[UK-CONTEST] 2x6 Antenna Switch

[Jim Martin]

I am looking to build a six antenna to two radio switch box.  I cannot
justify a commercial unit at £300+.  Having only two antennas at the home
QTH it will only be used when out portable contesting (that is until we buy
our Highland B&B and build a huge antenna farm!!)
Two articles I have found so far are http://www.qsl.net/ei7ba/remote.htm
from John's excellent site and
http://www.qsl.net/k5lxp/projects/CoaxSwitch/CoaxSwitch.html which is very
close to what I am after.  With this design I could complete the project for
about £120, using 5amp relays from Maplin. (P/No. QC82D rated 240v X 5amp =
1200w, maximum output at the moment is 100w and hopefully these relays would
cope with 400w in the future?)
I have a slight concern using this in a multi-op environment. If an antenna
is in use by station A it cannot be selected by station B which saves me
sending 100w into the other rig. Unfortunatly this rig is then left without
an antenna and is shorted to ground.  Disaster if the operator is not paying
attention to antenna selection.  Are there any newer designs  which address
this problem or have additional input from the band decoders?
The current set up is 2 x MP-STUBS relay switched controlled by band
decoder-auto BPF controlled by band decoder-antenna(soon to be 2x6 switch
box, manual control)
Having spent years keeping the coax and antennas from two stations as far
apart as possible I am feeling a bit anxious at having both 100w outputs
within a few inches of each other on a PCB!  Is there anything specific I
need to do to ensure isolation of the two signals and a restful nights
sleep?
Are there better relay options?  I will need 20 in total as I need to build
a new stub switching unit.
As always your thoughts and advice would be appreciated.
73
Jim,  MM0BQI