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Thread: Wireless Range

  1. #71
    Just burned his ISO Dimus's Avatar
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    tetra brik? what is that?
    +Dimus+

  2. #72
    My life is this forum Barry's Avatar
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    Quote Originally Posted by Dimus View Post
    tetra brik? what is that?
    Those plastic coated cardboard boxes with a foil lining. They can make halfway decent quick cantennas.


    http://www.drivebywifiguide.com/TetraBrikHowTo.htm


    Jeff is a pretty cool guy by the way.
    Of course, if you really wanted to have some fun, go to Wal-Mart late at night and ask the greeter if they could help you find trashbags, roll of carpet, rope, quicklime, clorox and a shovel. See if they give you any strange looks. --Streaker69

  3. #73

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    Quote Originally Posted by Barry View Post
    Those plastic coated cardboard boxes with a foil lining. They can make halfway decent quick cantennas.


    http://www.drivebywifiguide.com/TetraBrikHowTo.htm
    If it doesn't work as an antenna, you can always use it to smoke hash
    The link budget is not a problem, we intend on splitting the bill...

  4. #74
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    While people argue amps are no good, I have a 1 watt TeleTronics (FabCorp) amp that makes it possible to detect half as many more APs in Netstumbler when using my 14dbi Buffalo yagi.

    This could be because Netstumbler uses an active process for detection sending out beacon requests, and the boosted TX power helps this. Or the advertised ~3db receive gain on the amp is actually working.

    It should be noted though amps can increase TX output to dangerous levels, especially with something like a 1w amp + 24dbi antenna = ~250w EIRP, so never look at or stand between the transmitting end.

  5. #75
    My life is this forum Barry's Avatar
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    Hey, if they don't know what the hell they're doing let them stand in front of it. They call that Darwinism in action.
    Of course, if you really wanted to have some fun, go to Wal-Mart late at night and ask the greeter if they could help you find trashbags, roll of carpet, rope, quicklime, clorox and a shovel. See if they give you any strange looks. --Streaker69

  6. #76
    Senior Member streaker69's Avatar
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    Quote Originally Posted by norm360 View Post
    It should be noted though amps can increase TX output to dangerous levels, especially with something like a 1w amp + 24dbi antenna = ~250w EIRP, so never look at or stand between the transmitting end.
    Standing in front of one at Crotch level is known as "Electro-Vasectomy".

    It only hurts for a little bit.
    A third party security audit is the IT equivalent of a colonoscopy. It's long, intrusive, very uncomfortable, and when it's done, you'll have seen things you really didn't want to see, and you'll never forget that you've had one.

  7. #77
    Senior Member Thorn's Avatar
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    Quote Originally Posted by norm360 View Post
    While people argue amps are no good, I have a 1 watt TeleTronics (FabCorp) amp that makes it possible to detect half as many more APs in Netstumbler when using my 14dbi Buffalo yagi.

    This could be because Netstumbler uses an active process for detection sending out beacon requests, and the boosted TX power helps this. Or the advertised ~3db receive gain on the amp is actually working.
    Both the fact that NS uses an active probe and the RX gain could account for the increase number of APs seen.

    Quote Originally Posted by norm360 View Post
    It should be noted though amps can increase TX output to dangerous levels, especially with something like a 1w amp + 24dbi antenna = ~250w EIRP, so never look at or stand between the transmitting end.
    Exactly. I've said this before, but it's worth repeating: You can hurt yourself and other with RF energy if you don't know what you are doing.

    One other consideration is the legal amount of power. If you are in the US and are not a Ham (Part 97), then you fall under the FCC Regulations Part 15 with regards to WiFi. Operating a 1W (30dB) amplifier with a 24dBi antenna under Part 15 is illegal as well as dangerous. According to the regulations, for antennas with gain greater than 6 dBi, you are supposed to reduce the gain of the amplifier by 1dB for every 3 dB of additional antenna gain beyond 6 dBi. For a 24dBi antenna, the power at the amplifier must be reduced by 6dB (30dB - 6dB = 24dB or 250mW). Operating over these limits puts you at the very real risk of being fined by the FCC. Like most federal agencies, the FCC isn't exactly shy about small fines; their typical fine start at $10,000.

    FAB Corp. has a good summary power/gain/antenna chart here:
    http://www.fab-corp.com/pages.php?pageid=1
    Thorn
    Stop the TSA now! Boycott the airlines.

  8. #78
    Just burned his ISO
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    thanks
    i'ts cool bayyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy

  9. #79
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    Nice post, it got me thinking:

    You say reception/quality varies by multiple factors, including different frequencies. Could it be that a certain frequency has better reception? (IE using a different channel, say 1 instead of 11). I'm not talking big frequency shifts here like from 2.4 to 5 GHZ, just the channel freqs.

    Also, I did some calculations, and discovered the popular Alfa can be illegal when used with a 10 DBi Omni, producing an EIRp of 5 watts (!), where the maximum in america is 4 watts (36 DBM).
    In europe, it get's worse, there the EIRP is 100 mW (20 DBm).

    So, for you americans heading over to europe: keep it in mind

    I think I did all the calculations correctly, but corrections are of course always welcome.

    EDIT: here's a useful table + conversion link: http://www.moonblinkwifi.com/dbm_to_watt_conversion.cfm

  10. #80
    Just burned his ISO imported_RaderCad's Avatar
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    Default Here is a dBm to Watt chart with the rules for the usa

    The FCC rules allow for stronger rigs at the Antenna than 36 dBm.

    If you have a 30dBm amplifier then you can only have a 6dBi antenna. However! For every 1dBm amplifier drop you can have 3dBi of antenna gain.

    For example, if an installation reduced power at the transmitter to 29dBm, it could use an antenna having a gain of 9dBi. Or in the case of the ALFA 27dBm + 15dBi for the maximum transmitter and antenna combination.

    That is why our 40.2dBm rig is legal in the USA. Europe is way more restrictive.

    Here is a good site with the conversion table and the rules. Oops! I am a newbi so I had to take it apart.

    http : // www . cpcstech.com / dbm-to-watt-conversion-information . htm to Watt Conversion Table

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