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Newbie: Indoor antenna ranges


Please excuse a newbie on radiowaves, antenna, dBi and stuff like that.

Is there a "simple" way to calculate the range (in feet or meters) for a antenna and are there any tables for how much a wall dampens that range ?

For example: To me it seems like AIR-ANT3213 has a nice radiation pattern suitable for a floor in a building and on the radiation pattern there is a value of 5.2 dBi, but if I would like to know the range (roughly) of the signal (in meters) ?

And if I know that the most far office is 14 2-inch thick plasterwalls and 2 4-inch massive woddenwalls away, how many meters does that reduce the signal ?

Maybe I must buy another AP instead, but then maybe it will work fine with the standard dipole...

We´re about to implement WLAN in a relatively big scale, in lots of different buildings, with different wallmaterials, different shapes and so on, and to hire a consultant is not an option.

Hints, URLs, Tricks ? Anyone ?

Thanks in advance ! / Per

2 Replies 2


There really is no (simple) rule-of-thumb other than "Higher is better" and "Clear Line of sight is good" (they are related).

Above about ~400Mhz, signals don't penetrate; they bounce. If the surface they bounce from is smooth, the signal remains relatively intact. If it's rough, the signal is scattered to larger degree.

Organics / water filled things (like humans and plants) absorb the signal.

Signal loss through a conductor (the cabling) is very high at 2.4 gig. Less cable is generally better (i.e., an AP with directly attached antennas is likey to perform better (better signal quality) that an AP with high-gain antennas and a bunch of cabling - put the APs in the ceiling and use PoE instead of putting the APs in the Data Center and connecting to antennas 100 feet away.

Your best friend is a good Signal-to-Noise Ratio, your worst enemy is Multipath (it may look like a strong signal, but the quality is very bad .... poor connection, low data rates).

These are the top couple for me. Hope they help.



The only specifications I know of are for general antenna distance coverages. In site surveys, it is often hard to predict how the signal will react to certain obstructions and materials. Often times there are air ducts, lights, water pipes, security equipment, steel columns etc, and they are not always things that are in plain site. RF does crazy things and the signal is great when you think it won't be, and bad when you think you have a great AP location. If you have the specific antenna and AP that you want to use, you may use that to survey the buildings to verify coverage. You can do that yourself. Get a map, test your coverage and draw your coverage cells. Then you can assign your channels and power settings - and work the puzzle.

Hope this helps.

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