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 !

On Wed, 24 Sep 2008 22:39:23 -0700 (PDT), Penang
wrote:

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 !
Yeah, you are welcome.

98% of all WIFI antenna tutorials on the www are bad,
unuseable or simply blatantly wrong. Their objects
(avoid calling them "antennas") have the functionality
of a bare piece of wire, which works also.

So I made a 100% WIFI antenna to have an object for a tutorial.
But it is not one of the broadcast type you requested,
I made a 10 turn 2,4 GHz helix with bandpass stub.

I just moved over to grab the camera for a quickie,
the antenna dropped down to the floor, the tripod
fell over my coffee and the cat jumped into my apple pie.

My scalar analyzer failed last week and is on repair,
so I cannot make the proofing screenshots: 50 Ohms over
the whole WLAN channels 1 to 13 with an SWR 1,5
(and the stub prevents overload by cellular & TV).

Why is everything that complicated?

w.

hwabnig@ .- --- -. dotat wrote:
Yeah, you are welcome.

98% of all WIFI antenna tutorials on the www are bad,
unuseable or simply blatantly wrong. Their objects
(avoid calling them "antennas") have the functionality
of a bare piece of wire, which works also.

So I made a 100% WIFI antenna to have an object for a tutorial.
But it is not one of the broadcast type you requested,
I made a 10 turn 2,4 GHz helix with bandpass stub.

I just moved over to grab the camera for a quickie,
the antenna dropped down to the floor, the tripod
fell over my coffee and the cat jumped into my apple pie.

My scalar analyzer failed last week and is on repair,
so I cannot make the proofing screenshots: 50 Ohms over
the whole WLAN channels 1 to 13 with an SWR 1,5
(and the stub prevents overload by cellular & TV).

Why is everything that complicated?

w.

Because there IS a God, and She has a twisted sense of humor.

Roy Lewallen, W7EL

Roy Lewallen writes:

hwabnig@ .- --- -. dotat wrote:
Yeah, you are welcome.

98% of all WIFI antenna tutorials on the www are bad, unuseable or
simply blatantly wrong. Their objects
(avoid calling them "antennas") have the functionality
of a bare piece of wire, which works also.

So I made a 100% WIFI antenna to have an object for a tutorial.
But it is not one of the broadcast type you requested,
I made a 10 turn 2,4 GHz helix with bandpass stub.

I just moved over to grab the camera for a quickie,
the antenna dropped down to the floor, the tripod
fell over my coffee and the cat jumped into my apple pie.

My scalar analyzer failed last week and is on repair,
so I cannot make the proofing screenshots: 50 Ohms over
the whole WLAN channels 1 to 13 with an SWR 1,5
(and the stub prevents overload by cellular & TV).

Why is everything that complicated?

w.

Because there IS a God, and She has a twisted sense of humor.

A glance at modern physics is enough to convince you of that.

Starting with one or two basics;

- Keep the losses down
- Channel as much of the radiation as possible in the direction you need it

Losses in this sense more come from coax runs and connectors. Keep the
run short, dont use joiners and if possible mount the WiFi box close to
the antenna. You have to also allow for obstructive losses like trees
and buildings. The other path loss is from errant reflections. Moounting
the antenna high up in the clear resolves many of these issues.

Radiating in the right direction isnt rocket science in theory. The
average "omnidirectional" antenna is actually "all directions" only
parallel to the ground. ie you dont waste radiation skyward or warming
the dirt! In terms of distance covered though an omni of this kind wont
be as good as employing an antenna that "beams" in one direction.
Consider this as a kind of flashlight with reflector and you'll get the
right idea. In terms of time/construction/distance investment you'll do
a lot better with this kind of antenna than an omni, elthough you will
need to point them in the right direction. Which one you choose depends
on its intended use.

You have probably figured out that the antenna gain figure (in dB) is
the measure that is used to determine how much better one antenna is
over another. It is a log comparison of the desired radiation direction
"strength" vs that of an antenna that radiates eqaully in all
directions. An omni however will almost always have a lower gain than a
"beam" type antenna. 9 and 12 dB are some fairly high omni gains but
"beam" gains can go 15-30dB. The higher the number the greater the range
in the desired direction.

So my view.. If you intend one site being fixed and the other movable
then you'll at least need an omni at the base site. If you only want a
point to point link then a "beam" variety at each end is the way to go.
I wouldnt go for "best" but engineer the path/strength requirements to
determine the antenna gain needed. If I was making the antennas I'd
probably use end fire helixes as they seem to be most forgiving in
construction errors vs best gain.

You might want to tell us your end application, distance to cover,
movement of sites and so on so we can suggest something a little more
finite.

Cheers Bob

Penang wrote:


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 !

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.



--
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

"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

hwabnig@ .- --- -. dotat wrote:

Yeah, you are welcome.

98% of all WIFI antenna tutorials on the www are bad,
unuseable or simply blatantly wrong. Their objects
(avoid calling them "antennas") have the functionality
of a bare piece of wire, which works also.

So I made a 100% WIFI antenna to have an object for a tutorial.
But it is not one of the broadcast type you requested,
I made a 10 turn 2,4 GHz helix with bandpass stub.

I just moved over to grab the camera for a quickie,
the antenna dropped down to the floor, the tripod
fell over my coffee and the cat jumped into my apple pie.

My scalar analyzer failed last week and is on repair,
so I cannot make the proofing screenshots: 50 Ohms over
the whole WLAN channels 1 to 13 with an SWR 1,5
(and the stub prevents overload by cellular & TV).

Why is everything that complicated?

w.

Yeah, sounds like a good start for a comic book series; successful ones
have been created on less--I suppose ...

Regards,
JS

"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/