Re: Need a lot of Help with setting up wireless

On Thu, 7 Feb 2008 22:42:38 -0500, cliffjag
<cliffjag.34g1j8@no-mx.wirelessforums.org> wrote in
<cliffjag.34g1j8@no-mx.wirelessforums.org>:

>I have to connect to routers together.

Wirelessly? That would only be possible if one of them can be
configured as a wireless Ethernet client bridge.

Wired? Then one should be configured as a wireless access point, not a
wireless router.

>But that is not the problem what
>i want to know is that the distance between the two points is approx
>160-170 m. With my clear eye i see that there is an Clear Line of Sight.
>I wanted to be sure so i download google earth.

It has to be clear including the fresnel zone, which is pretty big over
that distance. If you're just looking through a small hole, that
doesn't really qualify as clear line of sight.

>Question?
>Which antenna should i buy. How much dbi?

Hard to say without knowing what's in the middle.

>If you have a solution which
>kind of antennas i need please tell me. Note: the antenna's must be
>little for eg. Yagi antenna. It must not be bigger then 30 cm.
>Criteria:
>>>>Must get atleast 11mbps
>>>>No link loss ( 10% is ok ) i think
>What can you guys advice me

I would go with panel or dish, not yagi.

--
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On Feb 7, 10:11 pm, John Navas <spamfilt...@navasgroup.com> wrote:

>
> I would go with panel or dish, not yagi.
>



Just out of curiosity John, why is that?

I was just looking at a 2.4 Ghz Yagi, which are commonly used for
cellular, and wondering why panels and dishes are more common in WiFi.

Steve

On Fri, 8 Feb 2008 11:39:52 -0800 (PST), seaweedsteve
<seaweedsteve@gmail.com> wrote in
<cf44fb85-9010-4355-9a79-8be326573425@m34g2000hsb.googlegroups.com>:

>On Feb 7, 10:11 pm, John Navas <spamfilt...@navasgroup.com> wrote:
>
>> I would go with panel or dish, not yagi.
>
>Just out of curiosity John, why is that?
>
>I was just looking at a 2.4 Ghz Yagi, which are commonly used for
>cellular, and wondering why panels and dishes are more common in WiFi.

Less critical aiming.

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

seaweedsteve wrote:
> I was just looking at a 2.4 Ghz Yagi, which are commonly used for
> cellular, and wondering why panels and dishes are more common in WiFi.

There is no single answer, but rather the selection is based on the
application.

Yagi are easily detuned by ice (a moot point in southern climates),
but can have a radome. They have significant side and rear lobes
(the severity depends on the antenna gain).

Flat panel antennas have significant wind loading, but are almost
immune to ice build up (especially is faxed). They have excellent side
and rear lobe rejection. Gain and pricing is comparable to a Yagi.

Dish antennas - the solid dish has significant wind loading, but that
can be reduced with a radome. They have some minor spill over. Highest
priced, but the highest gain.

BBQ dish antennas - Gain is less that a solid dish, but little wind
loading. Price is comparable to a panel, half of a solid dish.

To answer your question.. Very few people use a gain antenna for
a cellphone, but everyone uses it for 2 to 8 mile wireless
broadband clients. Check all the supplies, how many do you see
selling Yagis for WiFi...very few.

The above information is based on professional everyday experience
where system reliability and profits are important. Not from some
amature hack that recommends consumer grade wireless products for
an occasional wireless link, and that doesn't have $50,000 a year set
aside to play with nor $30,000 worth of test equipment.

On Fri, 8 Feb 2008 11:39:52 -0800 (PST), seaweedsteve
<seaweedsteve@gmail.com> wrote:

>On Feb 7, 10:11 pm, John Navas <spamfilt...@navasgroup.com> wrote:
>> I would go with panel or dish, not yagi.

>Just out of curiosity John, why is that?

Hint. How long do you thing a 2.4GHz yagi would be in order to equal
the gain of a 24dBi dish antenna? (Answer is at bottom of this
message).

>I was just looking at a 2.4 Ghz Yagi, which are commonly used for
>cellular, and wondering why panels and dishes are more common in WiFi.

Well, cellular is at 800/1900Mhz in the USA. That makes for a
somewhat larger antenna. A dish for 900Mhz would just be too large.
Many cellular yagis also end up in peoples car trunks for long range
use when in remote areas. A dish just wouldn't fit.

There are two problems with a yagi that makes it a bad fit for Wi-Fi.

The typical yagi has lots of side lobes, which causes lots of
reflections, and potentially picks up interference from the side and
back. Panels and dishes have much less side lobe junk.

The construction of the yagi is fairly critical and complex when
compared to the typical panel and dish. In fact, the dish can be
fairly sloppy, and still work. Same with a corner reflector. The
panel or patch antennas lend themselves to mass production. They're
usually nothing more than a plated circuit board inside. Once the
dimensions are determined, they can be cranked out automagically, with
little variations from unit to unit. I can't say the same for
mechanical contrivances like a yagi.

Yagi's are also susceptible to icing, bird perching, and being used as
a foot peg when climbing a tower. The traditional end mounting causes
problems in routing the coax cable so that it does not detune the
yagi.






Answer:
A 15dBi yagi is about 18" long. For example:
<http://www.mfjenterprises.com/Product.php?productid=MFJ-1800>
The antenna gain increase 3dB for every doubling in the length of the
yagi. So, doing it the hard way:
Gain Length
(dBi) (inches)
15 18
18 36
21 72
24 144
So, to equal the gain of a 24dBi 2.4GHz dish, you need a 12 ft long
yagi. I don't think that would sell too well.



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 jeffl@comix.santa-cruz.ca.us
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

Thanks guys. Appreciate the education.

Back to topic.

Steve