[Elecraft] Receiving with Skimmer SDR on K-3 transmit antennas

[Edward H Russell]

Some SDRs have a mute input that can be connected to KEY OUT on the K4. This
prevents self-spotting. I use this with the RFSpace SDR-IQ. Hopefully when
available the K4 IQ stream will (perhaps optionallyu) mute during TX.


ED / W2RF




-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On
Behalf Of Bob Wilson, N6TV
Sent: Tuesday, June 8, 2021 9:21 PM
To: N4ZR <n4zr at comcast.net>
Cc: Elecraft List <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] Receiving with Skimmer SDR on K-3 transmit antennas

I documented the procedure about 13 years ago in this presentation, linked
at the very bottom of my QRZ.COM page <https://www.qrz.com/db/n6tv>, which
includes the recommended Mini-Circuits 50 ohm splitter (ZFSC-2-6
<https://www.minicircuits.com/pdfs/ZFSC-2-6%2B.pdf>).

   - Adding a Software Defined Radio (SDR) to an SO2R station
   <http://tinyurl.com/4zama4>

High power cannot exit the RF ANT OUT jack, so it's safe, but there's no way
to prevent a local skimmer from spotting you.  Skimmer won't spot your own
call, but it will usually spot busted variants.  I recommend disconnecting
your skimmer from the RBN when operating at the same site.

Local RF will usually leak into the SDR even with no antenna connected; the
SDR is very sensitive.  Probably no way to mute it completely during TX.

73,
Bob, N6TV


On Mon, Jun 7, 2021 at 6:50 PM N4ZR <n4zr at comcast.net> wrote:

> I would like to be able to connect my SDR (an RP-16) to my 
> transmitting antennas, and have it automatically muted when my 
> K3/KPA-1500 goes to transmit.  The idea is to have the best possible 
> antennas available for Skimming while active in contests.
>
> It seems to me that I should be able to connect a splitter between the 
> RX Out and RX In ports on the K3, and use that to feed the SDR by 
> pressing the RX Ant button  (at a cost of ~3.5 dB loss, of course).
> Question is, what happens when I go to transmit - is the RX Out line 
> muted so that my SDR won't try to spot me? Ideally, I'd think it would 
> be, but I've groped around in the K3 manual and Fred Cady's book, and 
> haven't found a concrete answer - can anyone help?
>
> --
> 73, Pete N4ZR
> Check out the new Reverse Beacon Network web server at 
> <http://beta.reversebeacon.net>.
> For spots, please use your favorite
> "retail" DX cluster.
>
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