After just spending $20k for the military to do exactly what Dave mentioned
below (copper to fiber to copper) just to open and close a security
gate from 2000ft away, and as W5WW and I hang more and more antennas,
rotors, controllers, control wires, power wires, connectors, joints,
splices, swinging gates, rotor plates, plus trencing, backfilling, tower
climbing, etc at the KC5FU antenna farm, where some towers are hundreds of
feet from the shack, it is beginning to dawn on me:
"FIXED
ANTENNAS"
Ron
N5QQ
on 12/4/07, Jim Lux <jimlux@earthlink.net> wrote:
>
>
> -----Original Message-----
> >From: David Robbins K1TTT <k1ttt@arrl.net>
> >Sent: Dec 4, 2007 3:32 AM
> >To: towertalk@contesting.com
> >Subject: Re: [TowerTalk] Fiber optics for amateur radio..
> >
> >Fiber is nice for transmitting control and data information. It of
> course
> >is a bit more complicated than just running copper with the same
> >information, but has advantages of being less susceptible to rfi. There
> is
> >one big thing that everyone forgets though, you can't transmit POWER via
> >fiber. You want to turn a rotor via fiber? You have to run copper to
> the
> >rotor for power, need relays or some other electronic converter to take
> the
> >control from the fiber and convert to signals to turn on the relays. So
> you
> >have taken what was a simple copper wire from a simple supply in the
> shack
> >and added at least 2 more complex (relatively) opto-electronic
> converters.
> >Want to get position indication back? You need another fiber (or you
> could
> >re-use the same one at the expense of more complex converters), some kind
> of
> >digitizer or analog to fiber converter, calibration, and decoding to some
> >kind of display in the shack... much more complex and prone to failure
> than
> >a simple copper connection from a pot to the meter in the box.
>
> I would venture to say that as technology improves, the model of
> unregulated power out and a fiber each direction, with some intelligence at
> each end, will be more reliable and less expensive than the "run separate
> wires for each function".
>
> Indeed, you have to get power to the loads, but nothing says that power
> has to come from your shack, from a special box (rotator controller or relay
> controller)..
>
> As far as reliability and calibration goes.. I think that with decent
> design, the remote sensor and digitizing scheme is better. No worries about
> changes in the properties of the wire or connections. Once you've bought
> into having any smarts at the far end, then it can do multiple things.
>
> Say you want a computer controlled rotor like the Green Heron box. The
> optical fiber approach isn't much different, except that some of the
> functionality now lives up on the tower, rather than back in the
> shack. Either way you have to convert a pot position to a digital
> number. Either way you have to turn power on and off to a motor. Either
> way you have to talk RS232 or some other interface.
>
> Likewise the relay boxes..
>
>
> I'd note that for the last few decades, the trend is away from the
> "separate wire for each function" in almost all other industries. CAN bus
> and similar in automobiles, MIL-STD-1553 for avionics systems... and all
> driven by some of the same basic reasons: reduce the number of wires that
> need to go from point a to point b. Each wire has a cost, not only in the
> raw material cost and weight (important in cars and planes), but in testing
> and manufacture (each connector pin costs something to install and test) and
> in increased reliability. Doubling the number of pins doubles the
> probability that any one pin will fail..Pretty quick (around 4 pins), it
> becomes more reliable to multiplex the data on a redundant pair of wires.
>
>
>
>
> Want to put
> >the rx/tx up the tower and feed by fiber... great, no feedline loss, but
> you
> >still have to run power up the tower to the box with the fiber so you
> still
> >have to worry about lightning protection, but now its in the direct line
> of
> >fire on the tower. And it has to be all remotely controlled via fiber...
> >final transistors fail in the middle of a contest??? Can't just pull a
> >spare rig off the shelf and plug it in, you have to drag it up the tower.
>
>
> Heh, heh.. just put the spare rig on the tower.. think of the desk space
> it will free up..
>
>
> I don't want to claim that this is the be-all, end-all today.. just that
> it's got a lot of potential, and the cost is no longer prohibitive. 20
> years ago, the cost alone was a significant disincentive. Maybe, folks at
> the edges of the hobby will come up with ways to address the concerns.
>
> Jim, W6RMK
> _______________________________________________
>
>
>
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