[Elecraft] K3 min. insulation between in band TX & RX?

[Jim Brown]

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