From OCAU Wiki
- provides speeds upto 11Mbps at 2.4GHz
- provides speeds upto 54Mbps at 2.4GHz
- provides speeds upto 54Mbps at 5.8 GHz
- an unratified standard that should provide speeds of upto 100Mbps (WWiSE and MIMO are two competing proposals for 802.11n)
- Line-of-sight; if two locations have a clear, unobstructed view of each other, they are said to have good LOS. Because microwave energy is absorbed by solid obstructions, LOS is required for a good wireless signal between two locations.
- The beamwidth of an antenna is the angle between the half-power (3 dB) points of the main lobe, when referenced to the peak effective radiated power of the main lobe, usually expressed in degrees (and usually given in the horizontal plane).
- the amount of data that can be transferred in a given time period, normally measured in kbps (kilobits per second) or Mbps (megabits per second).
- The number of cycles per second. The frequency of 802.11b ranges from 2.412 GHz (channel 1) to 2.477 GHz (channel 14).
- In antenna design, gain is the logarithm of the ratio of the antenna's radiation pattern to that of some ideal antenna, typically the theoretical isotropic antenna.
- a measure of the ratio between two quantities, and commonly used to measure signal-to-noise ratios.
- Signal-to-noise ratio is the power ratio of the signal (meaningful data) and the background noise.
Please see Wireless Network Security.
If you want to improve the range of the standard "rubber-ducky" antenna(s) on your wireless AP/router, before spending money on a higher gain antenna, try making some simple reflectors for the standard antenna, as detailed on the deep Dish Cylindrical Parabolic Template website.
- radiates a signal in multiple directions, typically 90, 180 or 360 degrees.
- typically focuses the signal in a single direction.
Omni-directional antennas are typically used in situations where multiple clients will be connecting, from multiple directions. A directional antenna is preferred for point-to-point links, as the signal is focussed in the direction you want, rather than being dispersed in multiple directions. Noise is also reduced, and you're also reducing the amount of RF "pollution".
Polarisation is defined as the orientation of the electric field of an electromagnetic wave. Two often used special cases of elliptical polarization are linear polarization and circular polarization. The initial polarization of a radio wave is determined by the antenna that launches the waves into space.
- Linear Polarisation
- the electric field vector stays in the same plane
- Circular Polarisation
- the electric field vector appears to be rotating with a circular motion about the direction of propagation (can be either right-hand or left-hand rotation)
The Helical antenna is circularly polarised, while all other antennas listed below are linearly polarised, with the linear polarisation being either vertical or horizontal, depending how the antenna is oriented.
The majority of the antennas listed below can be constructed at home with tools that most people will have in their shed.
- Biquad antenna construction - easy-to-build 11dBi antenna with approx 40 degrees beamwidth
- Double biquad antenna - 13dBi version of the biquad
- BiQuad 802.11b Antenna - theory behind the biquad antenna
- How to make a 'Downpipe' Slotted Waveguide Omni antenna
- 802.11b WLAN Waveguide Antennas - theory and design of the slotted waveguide
other Omni Antennas
Most major cities have a community wireless network (aka freenet), consisting of like-minded individuals who have established a wireless network between their houses and other elevated places with good LOS.
If you're interested in getting involved, contact your local freenet for more help and assistance.
- Air.Net (Canberra)
New South Wales
- Air-Stream (Adelaide)
- TasWireless (Hobart)
- WAFreeNet (Perth)