K3 min. insulation between in band TX & RX?

[Felipe Ceglia - PY1NB-2]

Hi folks,

There is a recent thread commenting about the cleanliness of K3 TX...

My question is:

In a in band two K3 scenario (100w, no amp), how many dB's of insulation
would be needed between each rig's antenna connector in order to keep the
RX clean?

73,

Felipe Ceglia - PY1NB
-------------------------------------------------------------------------------------
PR1T team member /// Rio DX Group member /// Araucaria DX Group member
http://dxwatch.com /// http://reversebeacon.net /// http://riodxgroup.com
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[Jim Brown-10]

On 9/14/2012 6:59 AM, Felipe Ceglia wrote:
> In a in band two K3 scenario (100w, no amp), how many dB's of insulation
> would be needed between each rig's antenna connector in order to keep the
> RX clean?

I can tell you what I do, and I can run two K3s into 1,5kW Titan amps
into beams separated by about 180 ft on the same band. Depending on how
the antennas are pointed, I can be within 60 kHz one K3 doesn't know the
other one is there.  For example, when I point the two antennas to the
ENE (the east coast of the US), they are at right angles to each other.  
If I point one antenna at the other, the radio will usually be
overloaded, the preamp will turn off, and the attenuator will turn on,
but I can often hear  strong stations and work them in between
transmissions by the other rig. As an example, I might have one antenna
pointed east and the other one NNW to work KL7 or UA0.

Another important part of the equation is feedline.  The long runs to my
antennas are mostly Hard line, and all the other coax in the system
(including jumpers in the shack)  is very high quality RG8 (similar to
LMR400) with a  robust copper braid plus foil shield. All of the
connectors are Amphenol 83-1SPs, all are carefully soldered, and all
connections are tightened with a wrench

Each year, I'm part of a group that takes our K3s to a remote county for
the California QSO Party (coming up in a few weeks). Our setup allows
spacing of about 150 ft between two tri-banders, carefully located so
that when we point them ENE (about 70 degrees, which gets us the East
Coast, EU, and the Caribbean)  they have a null to each other.  We use
our K3s with 600W amps, mostly KPA500s, but also sometimes a Yaesu or a
Ten Tec Hercules II.  With this setup, we can have a CW station and a
SSB station on the same band and work signals down to about the S5-S6
level. To work weaker signals one of the stations has to switch bands.  
The primary difference, I think, are the feedlines, which are made from
coax pooled from several members of the team. Some very good cables and
connectors, some not so good, some connectors crimped rather than
soldered, some good soldering, some not so good.

73, Jim K9YC


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[Felipe Ceglia - PY1NB-2]

Hi Jim,

Thanks for your testimonial. By any chance do you have means to measure the
isolation  at your qth in dB?

My setup has already evolved to 7/8 andrew hardlines, silver plated shell
and pin connectors, etc. I have 4 7/8 and 2 1/2 coax lines entering  into
shack into a big 4 inch galvanized steel pipe (I think you know where I
learned about it.. hihi). I measured the RX antenna coaxial and it has no
discernible common mode signals flowing in.

So far I´ve got 80db isolation in worst case, but I have some all band mush
when transmitting in SSB. CW is  abit clearer.

Anyway I´d like to know how to derive this figure from power output in dBm
and, I guess, published IMD figures.

73,

Felipe Ceglia - PY1NB
-------------------------------------------------------------------------------------
PR1T team member /// Rio DX Group member /// Araucaria DX Group member
http://dxwatch.com /// http://reversebeacon.net /// http://riodxgroup.com



On Fri, Sep 14, 2012 at 1:46 PM, Jim Brown <[hidden email]>wrote:

> On 9/14/2012 6:59 AM, Felipe Ceglia wrote:
> > In a in band two K3 scenario (100w, no amp), how many dB's of insulation
> > would be needed between each rig's antenna connector in order to keep the
> > RX clean?
>
> I can tell you what I do, and I can run two K3s into 1,5kW Titan amps
> into beams separated by about 180 ft on the same band. Depending on how
> the antennas are pointed, I can be within 60 kHz one K3 doesn't know the
> other one is there.  For example, when I point the two antennas to the
> ENE (the east coast of the US), they are at right angles to each other.
> If I point one antenna at the other, the radio will usually be
> overloaded, the preamp will turn off, and the attenuator will turn on,
> but I can often hear  strong stations and work them in between
> transmissions by the other rig. As an example, I might have one antenna
> pointed east and the other one NNW to work KL7 or UA0.
>
> Another important part of the equation is feedline.  The long runs to my
> antennas are mostly Hard line, and all the other coax in the system
> (including jumpers in the shack)  is very high quality RG8 (similar to
> LMR400) with a  robust copper braid plus foil shield. All of the
> connectors are Amphenol 83-1SPs, all are carefully soldered, and all
> connections are tightened with a wrench
>
> Each year, I'm part of a group that takes our K3s to a remote county for
> the California QSO Party (coming up in a few weeks). Our setup allows
> spacing of about 150 ft between two tri-banders, carefully located so
> that when we point them ENE (about 70 degrees, which gets us the East
> Coast, EU, and the Caribbean)  they have a null to each other.  We use
> our K3s with 600W amps, mostly KPA500s, but also sometimes a Yaesu or a
> Ten Tec Hercules II.  With this setup, we can have a CW station and a
> SSB station on the same band and work signals down to about the S5-S6
> level. To work weaker signals one of the stations has to switch bands.
> The primary difference, I think, are the feedlines, which are made from
> coax pooled from several members of the team. Some very good cables and
> connectors, some not so good, some connectors crimped rather than
> soldered, some good soldering, some not so good.
>
> 73, Jim K9YC
>
>
> ______________________________________________________________
> 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
>

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