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Thread: Wireless Range

  1. #21
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    Quote Originally Posted by operatorone View Post
    I have gotten my hands on one of these...

    http://www.pheenet.com/product/produ...2&parent_id=13

    but I haven't had a chance to try it yet. I will let you know if I ever get around to it. Is this the same thing you are talking about Xploitz?
    Nearly identical. Yes its the same type of amp.
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  2. #22
    EnculeurDePoules
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    Quote Originally Posted by harry View Post
    Environmental conditions have a serious affect on propagation too.

    During the early morning or very late at night propagation is at its best and attenuation is at it's lowest; damp and humid conditions help the signal propagate even further.

    If you get intermittent connectivity with an AP during the day, try again at night or in the morning and chances are you will get a workable signal. If the air is damp or the ground is wet maybe due to rain or dew then your further your chances even more of getting a workable signal . Attenuation can be reduced by up to 45% on a damp cold morning/night.

    If it is a dry hot day and you are in a busy area then anything up to +60% attenuation is possible.

    (Although this does still apply somewhat if the AP is in your own house, it obviously applies more if the AP you are trying to associate with is in another building or similar)

    Just because you can receive a signal from an AP does not mean you can send to it, as APs usually have a lot more range than a wireless adaptor.
    I was going to comment on that!!!
    It sounds silly but after a year of using wireless, I observed many often changes in the recption while still not moving from my room!
    When its rainy its less signals than in other times... sometimes I receive plenty of signals, sometimes not!
    Sometimes by moving like 1 meter away I have better signals and so on!!
    weird, i'd like to have a tool to mesure exatcly theses!!

  3. #23
    EnculeurDePoules
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    and what about the Cantenna?

    Apparently I read that normal wireless card in laptops are approx 1-2 db reception, but we can increase up to 10-20 db with a simple home made cantenna!!
    Well "simple", I tried to make one I screwed up, but apparently its simple!

    example of cantenna:try google, haha!
    im not allowed to post urls!

  4. #24
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    Didn't see anyone else mention anything about this. But, some of your results might be effected to the use of the 10dBi antenna. When choosing an antenna you have to consider its beam width. Omni antennas once they reach a certain dBi have a very narrow beam width. Typically around 8-10 degree vertical. As compared to my D-Link 7dBi omni which has a stated beam width of 40 degrees. This is what is noted on the packaging. Though manufactures web site if I'm recalling correctly states it have a 27 degree. Either way I too have a 10dBi omni that I had received. The results with the 10dBi are pretty horrible. You really have to tweak it in to find that sweet spot. Even so having a greater beam width can have an impressive result.

    In my results living in a rural area. I've been able to detect/authenticate with AP's around ~600ft using the 7dBi. While the 10dBi only picked up a fraction of those APs with a dramatical decrease in S/N ratio. Even using the ever so popular "cheap parabolic reflector" with the 10dBi I still have poor results. While the 7dBi omni and reflector allow me to have a steady consistent 11Mb connection at 500ft. The 10dBi omni and reflector barely allowed a 2Mb connection.

  5. #25
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    Since a wifi system is a duplex system, adding power to your end alone makes absolutely no sense at all. You could be 200 miles away from your desired AP and be transmitting 1 MEGAWATT, but without a significant improvement in the receiver sensitivity on your end, you cannot connect (they can "hear" you, but you cannot "hear" them).

    If you desire an increase in range, you need to have better antennas (most antennas have the property of reciprocity - the transmit gain is the same as the receive gain). What tybalt said about antennas is somewhat true. Sometimes a 7dBi antenna can appear to perform better than a 10dBi antenna, especially if the extra effort to "steer" the beam is not performed. A co-linear antenna's vertical beamwidth does get smaller as the number of elements increase. That is the price for increased gain in the azimuth. A co-linear antenna is omnidirectional. Above a certain gain requirement, the antenna needs to be directional. But using a directional antenna, you can get some amazing gains (but you have to properly "aim" the antenna). Simple horn antennas can give you gains of 50 or 60. With dishes, the gains can even exceed 200. But, with the increased gain, the precision of the alignment also increases.

    So, if you really want to increase your range by adding amplifiers, you need to add the same amplifier to the access point that you added to your station. If not, you have wasted your time and money.

  6. #26
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    Quote Originally Posted by theprez98 View Post
    When searching for a wireless card, people often want to find one with the best range. Most often, this decision is solely limited to the transmit power of the card. While transmit power is one factor in determining range, there are others that ought to be considered when determining overall range.

    *Transmit power
    *Transmit antenna gain
    *Frequency and distance (path loss)
    *Receiving antenna gain
    *Receiver sensitivity
    Sorry guys if the question is stupid...
    but how can i know the receiver sensitivity of the card? i only know that the
    transmit power id 300mW, and u correctly told me that transmit power is not all. There is a way to test and judge the others important values of the card? i have a wifi ubiquity pcmcia 300mW.

    Thanks in advance,
    bobbolo.

  7. #27
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    Quote Originally Posted by SLK001 View Post
    (most antennas have the property of reciprocity - the transmit gain is the same as the receive gain).
    "most antennas"... So which antennas don't have reciprocity?

    On this topic, external receiver amplifiers used to make sense. But with modern hardware, aren't they obsolete? For example the AWUS036H sensitivity is already at -92dBm @ 1Mbps according to the manual. The Engenius 362EXT is at -96dBm @ 1Mbps, which is pretty close to the thermal noise floor.

  8. #28
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    Quote Originally Posted by sergeikolomov View Post
    "most antennas"... So which antennas don't have reciprocity?
    Well, all antennas do. However, antennas with integrated amps do not and I wanted to avoid agruments like "my antenna works well in receive, but like crap in transmit".


    Quote Originally Posted by sergeikolomov View Post
    For example the AWUS036H sensitivity is already at -92dBm @ 1Mbps according to the manual. The Engenius 362EXT is at -96dBm @ 1Mbps, which is pretty close to the thermal noise floor.
    Not really. They are "cheating" with their specs. If you look at their spec for a 54Mbps channel, it is -76dBm - not bad, but definitely not state of the art. This is the only measurement that uses the entire 20MHz bandwidth, so this is where your kTB calculation will give you a true representation of their sensitivity. As their bitrate drops, the needed bandwidth also drops, so B has to be adjusted downward. At 1Mbps, I'll be generous and give them a 1MHz bandwidth in which to transmit. This gives them a noise floor of -114dBm. Far from state of the art.

  9. #29
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    Quote Originally Posted by bobbolo View Post
    how can i know the receiver sensitivity of the card? i only know that the
    transmit power id 300mW, and u correctly told me that transmit power is not all. There is a way to test and judge the others important values of the card? i have a wifi ubiquity pcmcia 300mW.
    You can't determine the sensitivity without equipment which none of us can afford. You have to rely on the manufacturer to tell you the truth. But you can determine the relative sensitivity compared to other cards by just swapping them out and checking which can detect distant WAPs which the other card can't, assuming they have the same type of external connector so you're not changing anything besides the card itself.

  10. #30
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    Quote Originally Posted by SLK001 View Post
    Well, all antennas do. However, antennas with integrated amps do not
    Thank you. So it turns out that a nonreciprocal "antenna" isn't just an antenna. That's something I've been wondering about for a while since I've seen references to nonreciprocal antennas sometimes (not worded that way, I don't remember how it was worded, but the point was the same) and I wondered "how is that possible?"

    Not really. They are "cheating" with their specs. If you look at their spec for a 54Mbps channel, it is -76dBm - not bad, but definitely not state of the art. This is the only measurement that uses the entire 20MHz bandwidth, so this is where your kTB calculation will give you a true representation of their sensitivity. As their bitrate drops, the needed bandwidth also drops, so B has to be adjusted downward. At 1Mbps, I'll be generous and give them a 1MHz bandwidth in which to transmit. This gives them a noise floor of -114dBm. Far from state of the art.
    Yes, I was mistaken about the noise floor. Thanks for the correction.
    They're not being misleading with their specs, since they always give the bitrate when they give a sensitivity (they're not like some webcam vendors who say "Up to <some really high resolution>! Up to 30fps!" but don't tell you that the webcam can't do both at the same time). Giving specs for lower bitrates is legitimate, since the WiFi standard allows radios to make the tradeoff when necessary. I was accidentally being misleading when I said -96dBm @ 1Mbps is close to the noise floor (my mistake, not theirs).
    But isn't the 362 state of the art if cost is accounted for? Or is there any device for sale which can do better and doesn't cost thousands of dollars?

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