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Kenwood 900 MHz Notes
Compiled by Mike Morris WA6ILQ
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Straight Info on Kenwood radios and the Amateur 900 MHz Band
Don't let anyone sell you a TK-430, TK-480, TK-930, TK-940 or TK-980 radio as they are all 800 MHz and will not work on amateur 900 MHz.

Kenwood hasn't yet imported an amateur 900 MHz radio so the USA hams that choose Kenwood are forced into using surplus commercial radios - the TK-431 and TK-481 handhelds and the TK-931, TK-941 and TK-981 mobiles.

The TK-431 and TK-941 are not too useful for amateur 900 MHz since they have a -39 MHz repeater offset that is fixed in the firmware, and despite several man-months of reverse engineeering time there appears to be no way to change it to a -25 MHz offset. They can be used by programming two channels, one set up to transmit on the repeater input, the other set up to receive the repeater output, then turn on the scan function. Unfortunately this means that you have to wait for the carrier delay timer in the repeater to drop out before you can transmit. Plus, if you have more than one active system in the area, the scan can stop on the wrong output and you will get cut out of your conversation. As a result, the TK-431 makes a good simplex handheld, or a portable monitoring receiver, and the TK-941 mobile makes a good repeater exciter, a 15 watt simplex or point-to-point link radio, or a reasonable link receiver when placed behind a good pass-notch duplexer (but you have to change the front end filters to the ones that pass 902 MHz). Some folks simply jumper out the filters and use the filtering provided by an external duplexer.

On the other hand, the TK-481 handheld and both the TK-931 and TK-981 mobiles are excellent amateur 900 MHz radios as they are not design-locked as to offset and therefore can all do the amateur standard -25 MHz split. The TK-931 has simplex and a single repeater offset, the TK-981 programs the receiver and transmitter frequencies separately, hence can support a different offset on every channel. This feature can be vital in some areas that use offsets that are not specifically 25.00 MHz to get around an interfering signal...

You will need a computer with a real serial port, the software and an appropriate programming cable to set up your radio...
The DOS programs listed below CAN NOT use a USB-based programming cable.
Radio   Software   System Cable Comments
TK-431 handheld KPG-16D DOS KPG-22 -39MHz offset only
TK-481 handheld (early)
serial number before
30100001 ("Version 1")
KPG-35D DOS KPG-36  
TK-481 handheld (late)
serial number of 30100001
or greater ("Version 2")
KPG-49D Windows KPG-36 Preferred, you can have simplex and the repeater offset different on each channel (the receive and transmit frequency are programmed separately)
TK-931, TK-931D,
TK-931HD mobile
KPG-5D DOS KPG-4 or KPG-46 Preferred, however you can have simplex and only one repeater offset that must be same for all channels.
TK-941 mobile KPG-25D DOS KPG-4 or KPG-46 -39MHz offset only
TK-981 mobile KPG-49D Windows KPG-4 or KPG-46 Preferred, you can have simplex and the repeater offset different on each channel (you program the receive and transmit frequency separately)
The programming cables are essentially RS-232 to TTL converters and homebrew diagrams are on this page. The handheld programming cable plugs into the speaker-microphone connector(s), the mobile cable plugs into the front panel microphone jack. The KPG-4 uses a 6 pin RJ-11 plug, the KPG-46 uses an 8 pin RJ-45 plug. Whatever programming cable you us, it connects a serial port from your computer to the radio and is used to load your frequencies and other parameters into the radio. None of the above radios are front panel programmable like a made-for-amateur-radio Kenwood.
TK-481 version 1 radios CANNOT be Firmware upgraded to Version 2.0 - there are hardware differences. The feature differences between the both is that V2 radios have Fleetsync - if you using the 981/481 for conventional amateur use you are not using Fleetsync and never will. These differences are noted in Kenwood bulletin I-01-26LM. From an amateur radio operators point of view the only difference that is noteable is that the Version 1 radio can ONLY be programmed with KPG-35D (DOS Based) software, the Version 2 radios are programmed with (KPG-49D Vers 4.01 or 4.02) Windows based software.
Note that Kenwood numbers the microphone jack pins backward from Ethernet. The KPG-4 and the KPG-46 are the exact same unit except for the RJ connector on the radio end of the cable. The KPG-4 has a 6-pin (RJ-11 / RJ-12-style) connector. The earlier KPG-46 has an 8-pin connector (RJ-45 style) and the center 6 pins are wired the same and the outer 2 pins are not used. If you are careful the 6-pin KPG-4 will work in the 8-pin mic jack. The plastic tab should only let you put the 6-pin plug into the middle of the 8-pin jack since pins 1 and 8 on the 8-pin jack aren't used for programming purposes. However, I'd build an adapter starting with a 6-pin RJ-12 jack wired to a stub of a common 8-pin RJ45 ethernet cable (or a 6 pin jack wired to a 8 pin jack, and plug a common 8-pin ethernet patch cord into the 8-pin jack). See this schematic for a KPG-4 and KPG-46 cable. Or look here for another one that has a lot more detail (thanks to Art Bross KC7GF for the second one).
If anyone would like to put together a programming article (with screen shots? They are not hard to do) we'd be happy to put it here.
The early TK-931 (FCC ID ALHTK-931-1) is a 15 watt radio, has fewer channels and the display only shows channel numbers, no alphanumerics. The TK-931D (FCC ID ALHTK-931D-1) is also 15 watts. The TK-931HD (FCC ID ALHTK-931H-1) is a 30 watt radio. The TK941 and the TK981 are 15 watts, and have internal speakers, but you will be much happier if you use a larger external speaker - a KES-3 (8 ohm) or KES-4 (4 ohm), or a similar one from GE or Motorola - just change the plug. The radio speaker jack is a 1/8 inch (3.5mm). The front panel on the TK981 (and maybe the others, I don't know) can be removed, flipped over, and reinstalled to allow the normally top-facing internal speaker to face downwards.

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 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.