Keith, one of the manufacturers of the Telemetrum GPS altimeter, and I were talking about the radio opaqueness of Performance Rocketry graphite nose cones. If they were truly 100% graphite, then they shouldn't be radio transparent for the same reason that Carbon Fiber isn't. After all, graphite is just another carbon material.
So I did some testing using GPS and 70cm radio transmissions inside of a 75mm PR "Graphite" nose cone. The Telemetrum had no trouble getting GPS lock or transmitting on the 70cm band through the nose cone.
It locked within 5 minutes from a cold start, and was picking up 6-8 sats on the ground (depending on wether the antenna was pointing slightly towards the ground or slightly towards the sky) and 9-10 satellites 5 feet in air. Heck, it even picked up 3-6 sats from inside my house. The board was slightly offset in the middle of the nose cone with the receiver facing outwards, next to some quarter inch threaded rod that I installed down the center of my cone and the 70cm antenna just underneath the aluminum tip.
Overall, I was able to detect no difference between using it inside of fiberglass vs inside of "PR Graphite." Art Upton also did some testing using a Big Red Bee unit (not sure if it was GPS or RDF) inside of a PR graphite 54mm conical cone, and detected no substantial interference using more sophisticated equipment than what I have.
I'm not sure whether these cones are really graphite, or a special type of graphite, fiberglass with graphite infused epoxy, or what, but I do know that they're excellent for trackers and they can withstand Mach 3 with ease.
But, does anybody know what these are actually made of? I'd like to know just how far we can push them thermally and stress-wise.
So I did some testing using GPS and 70cm radio transmissions inside of a 75mm PR "Graphite" nose cone. The Telemetrum had no trouble getting GPS lock or transmitting on the 70cm band through the nose cone.
It locked within 5 minutes from a cold start, and was picking up 6-8 sats on the ground (depending on wether the antenna was pointing slightly towards the ground or slightly towards the sky) and 9-10 satellites 5 feet in air. Heck, it even picked up 3-6 sats from inside my house. The board was slightly offset in the middle of the nose cone with the receiver facing outwards, next to some quarter inch threaded rod that I installed down the center of my cone and the 70cm antenna just underneath the aluminum tip.
Overall, I was able to detect no difference between using it inside of fiberglass vs inside of "PR Graphite." Art Upton also did some testing using a Big Red Bee unit (not sure if it was GPS or RDF) inside of a PR graphite 54mm conical cone, and detected no substantial interference using more sophisticated equipment than what I have.
I'm not sure whether these cones are really graphite, or a special type of graphite, fiberglass with graphite infused epoxy, or what, but I do know that they're excellent for trackers and they can withstand Mach 3 with ease.
But, does anybody know what these are actually made of? I'd like to know just how far we can push them thermally and stress-wise.
