My high school is in the process of brainstorming a design for a
BattleBotsIQ competition for next year. We have entered previous
robotics competitions, and we always reuse our Isaac16 robot controller
(ifirobotics.com). For the upcoming competition, durability is an
issue. Because our teacher is INCREDIBLE a getting sponsorships, we are
used to making things out of carbon fiber (we made a high mileage
). We are seriously
considering making a carbon fiber exterior for our robot; this way we
can keep the robot VERY light and protect form attacks from other
robots. The only problem is that carbon fiber blocks radio signals :-(.
To summarize, the Isaac16 antenna is interior. Does anyone know how or
know any articles about adding an exterior antenna to the controller,
or possibly modifying the current one?
It actually doesn't look to be that hard. I had a look at the
replacement antenna and it looks as if you have a couple of ways to go
about this. BTW I'm a technician working in the RF field, so I'll try
not to blow any smoke up your @#%#$@%...
First off, why not try to just mount the transceiver high up in the
robot's frame and allow the antenna to poke through the shell. That
would be the easiest thing to do. Don't let it touch the shell. Use a
little RTV to form a gasket for the antenna to poke through.
Secondly, the replacement antenna is a chrome whip which could be long
enough to poke out through the top of the shell if you can't pull off
mounting the radio unit high up.
Thirdly, and this will require a little expirementation on your part, it
looks as if the antenna has a screw hole at its base inside of the RF
unit, which is where the connection is made to the RF board or to a wire
going to the RF board. You could attach the center conductor of some
RG58 coax to that point and leave off the shield connection. Then at the
point where you want to mount the antenna loop the center conductor
around the mounting screw and make sure to get a tight connection
between the antenna and the center conductor.
The reason I say to use the coax is to allow the RF to pass through the
cable, but not allow it to radiate. The shield, not being connected,
will keep you from throwing the antenna out of tune with the circuits
feeding it. This is VERY important as you would loose most of your range
and possibly fry a $500 piece of equipment in the process if you did it
the other way.
I need to check with one of the geezers in my shop... :-) ... to see if
it would help in any way to connect up one end of the shield of the coax
to ground. That would act as a minor filter to dump off any stray RF
and keep it from affecting your radio. The other side of this is that if
you ended up cuting the coax to just the right length, it might detune
the RF unit and act as an antenna for the wrong freqs.
OK, stepped out for a sec and ran into the Ham radio operator I've got
living next door. DEFINITELY, hook up the shield to a GOOD ground on the
end closest to the antenna. Do NOT hook up the other end. Otherwise the
coax will become part of the antenna and you will throw the radios front
end out of alignment. This is a bad thing... :-)
I know I went long on this, but the wavelength for 900MHz is only about
3 or 4 INCHES long and even a quarter inch length in either direction
would throw your radio out of tune and you would start loosing data and
competitions very quickly.
Maybe he could get you some Kevlar. You could use it with the carbon so
that you don't have a completely enclosed conducting shell or you could use
it instead of the carbon entirely if you can tolerate the reduction in
compressive strength. Your application might even benefit from the better
impact resistance of Kevlar. There are also Evlar/carbon blends.
We normally do layups with both carbon and kevlar. The carbon is
incredibly strong, but quite flexible by itself. We normally add kevlar
to make it sturdy.
I don't recall us doing any layups with just kevlar. It definetly seems
like a distinct possibility, I'd have to ask my teacher.
I'm not sure I understand this. Once you lay up pure carbon or pure Kevlar
with epoxy, either one becomes extraordinarly stiff. The main difference is
that carbon is better in compression and Kevlar is better for impact
resistance. It sounds like these would not be meaningful differences for
the kind of housing you are making.
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