7 dBi Antenna

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?

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.

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 -

On Jun 7, 10:13*am, "ps56k" <pschuman_no_spam...@interserv.com> wrote:
> 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 -




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?

On Sat, 7 Jun 2008 14:09:00 -0700 (PDT), Dennis
<dennispublic@hotmail.com> wrote:

>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

Dennis wrote:
> On Jun 7, 10:13 am, "ps56k" <pschuman_no_spam...@interserv.com> wrote:
>> 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 -
>
>
>
>
> 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?

a quick random search..... for antenna pattern info -
http://www.cisco.com/en/US/tech/tk72...807f34d3.shtml

In article <9bbd2684-971a-419a-81b2-1b2888f49c77@
2g2000hsn.googlegroups.com>, dennispublic@hotmail.com says...
> But I'm wondering why nics/routers come with 2 dBi antennas by
> default.... why isnt 5 or 7 dBi the default?

Cost, size, appearance, directionality.