Extending the antenna on the Isaac16 Robot Controller

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 vehicle:
http://imagine101.com/stout02/pit.JPG ). 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?
Sincerely, Chris
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Christopher Waclawik wrote:

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.
Eljin
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Christopher Waclawik wrote:

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.
Mitch
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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.
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Christopher Waclawik wrote:

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.
Mitch
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By the way, this is the first time I've posted in this group and I'm VERY impressed with what you guys have to offer. I'll definetly be coming back often.
Chris
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