In this article we present a short introduction to the Theory of Radio WLAN, with a comparison table between dBm and power transmission networks in watts for Wireless, WLAN.

When we acquire a WLAN kit, whether for home or office one tends to ask the seller of what is the scope, and this will always respond;

... More or less 300 feet or 100 meters, but it always depends ...

Ahhh the famous always depends not really know what they are talking estanb. This is because the manufacturers in training its dealers to make them repeat from memory all the specifications of their equipment, without actually achieving that sellers understand how? or why?

Because of that today almost all manufacturers of WLAN technology are some product, it's hard to know for sure that what one needs is what you are selling.

Let's talk for a moment of the DWL-510 D-Link, this is an 802.11b PCI Adapter, for the 2.4 GHz band. This adapter comes with an antenna R-SMA (reverse SMA connector) external, removable. This antenna does not measure more than 3 inches, and according to the manufacturer 2dBi, the team also offers a transmission power of 16dBm (40mW) with which we can say that the power transmission equipment is 41.6 mW.

When the seller or the product box about 100 meters connection, it is because such measures have been carried out in laboratory-controlled media.

Should know from experience that almost any obstacle or source of radiation may severely affect the performance of WLAN equipment. Indoors, getting a connection to more than 30 meters with these teams is impossible, because this wall either chart plaster, wood, brick or wood causing interference, and concrete or metal barriers causing total loss of the transmission .

In order to understand and put into practice the above is a series of articles on this site, which contain the necessary formulas to be able to plan theoretically any link WLAN distance.

By the time we left the table values dBm'sy Watts, plus the following endorsements made for connecting the first and second node guatewireless originals.

We have two focal points, separated by more or less 8 kilometers, the node A located in the area 12, have a low loss cable 8 meters which is equivalent to-7.2dB and an antenna 8dBi gain. In the node B, located in Ciudad San Cristobal, the transmitter has a 30dBm power cable of a low-loss 0.27dB and a 12dBi antenna with an amplifier of 15dBm.

Transmitter
Energy output of the transmitter 30 dBm
Cable loss
(negative value!) 		-0.27 DBi
Gain Antenna 27 dBi
Spread
Loss of free space
(negative value!) 		-118.4 DBi
Receiver
Loss of free space
(negative value!) 		-118.4 DBi
Gain Antenna 8 dBi
Cable loss
(negative value!) 		-7.2 DB
Receiver Sensitivity
(generally negative value) 		-84 DBm
Overall
Margin 		23,068 dB

With the calculations above, our current wlan link has more than enough power for 8Kms away. Further calculations show that our link has a theoretical maximum range of 110 kms.

These calculations alone make me think that I should throw down to work and see if the theory is correct, and see if our link can be seen from across the city.

dBm Watts dBm Watts dBm Watts dBm Watts dBm Watts
0 1 mW 1 1.3 mW 2 1.6 mW 3 2 mW 4 2.5 mW
5 3.2 mW 6 4 mW 7 5 mW 8 6 mW 9 8 mW
10 10 mW 11 13 mW 12 16 mW 13 20 mW 14 25 mW
15 32 mW 16 40 mW 17 50 mW 18 63 mW 19 79 mW
20 100 mW 21 126 mW 22 158 mW 23 200 mW 24 250 mW
25 316 mW 26 398 mW 27 500 mW 28 630 mW 29 800 mW
30 1 W 31 1.3 W 32 1.6 W 33 2 W 34 2.5 W
35 3.2 W 36 4 W 37 5 W 38 6.3 W 39 8 W
40 10 W 41 13 W 42 16 W 43 W 20 44 25 W
45 32 W 46 40 W 47 50 W

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