Bill prove me wrong thats all you have to do prove me wrong
Its a simple statement detuned elements create inefficiency
Avoid it like a plague you say, it is to late in your life to think
about getting an education You have presented nothing of value
to the question, absolutely nothing. I suggest you continue to
be a lemming and follow the others. Doesnt it worry you
that you have placed yourself out on a limb by preceeding
experts comments instead of waiting so you can follow ?
Seems like the antenna group is still happy with their fellow
associates in the group so pick up some more stones say
some swear words and impress
the others.
See you maybe in a couple of weeks when I may drop back in.

so save some of those projectiles!


Bill Turner wrote:
ORIGINAL MESSAGE:

On 1 Dec 2006 18:29:51 -0800, "art" wrote:


Since two elements out of the
three are producing reactive impedances and wherein
the reactive portions of impedance is pure waste
pray tell me how one can consider a yagi as efficient?

------------ REPLY FOLLOWS ------------

Please let us know what electronics school you attended so we can
avoid it like the plague and, if at all possible, have it
de-certified.

Thanks,

Bill, W6WRT

Hi Art

You know, I am really a slow learner. I still dont understand how
efficiency is defined. Can you try again to teach me how efficiency is
defined??

Thanks
Jerry



"art" wrote in message
ups.com...
Hi Jerry perhaps I am wrong that there ARE people who want to talk
antennas
We went thru this some time ago and I was referring to efficiency of
the yagi antenna
with respect to the radiation field where much is reflected to areas of
no concern.
Others did not like this and said efficiency referred to is one of the
radiation facets of a radiating array and the yagi is efficient and
then the sniping statrted and the newsgroup went down hill as others
joined to emulate and perpetuate abrasive non antenna related
subjects. I just popped back to see if the group wanted to change back
to antenna talk
and posted the term efficiency of the yagi in terms of radiation which
everybody was
auguing about. Well things haven't changed they still just want to
throw stones and more will join in as the thread goes on., Ill stick it
out for an hour or so and then move on again.
Cant wait for somebody to compare with free space stuff to add to the
confusion, I know it will come




Jerry Martes wrote:
"art" wrote in message
ups.com...
Some time ago I mentioned how inefficient Yagi design
antennas were thinking more in the way of how little of
the radiation used got to its required direction.
At that time people said the antenna was efficient though
they wanted to talk about
actual radiation efficiency and the sniping began
.Nobody but nobody came back with the radiation
efficiency of a Yagi as they saw the question, they
just wanted to throw stones.Imagine that antennas
was not what the experts wanted to talk about and
the newsgroup took a turn for the worst
So I join in with the thoughts of radiation efficiency
of a yagi unless you prefere to give up this antenna
newsgroup. But before you scream out and throw
stones again I will referr to efficiency as most of the
members of this group what's left of them think of the term.
So let's look at that if that is what you preferr..

The basic small yagi has three elements one driven,
one a reflector and one a director yet only one
element has a truly resistive impedance whereas
the other two do not. Since two elements out of the
three are producing reactive impedances and wherein
the reactive portions of impedance is pure waste
pray tell me how one can consider a yagi as efficient?
And please, please don't waste time on "I don't understand"
otherwise everything drops down to the subject of spark noise
which was really decided by hams a long while ago.
On the other side of the coin, if the reactive portion of an
impedance is not waste then why is LCR
type mesh circuitry only revolve around lumped circuitry?
HINT add up the power emminating from each element
P =I sq times real resistance for those who are just followers.

There again maybe it is best that you be honest and say
you don't understand! Better that than join those who have
nothing to say about antennas!


Hi Art

OK, I dont understand. Perhaps I could begin to understand if I was
given the definition of efficiency we are using in this discussion. How
do
you define efficiency?

Jerry

Jerry Martes wrote:
...
How do you define efficiency?

Jerry



Jerry:

You make that sound like such a simple question.

Antenna efficiency is a complicated and often misused figure.

All antennas suffer from losses. A simple horn antenna for example will
not be as efficient as a perfect aperture of the same size because of
phase offset. The real efficiency of an antenna combines impedance match
with other factors such as aperture and radiation efficiency to give the
overall radiated signal for a given input. The best and mostwidely used
expression of this efficiency is to combine overall efficiency with
directivity (of the antenna) and express the efficiency times
directivity as gain.


The above is NOT mine, but taken from the web...
http://www.tmcdesign.com/antenna%20c...nformation.htm

So, we need to know if we are discussing antenna efficiency, or
radiation efficiency, or the skin effect as related to the ether
efficiency, etc. grin

Good that you are asking him!

Regards,
JS

"John Smith" wrote in message
...
Jerry Martes wrote:
...
How do you define efficiency?

Jerry



Jerry:

You make that sound like such a simple question.

Antenna efficiency is a complicated and often misused figure.

All antennas suffer from losses. A simple horn antenna for example will
not be as efficient as a perfect aperture of the same size because of
phase offset. The real efficiency of an antenna combines impedance match
with other factors such as aperture and radiation efficiency to give the
overall radiated signal for a given input. The best and mostwidely used
expression of this efficiency is to combine overall efficiency with
directivity (of the antenna) and express the efficiency times directivity
as gain.


The above is NOT mine, but taken from the web...
http://www.tmcdesign.com/antenna%20c...nformation.htm

So, we need to know if we are discussing antenna efficiency, or radiation
efficiency, or the skin effect as related to the ether efficiency, etc.
grin

Good that you are asking him!

Regards,
JS

Hi John

It really *is* a simple question. Again, how is Efficienct being defined
for this investigation?? As you have written, that question has to be
answered by Art, the original poster, ?doesnt it?

I was a little embarrassed because that "definition" of gain in the
referenced site was really difficult for me to understand. I really admire
you guys who understand phrases like "phase offset" as related to
efficiency.

Jerry

"art" wrote in message
Some time ago I mentioned how inefficient Yagi design
antennas were thinking more in the way of how little of
the radiation used got to its required direction. etc
_________________

The above statement does not agree with the measured patterns and
performance results of Yagi antennas.

A well-designed, 6-element Yagi has a peak gain of at least 10 dBi, which
means that it radiates about 6.3 times more power in that direction than if
the same input power was radiated by a reference 1/2-wave dipole, and
measured in its direction of maximum gain.

RF

For those who wish to actually learn and not just insult each other,
get a calculator, learn how to calculate Cosine Theta a trivial math
problem that any 9th grader can be taught in 5 minutes flat, get a BIG
piece of paper reason to come, and actually calculate the shape and
vector length of the lobes of a two element Yagi-Uda antenna... Do the
calculation in both the horizonal and vertical planes... From that you
can calculate the volume of each lobe, which is proportional to the
percentage of power in each lobe... From that number you can very
simply calculate what percentage went into the lobes you prefer and
what went in the lobes you don't prefer...

Now, the reason for the BIG piece of paper... The antenna patterns you
see on the screen with EZNEC, or in the antenna handbooks, are
logarithmic, not linear and there are flavors to them, ARRL, linear
logarithmic, modified logarithmic... So, the patterns are
distorted... Why is that? Because if they were linear and the front
lobe and the rear lobe are to the same scale the front lobe will take
up the entire length of the screen/paper and the rear lobe will need a
magnifying glass to be seen... A rear lobe that is 20dB down from the
front lobe is down by the power ratio of 100... So, if your forward
lobe calculates out to be 10 inches long, the rear lobe will be be 1/10
of an inch.... I'll let you figure out the size of a lobe that is 30dB
down (get out your microscope)

For those who want to review do a search on Joseph Reisert, who has
published numerous writings on antennas and patterns... There many are
others also, but Joe is published on the web, and very readable...

cheers ... denny / k8do

"Denny" wrote in message
oups.com...
For those who wish to actually learn and not just insult each other,
get a calculator, learn how to calculate Cosine Theta a trivial math
problem that any 9th grader can be taught in 5 minutes flat, get a BIG
piece of paper reason to come, and actually calculate the shape and
vector length of the lobes of a two element Yagi-Uda antenna... Do the
calculation in both the horizonal and vertical planes... From that you
can calculate the volume of each lobe, which is proportional to the
percentage of power in each lobe... From that number you can very
simply calculate what percentage went into the lobes you prefer and
what went in the lobes you don't prefer...

Now, the reason for the BIG piece of paper... The antenna patterns you
see on the screen with EZNEC, or in the antenna handbooks, are
logarithmic, not linear and there are flavors to them, ARRL, linear
logarithmic, modified logarithmic... So, the patterns are
distorted... Why is that? Because if they were linear and the front
lobe and the rear lobe are to the same scale the front lobe will take
up the entire length of the screen/paper and the rear lobe will need a
magnifying glass to be seen... A rear lobe that is 20dB down from the
front lobe is down by the power ratio of 100... So, if your forward
lobe calculates out to be 10 inches long, the rear lobe will be be 1/10
of an inch.... I'll let you figure out the size of a lobe that is 30dB
down (get out your microscope)

For those who want to review do a search on Joseph Reisert, who has
published numerous writings on antennas and patterns... There many are
others also, but Joe is published on the web, and very readable...

cheers ... denny / k8do

Hi Denny

Does Joseph Reisert define Efficiency as applied to this question about
Yagi antennas?

Jerry

"art" wrote in message
oups.com...
There you go Tom still giving comments but no substance. Pretty simple
accept that a yagi
is not the best thing since sliced bread starting with the use of
detuned elements.
If you do not understand what detuning elements do then you can have
nothing reasonable to offer so don't blame me for that. If you have a

ok, so educate us, what do detuned elements do?

art wrote:
Its a simple statement detuned elements create inefficiency

Do detuned elements increase I^2*R losses?
Do detuned elements increase dielectric losses?
Do detuned elements increase ground losses?
--
73, Cecil http://www.w5dxp.com

Jerry Martes wrote:
Can you try again to teach me how efficiency is defined??

What kind of efficiency? antenna? beam? aperture?
overall? conduction-dielectric?

Balanis defines overall antenna efficiency as the
product of:

1. reflection (mismatch) efficiency
2. conduction efficiency
3. dielectric efficiency

He gives the conduction-dielectric efficiency as:

Rr/(RL + Rr)

where Rr is the radiation resistance and
RL is the (conduction + dielectric) losses

He gives beam efficiency as:

(Beam cone power)/(Total radiated power)

He also says for a 1-dimensional aperture as a
function of taper: "The aperture efficiency is
a maximum with no taper, while the beam efficiency
is a maximum with full taper."
--
73, Cecil http://www.w5dxp.com