 PK232-TS440 via ACC2 plug connection.



SUBJ:  PK232 - Kenwood TS440 connection via ACC2 13-pin plug.
       Mike mute.

Hello,

A lot of PK232 users seem to have problems to connect this TNC
to the 13-pins accessoire plug (ACC2) at the rear of the Kenwood
TS-440 H.F. transceiver.
Here is the wiring diagram of the connection i already use for
quite some time without any problem, so fasten your seatbelts...

    PK-232                                         TS440 (ACC2)
    ------                                         ------------

 --green--* - -audio in - - - - - - - - - -data out *------ 3

 --red----* - -ptt - - - - - - - - - - - - standby -*------ 13

 --white--* - -mic - - - - - - - - - - - - data in  *------ 11

 --brown--* - -ground - - - - - - - - - - -grnd - - *------ 4 or 8 or 12
                                                    I
 --shield-* - - - - - - - - - - - - - - - - - - - - *

 Be aware that "data in" signal at ACC2 pin 11 is bypassing the
first microphone amplifier stage in the TS440. So you need more
audio signal level from the pk-232 to achieve full H.F. power output.
This can be done bij turning the little audio potmeter at the
rear of the PK-232 fully clockwise and/or change the resistor value of
R160 (3.3K) by soldering an additional resistor parallel to decrease
this value in the PK-232.
The advantage is that you get a much smoother H.F. power gain control
as you can adjust the mike potmeter at the front of the TS-440 for
full power with mike potmeter fully clockwise without overdriving
the PA of your expensive TS-440.
Another advantage is a much better audio signal to L.F. detection ratio
which solved my HF interference problems !
If you also use a VHF/UHF transceiver in FM mode you should remember
that the increased audio-level from the PK232 to the FM rig could cause
the deviation being too big. Adding a resistor in series with the audio
signal line from the PK232 TO the mike plug will cure this problem.
Depending on the rig's mike input layout you will have to experiment
a little bit for the correct resistor value. In my case it is 560 K.


MIKE MUTE
---------

The TS-440 manual very simply states that grounding of ACC2 pin
9 (MIC mute) "mutes the signal input from the MIC jack".
But as pin  13  is internally directly connected to the PTT switch
line of the TS-440 mike jack, you get the result that your microphone
is also muted when the mike PTT switch is pressed, which is not what
we want.
To circumvent this, you could add the following enhancement to the
wiring diagram above by adding 2 small simple glass-diodes in the
13-pins ACC2 plug as follows:

red (ptt pk232 cable)            diode           ACC2 pin 13 (standby)
---------------------------*------I<-----------------*
                           I
                           I     diode           ACC2 pin 9  (mic mute)
                           I------I<-----------------*

With this modification the mike is muted when using the PK-232 but
not muted when using the PTT switch of the mike itself !

Good luck, happy surgery, 73 Andre'  (PA3EJU).  BBS: PI8APN.
