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TM-431A Wide Band Transmit Modification This modification allows the TM-431A transceiver to transmit and receive from 420.000 MHz through 444.975 MHz with essentially full power throughout the band. 1. Disconnect power 2. Remove top cover 3. Locate a green jumper wire sticking out of the front panel assembly (behind VFO switch) 4. Cut the jumper in half and insulate the ends 5. Install diode D-209 1N914 on control board 6. Reassemble the radio. 7. This will reset the microprocessor and you will have to reprogram all channels
Modifications for the Kenwood TM-431 TM-431A Wide Band Transmit Modification This modification allows the TM-431A transceiver to transmit and receive from 420.000 MHz through 444.975 MHz with essentially full power throughout the band. 1. Disconnect power 2. Remove top cover 3. Locate a green jumper wire sticking out of the front panel assembly (behind VFO switch) http://www.kb2ljj.com/data/kenwood/TM-431A.htm (1 di 5)30/08/2009 18.15.44
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4. Cut the jumper in half and insulate the ends 5. Assemble radio 6. This will reset the microprocessor and you will have to reprogram all channels
9600 mod for TM431A Connect TX data to MO input at PLL circuit board (X58-3480-00) through a 100 kohms resistor. Connect RX data to DET output pin 12 at IC1 (FM IF HIC) The only problem is that you must mute the TX data when you RX, because this way you modulate the PLL. You can find these pins when you open the bottom cover. Locate the four points where the PLL circuit cover is soldered to. They are marked with 0 in the drawing.
FRONT PANEL
0 o o o
0
o o o MO> o 0
0 oooooooooooooooo ^DET
73 de Wes OH3NWQ @ OH3RBR.#TRE.FIN.EU PS. I have tried this - it works. TM-431E four 9600 Baud de DL1YCL @ DB0SGL Hallo OM's! http://www.kb2ljj.com/data/kenwood/TM-431A.htm (2 di 5)30/08/2009 18.15.44
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benutze seit langem meinen TM431E fuer 9600 Baud. Habe dazu PIN MO der PLL mit der zuvor mit einem Messer getrennten Lautsprecherbuchse verbunden. im schaltbild steht: X58-3480-00 PLL darunter das ic der anschluss rechts oben heisst MO Speise nun also die 9600 Baud-AFSK ueber die Lautsprecherbuchse ein. Das Demodulatorsignal liegt an der Mikrofonbuchse (PIN 6) und kann sofort verwendet werden. Der TM431E ist ein geradezu ideales Geraet fuer 9k6. Es kann sein, dass der Kondensator von MO (C 55 = .001) nach Masse (SMD-Technik) ausgeloetet werden muss, um den Frequenzgang der 9k6 AFSK nicht zu beeinflussen. Ich habs gemacht. Wuerde vorher aber mal probieren, ob man auf das Ausloeten auch verzichten kann. 1200 Baud speise ich ueber die Mikrofonbuchse ein. Das Demodulatorsignal an Pin 6 verwende ich fuer meine beiden Modems, 9k6 und 1k2. Viel Spass dies ist eine information von Christian in Hohenaspe, DK1QG JO43SX @ DB0HES ich markus aus datteln dl1ycl@db0sgl habe diese aenderung noch nicht durchgefuehrt und gebe diese information ohne gewaehr weiter. da ich so viele anfragen wegen des umbaus des tm431 bekommen habe spiele ich die info in die kenwood-rubrik ein. also alles ohne gewaehr und mit doppelten boden hihi. ihr koennt mir ja mal eine kurze info zukommen kassen ob der umbau geklappt hat da ich ihn selbst erst noch durchfuehren muss(warte noch auf mein tnc2h) so das wars von mir 73 markus Measure deviation using TM231,431,531 From AA9HX - ON7WP @ ON7RC.BT.BEL.EU To all technical Kenwood freaks, All people clever enough to know that they have to do something about the tremendous amount of people constantly over deviating, mainly all using off the shelf Kenwood equipment, coming straight from the factory adjusted at 6,7 or EVEN 8 KHz Peak deviation !!!! This article describes how YOU can use your Kenwood transceiver TM231, TM431, TM531 and apparently also the TMX41 range to measure ON THE AIR deviation of repeaters and all other stations... The principle of measurement is indeed very simple and DOES NOT NEED ANY MOD INSIDE YOUR TRANSCEIVER NOR EVEN OPENING IT !!! http://www.kb2ljj.com/data/kenwood/TM-431A.htm (3 di 5)30/08/2009 18.15.44
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Your microphone connector provides at pin 6 an audio output, straight from the FM detector. As all kenwoods use the same detector chip and coil, all give the same output voltage for a given deviation. The output at this pin 6 (and pin 8 as a ground) is linear up to 5 KHz deviation. As the IARU standard for amateur radio communication is 3 kHz peak deviation, this range from 0-5 KHz is perfect. Connect your oscilloscope to pin 6 and 8 as ground, 400 mV peak to peak voltage corresponds to 3 kHz deviation. So 200 mV is 1,5 KHz deviation and so on. CTCSS deviation should be around 300 Hz although most kenwood transceivers only react well from 400 Hz. Packet should be set to approximately 2 KHz. And additional an extra tip for improving the modulation quality of your kenwood TMx31: As the microphone amplifier is quite overdriven, modulation sounds very rough, due to extreme clipping of the signal, especially a nuisance in noisy environments, such as when mobiling in a not so luxury car. This can become much better just by changing or in some cases adding the input resistor of the microphone amplifier. Different types are used depending- ding on the market the transceiver was designed for. As they still believe at kenwood that Europe uses a 25 kHz raster and the states 20 kHz, Europe types get lesser attenuation before the amplifier then stateside trx's. Hey You there at the kenwood factory reading this: whole europe is changing to a 12,5 kHz raster, so will you please stop delivering your transceivers and portables with a deviation standard dating from Jurassic park time !!! schematic info: Deviation pot meter TM231 VR3 and decrease R64 Deviation pot meter TM431 VR2 and decrease R58 Deviation pot meter TM531 VR3 and decrease R60 So remember 3 kHz is the standard, do not discuss wither it is good or not, IT IS THE STANDARD FOR AMATEUR RADIO. It is the only way to live peacefully and to prevent wars between adjacent repeater or simplex channels. (and by the way, narrowing the receiver bandwidth extends your range...) Im looking forward to all comments, and I hope that somebody of the kenwood technical crew also will read this and do something about the adjustment of the new transceivers... 73 from Pedro M.J. WYNS AA9HX, ON4AWQ, ON7WP, full licensed transceiver doctor... HI ! ON7WP @ ON7RC.BT.BEL.EU All the mods are captured by Packet. KB2LJJ Radio Mods Database take now responsibility or liability for any damage resulting from this modification.
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I have been trying to help our ham radio with the radio modifications and have asked for any type of new radio mods. However, I haven't received too many. If all of you contributed a little more, I believe I would be able to help all the other ham's that are looking for these mods. I know it is possible to get more mods from all the Ham's because of the wide range that exist throughout the world. By doing this we can flourish and enjoy more of this hobby that we've taken part in for so many years. Furthermore, I ask you not to forget to send me any modifications that you might have through email. I would really appreciate it. Email
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73's John Ribeiro KB2LJJ
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