[Elecraft] Need coax relay to switch ant between K2 & K3

[Tom W8JI]

Vacuum relays can be quite good, as can a proper traditional relay, but all 
are only as good as the designer's ability to understand ground loops.

All isolation shortfalls come from either the wrong style relay, or a bad 
layout with ground loops or crosstalk between RF conductors. Many of the 
problems are because people insist on grounded unused ports, and the ground 
point has RF currents flowing through a common ground lead with a signal 
path. Worse yet, what applies to RF isolation generally applies to 
lightning.

Most trouble occurs because people forget the shield carries exactly the 
same current as the center conductor, and even one inch of path can drop 
enough voltage to cause a coupling problem.

If we look at the highest isolation switches on the market, the RCS-8V and 
the DXE switches, neither depend on RF shield currents flowing through the 
circuit boards. Neither use a groundplane transmission line on the boards. 
Both have connectors on a single flat plate with a design for radically 
flowing shield currents from the center common point.  The sheet metal the 
connectors mount to is the signal groundplane.

Most "trouble" occurs when people try to run RF grounds up through a 
groundplane on a circuit board or through point to point wiring. This is 
true in radio, audio lines, and antenna switches. It isn't good for 
lighting, ground loops, or RFI unless grounds go to a good common wall with 
very low impedance, solid connections, and well-planned current flow.

73 Tom