(k3) Key out redux

[N4ZR]

Thanks, everyone who responded to my earlier query - I now understand
that the circuit in the K3 is equivalent to the old bipolar transistor
switches we used to use for serial port CW/PTT keying.

So here's my problem - I have a small 12V DPDT relay that I want to use
to switch the power to my SDR's preamp and active antenna - in other
words, to cut them off when my K3 is in transmit.  What I can't figure
out (be patient with a history major, please!) is how to use the Key Out
jack to switch the power to the relay , while using the same 12V supply
to power both the relay and the preamp/active antenna combo.

Ideally, the 12V relay would only be on when the K3's PTT was on.  The
thing that's driving me nuts is that I had this working, once before,
and then tore it apart for not very good reasons. Now I can't replicate
what I had.

Would anyone be willing to go offline and help me figure this out?

--

73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

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[David Shoaf]

Here's  a link to the  basic discussion
<http://www.electronics-tutorials.ws/io/io_5.html>  .  See the wiring
diagram about half way through the article.

Cheers,

David



--
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[Don Wilhelm]

Pete,

Connect one side of the relay coil to your +12 volt supply, and connect
the other side to the KEYOUT jack.  Put a diode with the cathode
connected to the +12 volt side across the relay coil.  The negative of
your power supply has to connect to the shell of the KEYOUT connector.
The relay will be activated when the K3 KEYOUT is active - keying, TUNE
and PTT will all activate it.

Yes, you should be able to use the same +12 volt supply to power the
SDR's preamp and active antenna, but that is a different consideration
than activating the relay.

73,
Don W3FPR

On 10/14/2017 10:18 AM, N4ZR wrote:

> Thanks, everyone who responded to my earlier query - I now understand
> that the circuit in the K3 is equivalent to the old bipolar transistor
> switches we used to use for serial port CW/PTT keying.
>
> So here's my problem - I have a small 12V DPDT relay that I want to use
> to switch the power to my SDR's preamp and active antenna - in other
> words, to cut them off when my K3 is in transmit.  What I can't figure
> out (be patient with a history major, please!) is how to use the Key Out
> jack to switch the power to the relay , while using the same 12V supply
> to power both the relay and the preamp/active antenna combo.
>

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