[TowerTalk] Further data on DPDT Coaxial Relay question

[Jim Lux]

At 11:29 AM 4/8/2007, Clint Talmadge wrote:
>Jim is correct. The Phase shift is 180 degrees and is added to two 
>equal lengths of coax making the antennas In-Phase with the switch 
>in one position and Out-Of-Phase in the other position.

OK.. there's a fairly easy way to do this with 1 SPDT relay...

Antenna one: some number of halfwavelengths of coax: contact A: 
halfwave of coax: contact B: some number of half wavelengths of coax: 
Antenna B.

You feed either at Contact A or Contact B...

Since you're always halfwavelengths, all the Z's sort of work 
out.  (bearing in mind that the feedpoint is going to look like 
Zantenna/2 (because they're in parallel)..

ALmost any relay would work here. There's leakage C and Ls, but not 
huge, and probably there's that much stray reactance on the antennas 
that you'd have to deal with anyway.