[Elecraft] Digital Mode Interface for the KX3 for WSJT modes

[Joe Subich, W4TV]

> Given that the KX3 supplied cables only have RXD and TXD signals,
> using the serial port to generate PTT requires that either you use 2
> serial ports (one may be the KX3 USB cable and the other can be a
> real port or USB to Serial adapter), or provide a "Y" adapter to go
> to your interface.

Or simply provide a 3.5mm stereo jack on the interface for connection
to the KX3 CAT jack.  Properly wired, TxD/RxD go to the KX3 while
DTR and RTS get split off (in the box) to a pair (or more) of NPN
transistors for CW and PTT.

The difficulty in dealing with a computer interface for the KX3 is
the last of a fixed level audio output and the need to share audio
with the operator headphones/speaker.  Levels for computer decoding
and operator comfort are not always the same <G> which means a
buffer/splitter amplifier, external speakers with separate volume
control and headphone jack or some other "extra box".

73,

    ... Joe, W4TV



On 7/13/2012 10:12 AM, Don Wilhelm wrote:
> Bill,
>
> You may want to re-think using the serial port on your interface.
>
> Most data mode applications like to use the same COM port for rig
> control (OK, maybe just frequency display) as they use to activate DTR
> or RTS for PTT.
>
> Given that the KX3 supplied cables only have RXD and TXD signals, using
> the serial port to generate PTT requires that either you use 2 serial
> ports (one may be the KX3 USB cable and the other can be a real port or
> USB to Serial adapter), or provide a "Y" adapter to go to your
> interface.  Use of the "Y" adapter precludes the use of the KX3 USB cable.
>
> There is nothing wrong with generating PTT from the audio stream, or
> just using VOX in the KX3.
>
> 73,
> Don W3FPR
> On 7/13/2012 9:51 AM, Bill Conkling wrote:
>> I am working on an interface in a box w/pcb.  Once you use a box, you can do
>> anything.  I plan to have full serial port and two audio cables from
>> computer.  Transformers in the audio chain and a 10K/1k attenuator in mic
>> input to KX3.  I will split the serial port to provide proper connections
>> for CAT, PTT, and CW as n1mm handles the K3.
>>
>> Whole thing in a 2.5X2.5X1 box.
>>
>> Big plans....
>>
>> ...bill nr4c
>>
>
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