[Elecraft] K3 to K3/0 Mini Direct Connection

[Warren Merkel]

Riding on Ted's coattails...

Wish I had a K3/0 lying around,  I could whip up something like this
pretty easily :)

As for the RS232 to TTL, that is really easy.  The MAX232 chip and
similar family chips do that with minimal parts.  Usually just 4 small
electrolytics and the chip itself.   The caps form a charge pump to
allow full +12/-12V RS-232 swings.  There is another model, that works
without the caps as well.

See: https://www.sparkfun.com/tutorials/104   for a quick guide.  You
can buy MAX232 boards from that same site.   You want a 5V model (for
TTL) not a 3.3 volt one)

If you have an old Icom CI-V to RS-232 interface on the shelf, you can
reuse it as the level converter.  The CI-V interface is TTL level on the
1/8 stereo mini jack side.   (RS-232 of course on the other)

The turn "ON" command is easily done through wiggling a pin the K3 ACC
port, however the turn off sequence would take a slight bit of serial
bits from a PIC or Arduino microcontroller to inject the "Turn K3 OFF"
Macro sequence.  There might be other ways, but I haven't dug in too
deeply yet. 
You certainly don't want to just remove power from the K3 supply line as
that doesn't give the K3 a chance to write the current settings/state to
flash memory.

Warren, KD4Z
K3 #8902

On 4/20/2015 2:42 PM, Dauer, Edward wrote:
> Following up on the earlier post, in which a couple of others also
> expressed an interest:  The quick answer is no, the K3 cannot be cabled
> directly to the K3/0-Mini acting as a control head.  Elecraft support
> writes: "The biggest obstacle is the K3/0 communicates using TTL and the
> K3 communicates using RS232. Someone would have to build a TTL to RS232
> converter to start. The other issue would be a circuit to turn on and off
> the K3. That would have to be configured. I am attaching a simple circuit
> to do this.²  If anyone has experience with a TTL-to-RS232 converter that
> might do the trick, I would be much obliged to hear suggestions . . .
> Thanks,
>
> Ted, KN1CBR
>
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