7 dBi Antenna
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Posted by Dennis on June 7, 2008, 4:29 am
Please log in for more thread options wireless NIC. Not sure its going to help me, but I figure its worth a shot. But I'm wondering why nics/routers come with 2 dBi antennas by default.... why isnt 5 or 7 dBi the default? | |||||||||||||||||||||||||
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Posted by David Fairbrother on June 7, 2008, 6:01 am
Please log in for more thread options Almost all, I think. As to the 5/7dbi default suggestion, it's a matter of cost. Many home users won't desire anything above 2dbi - and would whinge if they were paying $30AUD extra for something they don't really need. | |||||||||||||||||||||||||
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Posted by ps56k on June 7, 2008, 10:13 am
Please log in for more thread options David Fairbrother wrote:
> Dennis wrote:
>> Thinking about grabbing a Dlink 7 dBi omni-directional antenna for my
>> wireless NIC. Not sure its going to help me, but I figure its worth a >> shot. >> >> But I'm wondering why nics/routers come with 2 dBi antennas by >> default.... why isnt 5 or 7 dBi the default? >
> Almost all, I think. > > As to the 5/7dbi default suggestion, it's a matter of cost. > > Many home users won't desire anything above 2dbi - and would whinge if > they were paying $30AUD extra for something they don't really need. also - there is no "free lunch".... There is X amount of power delivered to the antenna connector & antenna. That energy can be highly focused in one direction with a dish, or spread around with an onmi-directional antenna. And then - even with the omnis - the donut shape that surrounds the antenna, as if the donut was sitting over the stick - the "roundness" vs "flatness" of the donut is the amount of db gain you want. SO - you flatten out the donut - and expand the horizontal range, but then give up the vertical roundness and coverage - up or down to other floors - | |||||||||||||||||||||||||
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Posted by Dennis on June 7, 2008, 5:09 pm
Please log in for more thread options > David Fairbrother wrote:
> > Dennis wrote:
> >> Thinking about grabbing a Dlink 7 dBi omni-directional antenna for my
> >> wireless NIC. Not sure its going to help me, but I figure its worth a > >> shot. >
> >> But I'm wondering why nics/routers come with 2 dBi antennas by
> >> default.... why isnt 5 or 7 dBi the default? >
> > Almost all, I think.
>
> > As to the 5/7dbi default suggestion, it's a matter of cost.
>
> > Many home users won't desire anything above 2dbi - and would whinge if
> > they were paying $30AUD extra for something they don't really need. >
a,
> also - there is no "free lunch".... > There is X amount of power delivered to the antenna connector & antenna. > That energy can be highly focused in one direction with a dish, > or spread around with an onmi-directional antenna. > And then - even with the omnis - the donut shape that surrounds the antenn= > as if the donut was sitting over the stick -
> the "roundness" vs "flatness" of the donut is the amount of db gain you > want. > > SO - you flatten out the donut - and expand the horizontal range, > but then give up the vertical roundness and coverage - up or down to other= > floors -
I'm similar with the donut shape omni directional antennas create. But here's a question: What is the approximate veritical height of the donut? 20 feet? 200 feet? (on a 2 dBi 2.4gzh antenna) and what is the veritical height when using a 7 dBi antenna? | |||||||||||||||||||||||||
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Posted by Jeff Liebermann on June 7, 2008, 7:30 pm
Please log in for more thread options On Sat, 7 Jun 2008 14:09:00 -0700 (PDT), Dennis
>I'm similar with the donut shape omni directional antennas create. But
>here's a question: What is the approximate veritical height of the >donut? 20 feet? 200 feet? (on a 2 dBi 2.4gzh antenna) > >and what is the veritical height when using a 7 dBi antenna? The donut does not have a "height". I does have a width, measured at the half power (-3dB) points. I just ran some quicky 4NEC2 antenna models for some typical vertical collinear antennas. The -3dB vertical radiation angle is approximately: Dipoles Approx length Gain Vertical (with decoupler) -3d rad angle cm dBi degrees 1 9.5 2 85(?) 2 15.8 5 40 4 28.4 8 15 8 53.6 11 8 16 104 15 4 Note that the length of the antenna doubles for every 3dB gain. The antenna length does NOT include any consideration for downtilt, phasing section losses, or length added by top isolation or mounting contrivances. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 | |||||||||||||||||||||||||
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> wireless NIC. Not sure its going to help me, but I figure its worth a
> shot.
>
> But I'm wondering why nics/routers come with 2 dBi antennas by
> default.... why isnt 5 or 7 dBi the default?