Antennas

Antennas are one of the most important components of wireless communications. Good antennas are far more important than higher power outputs.

This article should focus on specific antennas we use, much like the Wireless Cards article focuses on specific radio cards we use.

Beamwidth

Antennas should be chosen with both horizontal and vertical beamwidth in mind. Generally, the higher the power, the narrower the beamwidth. For a point-to-point link, narrower is better. For point-to-multipoint, you need to to have enough beamwidth to cover the clients. Bear in mind that a high-power sector antenna may have a very narrow vertical beamwidth.

The quoted beamwidths describe the angle at which the signal strength is reduced by half (-3 dBm). Since this is the same difference as that between a 200 mW and a 400 mW radio card, it is an issue worthy of attention. It is best to consult the graphs showing signal strength as a function of vertical and horizontal angle. In some cases, the signal drops off quickly and in some cases much more gradually as you move to the nominal beamwidth and beyond.

Remember that "receive" is just as important as "transmit". One problem with wide-angle antennas is that they can hear more noise. One way to cope with a noisy environment is to use multiple radios, each covering a relatively narrow angle.

Point-to-Point Antennas

• Pac Wireless 5GHz Grid Dish Antenna
  • These have performed great for me, right to specs. Relatively small wind load for a high-gain PTP antenna and the construction is sturdy enough. I've only used the 26dBi grid. You might want to check out the solid dish for 29 and 32dBi. -Tog
  • I rely on all three of these, 22, 26, 29. The 22 is incredibly small and cute. I use it in locations where winds can get well above 100 mph. -Handyman

Special Purpose Antennas

• Pac Wireless "Rootenna"
  • 2.4GHz, 5GHz, 900MHz and even a model that is dual-band 2.4 and 5GHz. Two sizes (lower and higher gain) and two profiles (low-profile/thin and deeper more roomy enclosure.) Words cannot express how useful these are. I use these for CPE and sometimes even for PTP links and microcell APs (drill a hole, add an external N-type connector!) Pac Wireless is constantly making design improvements, too. -Tog
  • Ditto. The higher gain Rootennas are large enough to possibly cause problems aesthetically or wind-wise. -Handyman

• Arc Wireless Antenna enclosure
  • Higher gain than the standard Rootenna but smaller and sturdier than the high-gain Rootenna. 2.4 GHz, 19 dBi. Available at Titan Wireless -Handyman

Sector Antenna, 2.4GHz.

• Pac Wireless "H-Pol Sectors"
  • This is a very well constructed antenna, with your choice of scissor bracket or single mast mount. Available in 12 & 16dbi models the 95 degree beamwidth of this anttenna works extremely well with lower powered cards, such as the Atheros CM9. The antenna is made from aluminum and has a powder coat finish. The N-Connector is securely mounted to the bottom front of the antenna. See it in action tcw.wisp

• Maxrad WISPerformance WISP24014-90PTNF and WISP24013-120PTNF
  • These vertically-polarized 14-dB, 90-degree and 13-dB 120-degree antennas are affordable and compact with a nice mounting system. They are available at Electro-comm at a good price once you set yourself up with a company account and get the discount.
  • The Maxrad web page is incoherent and virtually impenetrable. It's a prime example of corporate bloat. Still, the antennas are good. -Handyman

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