RadioBanter - Yagi efficiency

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David are you going nuts? I used the word impedance whichcan mean two
components only one of which is used for power. What on earth are you
trying to say now or are you looking for a reason to thro stones. Now
calm down and point out where I was not CORRECT as you put it and what
are the consequences of this error relative to what we are talking
about?
If your point is that I didn't emphasise the word complex then there is
no need to respond, you can have it your way I don't mind if it helps
you out with your apparent anger.

Dave wrote:
art wrote:

Help me help me please , a detuned element has a reactive impedance
value, simple fact.

NOT CORRECT! It is a complex impedance that contains both a resistive and an
reactive component.

Now with your superior knowledge and education show not just me but all
of us how the production of a reactive impedance does not or cannot
impede the formation of emmited flux? I dont want just comments or
guesses just an explanation of your position which aligns with the laws
of Kirchoff, Ampere, Green ,Laplace etc as a group or as single people
to give your response some credability . Cecil has given you a starting
point as to what exactly reactance is so the rest should be easy for
you considering how easily you can dismiss my logic and education
regarding the Yagi antenna. Bill I cant wait to hear the mutterings of
a master of your station, a chance to learn something really new, maybe
not even written in a book Go man go! Well I know you can't.... but I
am just demonstrating that if you want to snipe then others will be
encouraged to snipe and it is not nice. Knoweledge is what I am after
not errent gun shots

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

Tom Ring wrote:
Dave wrote:
...
I am plonking this thread, and art.

tom
K0TAR

Ahhhh. Mr. Tom Ring. I would almost bet he shares much in common with
the average IBM employee!

Graduated with a C+ grade point average!

JS

Tom it is no good plonking me for what david is saying because he is
not quoting me, in fact some of it is a requote of what he said not me.
I think he is creating a straw man that he can argue with, is that what
you call reality? He has spent most of his time in space and I believe
him

Tom Ring wrote:
Dave wrote:

SNIPPED

Art, It has absolutely NOTHING to do with measurements, or with 95 watts
or 5 watts, or antenna patterns, or the reactive components.

It is defining efficiency properly!

Net radiated power divided by power input is Efficiency. Measure it or
calculate it any way you want!

An antenna with -3 dB loss is a 50% efficient antenna independent of the
actual input power. Choose any power input you like. An antenna with -3
dB loss is a 50% efficient antenna regardless of gain, directivity,
antenna patterns, patents, claims, marketing Bull S--t, or anything else.

Put your favorite antenna inside a sphere of any suitable diameter that
contains the antenna. The total rf power coming out of the sphere
divided by the total rf power into the antenna [sphere] is the antenna
efficiency. There is NO OTHER definition!

Reducing power in the back and side lobes has absolutely NOTHING to do
with efficiency. It has to do with directivity.

Design of a Yagi, traps, conductors, element spacing etc. will produce
variations in gain, directivity, efficiency [variations in losses,
heat]. Practically, the difference in efficiency between a 90% efficient
antenna and a 98% efficient antenna is swamped by variations in the path
loss physics.

I spent years of my life designing rf systems for telemetry from space
vehicles through reentry to a ground station. Data integrity at the
ground station was and still is the dominating requirement. Based on
allowable data error rates, the total path equation required S/N ratios
of 12 dB or more. The solution is a systems solution where the minor
variations in antenna efficiency get lost in the calculations.

Art doesn't care about reality, he thinks he can create a new one which
ignores physics. You are wasting your time.

I am plonking this thread, and art.

tom
K0TAR

Hi Art

If this was a car news group I'd realize that you have left me in your
dust. I just cant keep up with you. I thought I understood antennas and
I even thought I could design them. But, I dont even know the meaning of
the words you use, and I am too lazy to study and learn about things like
"emission of flux".
I had designed and built some Yagi arrays that worked pretty but I was
never aware that I detuned any of their elements. I just thought they were
as efficient as any other array of similar size.
It is obvious to me that I'll never understand why those Yogis are
considered inefficient.

Jerry

"art" wrote in message
ups.com...
No Jerry you are on the right path, the envelope under question is the
application of power that produces the emmission of flux in the near
field You have to be carefull as to what radiation refers to and where
or sniping will start because some radiation starts in the near field
does not really take off because of radiation that cancells or
neutralises the emitted flux
so far field radiation does not occur so you have to be carefull after
the flux flows when you really only have two fields acting in concert
You will also here people refer to the gain of a radiated field as an
indication of efficiency which is just comparing the position of choice
to another position iof choice without regard to the volume enclosed in
a radiation field which is normally spread in all directions whether
you want it or not. So we are looking strictlyat how much energy we
lose in the providing flux emmisions which profides radiation without
concern where it goes otherwise you will get into a sqogmire of
confusion. Frankly I can tell you that a element detuned is the root of
all the inefficiences experienced with a Yagi.Period
but others resist this notion or fact
Art

Jerry Martes wrote:
"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

Well I obviously misunderstood the question
What I have done is to make elements resonant with possesion of
different lengths
This is not that unusual with antennas. Now 'how' you make a shorter
element resonant at the same frequency is where we part. I would make
the element resonant by the addition of nearby elements not by adding a
constant like an inductance ,so obviously I have not plotted anything
according to what you are pointing to

John Smith wrote:
art wrote:
Well now I am not sure what you want plotting if you are making the
reflector resonant
other than the design frequency of the array.
JS

Art:

No, the reflector would remain the same ~5% longer (electrically and
physically) than the de. And, the director remains physically shorter
than the de, but made resonate with the proper addition of a coil,
somewhere in its length, so as to be made resonate at the same freqs as
the de (or approx. so, since the coil will undoubtedly change some
characteristics from that of the resonate de.

Art, you are rapid losing me here. Either I am not able to see what you
are getting at, or else I suspect you of having some facts or formulas
twisted about here...

Regards,
JS

I wouldn't worry about that, you have made them and they work in a
manner that satisfies you what more could you want of an antenna?
Remember an extra DB in performance lookes like an achievement when
dealing with design but the fact is you would not see a difference if
you upgraded your antenna, so efficiency is not a factor for you as a
user. Increasing efficiency is just one small step that when added to
other small steps it gets everybodies attention it is at that point you
will take the step to upgrade. Enjoy and remember efficiency is a very
relevant term as it could be refering to something that is desired but
impossible to improve
Art

Jerry Martes wrote:
Hi Art

If this was a car news group I'd realize that you have left me in your
dust. I just cant keep up with you. I thought I understood antennas and
I even thought I could design them. But, I dont even know the meaning of
the words you use, and I am too lazy to study and learn about things like
"emission of flux".
I had designed and built some Yagi arrays that worked pretty but I was
never aware that I detuned any of their elements. I just thought they were
as efficient as any other array of similar size.
It is obvious to me that I'll never understand why those Yogis are
considered inefficient.

Jerry

"art" wrote in message
ups.com...
No Jerry you are on the right path, the envelope under question is the
application of power that produces the emmission of flux in the near
field You have to be carefull as to what radiation refers to and where
or sniping will start because some radiation starts in the near field
does not really take off because of radiation that cancells or
neutralises the emitted flux
so far field radiation does not occur so you have to be carefull after
the flux flows when you really only have two fields acting in concert
You will also here people refer to the gain of a radiated field as an
indication of efficiency which is just comparing the position of choice
to another position iof choice without regard to the volume enclosed in
a radiation field which is normally spread in all directions whether
you want it or not. So we are looking strictlyat how much energy we
lose in the providing flux emmisions which profides radiation without
concern where it goes otherwise you will get into a sqogmire of
confusion. Frankly I can tell you that a element detuned is the root of
all the inefficiences experienced with a Yagi.Period
but others resist this notion or fact
Art

Jerry Martes wrote:
"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

art wrote:
Tom it is no good plonking me for what david is saying because he is
not quoting me, in fact some of it is a requote of what he said not me.
I think he is creating a straw man that he can argue with, is that what
you call reality? He has spent most of his time in space and I believe
him

Tom Ring wrote:
Dave wrote:

SNIPPED

Art:

First, you must learn "theory" (and there IS a reason they term that
THEORY! it is JUST THAT!) the way they learned it, so you can quote it
to them verbatim, else they can't relate, else they are quick to
dismiss. It helps if every once in awhile you say, "I know the accepted
way of thinking says this, or that... but what about this other, or that
other?" (yanno what I mean?)

Then you can really begin "thinking."

However, that is not all bad, it gives common ground so we ALL can
communicate on a level which gives some understanding and purpose,
perhaps to a final goal ...

.... and beware, there are "other thinkers" here, they just choose to
remain hidden and duck the wrath and arrows of the "rote-ly educated."

JS

"art" wrote in message
oups.com...
From a theoretical way of getting at the answer it seems
a logical way of proceding. So now to the rest of the task.1 how do we
determine volumes that you talk about that are a result of deflection 2
How do we determine
radiation that was cancelled or neutralised and 3 How do you determine
the radiation volume created by ground reflection so we can work back
to search for ground losses. That last one really bothers me as I have
never got a good handle on the contribution of ground reflection to any
particular part of the radiation envelope.

Art

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...

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

The radiation IS NOT cancelled or Neutralized. You need to learn more about
what is going on with an antenna. I suggest you do some serious reading,
actually reading with an open mind and not reading trying to find little
phrases that seem to you to prove your beliefs. It should be fairly obvious
that if an antenna worked by neutralization or cancelation that it would
take more energy to cancel out radiation in the undesired direction of a
yagi than is available in the desired direction. Therefore a Yagi or any
other antenna does not work by cancellation.

I gues I could express this a lot better but its late and whats the use.