An antenna is an electromagnetic device that collects or emits radio waves. It consists of material that conducts electricity arranged in such a way that it is in tune with the frequency of a radio signal. Like a tuning fork in the presence of a sound of the same pitch, an antenna tuned to a particular frequency will resonate to a radio signal of the same frequency.
http://www.skyscan.ca/Antennas.htm#6 Element Yagi Antenna
The dipole antenna dates back to the early RF experiments of Heinrich Hertz in the late 19th century. It consists of a conductor that is broken in the center so that RF power can be applied to it. One can think of the half wave dipole as an open circuited transmission line that has been spread out, so that the transmission line can radiate a signal into space.
http://www.ycars.org/EFRA/Module%20C/AntDip.htm
The N6ZAV J-Pole makes a great transmitter antenna. Using the above table, cut the tubing to the size shown for the desired band. The only section where size is not critical is the mast section. Use any size you desire for mounting purposes.
http://www.qsl.net/n6bg/thunt/jpole.html
Your transmit and receive pairs need to be just that - pairs. Single wires would not cut it trying to carry 10 megabit data rates. Particularly with this pinout, since pins 1 and 4 in your jack should be paired together. The crosstalk after just a few feet of wire would wipe the signal out completely.
http://www.epanorama.net/documents/lan/ethernet_balun.html
Lamenting the passing of local AM radio? Desert island or outback mining camp based? Unable to clamber up on the roof for a long wire aerial anymore? Here is a simple medium wave tunable loop that, even indoors, will bring signals out of thin air.
http://www.siliconchip.com.au/cms/A_111084/article.html
http://df2ck.de/tech/MMANA/13cm_helix.html
A cheap and easy way to add an elevation sensor to an existing antenna systems is described here. The Analog Devices accelerometer chip ADXL202E is the core device.
http://df2ck.de/tech/tilt
Here is a 70cm (440 Mhz) J-Pole antenna that is inexpensive, and easy to build using 1/2 inch copper pipe, and the associated fittings necessary. The dimensions are not typical however, this is what it took to get its SWR low.
http://www.wb8erj.com/440jpole.htm
It uses one, six foot square, six turn loop, and is aperiodic in nature, covering the frequency range 50KHz - 5000KHz.
http://www.zen22142.zen.co.uk/Circuits/rf/6x6loop.htm
A 915 MHz microstrip antenna will be designed, constructed, and measured-tested. The microstrip elements will be a quarter of a wavelength at the design frequency. Quarter-wave microstrip antenna theory will be discussed. The antenna will consist of two microstrip elements in a phased array.
http://ee.eng.usf.edu/undergraduate/seniordesign/projects-sp01/oconnor.pdf