Modifications for the Kenwood
TM-431
19-07-1998 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.
- Disconnect power
- Remove top cover
- Locate a green jumper wire sticking out of the front panel assembly
(behind VFO switch)
- Cut the jumper in half and insulate the ends
- Assemble radio
- This will reset the microprocessor and you will have to reprogram all
channels
19-07-1998 9600 mod for
TM431A
Connect TX data to MO input at PLL circuit board
(X58-3480-00) through a 100 kohm 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 0
o
o
o
o
o
o
MO> o
0 0
oooooooooooooooo
^DET
73 de Wes OH3NWQ @ OH3RBR.#TRE.FIN.EU
PS. I have tried this - it
works.
19-07-1998 TM-431E
fuer 9600 Baud
de DL1YCL @ DB0SGL
Hallo
OM's!
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
19-07-1998 Measure deviation using
TM231,431,531
From AA9HX - ON7WP @
ON7RC.BT.BEL.EU
To all technical kenwood freaks,
All people clever
enought to know that they have to do something about the tremendous amount of
people constantly overdeviating, 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 !!!
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. Differnt types are used depen- 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 portabels with a deviation standard dating from
jurassic park time !!!
schematic info:
Deviation potmeter TM231 VR3
and decrease R64
Deviation potmeter TM431 VR2 and decrease R58
Deviation
potmeter TM531 VR3 and decrease R60
So remember 3 kHz is the standard, do
not discuss wether 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