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Thread: Why buy the Alfa AWUS036H?

  1. #1
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    Default Why buy the Alfa AWUS036H?

    I'm curious, what's the point of spending 75+ dollars for the alfa awus036H card, which has 500mW power, when you can get the edimax 7318usg or alfa awus036s, which has 17 +/- 2 db power (a 'measly' 50mW) and slap on a 10dbi antenna for 10 bucks? This will add up to 17+10 = 27db = 501.19 mW of power, am I right?

    *edit* ok silly me, didn't realize that the H card has a RP-SMA for a 10 dbi antenna too, which makes it much more powerful... But still, are my inferences above correct?

  2. #2
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    You don't add more mW of power to a card or USB just because you put an antenna on it! All your doing by adding an antenna is increasing the dBi rating of the card that affects the Tx and Rx power. More power can only be achieved by adding a signal booster or AMP inline at the antenna and card. And the alfa awus036h already has an amp in it. Thats why its better to buy the awus036H over the awus036s.
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  3. #3
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    I see, thanks for clearing it up!

    *edit* Does anyone know how significant a boost would result from going from a 4dbi antenna to a 10dbi antenna in terms of distance?

  4. #4
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    Considering the fact that a 10 dBi antenna is over double the dBi of an 4dBi antenna, I'd say you'd see a moderate increase of range of about 100ft. But remember, its only increasing the Tx (broadcast power) not necessarily the Rx (receiving power). to increase the receiving power you need an amp or a homemade parabolic reflector. Search the forum for my little demo/tutorial on parabolic reflectors in the tutorial section for more info.
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  5. #5
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    A 10db antenna will have 4x the gain of a 4db one, you will also see a similar increase in the receive performance although it should be noted that noise will also be similarly amplified in both receive and transmit.

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    Great! thanks for the info both of you. Btw, I already looked at that cardbox parabolic reflector post, thats why I'm suddenly interested in antennae ;-)

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    Quote Originally Posted by balding_parrot View Post
    A 10db antenna will have 4x the gain of a 4db one, you will also see a similar increase in the receive performance although it should be noted that noise will also be similarly amplified in both receive and transmit.
    Curious, how did you arrive at 4x the gain? From wikipedia'ing a little bit, I noticed that gain is in the units of db's and is a logarithmic function of power input and output. Since the power in and power out would remain the same while just replacing the antenna, shouldn't the gain be a linear function of the decibel rating of the antenna then? Again, I am a total newbie at this stuff, so please excuse me if I just stated something obviously wrong (again)

  8. #8
    Senior Member streaker69's Avatar
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    Quote Originally Posted by StriderZ View Post
    Curious, how did you arrive at 4x the gain? From wikipedia'ing a little bit, I noticed that gain is in the units of db's and is a logarithmic function of power input and output. Since the power in and power out would remain the same while just replacing the antenna, shouldn't the gain be a linear function of the decibel rating of the antenna then? Again, I am a total newbie at this stuff, so please excuse me if I just stated something obviously wrong (again)
    A general rule of thumb in any kind of RF transmission calculations is to double your distance you need to square your power.

    So if your transmitter currently goes 1 mile at 2W, and you want to go 2 miles, you'd need to output 4W, 4 miles=16W and so on and so forth. This does not take into account for atmospheric conditions that allow a low power transmission to skip between atmospheric layers.

    I'm just saying this to give you a point of reference, not to re-enforce what the previous person stated.
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  9. #9
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    Quote Originally Posted by StriderZ View Post
    Curious, how did you arrive at 4x the gain? From wikipedia'ing a little bit, I noticed that gain is in the units of db's and is a logarithmic function of power input and output. Since the power in and power out would remain the same while just replacing the antenna, shouldn't the gain be a linear function of the decibel rating of the antenna then? Again, I am a total newbie at this stuff, so please excuse me if I just stated something obviously wrong (again)
    No, because the decibel is a logarithmic measurement of the ratio of input to output of a system.

    It's not an easy thing to explain in a forum.

    3db is a rise in gain, or power of 2x the original input level, so 6db is 2x + 2x = 4x

    You may find that this although quite simplistic can explain it better than I will be able to in a forum.

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