[Elecraft] RX Ant Preamps and the K3 12v Accessory Jack

[David Cutter]

I'm thinking this might also act as a gate to prevent excessive rf getting 
into the K3 2nd rx.  I'm planning to have a horizontal receive antenna 
located adjacent to my vertical transmit antenna for diversity reception.  I 
was just investigating the ICE196, but this idea might be better.

David
G3UNA


> Hi Rich,
>
> You could control 12 V to an external RX antenna or preamp using the
> KEY OUT signal pretty easily. This signal "floats" (open, or hi-Z)
> during receive, and goes to 0 V (ground) during transmit. The timing
> is perfect for such an application, because there's a delay between
> activation of KEY OUT and actual RF output.
>
> The KEY OUT signal would have to be buffered to create a "12 V on RX/0
> V on TX" signal capable of powering the external device. An
> alternative would be to use the signal to directly control an enable
> line on the device, if available and of the correct polarity.
>
> 73,
> Wayne
> N6KR
>
>
> On Aug 20, 2010, at 8:58 PM, K3RWN wrote:
>
>> I had a thought for a future feature request.  For those of us who
>> use RX
>> antennas (active and/or preamp).  It would be really cool if the 12v
>> output
>> on the K3 could be triggered by the PTT.  If the 12v output jack
>> could be
>> set in the menus to 0v (OFF) on PTT we could power our preamps via
>> that jack
>> and kill the power on TX.  The K3 already has a built in delay for
>> RF output
>> to amplifiers which can be set in "ms" as needed.  Most modern
>> preamps go to
>> ground when power is removed.  This would be nice but I would assume
>> that
>> the 12v output is not under control of the firmware.  Just a thought
>> for
>> future expansion.
>
>