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Thread: Anyway to calculate wifi antenna range?

  1. #1
    Newbie bizahh's Avatar
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    Anyway to calculate wifi antenna range?

    If you know some varibles about the antenna is there anyway to calculate the aprox range you will be getting?

    Say for instance you knew this (taken from http://www.radiolabs.com/products/an...4-mobile7.html):

    Frequency Range: 2400 - 2500 MHz
    VSWR: <1.5 @ 100MHz bandwidth
    Impedance: 50 Ω
    Gain: 7 dBi
    Polarization: Vertical
    Max. Power input: 50 Watts
    Ground Direct Ground: (RF chassis ground with mag-mount)
    Connector: type N-Female, TNC, M or SMA
    Dimensions: 18" tall
    Weight: 1.5 pounds
    Maximum wind velocity Will stay on metal roofed vehicle at any speed!
    Radiator Material Stainless Steel hardware, UV resistant magnetic mount base

    Can any of these values be used in some sort of equation to determine the range?

  2. #2
    FLAC DodgeCummins's Avatar
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    Probably, but the other factor is the wifi system on the other end.

    That does sound like a hellofa nice antenna though.

    Realize though, even if the antenna can handle 50watts...your wifi card will not put out more than a watt in power.

    Sounds like a radio engineer question, power, gain, frequency...


    http://www.signull.com/fsc.php

  3. #3
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    I don't know how to answere your question, but you can extend the range and amplifify the signal with a simple little device.

    http://osiris.urbanna.net/antenna_de...ects/template/

    I don't know exactly what you are planning, but I wouldn't have a great deal of confidence in being able to use wifi on the move with a stationary point elsewhere. I use the parabolic reflectors on my home router, and I have good signal whereever I point them.

    I made mine out of some styrofoam, a cerial box, and aluminum foil.

  4. #4
    Newbie bizahh's Avatar
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    Quote Originally Posted by DodgeCummins
    Probably, but the other factor is the wifi system on the other end.

    That does sound like a hellofa nice antenna though.

    Realize though, even if the antenna can handle 50watts...your wifi card will not put out more than a watt in power.

    Sounds like a radio engineer question, power, gain, frequency...


    http://www.signull.com/fsc.php
    Interesting url, I wish I knew what values to put in.

    I understand what you mean about the system on the other side. Lets say for example I am using a DWL-AG520 AirXpert Tri-Mode Dualband 2.4/5GHz (802.11a/11b/11g) Wireless PCI Adapter and the other side is a DWL-7000AP AirXpert Tri-Mode Dualband 2.4/5GHz (802.11a/11b/11g) Wireless Access Point.

    Looking at the specifications on both the PCI Adapter and the Wireless AP reveals a Transmitter Output Power of 15 dBm 2dB and a Wireless Transmit Power of 15 dBm (32 mW) 2dB, respecfully.

    I actually have no idea what this means but hopefully someone does.

  5. #5
    Newbie bizahh's Avatar
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    Quote Originally Posted by RobbieIG
    I don't know how to answere your question, but you can extend the range and amplifify the signal with a simple little device.

    http://osiris.urbanna.net/antenna_de...ects/template/

    I don't know exactly what you are planning, but I wouldn't have a great deal of confidence in being able to use wifi on the move with a stationary point elsewhere. I use the parabolic reflectors on my home router, and I have good signal whereever I point them.

    I made mine out of some styrofoam, a cerial box, and aluminum foil.
    Thanks, I will be sure to try this out when the hardware arrives.

    Can anyone help me out with calculating the aproximate range though?

  6. #6
    FLAC DodgeCummins's Avatar
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    Yea, my IE crashed when I was going to edit my post.

    If you go to the links on that calculator site, it gives a lists a bunch of hardware and the associated numbers for the formula.

    I ran some basic numbers with my equipment and your antenna, and I got a whopping 0.19miles. about 500 feet.

    I was going to guess a thousand...I would have been off by quite a bit.

  7. #7
    Constant Bitrate StationRocket's Avatar
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    Thumbs down It's like forcasting the weather

    So I'm an engineer, i went to school for light waves not radio waves but the difference is just a matter of size and i have worked as a RF eng.

    Anyway predecting 2.4GHz range with the 802.11 signal is a lot like forcasting the weather, lots of real smart folks with lots of big computers try like hell but are almost never right outside of the painfully obvious.

    There are a number of things that will cause range to change dramatically. For example I have an antenna on top of a pub out in Seattle that has no trouble serving 802.11b to some locations almost 2 miles away but fails to serve others that are as close as 100 yards.

    As a quick rule of thumb if you can see one antenna location from the other it will be possible to get a good link with the right antenna and what that antenna is will bepend on the distance.

    If there's stuff inbetween then it get's complicated. Just like glass is clear to light and wood isn't some stuff is clear to 2.4 GHz and some stuff isn't. In general anything with moderate to high water content will block it pretty good.

    There are lots of different antenas availible at http://www.hyperlinktech.com/

    Just remember that as gain goes up beamsize goes down so you will need to aim the antenna.

    Hope this helps

  8. #8
    Newbie bizahh's Avatar
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    Quote Originally Posted by StationRocket
    So I'm an engineer, i went to school for light waves not radio waves but the difference is just a matter of size and i have worked as a RF eng.

    Anyway predecting 2.4GHz range with the 802.11 signal is a lot like forcasting the weather, lots of real smart folks with lots of big computers try like hell but are almost never right outside of the painfully obvious.

    There are a number of things that will cause range to change dramatically. For example I have an antenna on top of a pub out in Seattle that has no trouble serving 802.11b to some locations almost 2 miles away but fails to serve others that are as close as 100 yards.

    As a quick rule of thumb if you can see one antenna location from the other it will be possible to get a good link with the right antenna and what that antenna is will bepend on the distance.

    If there's stuff inbetween then it get's complicated. Just like glass is clear to light and wood isn't some stuff is clear to 2.4 GHz and some stuff isn't. In general anything with moderate to high water content will block it pretty good.

    There are lots of different antenas availible at http://www.hyperlinktech.com/

    Just remember that as gain goes up beamsize goes down so you will need to aim the antenna.

    Hope this helps
    Thanks I was looking for that url before. But one thing confuses me, how do I aim a omni-directional antenna?

    Maybe I am going about this the wrong way, what antenna should I use if I wanted to increase the range to about half a mile or more?

  9. #9
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    Hello,
    I was checking my Stats on the Radiolabs website and saw your posts about WiFi antenna range. 802.11 antenna range is a very subjective thing. The actual distance can be anywhere from 120 feet, to 36 miles (what we have actually been able to obtain). If anyone has any questions about WiFi antennas or mobile wifi range, please feel free to contact me directly at:
    [email protected]
    We have antennas from 3" long to 8' diameter ultra high-gain dishes. The Mobile7 antenna has excellent range if installed on a metal rooftop car or truck roof. We have been able to get over 1 mile range with this antenna alone.

    www.radiolabs.com/products/antennas/wifi.html
    WiFi communications is great. I speak with a friend in S. Africa all the time via the internet and a 2 mile WiFi connection and a very small card. 200mW to S. Africa is great

  10. #10
    FLAC LESLIEx317537's Avatar
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    If you amplify the signal and your anttenna is not properly tuned to the 2.4Ghz frequency, your signal will come back intot he unit and hence SWR.

    I had a SWR meter for my CB radios and built my own attenna before. I guess the same ideas???

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