Here is a simulation of the effects of adding a 70cm Yagi to a 13 cm helix on the same boom. Simulation is done using a freeware MMANA, based on NEC-math
http://df2ck.de/tech/MMANA/13cm_helix.html
Got no dough for a commercial WiFi antenna? Looking for an inexpensive way to increase the range of your wireless network? A tin can waveguide antenna, or Cantenna, may be just the ticket. This design can be built for under $5 U.S. and reuses a food, juice, or other tin can.
http://www.turnpoint.net/wireless/cantennahowto.html
http://www.qsl.net/n9zia/wireless/pics/900quagi.gif
These antennas are relatively small, easily constructed from common materials/tools and have surprising performance. The feed method is greatly simpified by directly soldering the coax to the driven element. No baluns or gamma matches are used in this design.
http://www.clarc.org/Articles/uhf.htm
http://www.qsl.net/n9zia/wireless/pics/915-colinear.png
A simple broadband yagi antenna that can be built on a 4 foot boom and used for portable ATV, SSB, or satellite work on the 70-cm band. The antenna design was optimized for broadband performance using YAGIMAX software.
http://www.qsl.net/kd2bd/yagi.html
Detailed instructions, diagrams and photos on making a helical antenna for the 2.4GHz ISM band. Suitable for long range wireless networking. The aerial was derived from information on helical antennas in the ARRL Antenna book.
http://www.wireless.org.au/~jhecker/helix/
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