Muting one K3 while other is transmitting

[dl1mgb]

Hi,

I have two K3s running equally on one band in SSB. If transceiver A
transmits, transceiver B should be muted to protect the RX of transceiver B.

When in SSB and a microphone connected and just pressing the PTT, you
also send with transceiver B.

I haven't found anything in the manual how to do this.

Hope there is help out there.

Many thanks.

73s Chris DL1MGB
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[Jim Brown-10]

On 3/8/2014 12:50 AM, Christian Janssen wrote:
> Hi,
>
> I have two K3s running equally on one band in SSB. If transceiver A
> transmits, transceiver B should be muted to protect the RX of
> transceiver B.

That depends on the spacing and directivity of the antennas to which the
two transceivers are connected.  I have run 2 K3s on the same band into
antennas separated by 125 - 200 ft with a KPA500 driving one antenna and
a Ten Tec Titan driving the other. I have done this on 20, 15, and 10M,
both at home, and on county expeditions for the California QSO Party. At
our CA QSO Party site, we have done it on 40M and 80M using antennas
separated by about 300 ft, and we are using KPA500s. We have one K3 on
CW and the other on SSB.

This setup does not work for all antenna setups and orientations -- at
CQP the antennas are carefully located so that their nulls are in the
direction of the other antenna on the same band.  We can do this because
Yagis aimed at 70 degrees azimuth provide a very good pattern to work
the US, EU, AF, and northern SA.

73, Jim K9YC
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[k6dgw]

To the original post: "muting" the second K3 [i.e. silencing it] does
nothing to "protect" it from excessive RF input ... and possibly I
misunderstand the post too.

This was the subject of a thread not long ago on the list.  If the two
antennas are in each others' near fields, the antennas are a coupled
system and the power delivered to the receiver from the other antenna
can be [and likely will be] enough to damage the receiver.  I've seen it
happen to a K3.

Unfortunately, the end of the near field and the beginning of the far
field is undefined at HF, near just fades into far.  It's a function of
wavelength and size of the antenna among many other factors.  The near
field of a Voice of America sterba curtain on 20 MHz is likely much
larger than that of a ham dipole on 80 meters.

I would advise great care and some measurement unless you can assure
that the two antennas are definitely not parasitically coupled.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 3/8/2014 10:25 AM, Jim Brown wrote:

> That depends on the spacing and directivity of the antennas to which the
> two transceivers are connected.

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[Jim Brown-10]

On 3/8/2014 11:59 AM, Fred Jensen wrote:
> I would advise great care and some measurement unless you can assure
> that the two antennas are definitely not parasitically coupled.

Yes. There's an excellent discussion on how to determine this in the
first chapter(s) of W2VJN's classic "Managing Interstation
Interference,", which is sold by Inrad, the crystal filter folks.

73, Jim K9YC
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[Phil Salas]

Take a look at the transceiver front-end protector in the “Articles” section of my website at www.ad5x.com.  Very easy to build, and it is even fully QSK capable.

Phil – AD5X
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