[TowerTalk] Antenna switch isolation?
Jim Thomson
jim.thom at telus.net
Sat Jun 5 23:03:23 PDT 2010
Date: Sat, 5 Jun 2010 23:48:56 +0700
From: "Martin Sole" <hs0zed at csloxinfo.com>
Subject: Re: [TowerTalk] Antenna switch isolation?
Back to my switch project it seems clear that layout is critical as may be
the choice of relay to minimise coupling. Whilst I think I have a stray
coupling problem there also seems to be quite a few variables at play.
Martin, HS0ZED
p.s. This switch box is for my quad project, feeding the loops ONE at a
time.
## OK... since this appears to be a 1 in 3-5 out box... for a quad... then
why do u require all the isolation?? My Array solutions 1 in 6 out box uses
6x DPDT relays. They use 3/4" wide Cu strap..exactly 5/16" above the chassis.
This forms a 50 ohm strip line. Input is at far left... and outputs 1-6 are to the
right of this. COM of each relay is connected to the center conductor of each coax
connector [7-16 din]. ALL NC contacts are connected to the grnd buss.. which is just
more 3/4" wide cu strap..running the entire width of the box. ALL the NO contacts
are connected to the hot 2 kw buss. [ more cu stap]. Far left hand side of this hot buss is
connected to the input connector.
## in normal operation... any relay that has it's coil DE-energized.. [ not operated]
has it's ant center conductor grnded ! Any relay operated has it's ant center conductor
fed to the input hot buss. There really is no port to port isolation per se.... since all unused
ports are dc grnded. They have also paralleled all contacts to increase power hanndling by 4 x .
## I also have the AS 6 pack box... uses 12 x relays. They have the diagram of it on the AS site.
These box's use 12 x 3PDT relays. The 3rd set of contacts is used to control the ..'master-slave'
function.. so which ever of the 2 x ops gets the ant 1st.... locks out the 2nd op. There is loads
of isolation with the remaining contacts. Each of the 6 x ant ports has a PAIR of 3PDT relays.
## If you just require a remote switch box to save on coax... and toggle ONE xcvr between a bunch
of DE's on your quad... then almost anything will suffice. Isolation in that case is a non issue.
later........ Jim VE7RF
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