Wireless G db antenna question?
Hi, If I had a wireless G router with a standard 2db antenna with a laptop with a wireless G adapter, how far can I go (in feet) remain in the crosshairs of the router?
What about a 7DB, 14dB and 15dB antennas?
Imagine a light bulb. It radiates light uniformly in all directions. It is an isotropic radiator. Antennas are passive devices. They do not amplify the signal. What they do is concentrate the signal power in a smaller volume. Suppose I put a mirror on one side of the bulb. Now, one side of the mirror is dark and the other side is twice as light. We can say that the mirror is an antenna 3 dBi. 10 ^ (3 / 10) = 2 twice more light on the illuminated side.
To what extent does your antenna will reach depends on several factors.These include your input power, the loss in the cable between the source and your antenna, interference in the chain - which means the radio frequency (RF) noise in the air between your transmitter and receiving antennas, the loss of open space - which increases by the square of the distance between the transmitting antenna and receiving antenna, signal to noise ratio of your source, receiver sensitivity, receiving antenna gain, the noise temperature of your system to receive and data rate [1]. 802.11g suffers from interference because it operates in the already crowded 2.4 GHz range.Other devices in this range include: microwave ovens, Bluetooth devices, baby monitors and (in USA) on digital cordless phone [2].
For 802.11g, the rated speed is 54 bits Mb / s, but the signal is weak or noisy environments the transmission speed is slowed to allow more power per bit. For a successful reception, the signal power per bit must be above the noise power per bit. By slowing the speed of transmission, each bit is transmitted over - give more signal strength per bit. 802.11g specifies DSSS OFDM modes with data rates of charge 6, 9, 12, 18, 24, 36, 48 and 54 Mbps as the signal to noise ratio decreases [3]. So how your antenna achieved depends in part on the data rate you are willing to accept.
Free space loss varies with the square of the range. See equation 5.13 [1]. Provision for 802.11g is 38 meters (124 ') inside and up to 140 meters (459') outside in good conditions RF [4].
An antenna 7 dBi 5 dBi give more than the standard 2 dBi. The calculations for the range is sqrt (10 ^ (5 / 10)) = 1.8. Antenna 7 dBi you give about 1.8 times the range of 2 dBi.
Similarly for 14 dBi, sqrt (10 ^ (12/10)) = 4. About four times the range.
For more than 15 dBi, sqrt (10 ^ (13/10)) = 4.5. About four and half times the range.
There is a practical radio link budget calculator available online at [5]. Examples of issues for configuring the router with wireless and portable use:
Frequency GHz: 2.4
Diameter antenna Tx: .06
Tx antenna efficiency: .65 (default)
Tx power to the feed (W): .3
Range (km): .140
Bandwidth: 22000000 (default)
Antenna diameter Rx:.01
Rx Antenna Efficiency: 0.65 (default)
Rx system noise temp (degrees K): 440 (default)
Receiver Sensitivity -80 (this is a wireless card very good)
You get -69 dBm at the receiver - About correct for most wireless cards.
These estimates are consistent with my experience. FWIW, I attached the antenna in [6] to my laptop via a short tail. With this configuration, I am able to pick up 802.11b / g access points to about 1 / 2 mile away.
Also, you might consider moving to 802.11n. 802.11n uses multiple input, multiple (output MIMO) technology.Basically, he phase shifts of several small antennas digitally "steer" the waveform to improve the transmission and receiving interval [7].
If this does not help, send me an email and I can point to more info on the calculation of link budgets [8] [9].
