Some notes on interfacing to the Kenwood TKR-720 and TKR-820 repeaters

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Back to Home Some notes on interfacing to the Kenwood TKR-720 and TKR-820 tabletop repeaters
By Mike Morris WA6ILQ

The TKR720 (VHF) and TKR-820 (UHF) interface the same. If Kenwood sticks to it's numbering plan a low band unit would be a TKR-620 if they make one. In this writeup I'm going to use the format of TKR-n20 just to keep things generic.

This is a "quickie" page that was put together in late January 2008 as there was a converation on the repeater-builder mailing list that asked some questions. I provided some info from my notes and thought that publishing them might help. So I pulled the two pages of handwritten notes from my file cabinet that cover interfacing a TKR-n20 repeater to an external repeater controller and made a web page from them. The second pass a few months later added the TS-64 notes.
Please don't email me asking for any other info as everything in that project file folder is here and I no longer have access to those TKR-n20s.

This web page is not pretty but it works. If someone has a TKR-n20 repeater and wants to add some info to this page just email me at (mycall) at repeater-builder dot com. If anyone wants to write an additional article just let me know.

Again, these are NOTES, not a step-by step procedure. You may have to play with some of the connections to make them work, as I took the notes as I did the work, and I may have missed writing something down. I also used the internal decoder on one TKR and a TS-32 decoder on another, and my old notes are not clear as to what was different between the two. If anybody wants to take what is here and write a real article from it, feel free to. And if Kenwood changed the accessory pinout (and therefore the interfacing techniques) in later production runs these notes may not apply to a later unit at all.

The square at the bottom right is the microphone jack

The connector under the middle of the gold heat sink is for an external backup battery

15-Pin Accessory Connector Info

Molex Part Numbers Digikey Part Numbers Mouser Part Numbers

Housing: 03-06-2152 WM1228-ND 538-03-06-2152

Pins: 02-06-2103 WM1000-ND 538-02-06-2103

McMaster-Carr also stocks the connectors but I don't have the part number info.

15-Pin Accessory Connector Info
	Molex Part Numbers	Digikey Part Numbers	Mouser Part Numbers
Housing:	03-06-2152	WM1228-ND	538-03-06-2152
Pins:	02-06-2103	WM1000-ND	538-02-06-2103

Information I don't have: (can somone provide them?)
1) Connector info for the backup battery.
2) A good sharp closeup photo of the acccessory connector (without anything plugged into it)
3) Info on TKR-n20 programming and any relevant notes (maybe some computer screenshots?)

The TKR-n20 Accessory connector

Pin Layout: (looking at the rear of the unit)
The connector is five rows of three pins across in this format:
1 2 3
4 5 6
7 8 9
10 11 12
13 14 15

Note that the connector in the TKR is a male body with female pins! You need to purchase a female socket and male pins. Radio Shack used to carry these a long time ago, and maybe can still get them. Unless you have a good electronics store close by you will probably have to order from McMaster-Carr, Mouser or DigiKey.

Pin Description and Notes

1 Internal Controller disable - Jumper to pin 11 (ground) - grounding this pin tells the TKR to disable the internal controller completely and use an external controller.

2 Audio ground.

3 Transmitter modulator in (used as external CTCSS tone encoder injection input - don't use this pin for anything else). If you are using shielded cable - recommended - tie the shield to pin 2.

4 Receiver discriminator out (connect this to the audio input of any external CTCSS or DCS decoder(s) here, otherwise don't use). Use pin 2 as the ground for any shielded wire.

5 Transmitter audio in (i.e. repeat audio from the external controller). If you are using shielded cable - recommended - tie the shield to pin 2.

6 External speaker ground (see pin 12) (jumper this pin to pin 11)

7 +12vDC out of the TKR. This pin will source up to 1 amp so you can power an external controller from this pin. My old notes don't mention if this pin is fused inside the TKR (or if it's fused separately from the radio electronics), so until you check be careful that you don't short it to ground accidentally. You don't want to melt a trace or a wire in the harness.

8 PTT input (ground to xmit) (see note 1)

9 Internal speaker (jumper to pin 12 to enable)

10 De-emphasized receiver audio (i.e. repeat audio out to the external controller). If you are using shielded cable - recommended - tie the shield to pin 2.

11 Ground

12 Internal speaker audio out (jumper to pin 9 to enable)

13 RUS out (see note 2)

14 Empty hole in the connector body (see note 3)

15 Empty hole in the connector body (see note 3)

The TKR-n20 Accessory connector
Pin Layout: (looking at the rear of the unit) The connector is five rows of three pins across in this format: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Note that the connector in the TKR is a male body with female pins! You need to purchase a female socket and male pins. Radio Shack used to carry these a long time ago, and maybe can still get them. Unless you have a good electronics store close by you will probably have to order from McMaster-Carr, Mouser or DigiKey.
Pin	Description and Notes
1	Internal Controller disable - Jumper to pin 11 (ground) - grounding this pin tells the TKR to disable the internal controller completely and use an external controller.
2	Audio ground.
3	Transmitter modulator in (used as external CTCSS tone encoder injection input - don't use this pin for anything else). If you are using shielded cable - recommended - tie the shield to pin 2.
4	Receiver discriminator out (connect this to the audio input of any external CTCSS or DCS decoder(s) here, otherwise don't use). Use pin 2 as the ground for any shielded wire.
5	Transmitter audio in (i.e. repeat audio from the external controller). If you are using shielded cable - recommended - tie the shield to pin 2.
6	External speaker ground (see pin 12) (jumper this pin to pin 11)
7	+12vDC out of the TKR. This pin will source up to 1 amp so you can power an external controller from this pin. My old notes don't mention if this pin is fused inside the TKR (or if it's fused separately from the radio electronics), so until you check be careful that you don't short it to ground accidentally. You don't want to melt a trace or a wire in the harness.
8	PTT input (ground to xmit) (see note 1)
9	Internal speaker (jumper to pin 12 to enable)
10	De-emphasized receiver audio (i.e. repeat audio out to the external controller). If you are using shielded cable - recommended - tie the shield to pin 2.
11	Ground
12	Internal speaker audio out (jumper to pin 9 to enable)
13	RUS out (see note 2)
14	Empty hole in the connector body (see note 3)
15	Empty hole in the connector body (see note 3)

Table notes:

If you trust your external controller you can disable the internal timeout timer in the TKR.
Pin 13 is Receiver UnSquelched (RUS), a signal that is either carrier driven or tone driven depending on how the receiver is programmed. This signal is about 3.5 volts with the receiver muted/squelch closed/no tone, and about a quarter of a volt with the receiver unmuted/squelch open/with tone, which is enough to drive most external repeater controllers, or an open collector driver transistor just fine.
Pin 14 and Pin 15 are empty holes in the chassis mounted connector (i.e. are not used in stock units). My personal preference is to leave the connections on pins 1-13 stock and to do any mods/additions by adding pins into the holes in positions 14 and 15. I suggest that you leave some kind of paperwork inside the cabinet for the next guy so he knows that it's not stock on those two pins, and what you've done...

If you want a system that is remotely switchable between carrier and tone (which I do on every repeater I build, and is very handy when you are trying to figure out what the grunge is) you need to do one of three things:

Program the unit for tone, and use a digital output from the controller to manipulate the changeover line that is attached to the front panel "Monitor" switch (maybe run a wire to pin 15).
Program the unit for carrier squelch even if you run a toned repeater, and mount a tone decoder or DPL decoder (or both) inside the unit. Run the RUS lead to the controller COR input, and run the output of the add-on decoder to the controller PL/DPL decoder input (maybe using pin 14 to bring it out of the TKR). There is plenty of room inside the cabinet for an add-on decoder board.
A variation on (1) and on (2) is to mount a TS32 or TS-64 tone decoder inside and use a digital output from the controller to ground or unground the hookswitch lead (the violet wire on the TS-64). The decode output and the hookswitch lead can be connected to pins 14 and 15.

Notes on the Com-Spec TS-64 tone decoder

Wire
Color Signal Description and Notes

Red + DC power in

Black Ground

Green AUDIO INPUT. Hook this to the receiver discriminator

Violet HANGUP input. Ground this pin to make it active. When it's floating the tone decoder is disabled. When it's grounded the tone must be present.

White MUTE - This is the actual tone decoder output signal. It is an active high open collector output, and it requires a pullup resistor (1K works fine). If the signal is upside down from what you need then install jumper JP7 to get an active low signal (it will go to ground on decode).

Yellow ENCODER output. This audio output is connected to the transmitter modulator.

Orange PTT input. Ground this to switch the tone encoder on. When ground is removed the encoder phase is shifted (i.e. reverse burst), and the encoder stops when the 160ms is over. In our application we connected the PTT output of the external repeater controller to this pin.

Grey PTT Output. This signal goes low when the orange wire is grounded and stays low for the duration of the grounded input plus the reverse burst timing. In normal radio usage the PTT lead from the microphone would be disconnected from the radio and be connected to the orange wire, and the grey wire be connected to the point in the radio where the microphone PTT lead was. In our application this pin went to the transmitter PTT input.

Blue FILTERED RECEIVE AUDIO OUT. The path from the green wire (in) and the blue wire (out) has a high pass / low cut audio filter in line, designed to remove the subaudible tone from the user audio. This is an installers choice - You can feed the blue wire back into the receve audio connection. This type of radio surgery is very radio dependent and cannot be covered here. Many radios have a tone removing high pass filter in them from the factory and in that case you can simply tape off the blue wire and ignore it.

Notes on the Com-Spec TS-64 tone decoder
Wire Color	Signal Description and Notes
Red	+ DC power in
Black	Ground
Green	AUDIO INPUT. Hook this to the receiver discriminator
Violet	HANGUP input. Ground this pin to make it active. When it's floating the tone decoder is disabled. When it's grounded the tone must be present.
White	MUTE - This is the actual tone decoder output signal. It is an active high open collector output, and it requires a pullup resistor (1K works fine). If the signal is upside down from what you need then install jumper JP7 to get an active low signal (it will go to ground on decode).
Yellow	ENCODER output. This audio output is connected to the transmitter modulator.
Orange	PTT input. Ground this to switch the tone encoder on. When ground is removed the encoder phase is shifted (i.e. reverse burst), and the encoder stops when the 160ms is over. In our application we connected the PTT output of the external repeater controller to this pin.
Grey	PTT Output. This signal goes low when the orange wire is grounded and stays low for the duration of the grounded input plus the reverse burst timing. In normal radio usage the PTT lead from the microphone would be disconnected from the radio and be connected to the orange wire, and the grey wire be connected to the point in the radio where the microphone PTT lead was. In our application this pin went to the transmitter PTT input.
Blue	FILTERED RECEIVE AUDIO OUT. The path from the green wire (in) and the blue wire (out) has a high pass / low cut audio filter in line, designed to remove the subaudible tone from the user audio. This is an installers choice - You can feed the blue wire back into the receve audio connection. This type of radio surgery is very radio dependent and cannot be covered here. Many radios have a tone removing high pass filter in them from the factory and in that case you can simply tape off the blue wire and ignore it.

All of the above TS-64 information is in the Instruction Sheet that is packed with the TS-64 itself. In addition it can be downloaded from the Com-Spec web site, or from the TS-64 page at this web site.

I included the TS-64 info above instead of the TS-32 as it's current product, and easier to use. If you take the above info, a TS-64 data sheet and a TS-32 data sheet and compare them you can figure out the hookup of a TS-32.

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This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.