Robert W5AJ


A discussion on another reflector about remote control of K3 dealt with turning K3 on/off remote

and I’m also posting it to K3 reflector for IDEAS, etc…


this email covers method for the Remote K3 ON/OFF control.


My first thought was leave the rig on when departing remote site but power failures do occur and K3 will be dark when power restores.


The Breadboard type wiring/tests good and no smoke got out This method below is not approved or commented on by Elecraft, any reproduction  at your own risk.... etc. etc.

Ideas always welcome



The K3 uses a momentary switch on front panel to turn rig on/off.

The schematic shows the POWER button has 12VDC one side of switch and the other side to control circuit, which when 12vdc is supplied & removed by pushing POWER button, whatever state the radio is in, will change to other state.


The back side of the PC board on K3 front panel has two feed throughs to on/off switch.

the furthest away from side is the one of interest (the closest feedthrough has the 12vdc - which is available elsewhere)


I Installed an insulated stranded #20 to POWER button - cut away few strands and soldered the #20 to connection of interest of the on/off switch.  I will call this the control wire for this discussion.

Brought control wire out through back of rig (reference port opening for now)


put power cables on K3

attach volt meter to control wire and to K3 ground.

TEST:   push on button on front of K3, 13VDC appears on control wire.

release power button, voltage drops to zero.  same when turning K3 off.

Confirms method being used in K3.


I have W3YY FSK/CW interface which contains three optical isolated switches - the CW one is unused (as I key CW another method).

Call it the DTR switch for this application.

I'm using the YY device as it's already connected to desktop and has solid state switch ready to go.  Certainly other switches or relay contacts should work too.

The important item is there is a spare "switch" and it's wired to DTR on com port into desktop.

Took 12vdc to one side of the DTR switch output, and connected the control wire from K3 to the other side of DTR output of YY interface device.

observing correct polarity


Plug power cable into back of K3,

Open WSJT program to test toggle DTR(your method may vary) change the PTT to DTR and push test PTT (after confirming rig communications) release TEST PTT

K3 under test powers up... YEAH!

click TEST PTT again - release, rig powers off   YEAH!!

repeat several times - no smoke, works.


don't hold TEST PTT long when powering up, that might be sign to K3 to enter some special mode or failure mode (I'm not privy to such info).


The breadboarded concept for remote ON/OFF works, after FD will work on cleaning up.

some forward thinking: bring new control wire out on same connection that is on ACC port for powering ON (remove existing POWER ON, then replace with new control wire) Or Install new connector at reference port

Need clean way to bring Control wire outside K3  

Find program/method to fire DTR on com port that is available at control site (can be done remote)


IF one is using FIDI USB to RS232, set "Disable Modem Ctrl At Startup"


On wiring the front K3 PC board.

Need to be proficient on soldering  & use small pencil type heater with small diameter solder.

Even then, it's like three hands needed...


After Field Day, will see about schematic and post on web page.


& finally, as someone is thinking but the K3 has a power on the ACC pin 8.  It’s known…


73 W5AJ


Midland, Texas




David Robinson

I had a similar issue when wishing to power up the K3 at the remote station every time the 12V power supply was switched on. My solution was an 8 pin PIC, see


Robert W5AJ


The remote on/off of power at 120vac level is next.

73 W5AJ

On Tue, Jun 30, 2020, 2:56 PM David Robinson <g4fre@...> wrote:
I had a similar issue when wishing to power up the K3 at the remote station every time the 12V power supply was switched on. My solution was an 8 pin PIC, see