[TowerTalk] DPDT Coaxial Relay question or alternative

[Jim Lux]

At 07:41 AM 4/8/2007, Jim Rhodes wrote:
>Why go to all that expense of coaxial relays for 30 meters? Why not
>just use a simple spst relay to short out the quarter wave loop when
>you don't want it? Build the whole thing in a box with connectors for
>the feedline, antennas and loop, then power it via the feedline.

If you just short out a quarter wave loop, you're essentially putting 
in a stub (open ended stub 1/8th wave at half the Z of the line). A 
SPDT gives you either the 1/4 wave in line, or an open 1/4 wave stub 
(which will look like a short!).  A DPDT is the practical way to do it.

Jim, W6RMK