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Wireless G db antenna question?

Dec 18, 2008 by houstonjln | Posted in Computer Networking

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].

what is antenna db?. is 18db much better than 13db?.?

Apr 30, 2007 by jbgorecom | Posted in Computer Networking

I have wireless 900mhz internet broadband. sometimes erratic. trying to get better signal. hoping new higher db antenna will help.
any help?

Here's a good excerpt for you for antenna decibel ratings:

The gain of an antenna is a passive phenomenon - power is not added by the antenna, but simply redistributed to provide more radiated power in a certain direction than would be transmitted by an isotropic antenna. If an antenna has a positive gain in some directions, it must have a negative gain in other directions as energy is conserved by the antenna. The gain that can be achieved by an Antenna is therefore trade-off between the range of directions that must be covered by an Antenna and the gain of the antenna. For example, a dish antenna on a spacecraft has a very large gain, but only over a very small range of directions - it must be accurately pointed at earth - but a radio transmitter has a very small gain as it is required to radiate in all directions.

...
The ultimate figure of merit for all receiving antennas is the G/T (pronounced "G over T"); that is, the gain of the antenna (in dB) minus the noise temperature of the receiving system (in dB). A typical C-band system will have a G/T of around 20 dB/K, while most Ku-band digital direct to home systems have a G/T of 12.7 dB/K. The more powerful the satellite signal, the lower the G/T value that will be needed at the receiving system down on the ground.

WG

yagi wifi antenna long range

a 12+ db gain wifi antenna long range for sharing wifi and internet get a 18db anttena here(better then this one!) www.dealextreme.com found a amp ...

D-Link ANT24-0700 2.4 GHz 7 dBi Wireless Antenna: To Buy Or Not To ...

by Komeil Bahmanpour

Foreword

Wireless signal strength has always been a big challenge inside houses and small offices. The coverage depends of how strong both the transmitting access point and the receiving handheld are. Nothing comes close to checking Live Mail on a WLAN-equipped N-Series laid in bed. To do so, you’ll need a strong wireless network, that’s for sure, although those tiny creatures deliver signal reception stronger than many laptops!

Where I performed the test, three stories of less than a thousand square feet each, a D-Link DWL-G700AP wireless access point is installed in the 1st floor, secured via both WEP 128-bit and MAC-filtering, sharing the network to different portables, including my Nokia N95 8GB (RM-320) and Dell XPS M1330.

Evaluation

It’s more than 2 months since I enhanced an existing D-Link DWL-G700AP wireless access point with a recently-purchased D-Link ANT24-0700 wireless antenna.

It’s a 7 dBi indoor omni-directional antenna which should increase the effective wireless operation range of 802.11b and 802.11g devices. It works with AP/routers to improve signals in the omni 360 degrees direction and to provide point to multi-point coverage. It can be attached to wireless networking devices equipped with RP SMA (small) or RP TNC (big) connectors.

But it wasn’t that better when the antenna kit was attached to the access point with the provided cable. Was it the most disappointing $30 purchase I’ve ever done, or was I doing something wrong?

Because a cable loss (2.1 dB in this case) was obvious, I tried disassembling the big antenna from its base, and then attached it directly to the access point. This time signal was obviously stronger, but it wasn’t what I predicted at all, comparing to the time when the AP was working with its primary small antenna attached. It’s ridiculous the antenna kit with the base and cable is useless. I also tried different channels, but it didn’t improve the range, except for lower channels conflicting with neighbor’s Panasonic cordless phones, which has always been annoying.

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