I came across a reference about adaptive beamforming in the ARRL
Handbook. The reference was from QEX which I don't yet subscribe to.

Anyone care to explain/discuss this neat concept?

John
AB8WH

well, 'adaptive beamforming' is two words...

'beamforming' means forming a directional 'beam' using an antenna. be it a
simple parasitic array like yagi's or a complex array of driven elements
like a flat panel radar. most often when you talk about beamforming it is
more like the radar arrays or other large array that combines signals from
many small antennas to form a very directional beam.

'adaptive' means forming the beam in a way that makes it work better in the
environment, or adapt to it's surroundings. this is often used to form
beams to maximize a received signal while notching out interference. so you
use an algorithm to measure s/n ratio or some other parameter and adjust
power and phasing of the individual elements to get the best signal you can.
its harder to adapt a transmitting antenna since you need some kind of
feedback from the far end to let you know if the beam is getting better or
worse as you adjust it.


"john" wrote in message
...
I came across a reference about adaptive beamforming in the ARRL Handbook.
The reference was from QEX which I don't yet subscribe to.

Anyone care to explain/discuss this neat concept?

John
AB8WH

jawod wrote:
Dave wrote:
well, 'adaptive beamforming' is two words...

'beamforming' means forming a directional 'beam' using an antenna. be
it a simple parasitic array like yagi's or a complex array of driven
elements like a flat panel radar. most often when you talk about
beamforming it is more like the radar arrays or other large array that
combines signals from many small antennas to form a very directional
beam.

'adaptive' means forming the beam in a way that makes it work better
in the environment, or adapt to it's surroundings. this is often used
to form beams to maximize a received signal while notching out
interference. so you use an algorithm to measure s/n ratio or some
other parameter and adjust power and phasing of the individual
elements to get the best signal you can. its harder to adapt a
transmitting antenna since you need some kind of feedback from the far
end to let you know if the beam is getting better or worse as you
adjust it.


"john" wrote in message
...

I came across a reference about adaptive beamforming in the ARRL
Handbook. The reference was from QEX which I don't yet subscribe to.

Anyone care to explain/discuss this neat concept?

John
AB8WH



Dave,

Thanks for responding.

Given the need for "stealth" antennas, Is there /are there design(s)
that create small footprint antennas that function as larger traditional
ones?

Can a longwire be divided into small segments that are independently
controlled such that the sum of the parts behave differently than the
whole?...and can this effect be altered via software?

Has anyone been working on this approach?

John
AB8WH

You can do it with dipoles, like the HAARP transmitter. It has the most
gain per acre than any other antenna. You can really use any antennas,
just the phasing becomes complicated. You need to ensure all antennas
are identical and have the same impedance and reactance etc etc.

Its a bloody complicated exercise to design such an array. Look up
the varios web pages on google.

The DF arrays used around the world are receive only versions of these
antennas. Look up "super resolution DF arrays. They amazing stuff!

A number of ANtenna companies sell wide band vertical arrays for
transmitting. They consist of 12 vertical in a circle with a radiator in
the centre. They then have a smaller inner circle for the higher
frequencies.

I would like to pick up one of the Super DF arrays one day on the
surplus market, oh boy what fun you can have! They can work out the
location of a station with one DF receiver. Called single station
Location.

Beam forming on receive and transmit are the same thing in reality.
However its not as easy building phase stable antennas on transmit that
cover 1.8 to 30 mhz.

If you work it all out and can do it for 500 dollars let me know. I
would like to buy a beam forming antenna for shortwave receive. With
cost of DSP chips dropping who knows maybe some day some smart ham will
come up with a Super resolution cheap df system/ beam forming transmit
system.

Ocean radar also use these complicated systems.

HF antennas for all locations RSGB has a article in their for beam
forming using compact 1 metre loop antennas, you might want to check it
out. Its a homebrew version of the Hermes Loop system. Same thing
could be done on transmit with magnetic loops. If you took a ham 8
circle vertical array and substituted magnetic loops you could perhaps
do it. You need someone smart like W8JI to figure out all the
mathematics and details.

Pat

"jawod" wrote in message ...
Dave wrote:
well, 'adaptive beamforming' is two words...

'beamforming' means forming a directional 'beam' using an antenna. be it
a simple parasitic array like yagi's or a complex array of driven
elements like a flat panel radar. most often when you talk about
beamforming it is more like the radar arrays or other large array that
combines signals from many small antennas to form a very directional
beam.

'adaptive' means forming the beam in a way that makes it work better in
the environment, or adapt to it's surroundings. this is often used to
form beams to maximize a received signal while notching out interference.
so you use an algorithm to measure s/n ratio or some other parameter and
adjust power and phasing of the individual elements to get the best
signal you can. its harder to adapt a transmitting antenna since you need
some kind of feedback from the far end to let you know if the beam is
getting better or worse as you adjust it.


"john" wrote in message
...

I came across a reference about adaptive beamforming in the ARRL
Handbook. The reference was from QEX which I don't yet subscribe to.

Anyone care to explain/discuss this neat concept?

John
AB8WH



Dave,

Thanks for responding.

Given the need for "stealth" antennas, Is there /are there design(s) that
create small footprint antennas that function as larger traditional ones?

Can a longwire be divided into small segments that are independently
controlled such that the sum of the parts behave differently than the
whole?...and can this effect be altered via software?

Has anyone been working on this approach?

John
AB8WH


no, you can't make antennas smaller this way... you can make small parts
behave differently, but you can't get more gain or efficiency than a
simillarly sized 'normal' antenna. i don't know of any hams actively
working in this area, mostly because on hf the antennas get huge quickly.
and on vhf/uhf and up there are much simpler ways to get gain for single
point to point use that most hams are interested in. the real applications
for things like this are radar and multi-point fixed or mobile systems that
have to deal with multipath reflection and interference.

On Sat, 29 Jul 2006 11:00:54 -0000, "Dave" wrote:

[snip]

The real applications
for things like this are radar and multi-point fixed or mobile systems that
have to deal with multipath reflection and interference.

And things like this:

http://www.raytheon.com/products/pgs/index.html#agr

Glenn Møller-Holst wrote:

john wrote:

I came across a reference about adaptive beamforming in the ARRL
Handbook. The reference was from QEX which I don't yet subscribe to.

Anyone care to explain/discuss this neat concept?

John
AB8WH


Hi John

Look at:

http://en.wikipedia.org/wiki/Beamforming

http://en.wikipedia.org/wiki/Multipl...ultiple-output

http://en.wikipedia.org/wiki/Synthetic_aperture_radar

Glenn

Found this illustative article about beamforming:

How to create beam-forming smart antennas using FPGAS:
http://www.embedded.com/showArticle....cleID=60401726
Quote: "...The adaptive process permits narrower beams and reduced
output in other directions, significantly improving the
signal-to-interference-plus-noise ratio (SINR). With this technology,
each user's signal is transmitted and received by the base station only
in the direction of that particular user. This drastically reduces the
overall interference in the system..."

Glenn

On Fri, 28 Jul 2006 23:25:10 -0400, jawod wrote:

Dave wrote:
well, 'adaptive beamforming' is two words...

'beamforming' means forming a directional 'beam' using an antenna. be it a
simple parasitic array like yagi's or a complex array of driven elements
like a flat panel radar.
....
'adaptive' means forming the beam in a way that makes it work better in the
environment, or adapt to it's surroundings.
....
Given the need for "stealth" antennas, Is there /are there design(s)
that create small footprint antennas that function as larger traditional
ones?

Can a longwire be divided into small segments that are independently
controlled such that the sum of the parts behave differently than the
whole?...and can this effect be altered via software?

Has anyone been working on this approach?

Hi John,

As David and others offer, this adaptability and beamforming
characteristic is a product of both massive duplication and a large
area with respect to the wavelength of interest. To put it in rather
more traditional terms:
"There's no such thing as a free lunch."

You ask about controlling small segments independently. Can you
imagine that this maze of control wires would in itself be a more
capable antenna? This is the price of complexity: if you can afford
these elaborations in design, why not do it the traditional way? You
gain nothing in sensitivity, you gain nothing in efficiency (which is
most certainly the first characteristic to suffer by orders of
magnitude). And to offer it as a prospective "stealth" antenna is
defeated from the outset.

Think of a rather more practical example that is also a good metaphor.
Imagine the Fresnel lens. It performs its beamforming through
segmentation. Its advantage is that it is lighter than the complete
lens, but if you can tolerate the weight, it offers nothing else to
compensate for the elaboration of a complex set of lens segments piled
one atop the other.

Now, if you can pay the price of elaboration, you can spread antenna
elements about - disguised even. You can bury control cables and
signal cables - you will certainly need them both. You can devise a
control program to "focus" the antenna - which is what beamforming is
all about. OR you can twist knobs like the thousand armed Shiva to
achieve the same thing. For some, this technical challenge alone is
worth the struggle - forget the DX. And yes, you will actually gain
an advantage over a single fixed antenna.

Try with the four square antenna which encompasses all these topics
that interest you. If you can wrestle with the knots of its
complexity, you can step up to more sophisticated issues.

73's
Richard Clark, KB7QHC

If you can wrestle with the knots of its
complexity, you can step up to more sophisticated issues.

73's
Richard Clark, KB7QHC

Richard,

You need to chill out.

I've expressed this befo I don't need your imprimatur to post here.
This is an amateur group. As such, speculation on these matters need to
be welcomed, not derided.

I gladly defer to your expertise. However, I'll not defer to you in
speculative matters in an amateur venue.

You know, I really hate the term "outside the box", however, naive
perspectives, as you seem to deem mine, can be fruitful. Mutual respect
is the order of the day. If not, please refrain from responding.

"73's"
John
AB8WH

jawod wrote:
If you can wrestle with the knots of its

complexity, you can step up to more sophisticated issues.

73's
Richard Clark, KB7QHC


Richard,

You need to chill out.

I've expressed this befo I don't need your imprimatur to post here.
This is an amateur group. As such, speculation on these matters need to
be welcomed, not derided.

I gladly defer to your expertise. However, I'll not defer to you in
speculative matters in an amateur venue.

You know, I really hate the term "outside the box", however, naive
perspectives, as you seem to deem mine, can be fruitful. Mutual respect
is the order of the day. If not, please refrain from responding.

"73's"
John
AB8WH

Obviously, maybe I'M the one that needs to chill out.

A good design process starts with brainstorming unfettered by
practicality. The next step is to take those ideas and start applying
filters to the set of ideas you came up with in the first place, and to
turn a more pragmatic eye toward the realities of those ideas.

In a thread like this, I think that people chime in on different steps
of this process. With something like adaptive beamforming, which is
not a new idea, a lot of the practicalities have been hashed out and a
lot of people already know about them.

I think it's worth avoiding the interpretation of responses as
reflecting on one's abilities or character or intelligence. Richard is
good at pointing out in some detail why a very hard problem is very
hard.

73,
Dan