[Elecraft] two k3's on the same band

[Jim Brown]

On 3/21/2012 12:24 PM, Matt Murphy wrote:
> Just wondering if anyone has any experience using two K3's on the same band

YES!  My first experiences were on county expeditions for the California 
QSO Party, with four K3s feeding two KPA500s, a Ten Tec Herc II, and a 
600W Yaesu amp.  We had tribanders pointed roughly 70 degrees, carefully 
located so that they were at 90 degrees to each other, and were able to 
run one on CW with the other on SSB on the same band on 15 and 20M. The 
stations would hear each other at about S6-7, so we could work the 
roughly 60% of signals that were louder than that, then we would have 
one change bands so that both could work the weaker ones.

At home, I have a 3-el SteppIR at 120 ft on one tower, monobanders for 
20 and 15 at about 40 ft on a tower about 150 ft away, and a 4-el 10M 
Yagi about 50 ft further from the SteppIR.  During contests, I run Ten 
Tec Titan amps at legal power with two K3s. All of my antennas are fed 
with either CATV hard line or Heliax for most of their run, and 
everything else, including all patch cables inside the shack, is on very 
good RG213 with soldered Amphenol PL259s. With those Yagis optimally 
aimed to reject each other, I can operate as close as 50 kHz on 20, 15, 
and 10 and not know the other station is there. Pointing one at the 
other is another story, and can cause the receiving K3 to turn off the 
preamp and turn on the attenuator, but I can still work strong stations 
through my own QRM.

I mentioned the quality of my coax because that is quite important when 
you're trying to get a lot of rejection. Poor connections, or poorly 
shielded coax, or both, can couple common mode current from the outside 
of the coax to the inside of the coax at low levels. Coax shielding is a 
function of the resistance of the shield, the density of the shield, and 
the uniformity of the shield.  Thanks to skin effect, the larger the 
diameter of the coax the lower the RF resistance of the shield, assuming 
a shield of the same quality.

73, Jim K9YC