Yagi efficiency
 

ORIGINAL MESSAGE:

On 2 Dec 2006 05:36:05 -0800, "Denny" wrote:


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...
snip

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

The problem here is not math, it's English. You are calculating gain
and/or directivity, not efficiency.

Bill, W6WRT

Yagi efficiency
 

Cecil Moore wrote:
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."

Oops, Kraus said that, not Balanis.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

"Cecil Moore" wrote in message
. ..
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

Hi Cecil

How does Art define Efficiency for evaluating Yagi antennas?

Jerry

Yagi efficiency
 

Bill Turner wrote:

On 2 Dec 2006 05:36:05 -0800, "Denny" wrote:
... 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...

The problem here is not math, it's English. You are calculating gain
and/or directivity, not efficiency.

Maybe beam efficiency? (cone beam power)/(total radiated power)
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Jerry Martes wrote:
How does Art define Efficiency for evaluating Yagi antennas?

I don't know - I just joined this thread in the middle.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Cecil Moore wrote:
Jerry Martes wrote:
How does Art define Efficiency for evaluating Yagi antennas?

I don't know - I just joined this thread in the middle.

Cecil:

I think caution is best used. Reminds me of the three blind men who
went to see the elephant, one grabbed the trunk, one a leg, the other a
tail... and you know how the story goes from there.

I think there is confusion between the radiated power, only allowing for
resistance/dielectric losses; as opposed to why it is desirable to allow
some loss introduced by other elements because the net gain of
"focusing" the antenna is a benefit to you is the major crux of this
whole discussion. But then, I am not even sure of that, completely!

I suppose the most "efficient" antenna, with only taking into
consideration the power delivered to the antenna though the feed line
and actually arriving at the feed point to the antenna as the "antennas
input power" in relation to the actual "power radiated" (or delivered to
the ether) is what Art is looking at. And, in this one regard, I would
suppose a full wave dipole with large dia conductors (to allow for skin
effect), silver coated conductors and glass insulators would be the most
"efficient antenna" (and allowing for a "perfect match" setup being
installed.)

But, where is that power going into the lobes may not make it the most
desirable antenna!

In the yagi, because the reflector and director are so close to the de
in terms of wavelength do introduce some trivial? (depends again on
perspective) losses here.

And, here comes the fairies and the pinhead.

JS

Yagi efficiency
 

"Cecil Moore" wrote in message
t...
Jerry Martes wrote:
How does Art define Efficiency for evaluating Yagi antennas?

I don't know - I just joined this thread in the middle.

i think his efficiency is (watts at the rx i want to talk to)/(watts power
company is sending down the line)

Yagi efficiency
 

John Smith wrote:
Cecil Moore wrote:
Jerry Martes wrote:
How does Art define Efficiency for evaluating Yagi antennas?

I don't know - I just joined this thread in the middle.

Cecil:

I think caution is best used. Reminds me of the three blind men who
went to see the elephant, one grabbed the trunk, one a leg, the other a
tail... and you know how the story goes from there.

I think there is confusion between the radiated power, only allowing for
resistance/dielectric losses; as opposed to why it is desirable to allow
some loss introduced by other elements because the net gain of
"focusing" the antenna is a benefit to you is the major crux of this
whole discussion. But then, I am not even sure of that, completely!

I suppose the most "efficient" antenna, with only taking into
consideration the power delivered to the antenna though the feed line
and actually arriving at the feed point to the antenna as the "antennas
input power" in relation to the actual "power radiated" (or delivered to
the ether) is what Art is looking at. And, in this one regard, I would
suppose a full wave dipole with large dia conductors (to allow for skin
effect), silver coated conductors and glass insulators would be the most
"efficient antenna" (and allowing for a "perfect match" setup being
installed.)

But, where is that power going into the lobes may not make it the most
desirable antenna!

In the yagi, because the reflector and director are so close to the de
in terms of wavelength do introduce some trivial? (depends again on
perspective) losses here.

And, here comes the fairies and the pinhead.

JS

Of course, I always think of the parabolic reflector antenna as the
"most efficient!"

I have never seen one constructed for 160m (strange huh?); but when you
get into ghz, why would you ever use anything else? (well, unless you
wanted to chat off to someone on the side or back.)

JS

Yagi efficiency
 

Hi Jerry sorry that I didn't respond to you earlier but here goes
untuned elements which haveWhen you decide to get something going you
need a means to get there.
When you decide on the means you need to know if you are expending the
minimum energy to get there
In this particular case we have decided on generating a time varying
field around some reradiatiung elements to obtain a radiating field of
some sort Since we are applying energy
to elements we want to know if the elements are doing a good job or are
they losing out on energy translation by generating heat e.t.c instead
of it all going where I want it to. So what we do is find out what
energy we put in to obtain our objective and measure what we got out
towards our objective to see how effective we were which is a measure
of efficiency... Ideally we dont want to produce heat and all that
other stuff but the anteena array that we have chosen to do this is a
yagi array of elements which starts of with a resonant dipole which has
a purely resistive impedance. But the yagi then goes on to upset things
by adding which have a reactive impedance which detracts from the purly
resistive value of the impedance which means losses when we should have
added extra resonant elements to the set up as a means of adding to the
structure to maintain zero losses BUT the yagi does go a long way
towards our objectives so it has hung around for a long while. As a
side issue
we should also consider the environment that our array is working in
and also the type of element material we are using as well as the means
taken to input power but that gets more complicated so the question is
really revolving around the energy input versus a magnetic near field
generation that goes on to form a far field radiation field.
SOOOOOOOooooo
efficiency in this case compares the electrical power applied to the
yagi to generate a magnetic and electric fieldaround the yagi and to
check how much energy was lost on the way to our objective. Sorry for
the delay but fortunately I did check back in before I moved on to
other things
Regards
Art





Jerry Martes wrote:
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

Yagi efficiency
 

"art" wrote in message
ps.com...
Hi Jerry sorry that I didn't respond to you earlier but here goes
untuned elements which haveWhen you decide to get something going you
need a means to get there.
When you decide on the means you need to know if you are expending the
minimum energy to get there
In this particular case we have decided on generating a time varying
field around some reradiatiung elements to obtain a radiating field of
some sort Since we are applying energy
to elements we want to know if the elements are doing a good job or are
they losing out on energy translation by generating heat e.t.c instead
of it all going where I want it to. So what we do is find out what
energy we put in to obtain our objective and measure what we got out
towards our objective to see how effective we were which is a measure
of efficiency... Ideally we dont want to produce heat and all that
other stuff but the anteena array that we have chosen to do this is a
yagi array of elements which starts of with a resonant dipole which has
a purely resistive impedance. But the yagi then goes on to upset things
by adding which have a reactive impedance which detracts from the purly
resistive value of the impedance which means losses when we should have
added extra resonant elements to the set up as a means of adding to the
structure to maintain zero losses BUT the yagi does go a long way
towards our objectives so it has hung around for a long while. As a
side issue
we should also consider the environment that our array is working in
and also the type of element material we are using as well as the means
taken to input power but that gets more complicated so the question is
really revolving around the energy input versus a magnetic near field
generation that goes on to form a far field radiation field.
SOOOOOOOooooo
efficiency in this case compares the electrical power applied to the
yagi to generate a magnetic and electric fieldaround the yagi and to
check how much energy was lost on the way to our objective. Sorry for
the delay but fortunately I did check back in before I moved on to
other things
Regards
Art

Hi Art

As I read it, the efficiency (in percentage) we are using for this
discussion is Power Out divided by Power In, if the "objective" is to
radiate power. Or, correct me if I misread.

Jerry