Yes, but if you are going to have to run power you can just as easily run
control on the same cable, which might as well be the coax itself. If you
want to do some fancy encoding and remote processor that is fine, you just
have to keep the control frequency low enough that you can easily separate
it from the rf.
And don't count out the simple relay systems using the half wave AC scheme.
Consider this... using just the shield of the coax as ground and +/-
halfwaves on the center conductor you can get 4 states... add one more
conductor and you can extend that to 16, add 2 conductors and you have 64
combinations. add a few zener diodes to make the remote switch voltage
sensitive and you could probably get 9 or more states with just the coax.
Sometimes simpler is better, and lots cheaper. A couple years ago I was
looking for a better control box than the rotary switch that came with the
rcs8v... and I wanted ptt lockout. Lots of people suggested micro
controllers or some kind of a programmable thing. I wanted to stay away
from things that might cause interference or be susceptible to rf
themselves... with 6 or more stations running 1500w at once, I don't need
anything that needs extra care to make it work. the result was an all relay
box that gives 8 latched outputs, ptt lockout so it won't switch while
transmitting, and nice simple pushbuttons instead of a rotary switch... and
its easily 'reprogrammed' by moving a few diodes when the antenna selections
change. I've had 10 of them running for a couple years now without a single
failure.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: jimlux [mailto:jimlux@earthlink.net]
> Sent: Friday, January 30, 2009 23:34
> To: K1TTT
> Cc: 'TowerTalk'
> Subject: Re: [TowerTalk] fancy switches Re: Antenna Switch Needed
>
> K1TTT wrote:
> > Don't forget you'll still need power at the remote box for the receiver
> and
> > also for the relays themselves. Its easy enough to put dc or 60hz on
> > feedlines to power remote equipment, its easy to switch 4 relays with
> just
> > +/- half wave AC. an audio frequency pickoff would let you use something
> > like an old telephone modem for remote control... plenty fast enough for
> > antenna selection, rotors, etc.
> >
> > But for my money I just use rcs8v remove boxes with good old wire
> connecting
> > them to the shack.
> >
> >
>
>
> Yes.. but once you get past the switch one of 4 using rectified AC to
> get 2 bits to the other end, you're into some sort of remote control
> The rcs8v is fine, but once you start getting beyond that to more
> complex scenarios, you either wind up home-run-ing a raft of coax back
> to a central switching hub, or running a raft of control lines out to
> remote switches. (look at the radio arcala diagram, for example)
>
> I don't know where the "transition point" is between just stringing more
> wires and doing some form of multiplexing, but I suspect it's pretty
> close to the "anything more than an RCS-8V". There's a reason why we
> don't have telephone poles with a zillion separate pairs on them anymore.
>
> The consumer world has made networking VERY cheap. Why not see what we
> can leverage.. especially with 802.11, it's even *radio*.
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