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Some Notes on the Kenwood Packet connector Compiled by Mike Morris WA6ILQ

Several of the Kenwood amateur mobile radios such as the TM-G707, the TM-V7, the TM-V71 and others have a "packet" connector on them. Some use the same DIN connector as a PS/2 computer keyboard or mouse or the TV "S-Video" connection. The pinout is fully decribed in the manual. The signals on this connector are also useful when you connect the radio as a point-to-point link, as a remote base, etc.

One point that is not made clear however is that the audio connections in the packet connector have two different modes, selected by an item in the radio's setup menu. One mode is described as being appropriate for 1200 baud data, the other for 9600 baud data. The difference is that the 1200 baud mode enables pre-emphasis in the transmitter and de-emphasis in the receiver whereas the 9600 baud mode treats it as flat audio. For more information on flat audio see the articles on the "Tech Info" page at this web site.

Several of these radios have a VERY annoying characteristic that shows up if you try to use the radio as a remote base or as a mobile repeater: the COS pin is carrier driven, not audio mute driven. This means that if you put the receiver into CTCSS mode the COS output still tracks the channel activity, not the squelch opening. Kenwood needs to change the firmware to add yet another menu item, one that selects the COS output to one of three modes:

1. Channel activity driven (the current behavior),
2. CTCSS driven or
3. Receiver unmuting driven (which takes into account the carrier/CTCSS mode).

Until Kenwood gets their act together, here's a quickie mod that applies to the TM-G707 and the TM-V7, maybe others, courtesy of Ken Arck AH6LE at Arcom, who says that Eric W2ZT first posted it:

The internal "SQ" line of the TM-G707A is active with an open squelch in carrier mode. When in "CT" (tone decode) mode it is active only when the proper PL frequency is received. This behavior in other manufacturers is named "audio mute" - it's a signal that takes into account the carrier squelch/CTCSS mode and the presence or absence of the CTCSS tone signal.

This "SQ" line can be found at CN4 pin 11 on the main TX-RX board or CN502 pin 11 on the Control board (behind the front panel). If you don't wish to perform this modification to the DIN socket (kind of intricate), you can simply attach a wire to one of these points, then route it out of the radio and connect it to an appropriate connector.

I modified my TM-G707A by routing the internal "SQ" line to pin 6 on the radio's mini DIN socket (replacing the current connection). My method of doing this required the cutting of a circuit trace on the Control board (current DIN connection) and routing a wire from pin 11 of CN502 to the side of the trace cut that connected to pin 6 of the DIN socket.

This mod will facilitate fully agile CTCSS decode and/or encode functionality using only the RC-210's A72xx1 or A72xx2 commands without the need for an external PL decoder. Additionally, the remote base controller port can be left in carrier mode. Don't forget to change the controller's remote base port setup from active high to active low.

Hope this helps someone.... de AH6LE

I have a follow on note to my article on modifying the Kenwood G707's packet connector for allowing a CTCSS decode signal to be available instead of a COS only signal.

One unwanted side effect - the modification described breaks the serial connection to the radio - it will not allow the PC programming software, the PG-4S cable or the cloning cable to work. To resolve this I added a miniature toggle switch to select between the old COS only signal (for use while programming) and the new COS and CTCSS signal (for day-to-day operation).

Bob Dengler NO6B made W4XE's mod to his radio, and emailed in these comments:

• The new combined CTCSS AND COS signal you get is active low, which is opposite of the COS-only signal that was there prior to the mod. This is documented in the file, but worth mentioning as you will have to reprogram the equipment connected to the radio.
• The volume control must not be turned all the way down, otherwise the signal stays inactive (high) at all times. This really threw me after performing the the mod as I left the speaker disconnected during testing, so I kept the volume turned all the way down to prevent damage to the speaker output driver. As a result, I couldn't get any change from the inactive 5vDC level on the new combined CTCSS AND COS signal output until I accidentally bumped the volume control. Also, anything that causes a beep such as pressing a front panel button will cause the signal to go active during the beep. You may want to put a 10 ohm resistor into a plug that matches the speaker jack so that you can leave the volume turned up a little and still have the speaker off.
• Page 9 of the PDF file notes a heavy build-up of flux around the 6 pin mini-DIN connector. I found that on my G707 as well; I wonder if all those connectors were hand soldered?

Bernie Parker K5BP did the same mod to a TM-271.

Contact Information:

The author can be contacted at: his-callsign // at // repeater-builder // dot // com.

Information provided from various sources as listed in the text.
Hand-coded HTML © Copyright date of last edit by Mike Morris WA6ILQ.

This page split from the main Kenwood index page 16-Nov-2011.

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.