At 08:57 AM 9/27/2006, Dick Green WC1M wrote:
>Jim Lux wrote:
>
> > Why not put all the electronics out at the antennas, and just
> > send ethernet or serial data out?
>
>Not a bad idea for a single array, but probably not physically practical for
>the complex system that will be hanging off my tower. All of the controllers
>can be operated via RS-232, so that's not the problem. The problem is that I
>would have to locate three SteppIR controllers, three Green Heron
>controllers, and one MicroHam StackMax at the tower. This would take a big
>NEMA box!
You betcha.. and it would need ventilation, etc/
> Also, I'd have to come up with an RS-232 controller for the SO2R
>switch, also located at the tower.
There's a variety of inexpensive RS232 to relay type
interfaces. I've used the Velleman K8056, which is $50 kit that
accepts 2400 bps serial data (doesn't have to be RS232 levels) and
controls 8 SPST relays.
> Could do that with a PIC I guess. Another
>complication is that I'd have to run AC to the tower, which I elected not to
>do this time because of the cost running buried conduit and the potential
>for running into ledge.
Yes.. that might be a problem if all the hardware doesn't run off DC.
And, I suppose some of that stuff (e.g. rotator motors) actually
draws a fair amount of current, and worse yet, wants to see 60 Hz AC
because they're using a reversible two phase motor. Cheap inverter?
However, power over coax isn't all that bad a solution.. RG-8/213/etc
is AWG 13 inside.. It's a bit out of the usual bias tee design
regime, but I've seen systems that sends several amps at several
hundred volts down the coax for remote sensing applications. Not
sure about the NEC implications, off hand...you'd be way, way out of
the power limited Class 2 sort of category.
The other thing is that your high power loads are intermittent, so
some sort of energy storage (e.g. a battery) at the tower end (which
is useful for other reasons) might work well. Run maintenance
charging current down the coax to keep the battery topped up, and it
supplies the juice to spin the antennas, etc. when you need it.
>However, I am planning on running CAT5e to the tower so I can bring my
>laptop down there and operate the station remotely. Great for testing rotors
>and TIC rings, doing power loss measurements, etc.
You might be best suited with the brute force approach, but, at least
you've got some "farther out of the box" ideas to work
with. Sometimes it pays to take a step back and look at all the
pieces a second time.
With my own stuff, I originally was going to put distributed
intelligence at the elements (because it's elegant), but then decided
that it was overly complex, and went to a "centralize everything"
sort of approach. Then, after assembling a good part of it, I went
to go get longer cables, and realized that the copper cost alone
(aside from the physical work of rassling all those wires around)
pushed towards the distributed solution, so I'm dismantling parts and
rebuilding it.
Such is the fun of developing new technology.
Jim, W6RMK
>73, Dick WC1M
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