The rcs-8v is 5 relays, each powered separately so you can connect one or
more output ports to the input. The normal output ports are open circuited
when not connected. The way I do it is this:
1. modify port 5 so that it shorts the output to ground when deenergized.
This takes one short piece of wire from one relay pin to ground.
2. make up two 1/4 wave coax jumpers to a T connector. Connect one to the
input port on the rcs-8v and the other to port 5. the T is now the input to
3. on my stacks I have 1 antenna on top to port 1, 2 in the middle fixed at
europe that come to a T at port 2, 1 antenna on a ring at the bottom that
goes to port 3, then one fixed south that goes to port 4. all coax from the
switch to the antennas are the same length.
4. using 1n4001 diodes on the back of the rcs8v box configure the following:
position 1 energizes only port 1
position 2 energizes only port 2
position 3 energizes only port 3
position 4 energizes only port 4
position 5 energizes ports 1,2,3,5
position 5 energizes port 1,3,4,5
the way it operates is when port 5 is not energized the coax going to it
looks like a 1/4 wave shorted stub (maybe giving a bit of harmonic filtering
at the box end as a bonus). When port 5 is energized it turns the 50 ohm
line into 25 ohms so when 3 or 4 antennas are connected at once it acts as a
transformer to bring the impedance back up nearer to 50 ohms. If you are
doing other combinations you can mix and match the stubs using 75 ohm coax
instead of 50.
You can get fancier with 2 boxes to select more antennas and to remotely
select different transformer impedances to improve matching with different
combinations of antennas. This could be done with any simple relay box at
the remote end as long as you can force it to short the stub ends when
deenergized, and can select individual relays in any combination.
David Robbins K1TTT
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: DENNIS BRICKEY [mailto:firstname.lastname@example.org]
> Sent: Saturday, April 03, 2010 03:00
> To: towertalk
> Subject: [TowerTalk] RCS-8 as a StackMatch---How?
> I would be interested in how to make said stackmatch from an Ameritron
> RCS-8. Thanks in advance for the guidance.
> Dennis N4DD
> TowerTalk mailing list
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