On Thu, July 5, 2007 7:24 pm, Pedro Almeida said: > Hello, Phillip, thanks for your reply; > > I thought the antenna to be omni-directional, the orientation to be > unimportant. I had a friend holding the mote from a distance, no concern of > orientation. I guess the test went kind of buggy, then...
I would like to add: The antenna itself is "omni-directional", but the PCB imparts some direction on it. Remember, the PCB is unshielded, and the antenna connector is essentially a very small directional antenna. Using some of my Mica 2s I can easily see the directionality without antennas, and notice some even with them on. Added to the fact is that having someone hold a transmitter is the best way to make funny things happen. The human body reacts to radio waves mostly because of capacitance, but can also shield and reflect signals. If you want proof, simply tune an AM or FM radio to a weak station, then touch the antenna. Depending on the position of the antenna, frequency, other transmitters in the area, and probably the phase of the moon, the signal can get stronger or weaker. Cartoons where someone is standing on the TV with an aluminum foil hat in a strange pose are not hyperbole, but may in fact get someone a weak signal! It's funny not because it is absurd, but because it's true. So, when you test, keep track of orientation. Keep your motes as far away from metal as possible. Keep them away from water, as water is a conductor (the human body is mostly water). Do not place them on a floor or table, but suspend them at least a foot (330 cm) above or below a flat surface. There is a surface effect around most items due to ferric impurities and moisture. A small plastic or wooden stand is the best course of action. Small sticks of balsa wood and superglue are common in most hobby stores around here, and very cheap. I'm not an expert on routing, especially in TOS 2, so I can't help you there. -Ben -- The difference between the right word and the almost right word is really a large matter- it's the difference between a lightning bug and the lightning. -Twain _______________________________________________ Tinyos-help mailing list [email protected] https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
