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Piano Wire Antenna for Experimental Rocket
On Sun, 24 May 2009 04:04:52 GMT, "Jerry"
wrote: Have you considered flush antennas, like slots? Slot antennas have the maximum lobe perpendicular to the rocket axis. There's very little signal below the rocket. This is why tracking stations are far away from the launch site. If the rocket were overhead, and going straight up, there's no signal. Slot antennas are also a power waste. You need 4 slots, run by a power splitter, in order to insure that at least one antenna is oriented in the direction of the receiver. Meanwhile, the other 3 slot antennas are radiating power to nobody in particular. Say goodby to about 3/4th of your tx power. Receive sensitivity is not affected. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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Piano Wire Antenna for Experimental Rocket
"Jeff Liebermann" wrote in message ... On Sun, 24 May 2009 04:04:52 GMT, "Jerry" wrote: Have you considered flush antennas, like slots? Slot antennas have the maximum lobe perpendicular to the rocket axis. There's very little signal below the rocket. This is why tracking stations are far away from the launch site. If the rocket were overhead, and going straight up, there's no signal. Slot antennas are also a power waste. You need 4 slots, run by a power splitter, in order to insure that at least one antenna is oriented in the direction of the receiver. Meanwhile, the other 3 slot antennas are radiating power to nobody in particular. Say goodby to about 3/4th of your tx power. Receive sensitivity is not affected. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 Hi Jeff Why are you so negative?? I have designed and built lots of slot antennas that were widely used on military aircraft. The efficiency is quite good. I am sure a smart guy like you could design a slot antenna and locate it for those guys with the 3G rocket. There hasnt been any text that restricts where the slot could be located. As I read the original post, they werent receiving signal from the accending rocket. Maybe they only want to receive data that was recorded after the rocket reached it's peak. There are lots of information that you and I dont yet know. But, my major question for you is "Why are you so negative?". Jerry KD6JDJ |
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Piano Wire Antenna for Experimental Rocket
On Sun, 24 May 2009 07:30:03 GMT, "Jerry"
wrote: "Jeff Liebermann" wrote in message .. . On Sun, 24 May 2009 04:04:52 GMT, "Jerry" wrote: Have you considered flush antennas, like slots? Slot antennas have the maximum lobe perpendicular to the rocket axis. There's very little signal below the rocket. This is why tracking stations are far away from the launch site. If the rocket were overhead, and going straight up, there's no signal. Slot antennas are also a power waste. You need 4 slots, run by a power splitter, in order to insure that at least one antenna is oriented in the direction of the receiver. Meanwhile, the other 3 slot antennas are radiating power to nobody in particular. Say goodby to about 3/4th of your tx power. Receive sensitivity is not affected. Hi Jeff Why are you so negative?? I have designed and built lots of slot antennas that were widely used on military aircraft. The efficiency is quite good. I am sure a smart guy like you could design a slot antenna and locate it for those guys with the 3G rocket. There hasnt been any text that restricts where the slot could be located. As I read the original post, they werent receiving signal from the accending rocket. Maybe they only want to receive data that was recorded after the rocket reached it's peak. There are lots of information that you and I dont yet know. But, my major question for you is "Why are you so negative?". Jerry KD6JDJ I don't think I'm being particularly negative or offensive. I offered what I consider to be a more reasonable alternative (CP turnstile antenna) and ran the path loss calculations to insure that it would work. I also itemized why a slot antenna would be an inferior solution. My main point is that with a vertically ascending rocket, the antenna pattern should be primarily ahead and behind the rocket, not perpendicular. I've seen one paper design that used insulated fins for the 4 turnstile antenna elements. However, I haven't seen the actual rocket. I also built a 2.4GHz antenna system for a model airplane for a video downlink. The initial design was a slot antenna system in the fuselage, which worked great when the aircraft was overhead, but did badly when near the horizon and out of the antenna pattern. Two vertical monopoles and a power splitter did much better, especially since it worked well in inverted flight. I must admit that I haven't designed a slot antenna system for a high power Mach 3 rocket. I did build a small "G" motor rocket without telemetry but that doesn't count for much. Anyway, we're both guessing. Without a clue as to the size, geometry, and construction of the rocket, the configuration of the ground station antenna, the location of the ground station, and the approximate trajectory (probably straight up), we can only speculate as to the optimal design. My guess is that this a level 1 rocket with an "H" or "I" motor which could barely tolerate the slight increase in diameter required for multiple slot antnnas. Wire or fin antennas don't add anything. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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Piano Wire Antenna for Experimental Rocket
Jeff Liebermann wrote:
On Sun, 24 May 2009 04:04:52 GMT, "Jerry" wrote: Have you considered flush antennas, like slots? Slot antennas have the maximum lobe perpendicular to the rocket axis. There's very little signal below the rocket. This is why tracking stations are far away from the launch site. If the rocket were overhead, and going straight up, there's no signal. That was my first thought on side mounted antennas. The best solution would be something on the fins if that were possible with the airframe design. -- Jim Pennino Remove .spam.sux to reply. |
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