wrote:
I did not want to choose a curve that matches my modelling which you
can
when presented with three different curves all of which are formulated
at different
times by different people. I would have thought that the advent of NEC
would
render these curves redundant !

The plot of many individual yagis does confirm the general idea of gain
being roughly proportional to boom length, and that is a very important
thing to understand.

Note that this is only for long-ish yagis with many elements. For yagis
of 2-3-4 elements on a short boom, the first few dB of gain come very
easily. Beyond that, the data points settle back towards the long-yagi
trend line.

To increase the gain by 3dB, you need to either double the boom length
(and redesign the yagi, obviously) or else stack two of the same
yagis... and either way, in practice you'll achieve slightly less than
3dB.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

wrote:

The above extract is lost on me as I was looking for maximum gain per
unit boom length based on NEC without regard to number of elements
required to attain that gain. Thus increases or decreases from
critical
coupling
can be ascertained..

You misunderstand what this curve is telling you.

There is a general law that gain is proportional to "aperture area". For
something like a dish, "aperture area" is the frontal area of the dish
itself (multiplied by an efficiency factor 1). For long yagis,
"aperture area" is roughly proportional to boom length.

This concept has nothing whatever to do with NEC! But it is the absolute
bedrock of all antenna engineering. What you really need right now is to
read the first few chapters of Kraus... and understand these most basic
principles.

NEC calculations will not tell you anything about this. NEC is simply a
tool to calculate what the gain of a particular antenna will be (or can
be, if you build it as modeled).


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Sun, 17 Oct 2004 17:01:22 -0400, "G&R" makes a claim and opens
himself up to skewering:

|Hi Art,
|
|While this was the common theory many years ago, there other ways to get
|gain from an antenna other than boom length and number of elements.
|
|ie On 2m we are able to get 11.2 dBd on a 45inch boom with 3 elements
|stacked 2 wide. Yes, this is range tested see results at
|http://www.csvhfs.org/ant/CSANT04.HTML

Uh Oh! The measured data show 11.2 dBd, the advertising shows 13.97
dBd. I thought maybe I went to the Raibeam site by mistake but no, I
went he

http://www.degendesigns.com/StackedVwave.htm

I love that precision BTW. I've done a fair amount of antenna range
testing using HP 8510s for measurement receivers and I've never been
able to establish gain within 1/100 dB.

But you can do it with a ham receiver and "subjective analysis".
Congratulations.

Since you're using two 45" booms spaced 58" apart, I would argue that
you should compare your design to a 148" boom Yagi and see what
happens.

How about posting your dimensions so we can see what modeling says
about them.

One further note: The Dataq DI-194 mentioned at:

http://www.degendesigns.com/Downloads.htm

WILL NOT work with all computers. This device is powered by the
serial port and my Toshiba laptops will not drive it.

Ian, All the points you made are very good especialy when you
stated that gain is ROUGHLY proportional to boom length and
then go on to mention "aperture'
The question I asked was very specific but not personal like the
presidential
debates this newsgroup uses the question as the basis for what they want to
say.
The reason I asked the specific question was to obtain a datum line for
antennas relative to gain and a well used term of boom length.
NEC programs can provide this basic if the latest revision is used
and the program is all encombassing.( Many are not)
Mention coupling and some experts go nuts
but NEC is all encompassing provides definitive answers that remove
measurement errors presently shown and cuts through a lot of garbage.
All encompassing is all important in that sufficient segments are available
together with the use of variuable dimensions as this gets away from use of
methods
to get around inadequacy of a particular program. You mention "aperture"
but I don.t believe it changes any results given by NEC. Others ridicule the
use of the term
critical coupling yet NEC shows that element currents can be changed via
coupling
and it is current placement that we are interested in, so why so much
redicule/
The same goes for element diameters NEC provides the correct construction
for
elements which is another important variable for gain
So in other words, a NEC curve would deflect most arguments and personal
agenders
from the beginning and if one supplies actual measurement that are contrary
to those of NEC
then we have a basis for truly specific debate. As somebody pointed out, one
slanging match
has been going on for more than eight years regarding the use of critical
coupling, another is
the subject of coils, actual measurement versus a manipulated program
calculation.
I pretty much have had it with excuses regarding inadequecies of some
programs,
If NEC is a really viable tool; then let us use it as a datum by using a NEC
program that
is all encompassing to judge measured claims against so hat true specific
can be judged.
It is possible after all that even NEC may obtain several more revisions
over time because of
actual measurement which can only aid all in the understanding of antennas
and the removal
of old wifes tales and private agendas that evolved prior to NEC.
Is it auguments that we yearn for on this newsgroup or true resolution of
ideas?
Art



"Ian White, G3SEK" wrote in message
...
wrote:
I did not want to choose a curve that matches my modelling which you
can
when presented with three different curves all of which are formulated
at different
times by different people. I would have thought that the advent of NEC
would
render these curves redundant !

The plot of many individual yagis does confirm the general idea of gain
being roughly proportional to boom length, and that is a very important
thing to understand.
clip

Wes,
You make the point quite well that I was trying to make before I read your
post (written simultainiously)
and at the present time NEC is seen as judge absolute.
Yes there are many ways to increase gain but you cannot use a shackled NEC
program to authenticate
the results and we often use such as a crutch.
On the subject of boom length
I was basing things on a single boom length where number, position and
physical atributes of additionion elements
are brought into play to overcome program idequacies and provide correction
of assigned dimensions to achieve maximum gain.(Is this to much to ask now
that we have the NEC tool/)
To often the accusation comes up that computor input was incorrect or not
enough segments provided e.t.c.
and a datum curve would prove a valuable tool, not only to those that use
computor modelling but also
to experimentors who seek real world answers and possibly challenge the
authenticicity of either methods
Thanks for the links,will read them later, have to get a floooooo shot now
Art


"Wes Stewart" wrote in message
...
On Sun, 17 Oct 2004 17:01:22 -0400, "G&R" makes a claim and opens
himself up to skewering:

|Hi Art,
|
|While this was the common theory many years ago, there other ways to get
|gain from an antenna other than boom length and number of elements.
|
|ie On 2m we are able to get 11.2 dBd on a 45inch boom with 3 elements
|stacked 2 wide. Yes, this is range tested see results at
|http://www.csvhfs.org/ant/CSANT04.HTML

Uh Oh! The measured data show 11.2 dBd, the advertising shows 13.97
dBd. I thought maybe I went to the Raibeam site by mistake but no, I
went he

http://www.degendesigns.com/StackedVwave.htm

I love that precision BTW. I've done a fair amount of antenna range
testing using HP 8510s for measurement receivers and I've never been
able to establish gain within 1/100 dB.

But you can do it with a ham receiver and "subjective analysis".
Congratulations.

Since you're using two 45" booms spaced 58" apart, I would argue that
you should compare your design to a 148" boom Yagi and see what
happens.

How about posting your dimensions so we can see what modeling says
about them.

One further note: The Dataq DI-194 mentioned at:

http://www.degendesigns.com/Downloads.htm

WILL NOT work with all computers. This device is powered by the
serial port and my Toshiba laptops will not drive it.

Hi Wes,

Yes I am aware of the difference between the advertising on the site and the
range results.

As you are aware antennas do not have even gain across the entire band. We
have designed the antenna to cover the entire 2m band and as a result do see
a variation in the perfromance across the band, hence max gain.

And before you cut down my comments, the precision on the results are from
the softare and we are in the process of redesigning the format to more
accurately reflect our actual results both modelled and actual.
Unfortunately our business is antennas and web design.

The results posted on the CSVHF society are valid as the antenna was tested
with a gain of 11.2dBd at 144.18MHz Horiz Polarization. Design Freq is
146.0MHz.

We are in the business of designing and selling antennas not developing
antennas and giving them away for free. However, if your serious about the
data for the antenna contact me directly so that we can discuss the details
(email listed below).

As to the DATAQ, well I have no answer for that one, as we don't build it or
sell it. Our software is designed to with run it. Strange though, my
Toshiba does and so does my SONY through a USB to SERIAL converter.

One final point, the purpose of the posting was that identify that an
antenna does not always need boom length and elements for gain and that
there are other ways to achieve this.

Respectfully,

Guenther VE3CVS

www.degendesigns.com






"Wes Stewart" wrote in message
...
On Sun, 17 Oct 2004 17:01:22 -0400, "G&R" makes a claim and opens
himself up to skewering:

|Hi Art,
|
|While this was the common theory many years ago, there other ways to get
|gain from an antenna other than boom length and number of elements.
|
|ie On 2m we are able to get 11.2 dBd on a 45inch boom with 3 elements
|stacked 2 wide. Yes, this is range tested see results at
|http://www.csvhfs.org/ant/CSANT04.HTML

Uh Oh! The measured data show 11.2 dBd, the advertising shows 13.97
dBd. I thought maybe I went to the Raibeam site by mistake but no, I
went he

http://www.degendesigns.com/StackedVwave.htm

I love that precision BTW. I've done a fair amount of antenna range
testing using HP 8510s for measurement receivers and I've never been
able to establish gain within 1/100 dB.

But you can do it with a ham receiver and "subjective analysis".
Congratulations.

Since you're using two 45" booms spaced 58" apart, I would argue that
you should compare your design to a 148" boom Yagi and see what
happens.

How about posting your dimensions so we can see what modeling says
about them.

One further note: The Dataq DI-194 mentioned at:

http://www.degendesigns.com/Downloads.htm

WILL NOT work with all computers. This device is powered by the
serial port and my Toshiba laptops will not drive it.

A graph from NEC data is going to be pretty much like a graph from the ARRL
books. By putting the data in a graphic form your are placing the same
limits on the data as they had to in the ARRL books. The ARRL graphs give
you a pretty good idea of what goes on when you change element spacing,
number of elements and so on. What they dont do is alllow you to perform
optimization like the NEC programs . Graphing a NEC program output would be
the same as going back to the time all you had was the graphs to go by
unless you are willing to do all the calculations on your slide rule or
calculator. What I am saying is that you already have this data. No point in
reinventing the wheel.Unless you think yiou can get a patent on it.

" wrote in message
news:65Zcd.150611$He1.116446@attbi_s01...
Jimmy,
I did not want to choose a curve that matches my modelling which you can
when presented with three different curves all of which are formulated at
different
times by different people. I would have thought that the advent of NEC
would
render these curves redundant !
Art

"Jimmie" wrote in message
. com...

" wrote in
message
news:xOzcd.263953$D%.243703@attbi_s51...
My ARRL books go back a decade or more
and the graph showing gain per boom length
has several curves based on different measurements
e.t.c. Has a graph been made based solely on NEC
program findings over say a perfect ground and at a uniform height?
Art


They probably have been done but there will not be much difference
between
them and the ARRL graphs. Its been long known how to calculate antenna
gain,
computers just take the teadous labor out of it.

" wrote in message
news:t4bdd.277152$D%.236528@attbi_s51...
Ian, All the points you made are very good especialy when you
stated that gain is ROUGHLY proportional to boom length and
then go on to mention "aperture'
The question I asked was very specific but not personal like the
presidential
debates this newsgroup uses the question as the basis for what they want
to
say.
The reason I asked the specific question was to obtain a datum line for
antennas relative to gain and a well used term of boom length.
NEC programs can provide this basic if the latest revision is used
and the program is all encombassing.( Many are not)
Mention coupling and some experts go nuts
but NEC is all encompassing provides definitive answers that remove
measurement errors presently shown and cuts through a lot of garbage.
All encompassing is all important in that sufficient segments are
available
together with the use of variuable dimensions as this gets away from use
of
methods
to get around inadequacy of a particular program. You mention "aperture"
but I don.t believe it changes any results given by NEC. Others ridicule
the
use of the term
critical coupling yet NEC shows that element currents can be changed via
coupling
and it is current placement that we are interested in, so why so much
redicule/
The same goes for element diameters NEC provides the correct construction
for
elements which is another important variable for gain
So in other words, a NEC curve would deflect most arguments and
personal
agenders
from the beginning and if one supplies actual measurement that are
contrary
to those of NEC
then we have a basis for truly specific debate. As somebody pointed out,
one
slanging match
has been going on for more than eight years regarding the use of critical
coupling, another is
the subject of coils, actual measurement versus a manipulated program
calculation.
I pretty much have had it with excuses regarding inadequecies of some
programs,
If NEC is a really viable tool; then let us use it as a datum by using a
NEC
program that
is all encompassing to judge measured claims against so hat true
specific
can be judged.
It is possible after all that even NEC may obtain several more revisions
over time because of
actual measurement which can only aid all in the understanding of antennas
and the removal
of old wifes tales and private agendas that evolved prior to NEC.
Is it auguments that we yearn for on this newsgroup or true resolution of
ideas?
Art



"Ian White, G3SEK" wrote in message
...
wrote:
I did not want to choose a curve that matches my modelling which you
can
when presented with three different curves all of which are formulated
at different
times by different people. I would have thought that the advent of NEC
would
render these curves redundant !

The plot of many individual yagis does confirm the general idea of gain
being roughly proportional to boom length, and that is a very important
thing to understand.
clip


There is no direct connection between boom length and gain. This is because
lengthing the boom also implies one has added elements and possibly made
adjustments to element spacing. A good source of the data you seek may be an
antenna catalog(or manufacturers web site). compare the published gains of
the different length antennas.

"Jimmie" wrote in message
. com...
A graph from NEC data is going to be pretty much like a graph from the
ARRL
books.

Come on Jimmy,' pretty much like' doesn't cut it on this newsgroup or in any
of the professions
The same as pretty close is not accepted when doing math at college.
The curves in the ARRL book were done on 'standard' yagis
measured in the field, at least two of the curves therefore have measuring
errors, and possibly
three of those do not match NEC formulated curves.
Since you do not want to reinvent the wheel which curve or formula do YOU
want all to
follow for short boom antennas i.e. which curve, and there are many,
represents the "wheel" .
that can be specifically used as the datum curve in response to my specific
request?

Note, a NEC produced gragh will produce a scattering of points for
different yagi's
but only ONE point for MAX GAIN PER UNIT LENGTH OF BOOM regardless of how
many elements are used which when used on short booms produce coupling
effects which
change current flow, an effect not generally seen when elements are not
critically coupled
as in the standard yagi..

Thus the reason I was specific in my request which should have
removed comments such as 'Patents" from those who seek arguments .

Art


By putting the data in a graphic form your are placing the same
limits on the data as they had to in the ARRL books. The ARRL graphs give
you a pretty good idea of what goes on when you change element spacing,
number of elements and so on. What they dont do is alllow you to perform
optimization like the NEC programs . Graphing a NEC program output would
be
the same as going back to the time all you had was the graphs to go by
unless you are willing to do all the calculations on your slide rule or
calculator. What I am saying is that you already have this data. No point
in
reinventing the wheel.Unless you think yiou can get a patent on it



Geez Jimmy you are just not reading posts of others ! If you have the
requested
data then point to a link, if I had the data already I wouldn't ask for help
seeking it,.
Art



" wrote in
message
news:65Zcd.150611$He1.116446@attbi_s01...
Jimmy,
I did not want to choose a curve that matches my modelling which you can
when presented with three different curves all of which are formulated
at
different
times by different people. I would have thought that the advent of NEC
would
render these curves redundant !
Art

"Jimmie" wrote in message
. com...

" wrote in
message
news:xOzcd.263953$D%.243703@attbi_s51...
My ARRL books go back a decade or more
and the graph showing gain per boom length
has several curves based on different measurements
e.t.c. Has a graph been made based solely on NEC
program findings over say a perfect ground and at a uniform height?
Art


They probably have been done but there will not be much difference
between
them and the ARRL graphs. Its been long known how to calculate antenna
gain,
computers just take the teadous labor out of it.

Jimmie wrote:
The plot of many individual yagis does confirm the general idea of gain
being roughly proportional to boom length, and that is a very important
thing to understand.
clip


There is no direct connection between boom length and gain. This is
because lengthing the boom also implies one has added elements and
possibly made adjustments to element spacing.

Sorry, I should have said that boom length is roughly proportional to
the *available* gain, if the whole length of the boom is populated with
elements in such a manner as to optimize the gain. That requirement is
usually taken as understood.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek