14-pin connector (CN601) for installing additional
Voice Scrambler
Table 1-4 Assigning signals to 14-pin connector
1234567891011121314
No. Pin name Input/Output Description
1 TXO Output Mic signal output
2 TXI Input Mic signal input
3 RXO Output Received audio signal output
4 AC Output Audio control signal output
5 BC1 Output Scramble code signal output 1
6 BC2 Output Scramble code signal output 2
7 BC3 Output Scramble code signal output 3
8 BC4 Output Scramble code signal output 4
9 PTI Input PTT signal input
10 CLRC Input Scramble code Clear signal input
11 RXI Input Received audio signal input
12 PTO Output PTT signal output
13 8C Output The repeater outputs 8 V interlocking with the power.
14 GND Output Ground

5Modification Information (MOD) Version: 1.02 USA
2 MODIFICATION OF THE ANTENNA
This section describes how to modify the antenna to
connect it to the antenna connector for transmission and
reception located on the TKR-750/850/751/851.
It allows to use as one antenna base by sharing an
external antenna connector for both transmitting and
receiving.
You must turn the power OFF before antenna
modification.
Follow the procedures below to modify the antenna.
1. Remove the rear side top panel.
Remove 6 screws (N33-3006-45, 3 mm diameter,
black) and pull the panel up.
2. Move location of C92 and C160 on the Final unit (B/2)
for TK750/751.
Move location of C81 and C160 on the Final unit (B/2)
for TK850/851.
3. Remove the front side top panel.
Remove 6 screws (N33-3006-45, 3 mm diameter,
black) and pull the panel up.
4. Remove the antenna cable.
4-1. Remove the receive cable from the CN18 of
the TX-RX unit (A/2).
4-2. Remove 2 screws (N33-2606-46, 2.6 mm
diameter, gold) on the BNC connector fixed to the
rear panel and pull the ANTENNA CABLE
backward.
5. Cut the coaxial cable of the ANTENNA CABLE at the
BNC connector side and remove the insulated part to
perform soldering on the board.
6. Connect the ANTENNA CABLE to the board.
6-1. Solder the cut surface of the coaxial cable
center pin to “RX” and the shield of cable to “E”.
CN18

Version: 1.02 USA Modification Information (MOD) 6
2 MODIFICATION OF THE ANTENNA
6-2. Connect the pin connector side of cable to the
CN18 of the TX-RX unit (A/2).
7. Short the “ANT SW” pads located next CN3 by solder.
8. Reassemble the top panels after modifying the
antenna cable.
Note:
"You must configure the operation mode of the channel as
Simplex. Refer to the “Field Programming Reference” for
details.
"To install the base radio on the location where the strong radio
interference may exist such as mountain top remote base
system, we recommend you coupling the external antenna
switching relay. You can prevent the degradation of the
reception performance caused by the internal antenna switch
diode.
Order Number: KSG-90/00-50 TX/RX Relay kit
Ask KENWOOD System for detailed information about this
product.

7Modification Information (MOD) Version: 1.02 USA
3 INSTALLING THE VOICE SCRAMBLER BOARD
It can install an optional Voice Scrambler board into the
TKR-750/850/751/851. This section describes how to
install the TRANSCRYPT SC20-460 in it. You can use the
KENWOOD service part (E37-0808-05) when installing
the SC20-460 board.
!Requirement Items
・TKR-750/850/751/851
・SC20-460
・KENWOOD Part (E37-0808-05)
・Cushion Tape
You must turn the power OFF before
installing the Voice Scrambler board.
3.1 Configuring and Modifying
the SC20-460 Board
1. Modify the SC20-460 board and change the RX Audio
Input method.
TKR-750/850/751/851 output a received audio after
De-emphasizing to input into the option board.
Therefore, it might be necessary to modify the voice
scrambler board.
(Confirm your SC20-460 is enabled de-emphasis.)
1-1. Cut the foil between E52 and E53.
1-2. Solder the position between E51 and E52 to
connect them.
1-3. Solder the position between E53 and E54.
3. Change the constant in conjunction with the TX/RX
Audio level.
3-1. Replace R1 with 100 kΩand R3 with 100 kΩin
conjunction with the RX Audio level.
3-2. Replace the R2 with 6.8 kΩand R4 with 6.8 kΩin
conjunction with the TX Audio level.
Note:
"The required modification must be performed to avoid
problems, such as too small audio signals from the speaker,
or too loud synchronizing noise.
"Refer to the Voice Scrambler board's instruction manual for
details.
4. Disconnect the cable connected to the SC20-460
board.
5. Solder the KENWOOD service parts (E37-0808-05)
cables to the SC20-460 board. You must connect the
part as shown in the as shown below. (Refer to 1.4 14-
pin Connector (CN601).)
Before modification After modification
R1, R3: 100 kΩR1, R3: 100 kΩ (No modification)
R2, R4: 100 kΩR2, R4: 6.8 kΩ
E51
E52
E53
E54
E51
E52
E53
E54
Before After
R4
R3 R2 R1

Version: 1.02 USA Modification Information (MOD) 8
3 INSTALLING THE VOICE SCRAMBLER BOARD
SC-20-460 E37-0808-05 CN601
Figure 3-1 Connecting the SC-20-460
Note: The KENWOOD service parts (E37-0808-05) have a
connector allowing you connect it to CN-601 of the TKR-
750/850/751/851.
6. Prepare the cushion having a double-sided adhesive
tape. In this case, the cushion tape (No. 4008,
No. 4016) manufactured by 3M can be used.
Cut the cushion tape in the same size as the SC20-
460 (24 mm x 33 mm).
Note:
"The 3M cushion tape having a double-sided adhesive tape has
following thickness.
No. 4016 (or No. 4416): 1.6 mm (1/16 inch)
No. 4008 (or No. 4408): 3.2 mm (1/8 inch)
"The above sizes are reference values. You must cut the
cushion tape into the same size as the Voice Scrambler.
7. Stick the cushion tapes both side of the SC20-460.
No. Signal
name Color No. Signal
name Color
ABIN.
CODE8 (WHT/ YEL) 1 TXO YEL
BBIN.
CODE4 (WHT/ GRN) 2TXI ORN
CBIN.
CODE2 (WHT/ RED) 3 RXO BLU
DBIN.
CODE1 (WHT/ BRN) 4AC VIO
E IRQ N.C. 5 BC1 WHT/
BRN
1BUSY N.C. 6BC2 WHT/
RED
2ECHO
PTT N.C. 7 BC3 WHT/
GRN
3INDICATO
RN.C. 8 BC4 WHT/
YEL
4 EMG N.C. 9 PTI BRN
5 TX IN (YEL) 10 CLRC WHT
6 RX IN (BLU) 11 RXI GRN
7SCRAMB
LE (WHT) 12 PTO GRY
8PTT (GRY) 138C RED
9 GND (BLK) 14 GND BLK
10 + V (RED)
11 RX OUT (GRN)
12 TX OUT (ORN)
24 mm 24 mm
33 mm 33 mm

3 INSTALLING THE VOICE SCRAMBLER BOARD
9Modification Information (MOD) Version: 1.02 USA
3.2 Installing the SC20-460
Follow the procedures below to install the board into the
TKR-750/850/751/851.
1. Remove the front side top panel of the TKR-750/850/
751/851.
Remove 6 screws (N33-3006-45, 3 mm diameter,
black) and pull it up.
2. Remove the FRONT PANEL of the TKR-750/850/751/
851.
Remove 6 screws (N33-4008-45, 4 mm diameter,
black) and pull the FRONT PANEL forward.
3. Remove the FRONT PANEL of the main unit.
3-1. Unhook 4 hooks located on the top and bottom of
the FRONT PANEL and pull it forward.
3-2. Remove two connectors (CN600, CN613).
You must be careful when removing the FRONT PANEL
since the panel is connected to the main unit board with the
cable.
4. Remove R742 and R653.
5. Install the SC20-460 board.
5-1. Connect the connector on the SC20-460 board to
the connector (CN601) on the PCB (TX-RX unit B/
2).
CN600 CN613
R653 R742

Version: 1.02 USA Modification Information (MOD) 10
3 INSTALLING THE VOICE SCRAMBLER BOARD
5-2. Peel off the cover of the tape on the rear surface
of the SC20-460 board and install the board to the
following location.
6. Reassemble the repeater after installing the SC20-
460 board.
Note: In case of test the operation of the TKR in PC Test Mode
and adjust the maximum deviation after installing the Voice
Scrambler board, the audio signal emitted from the local
microphone is not modulated. In this case, you must remove
the 12-pin cable connected to the CN601 connector of the
TX-RX unit (B/2) and perform soldering on the land of the
Display Unit. (Refer to the figure below.)
3.3 Configuration with the
Software
You can write the Voice Scrambler information to the
repeater using the KPG-91D after installing the board.
Follow the procedures below to write the Voice Scrambler
data to the repeater.
1. Install the KPG-91D in the PC and start the program.
The Main window of the KPG-91D appears.
Figure 3-2 KPG-91D Main window
Note: Refer to the “Field Programming Reference” for how to
connect the TKR-750/850/751/851 to the PC and install and
start the KPG-91D.
2. Select “Program” > “Read Data from Repeater”. Click
the icon on the Toolbar.
The “Read Data from Repeater” window appears.
3. Click “Read”.
You can read the configuration data from the TKR-
750/850/751/851 with the KPG-46 programming cable
by using the KPG-91D.
4. Select “Model” > “Model Information”.
The “Model Information” window appears.
5. Select “Voice Scrambler” from the “Option Board”
dropdown list and click “OK”.
Figure 3-3 Model Information
CN601
TX-RX unit (B/2)
Mount and fix the 
SC20-460 here.
12-pin cable
Solder here to
connect the
12-pin cable.

3 INSTALLING THE VOICE SCRAMBLER BOARD
11 Modification Information (MOD) Version: 1.02 USA
6. Configure the “Scrambler Setting” to be enable and
select scrambler code for each channel.
Figure 3-4 Channel Information
Refer to the “FPRG 6.2.17 Voice Scrambler” for
details.
7. Assign the “Scrambler On/Off” function to a function
key in the “Key Assignment” menu, if needed.
Figure 3-5 Key Assignment
Refer to the “FPRG 6.5 Key Assignment window” for
how to configure the function.
8. Or assign function port to scrambler on, off or on/off.
Figure 3-6 Function Port
9. Select “Program” > “Write Data to Repeater” or click
the icon on the Toolbar.
The “Write Data to Repeater” window appears.
7. Click “Write”.
You can write the configuration data containing the
Voice Scrambler information to the TKR-750/850/751/
851.

Version: 1.02 USA Modification Information (MOD) 12
4 MODIFYING THE DC POWER
It is possible to modify the DC power to prevent the TKR-
750/858/751/851 is turned ON with the erroneous
operation of the power switch. With this modification, the
DC power is always turned ON regardless of the power
switch operation.
Follow the procedures below to modify the DC power.
It must turn the power OFF before DC power modification.
1. Remove the front side top panel.
Remove 6 screws (N33-3006-45, 3 mm diameter,
black) and pull the TX-RX PANEL up.
2. Solder the PSW part located on the left side of the TX-
RX unit (A/2) to make a soldering bridge.
3. Reassemble the repeater after modifying the DC
power.
TX-RX unit (A/2)
Solder here to bridge.

13 Modification Information (MOD) Version: 1.02 USA
5 EXTRACTING RSSI SIGNAL FROM THE ACC 25-PIN D-SUB CONNECTOR
It is possible to extract the RSSI signal from the pin 1 of
the ACC 25-pin D-Sub connector (Default: No
Connection).
Follow the procedures below to modify the connector.
Note: The part number of the ACC 25-pin D-Sub connector is
“E37-0904-05”.
It must turn the power OFF before modifying the connector.
1. Remove the FRONT PANEL of the TKR-750/850/751/
851.
Follow the steps 1 - 3 in “ 3.2 Installing the SC20-460“.
2. Cut the connector 27-pin cable (CN606) located on
the printed board of the “E37-0904-05”.
Note: Cut and remove the wire from the top of connector.
3. Solder the wire to the RSSI land of the printed circuit
board.
4. Reassemble the repeater after modifying the
connector.
Connect the wire here.