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Old 10-Dec-2009, 9:04 PM   #1
Join Date: Dec 2009
Posts: 54
Quick Reference For Some Selected Antennas

This thread will hold information gathered for specific antennas.

A few notes about the information provided:
  • All gain figures have been adjusted to dBd (gain relative to a dipole antenna). This helps us make sure everything is being compared on an even scale. If you have an antenna that specifies its gain in dBi (gain relative to an isotropic antenna), then you'll need to subtract 2.15 dB from that number to get the equivalent value in dBd.

  • The Noise Margin numbers generated by the signal analysis tools are relative to a 0 dBd antenna. This means any antenna with a positive dBd value will help you gain NM (increase your net NM) and any antenna with a negative dBd value will cause you to lose NM (decrease your net NM). The reason we use dBd here is because of this convenient relationship to Noise Margin calculations.

  • Antennas are strongly affected by nearby objects, especially if they contain conductive materials. If you install an antenna too close to other objects, it can have a big impact on its antenna pattern and performance.

  • There is usually no one best antenna for any given situation. In addition to performance specifications, it is also important to consider factors such as aesthetics, mounting location, mounting difficulty, additional stress caused by snow/wind/ice, aiming sensitivity, resistance to multi-path, etc. Gain is good, but it is only one consideration among many when choosing an antenna.

  • All antenna patterns shown here have their main lobe (the part you want aimed at the transmitters) pointing to the right. The purpose of the antenna patterns is to provide a rough idea of what the "sweet spot" of the antenna looks like. In some scenarios it may be important to know how "squashed" the antenna pattern is in both the horizontal and vertical directions.

  • We'll try our best to provide accurate information here, but keep in mind that mistakes are always possible, and that most antenna specifications are just approximations. Variations in manufacturing consistency, damage to the antenna, effects from nearby objects, and other uncontrolled variables can cause the antenna performance to change. If you think there are errors, please let us know, and these posts will be updated as needed.

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Last edited by andy.s.lee; 17-Dec-2009 at 3:33 AM.
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