"Jeff Liebermann" wrote:
No. Brain damage is a known side effect and complication resulting
from trying to digest the entire field of antenna design all at once.
Just reading some of the posting in this newsgroup should adequately
demonstrate the extent of the damage. I suggest you approach antenna
design in the same manner as eating a loaf of bread. It's done one
slice at a time. If you try to shove the entire loaf down your throat
at once, you'll choke.

Reading one or two posts from Art will evoke chortles and guffaws, but
when taken in large, sustained doses, will make your head hurt.

Mike W5CHR
Memphis Tenn

On Thu, 25 Sep 2008 11:00:20 -0500, "Mike Lucas"
wrote:
"Jeff Liebermann" wrote:
No. Brain damage is a known side effect and complication resulting
from trying to digest the entire field of antenna design all at once.
Just reading some of the posting in this newsgroup should adequately
demonstrate the extent of the damage. I suggest you approach antenna
design in the same manner as eating a loaf of bread. It's done one
slice at a time. If you try to shove the entire loaf down your throat
at once, you'll choke.

Reading one or two posts from Art will evoke chortles and guffaws, but
when taken in large, sustained doses, will make your head hurt.

I was trying to be diplomatic and subtle. Apparently, I failed.

On another mailing list, I once had someone telling me that I'm wrong
because 90% of the universe is dark matter or dark energy. Since
these are total unknowns, 90% of everything is therefore unknown.
Therefore, 90% of my analysis must also be wrong. I rather like the
logic.

However, I was serious about taking it slowly on learning about
antennas. To really understand how they work and what they, it takes
far too many diverse diciplines (Maxwell's Eqn, modeling, propagation,
topography, material science, construction techniques, impedance
matching, surface geometry, etc) to absorb it all at once. Also, some
hands on experience is always useful.

It's like trying to recover an intelligent signal out of gaussian
white noise. Despite the best efforts of all involved, the noise
usually wins.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
It's like trying to recover an intelligent signal out of gaussian
white noise. Despite the best efforts of all involved, the noise
usually wins.

If I listen to white noise when I'm inebriated, I can hear
Willie Nelson singing, "You Were Always On My Mind". :-)
--
73, Cecil http://www.w5dxp.com
"According to the general theory of relativity,
space without ether is unthinkable." Albert Einstein

On Sep 25, 9:52 pm, Jeff Liebermann wrote:
On Wed, 24 Sep 2008 22:39:23 -0700 (PDT), Penang
wrote:

Specifically, my interest is in the "broadcast" type of antenna ...
trying to find a way to "extend" the range of a typical wifi
basestation using antennas alone (maybe with the help of MIMO
antennas), without "range repeaters" or whatnots.

Broadcast implies one way transmissions. Wi-Fi is bi-directional.

The common terms are "range extender" or "repeater". These normally
refer to store and forward transmitter/receivers use to extend range
by retransmitting the data. This is roughly how a MESH network
operates. There are some severe limits and compromises to using such
repeaters, none of which have anything to do with the antenna. Ask if
you need details.

My brain is now fully clogged, and I'm having difficulties digesting
all the stuffs that I've gotten.

One must suffer before enlightenment. You're doing fine.

Is there a place (a forum, a website, a tutorial, and whatnots) where
one can learn about antennas, without having one's brain clogged up,
like mine right now?

No. Brain damage is a known side effect and complication resulting
from trying to digest the entire field of antenna design all at once.
Just reading some of the posting in this newsgroup should adequately
demonstrate the extent of the damage. I suggest you approach antenna
design in the same manner as eating a loaf of bread. It's done one
slice at a time. If you try to shove the entire loaf down your throat
at once, you'll choke.

What's your suggestion / opinion on how to construct an excellent
(pair) of MIMO antenna for wifi (802.11 b/g/n) ?

I suggest you give up immediately and read about how MIMO works.
External MIMO antennas are a problem.

There are two basic types of MIMO. One is called "beam forming",
which uses an elaborate and flat array of internal antennas to
customize the antenna pattern. Major lobes are pointed in the
direction of users. Nulls are pointed in the direction of
interference. The key point is that antennas are internal and
therefore external antennas have no place to plug in.

The other type is called "spatial diversity". It uses multiple
antennas and multiple receivers to combine reflective signal paths. In
theory, each path is independent and carry an independent data stream.
Combining these paths results in enhanced speeds. Note that this form
of MIMO is all about speed, not range.

It is possible to attach external antennas to a spatial diversity type
MIMO system. However, there are limitations. You can't just install
3 directional antennas pointed in 3 different directions. Pointed in
opposing directions, the antennas will simply not pickup any
reflections. If there are any long path reflections, the delays will
probably be excessive and the data deemed useless. Attaching a single
antenna to a MIMO spatial diversity type router will function, but
only at 802.11g speeds. Without the time delayed reflections, there's
no MIMO speeds.

Anyway, I don't have any suggestions on how to construct an excellent
antenna. You haven't specified what you're trying to accomplish, what
you have to work with, what is your operating environment, and what
problem you're trying to solve. Different types of antennas are
designed to solve different problems. Without a clue as to the
problem and limitations, it's rather difficult to select a suitable
antenna.

Hint: Forget about using "N" or MIMO with external antennas. Unless
you're trying to move video, 802.11g speeds are good enough.

Since I'm toying with a community-type of wifi network, there are
walls, and foliage, and topologies (hills and valleys) that are
effecting the way the waves work. That is why I am trying to read as
much as possible, while experimenting with an array of weird looking
antennas and putting them in various spots to try out.

The longest (world record?) for a wifi transmission is somewhere at
the 147KM, someone in South America did that. I ain't gonna try to
break it, but would be more than happy -- in fact jumping in hoops !!
-- if I can find a way to make antennas that can successfully spread
the signal. 1 or even 2 miles away.

I'd be reading up the excellent points you and so many others have
given me here, and will try to tinker a bit here and there even more.

Thanks again !!



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Fri, 26 Sep 2008 02:45:59 -0700 (PDT), Penang
wrote:

Since I'm toying with a community-type of wifi network, there are
walls, and foliage, and topologies (hills and valleys) that are
effecting the way the waves work.

2.4GHz wireless does not go through hills. If you plan to have
coverage in the valleys, you'll need to have a radio somewhere in the
valley. NLOS (non line of sight) radio can be made to work, but
cannot be made to stay working. It may work for a while. Then,
something is moved, and it stops working. If you want to fill in
holes, look into wireless mesh networks.
http://www.open-mesh.com
http://meraki.com

I suggest you look into sector antennas, specifically AMOS or Franklin
antennas. These are quite suitable for covering a wide flat area.
Depending on construction, the horizontal beamwidth is anywhere
between 90 and 150 degrees, with a vertical beamwidth of approximately
10 degrees. The idea is to send most of the RF toward the horizon,
and not into the air or into the ground. Gain varies from 8dBi to
perhaps 15dBi depending on type and construction.

Articles on the AMOS antenna design at:
http://www.qsl.net/yu1aw/invertamos.pdf
http://www.qsl.net/yu1aw/amos_article.pdf

AMOS and Franklin type antennas:
http://pe2er.nl/wifisector/
http://yu1aw.ba-karlsruhe.de/ANT.htm
http://yu1aw.ba-karlsruhe.de/vhf_ant.htm
http://www.qsl.net/yu1aw/vhf_ant.htm
http://www.brest-wireless.net/gallery/AntenneAmos
http://www.brest-wireless.net/wiki/materiel:amos

You'll find that there's much more to running a WISP (wireless
internet service provider) than antennas and radios. If you plan to
grow the business, you'll find that it's exactly the same as a wire
line ISP, except you have a basically unreliable method of delivery.
One leaky microwave oven will trash connectivity for a very wide area.
Like a wire line ISP, you'll need a backhaul, billing, support,
installation, service, and troubleshooting. The usual oversight is
that wire line ISP's don't make much money from connectivity. They
make their money with secondary services such as web hosting. If
customers bring their own equipment, you'll need some way to
troubleshoot *THEIR* problems and possibly charge for fixing *THEIR*
computer. You could supply the radio equipment to the customers which
will put you in the equipment leasing business. Plenty to think about
but the one that usually causes problems for startup WISP's is "who is
going to answer the phone when the customer calls to report an outage
at 2AM?" Start reading about the WISP business he
http://www.bbwexchange.com/wireless_internet_access/
http://www.bbwexchange.com/howto/

Good luck.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Penang" wrote in message
...
My background isn't on antenna making, in fact, my training is in
Chemical engineering, not physics.

But lately I've spent a lot of times consuming materials I dig from
the Net about antennas, in the effect to learn how to make an
excellent (effective?) wifi antenna.

Specifically, my interest is in the "broadcast" type of antenna ...
trying to find a way to "extend" the range of a typical wifi
basestation using antennas alone (maybe with the help of MIMO
antennas), without "range repeaters" or whatnots.

My brain is now fully clogged, and I'm having difficulties digesting
all the stuffs that I've gotten.

So I desperately need you help.

Is there a place (a forum, a website, a tutorial, and whatnots) where
one can learn about antennas, without having one's brain clogged up,
like mine right now?

What's your suggestion / opinion on how to construct an excellent
(pair) of MIMO antenna for wifi (802.11 b/g/n) ?

Thank you all !

Hi Penang

Do you wish to broadcast to all azimuth directions? The antenna design is
highly dependent on the angle over which you want to 'extend wifi'. I
suggest you read some of Trevor Marshal's writing (Google his name)

I strongle recxommend that you use [router, bridge] at the antenna and use
CAT 5 to connect to your computer.

Jerry KD6JDJ

"Penang" wrote in message
...
My background isn't on antenna making, in fact, my training is in
Chemical engineering, not physics.

But lately I've spent a lot of times consuming materials I dig from
the Net about antennas, in the effect to learn how to make an
excellent (effective?) wifi antenna.

Specifically, my interest is in the "broadcast" type of antenna ...
trying to find a way to "extend" the range of a typical wifi
basestation using antennas alone (maybe with the help of MIMO
antennas), without "range repeaters" or whatnots.

My brain is now fully clogged, and I'm having difficulties digesting
all the stuffs that I've gotten.

So I desperately need you help.

Is there a place (a forum, a website, a tutorial, and whatnots) where
one can learn about antennas, without having one's brain clogged up,
like mine right now?

What's your suggestion / opinion on how to construct an excellent
(pair) of MIMO antenna for wifi (802.11 b/g/n) ?

Thank you all !

Often gain type antennas already came with the unit. The problem is in
putting the antenna where it will do some good. The other problem is in
losing signal getting it from the AP to the antenna. You can easily lose
any gain from a good antenna in the cable and connectors. On the other hand
it is worth that just to be able to put the antenna where it will do some
good. If it is any consolation, Cat5/6 is cheaper and faster than the AP
itself. Still it is a pain to have to climb and do acrobatics just to push
a reset button. There are excellent base station type antennas, hardware
and feedline that can certainly optimize a signal for blocks away, but they
are expensive and must be properly planned and executed to avoid wasting it
all.

This isn't amateur radio so it really isn't on topic. It sounds to me like
a business opportunity.
http://infotech.awardspace.com/

Penang wrote:

...
Specifically, my interest is in the "broadcast" type of antenna ...
trying to find a way to "extend" the range of a typical wifi
basestation using antennas alone (maybe with the help of MIMO
antennas), without "range repeaters" or whatnots.
...
Thank you all !

Much research is going on and designs/parameters advanced. These two
papers represent the direction this is taking:

http://ceta.mit.edu/pierl/pierl01/10.07111810.pdf
http://www.ece.uci.edu/~ayanoglu/MIMO_MRAA_IEEEAWPL.pdf

However, the DLM (Distributed Load Monopole) antenna by Robert Vincent
is an excellent design for such applications.

However, since size is not a major consideration in my external wifi
antennas, a conventional 1/2 or 5/8 wave end fed design is what I have
implemented, with a gamma feed ...

I use a biquad with a parabolic reflector (from a direct TV sat.
antenna) for directional antenna implementations ...

I am following the KISS method (or, Keep It Simple Stupid! -- NO insult
intended ...)

Regards,
JS

If by searching the web you haven't found a good wifi antenna you should
look again as there are lots that will work. If you're wanting to go into
business against the major carriers as your equals or competitors, then go
back to school for a little longer.....................

Penang writes:

What's your suggestion / opinion on how to construct an excellent
(pair) of MIMO antenna for wifi (802.11 b/g/n) ?

Not MIMO, but many weird looking, but mostly sound, ideas he

http://usbwifi.orconhosting.net.nz/

"Make 2.4GHz parabolic mesh dishes from cheap but sturdy Chinese
cookware scoops & a USB WiFi adaptor"

By placing the wi-fi adaptor in the antenna, you don't lose radio power in
cables and connectors. You have to be careful about waterproofing,
though.

Jon