right antennas can strengthen the chain by yielding better signal coverage, increased S/N ratio, reduced bit error rate, and lower power consumption all at very low cost
http://www.edn.com/archives/1996/060696/12dfcov.htm
All ATL-3 loop windings are centre tapped and balanced w.r.t. their amplifier/receiver chassis ground, and therefore electric field interference pick up tends to self cancel.
http://www.zen22142.zen.co.uk/Circuits/rf/atl3.htm
http://www.kyes.com/antenna/stacking.html
http://www.hard-core-dx.com/nordicdx/antenna/special/baloon.html
many examples on blauns built from coaxial cable.
http://www.geocities.com/CapeCanaveral/Lab/5185/circuit2.html#BALUNS
A rhombic antenna can be made of two obtuse-angle V antennas that are placed side by side, erected in a horizontal plane, and terminated so the antenna is nonresonant and unidirectional. The antenna is placed end to end and terminated by a noninductive resistor to produce a uni-directional pattern.
http://www.tpub.com/neets/book10/42o.htm
information on special antennas used in celluar networks.
http://www.iec.org/tutorials/dual_polar/index.html
A hidden antenna must be just that: hidden. So don't install an antenna, but something else. Lika a bird feeder.
http://www.hard-core-dx.com/nordicdx/antenna/hidden/birdfeed.html
For the Macintosh.
http://www.blackcatsystems.com/software/antenna.html
Often one needs to improve reception of a particular radio or television station. One effective way to do this is to build a Yagi-Uda, or Yagi, antenna.
http://www.ee.washington.edu/circuit_archive/circuits/yagi.txt