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Receiving with Skimmer SDR on K-3 transmit antennas

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N4ZR

Receiving with Skimmer SDR on K-3 transmit antennas

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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John Simmons

Re: Receiving with Skimmer SDR on K-3 transmit antennas

I've done exactly that! The only issue is that the local transmit signal
is very strong. Although I haven't done this yet, it'd be nice to use a
relay to insert some additional attenuation during transmit.

-de John NI0K rural Debs, MN

N4ZR wrote on 6/7/2021 8:49 PM:

Bob Wilson, N6TV

Re: Receiving with Skimmer SDR on K-3 transmit antennas

In reply to this post by N4ZR

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 <[hidden email]> 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.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Edward H Russell

Re: Receiving with Skimmer SDR on K-3 transmit antennas

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: [hidden email] <[hidden email]> On
Behalf Of Bob Wilson, N6TV
Sent: Tuesday, June 8, 2021 9:21 PM
To: N4ZR <[hidden email]>
Cc: Elecraft List <[hidden email]>
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 <[hidden email]> 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.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net Please help support this email
> list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]

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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html Message
delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]