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





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



At resonance it is the antenna as a whole that is resistive not just the
driven element.

Yagi efficiency
 

"art" wrote in message
oups.com...
Help me help me please , a detuned element has a reactive impedance
value, simple fact.
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

I have a better idea Art, since you are the ones making the claims why dont
you use these references to show your claims are correct. Subject yourself
to the same terms as you expect of others. Must of us have better things to
do than convince a green wall it is really green and not blue.

Yagi efficiency
 

art wrote:

David are you going nuts? I used the word impedance whichcan mean two
components only one of which is used for power.

No! You used the phrase "reactive impedance".

That is significantly different from "Complex Impedance"!

XL [2*Pi*f*L] is a reactive impedance, not a complex impedance!

XC [1/(2*Pi*f*C)] is a reactive impedance, not a complex impedance.

R[Rr + Rloss] + j[XL] is a complex impedance.

I still say you're using technical definitions that do not conform to the
standard definitions.

Yagi efficiency
 

"art" wrote in message
Really Cecil I am trying to get people to think
about elements containing inherranr directional properties so that
uneeded radiation is harnessesd for useful purposes but they are
shutting their ears.
__________________

Art,

The dipole elements (of all lengths) in a Yagi _do_ have their own
directional properties, and generate their own radiation patterns -- the
fields of which add/subtract in space as a function of their relative
magnitudes and phases to produce a net field that varies around the
radiation sphere centered on the antenna.

From reading between the lines, maybe you are relating antenna efficiency to
the free-space field strength that the antenna produces at a given distance
and direction in the far field when a given amount of r-f power is applied
to its input terminals, compared to the field produced for the same
conditions by a reference radiator such as a 1/2-wave dipole, or an
isotropic source.

For this definition it is reasonable to expect that both the test and the
reference antenna have negligible conductor and dielectric loss, and that
they both present a return loss of 30 dB or better to the transmission line
leading to the transmitter. All of that is practical to achieve. Also note
under these conditions that a return loss of 30 dB means that 99.9% of the
power applied to the antenna is radiated (somewhere), so if that is the
meaning of antenna efficiency, it is high indeed.

By this definition, the efficiency of a Yagi in its direction of maximum
field is very high, and does not indicate that sub-optimal choices were made
for its mechnical layout. In fact, the inventors of this antenna and many
others have spent much time and effort with physical and electrical models
of the Yagi to optimize its patterns and gains. The result of all that
finds that the director(s) should be shorter than the driven element, that
the reflector should be longer, and that using more than one reflector has
minimal effect. That is the "bottom line," and speculation to the contrary
won't change it.

Using this Yagi design and this definition of efficiency, a standard,
6-element Yagi has a main lobe peak efficiency of about 250% compared to a
1/2-wave dipole, and 316% compared to an isotropic radiator, which
correspond to radiated power ratios of about 610% and 1,000%, respectively.

IEEE Standard 145-1983 gives the standard definitions of terms for antennas
(gain, directivity, efficiency etc).

RF

Yagi efficiency
 

"Richard Fry" wrote in message
...
"art" wrote in message
Really Cecil I am trying to get people to think
about elements containing inherranr directional properties so that
uneeded radiation is harnessesd for useful purposes but they are
shutting their ears.

every thing that radiates has 'inherent directional properties'. it is
those properties that software like nec models. adding up all the
contributions of lots of little tiny pieces of radiating current is what
goes into designing all sorts of antennas, including yagis. there is no
magic wire that is going to get more power on target, no strange property
that is going to give you super gain, and no way to get rid of all the
'uneeded radiation'. There will always be some losses, power going where
you don't want it to, etc... believe me, many phd's have made their life
studies of reducing that last little bit of radiation off the side or back,
and the conclusion is??? you can't do it. there are many volumes on how to
reduce it in different cases, lots of spectacular designs that are totally
impractical for ham use, and some super applications of standard techniques
for things like the deep space network and radio astronomy.. but there is no
magic in a wire, no matter how you bend it or where you stick it.

Yagi efficiency
 

As soon as you explain what you mean by "efficiency" I can answer that
in detail..

What do you mean by efficiency? Is efficiency 100% of applied power
being in the forward lobe and 0% in sidelobes or rear lobes? If so,
better get a new hobby because it ain't gonna happen... Can't happen
due to the laws of physics... For discussion I'm going to assume that
this is your goal... Let's go up a bit in frequency where the antennas
are small and easy to work with... Telescopes... The only difference
between blue light and 20 meters is the frequency...

Now those telescopes are some really high gain antennas.. So, here we
have this super, duper, high gain antenna (I don't know what the gain
in DBI is, but it is huge, man, huge)... And we point it at a really
faint signal, say the star Rigel - which is an Isotropic radiator - a
point source... And we adjust the resonance (focus) for the best
possible signal we can get... We put a slit on the telescope and scan
across that signal and gasp it has side lobes! Not all the power
luminence is in the main lobe... Mathematically there will always be
side lobes off the main lobe... By reciprocity, it is impossible to
focus a point souce of light down to a point... The center brilliance
will be sorrounded by circles of confusion lobes... Like wise it is
impossible to build an antenna that has a response that is only a
single main lobe and no side lobes...

'Now, we can build arrays of antennas that enhance the main lobe and
diminish the side and rear lobes through pattern multiplication, and we
can get those unwanted lobes down to a few thousandths of the power in
the main lobe... One way is a broadside array of six of a dozen, or so,
more point sources with half wave spacing and fed in Quadrature, or
other current variations... Krause's book has a good set of patterns
and explanation of this method of synthesizing an antenna that is very
"efficient"... efficiency being defined as I 'assumed' above...
However, these antennas are not efficient in terms of time, labor,
size, cost, and complexity...

So, to reiterate, go to Reisert, and Krause, and Terman, et. al. to
find your magically 'efficient' antenna...

denny / k8do

btw, a thought just caught me... W8JI on his web site has a great table
of antenna 'efficiency' in low noise receiving antennas... Maybe this
is what you mean... GO look it up..

Yagi efficiency
 

"Denny" wrote in message
oups.com...
As soon as you explain what you mean by "efficiency" I can answer that
in detail..

What do you mean by efficiency? Is efficiency 100% of applied power
being in the forward lobe and 0% in sidelobes or rear lobes? If so,
better get a new hobby because it ain't gonna happen... Can't happen
due to the laws of physics... For discussion I'm going to assume that
this is your goal... Let's go up a bit in frequency where the antennas
are small and easy to work with... Telescopes... The only difference
between blue light and 20 meters is the frequency...

Now those telescopes are some really high gain antennas.. So, here we
have this super, duper, high gain antenna (I don't know what the gain
in DBI is, but it is huge, man, huge)... And we point it at a really
faint signal, say the star Rigel - which is an Isotropic radiator - a
point source... And we adjust the resonance (focus) for the best
possible signal we can get... We put a slit on the telescope and scan
across that signal and gasp it has side lobes! Not all the power
luminence is in the main lobe... Mathematically there will always be
side lobes off the main lobe... By reciprocity, it is impossible to
focus a point souce of light down to a point... The center brilliance
will be sorrounded by circles of confusion lobes... Like wise it is
impossible to build an antenna that has a response that is only a
single main lobe and no side lobes...

'Now, we can build arrays of antennas that enhance the main lobe and
diminish the side and rear lobes through pattern multiplication, and we
can get those unwanted lobes down to a few thousandths of the power in
the main lobe... One way is a broadside array of six of a dozen, or so,
more point sources with half wave spacing and fed in Quadrature, or
other current variations... Krause's book has a good set of patterns
and explanation of this method of synthesizing an antenna that is very
"efficient"... efficiency being defined as I 'assumed' above...
However, these antennas are not efficient in terms of time, labor,
size, cost, and complexity...

So, to reiterate, go to Reisert, and Krause, and Terman, et. al. to
find your magically 'efficient' antenna...

denny / k8do

btw, a thought just caught me... W8JI on his web site has a great table
of antenna 'efficiency' in low noise receiving antennas... Maybe this
is what you mean... GO look it up..


Hi Denny

You seemed to have missed the point completely. Maybe your news reader
didnt supply you with the original post where Art refers to Efficiency of a
Yagi as being low.
Art finally agreed that the efficiency he refers to with his Yagi is the
Power IN divided by Power Out kind of efficiency. Since I consider the
statement that the Yagi antenna is I squared R lossy to be entirely
erroneous, I realized that I had no place in such a frivilous discussion.
Now I find it difficult to understand why you want to write so extensively
about telescopes, and broadside arrays, and sidelobes when we are
considering Efficiency. You may want to refer to Apperature Efficiency,
but, you are doing a poor job of it.

Whats with you Denny??? Why do you think of yourself as so superior that
you raise your voice at me telling me to "GO look it up".

Jerry

Yagi efficiency
 

art wrote:
Even Cecil who I suggest with his extra deep physics
education gets mocked sometimes ...

Art, I'm flattered but it is wrong. I have a B.S.
degree in EE from Texas A&M and Masters work in
education from Sam Houston State. I took Balanis'
antenna course at ASU and he and I worked together
on GSM simulations because my real field of expertise
is digital electronics. What I am mocked for is
thinking outside the box, e.g. that the distributed
network model allows RF energy to be tracked through
an antenna system.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

John Smith wrote:
Cecil Moore wrote:
Actually Art, adding reactance reduces the current in
the element thus *decreasing* losses below what a resonant
passive element would have. Pure reactance is lossless.

On the surface, this is all very correct, however, you cannot induce
reactance without inducing some value (albeit it may, or may not, be
trivial) of pure resistance (ohmic dc), barring the use of
superconducting material, of course.

I assume you are saying that lengthening a passive
element increases the ohmic losses? Then wouldn't
shortening a passive element, to induce capacitive
reactance, decrease the ohmic losses? And in either
case, since reactance reduces the induced current
and since ohmic losses are proportional to the square
of the current while only being proportional to the
first power of resistance, wouldn't that still
decrease ohmic losses?

Can people who live by the trivial sword, also
trip and fall on that same trivial sword? :-)
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Dave wrote:
Cecil Moore wrote:

Dave wrote:
All other "definitions" are red herrings and do not contribute to the
answer.

Not if the question is: What is beam efficiency? :-)

ABSOLUTELY NOT!!!!

From "Antennas For All Applications", 3rd edition by
John D. Kraus and Ronald J. Marhefka, page 665:

"Turning now to the *beam efficiency E(m)*, or the
ratio of the solid angle of the main beam Omega(m)
to the total beam solid angle Omega(a), we have ..."

All emphasis is the book author's, not w5dxp's.

From "Antenna Theory, Analysis and Design", 2nd edition,
by Constantin A. Balanis, page 63:

begin quote:
2.10 BEAM EFFICIENCY

Another parameter that is frequently used to judge the
quality of transmitting and receiving antennas is the
*beam efficiency*. For an antenna with its major lobe
directed along the z-axis (Theta = 0), as shown in
Figure 2.4(a), the beam efficiency (BE) is defined by

power transmitted(received) within cone angle Theta(1)
BE = ------------------------------------------------------
power transmitted(received) by the antenna

end quote:

In trying to figure out what definition Art is using,
this definition seems to me to be the closest.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Remember only R is of consideration for the addition of power from each
element which provides flux unless you can quantasize reaction for me
as producing the emmision of flux other than a indication of the
direction it takes .

I assume you are talking about radiation resistance.
There are other R's that cause loss of desired radiation
including conduction-dielectric losses. Some signal
is lost to the ground after being radiated.

Assuming that your definition of efficiency includes
beam efficiency, I would suggest taking an optimized
two-element Yagi into EZNEC and determining the maximum
gain. Then replace the reflector by an element identical
to the driven element including the source signal. Using
the same amount of total driving power, if you can come
up with a gain superior to the Yagi, would that prove
the point you are trying to make?
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Jimmie D wrote:
The radiation IS NOT cancelled ...

Doesn't the performance of non-reflecting glass
depend upon EM wave cancellation? Doesn't the
gain of a beam depend upon EM wave cancellation
in some other direction?
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Dave wrote:
art wrote:
David are you going nuts? I used the word impedance whichcan mean two
components only one of which is used for power.

No! You used the phrase "reactive impedance".

It was more than likely an inclusive statement, not an
exclusive one. I suspect Art meant, "a reactive impedance
term value" when he said "a reactive impedance value".
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

"Cecil Moore" wrote in message
.. .
Jimmie D wrote:
The radiation IS NOT cancelled ...

Doesn't the performance of non-reflecting glass
depend upon EM wave cancellation? Doesn't the
gain of a beam depend upon EM wave cancellation
in some other direction?
--
73, Cecil http://www.w5dxp.com

The radiation is not cancelled in the way ART means, One of the problems of
replying to his post is you can not do really do it without sounding like an
idiot.

Yagi efficiency
 

Doesn't the performance of non-reflecting glass
depend upon EM wave cancellation?
This I can respond to (though I doubt that I should)

The term usually used is "anti-reflective" and refers to a specific
multi-coating technique on the glass (or other medium).

the "anti" refers to destructive wave interference for reflected light
by varying the refractive index of successive coatings. Thus, MORE of
the incident travels through the medium than is reflected back

If the goal is to increase the % of light refracted THROUGH the medium,
then anti-reflective coating increases the efficiency.

Take the same glass without the AR coating, and LESS light is refracting
THROUGH the medium (more reflecting back): lower efficiency.

This definition of efficiency only makes sense when you're interested in
light refracted through the glass.

P-in / P-out does not = this definition of efficiency.

The efficiency definition implies interest in directionality.

Is this not where the confusion lies in all these posts?

John

PS,
Think of a simple flashlight with a mirror and a lens.

As a simple analogy, the filament of the light is the driven element
with a mirror behind and a lens in front...a LIGHT Yagi, no?

No diff in P-in/p-out...just all light directed out of the flashlight
into a beam.

Yagi efficiency
 

Cecil Moore wrote:
art wrote:
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 ...

Actually Art, adding reactance reduces the current in
the element thus *decreasing* losses below what a resonant
passive element would have. Pure reactance is lossless.

This current that you are referring to, I used P =I squared R
which leads to lower power. Where did I go wrong
Regards
Art




Seems to me that the reactance in the passive elements
provides a phase shift that causes destructive interference
in the desired places and constructive interference in
the desired places.

I came in late and thus apologize if anyone else has stated
this earlier.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Cecil Moore wrote:
art wrote:
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 ...

Actually Art, adding reactance reduces the current in
the element thus *decreasing* losses below what a resonant
passive element would have. Pure reactance is lossless.

This current that you are referring to, I used P =I squared R
which leads to lower power. Where did I go wrong
Regards
Art




Seems to me that the reactance in the passive elements
provides a phase shift that causes destructive interference
in the desired places and constructive interference in
the desired places.

I came in late and thus apologize if anyone else has stated
this earlier.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

PS,
Think of a simple flashlight with a mirror and a lens.

As a simple analogy, the filament of the light is the driven element
with a mirror behind and a lens in front...a LIGHT Yagi, no?

No diff in P-in/p-out...just all light directed out of the flashlight
into a beam.

John,

You're right about the efficiency, but be careful with the flashlight
analogy. A light yagi might have ~ 200 nanometer long elements.

An 20m band reflector analogous to that in a mini maglight would have
to be 800 miles in diameter.

The analogy with respect to efficiency is fine... but there's no HF
antenna that can form a beam like that.

73,
Dan

Yagi efficiency
 

Interesting Jimmy
Could you show me how me how a vector directed at a socalled reflector
behaves with respect to a constant plane without the implication of a
neutralising effect.
Now the reflector "works" only as a part of a particular plane so
please go on from there.
I often read of additive and subtractive radiation in books written by
the masters and I have seemed to have got the wrong idea about these
matters
Art

Jimmie D wrote:
"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.

Yagi efficiency
 

Cecil Moore wrote:
Remember only R is of consideration for the addition of power from each
element which provides flux unless you can quantasize reaction for me
as producing the emmision of flux other than a indication of the
direction it takes .

I agree there are other losses but to prevent including losses that are
outside the E and H process change over such as ground reflections etc
is it not better to just accept The pure resistance only so there is no
need to characterize individual losses Once you go beyond the near
field it gets complicated as losses are created outside the EH
generation process.
Ii am not sure how the EZNEC thing functions but if you design the
array where all elements are driven you can then use the individual
element impedances to determine overall efficiency.i.e. power in versus
power out
Fortunately thats the way my program can operate
Art


I assume you are talking about radiation resistance.
There are other R's that cause loss of desired radiation
including conduction-dielectric losses. Some signal
is lost to the ground after being radiated.

snipe?
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Cecil Moore wrote:
John Smith wrote:
Cecil Moore wrote:

Can people who live by the trivial sword, also
trip and fall on that same trivial sword? :-)

Cecil:

Yes they can. And, that would be no trivial trip! It is just, in the
dark, like I am most of the time, I can't seem to avoid them, the trips.

However, what I am saying can be proved, or disproved in the real world.
What I am saying, is construct a SHF antenna and chuck a xmitter and
pa behind it. Encase the antenna in good insulating (polyurethane foam
for instance?) material and have a temperature sensor attached to each
element. Crank up the power and you will see some sort of rise in temp
in the director (indeed, it should be seen in ALL elements), since heat
= loss (actually, since we all accept the law of conservation of energy,
loss is a misnomer, really it is only a change in frequency, from rf to
infrared--beware a trivial trip!) we demonstrate an induced loss in the
system.

Next, remove all elements and materials to a distance from the de where
absolutely no coupling can occur. Tune and match the de to the pa
output, now bring the director into proximity to the de, observe the
power flow to the de as you finally set the director into proper
position to form a good frontal lobe, you MUST now re-tune and adjust
the de, this is because electrical factors (resistance, reactance and
possible other factors we are not even aware of) of the director are now
being "mirrored" into the de (an ohmic loss (heat) should also have
risen in the de due to the mirrored directors imperfections.)

That is all I am saying. Now we would have go get out our equipment
which can measure the weight of fly wings to know the real importance of
all that...

Geesh Cecil, you never ask ANY simple questions!

Warmest regards,
JS

Yagi efficiency
 

Jimmie D wrote:
The radiation is not cancelled in the way ART means.

Sorry, I came in late. Here's a quotation from a web
site concerning wave cancellation that might help:

"... when two waves of equal amplitude and wavelength
that are 180-degrees ... out of phase with each other
meet, they are not actually annihilated, ... All of the
photon energy present in these waves must somehow be
recovered or redistributed in a new direction, according
to the law of energy conservation ... Instead, upon
meeting, the photons are redistributed to regions that
permit constructive interference, so the effect should
be considered as a redistribution of light waves and
photon energy rather than the spontaneous construction
or destruction of light."

If the EM energy doesn't change form, the destructive
interference from wave cancellation must result in
an equal magnitude of constructive interference
somewhere else - like squeezing a balloon. Sorry if
this has been said previously.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

art wrote:
Cecil Moore wrote:
Actually Art, adding reactance reduces the current in
the element thus *decreasing* losses below what a resonant
passive element would have. Pure reactance is lossless.

This current that you are referring to, I used P =I squared R
which leads to lower power. Where did I go wrong

Lower power results in lowering the loss due to heat.
That leaves more power available to be radiated by
the antenna system but not necessarily radiated by
this single element that we are discussing. I suspect
two driven elements are theoretically capable of
better performance than a two element Yagi given
equal total power input into the elements.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Yagi efficiency
 

IIf you can design a bandpass filter in a RLC or complex circuitry
method then you can design an antenna array that does the same thing.
That is not out of the box thinking.Just remove coupling from the
overall function

Regards
Art
art wrote:
Even Cecil who I suggest with his extra deep physics
education gets mocked sometimes ...

Art, I'm flattered but it is wrong. I have a B.S.
degree in EE from Texas A&M and Masters work in
education from Sam Houston State. I took Balanis'
antenna course at ASU and he and I worked together
on GSM simulations because my real field of expertise
is digital electronics. What I am mocked for is
thinking outside the box, e.g. that the distributed
network model allows RF energy to be tracked through
an antenna system.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Exactly.That is similar to two equal forces acting to compressa piece
of steel Opposite to when you use tension the side forces press inwards
until a 45 degree break or shear angle occurs where the vectors forces
move out at right angles to the compressive force Newton is correct,
you cant destroy energy
Art:
Jimmie D wrote:
The radiation is not cancelled in the way ART means.

Sorry, I came in late. Here's a quotation from a web
site concerning wave cancellation that might help:

"... when two waves of equal amplitude and wavelength
that are 180-degrees ... out of phase with each other
meet, they are not actually annihilated, ... All of the
photon energy present in these waves must somehow be
recovered or redistributed in a new direction, according
to the law of energy conservation ... Instead, upon
meeting, the photons are redistributed to regions that
permit constructive interference, so the effect should
be considered as a redistribution of light waves and
photon energy rather than the spontaneous construction
or destruction of light."

If the EM energy doesn't change form, the destructive
interference from wave cancellation must result in
an equal magnitude of constructive interference
somewhere else - like squeezing a balloon. Sorry if
this has been said previously.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Cecil Moore wrote:
art wrote:
Cecil Moore wrote:
Actually Art, adding reactance reduces the current in
the element thus *decreasing* losses below what a resonant
passive element would have. Pure reactance is lossless.
Whoa Cecil i dont follow that at all
art





This current that you are referring to, I used P =I squared R
which leads to lower power. Where did I go wrong

Lower power results in lowering the loss due to heat.
That leaves more power available to be radiated by
the antenna system but not necessarily radiated by
this single element that we are discussing. I suspect
two driven elements are theoretically capable of
better performance than a two element Yagi given
equal total power input into the elements.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

More current is not necessarily used for reradiation .
You also have circulating current because of inherrant
inductance and capacitance since we are dealing with a series
circuit. You can add resistance to the circuit when you are at
some distance from resonance which is similar to forming band
pass shapes but the bottom line is that at resonance or near
resonance pure resistance rules To get closer to what is really
happening is to go back to 455 khz when used in radio
circuits to revive the memory
Art


Cecil Moore wrote:
art wrote:
Cecil Moore wrote:
Actually Art, adding reactance reduces the current in
the element thus *decreasing* losses below what a resonant
passive element would have. Pure reactance is lossless.

This current that you are referring to, I used P =I squared R
which leads to lower power. Where did I go wrong

Lower power results in lowering the loss due to heat.
That leaves more power available to be radiated by
the antenna system but not necessarily radiated by
this single element that we are discussing. I suspect
two driven elements are theoretically capable of
better performance than a two element Yagi given
equal total power input into the elements.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Tom Ring wrote:
art wrote:

Not a reasonable answer, could be speculation like some of the comments
I get from experts. The yagi is not totally efficient in changing the
time changing field to a radiative field
because it has detuned elements contrary to what Roy states that a
reflector aids the forward lobe.......that is trash talk but many of
the so called experts are following like lemmons


So why is it then, that Roy and several dozen others here have made good
livings, written respected books, and designed antenna systems that
defined how good it can get? And all you have done is call them names?
When I don't agree with them they call me names It is always them or
their followers and I eventually retaliate with a vengance and I think
I can do it better than them.
They are of a group that everything is known about antennas and is
written in books. If you refer to something that is not in the books
then they attack where I wish they would take a bit of time trying to
understand what I am getting at so I can make use of their superior
knowledge outside of yagis but yagis dominate their whole life to the
exclusion of anything else so we are at an impasse. Tough but it is of
their choice where I have offered my hand many times only to be
rejected.
Art







Sounds like the "so called experts" are a lot effing smarter than you.

All you have done is throw stones, which is what you accuse all of us
of, by the way. And you haven't given a microgram of proof that what
you believe is true.

tom
K0TAR

Yagi efficiency
 

art wrote:
Cecil Moore wrote:
Actually Art, adding reactance reduces the current in
the element thus *decreasing* losses below what a resonant
passive element would have. Pure reactance is lossless.

Whoa Cecil i dont follow that at all

Resonant passive elements absorb more power
than do non-resonant passive elements. Resonant
passive elements therefore dissipate more heat
than non-resonant passive elements.

With EZNEC, check out the feedpoint impedance
of a two element Yagi when both elements are
resonant Vs when one element is 5% longer and
a non-resonant reflector.

The following values are not optimized by any
means but will give you an idea.

With ten foot spacing between two 33 foot elements

The gain is virtually bidirectional at 10.7 dBi.
The feedpoint impedance is 20 ohms and the current
induced in the passive element is 0.84 amps.

Keeping everything else the same and adding one
foot to the reflector yields the following results.

The gain increases to 11.9 dBi with a F/B ratio
of about 8 dB. The feedpoint impedance is 30 ohms
and the current induced in the passive element is
lower at 0.75 amps.

Making the reflector non-resonant causes its current
to fall by about 0.1 amp thus reducing losses while
the feedpoint impedance has increased by 50% and the
gain has increased by 1.2 dB. There doesn't seem to
be any downside to non-resonant passive elements.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

art wrote:
You also have circulating current because of inherrant
inductance and capacitance since we are dealing with a series
circuit.

Every real world network contains both inductance
and capacitance. The circulating currents between
them are maximum at resonance, i.e. when the
reactances appear to disappear but they don't.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

art wrote:

IIf you can design a bandpass filter in a RLC or complex circuitry
method then you can design an antenna array that does the same thing.
That is not out of the box thinking.Just remove coupling from the
overall function


Designing an RLC circuit is trivial. The equations are simple and well known
to any 2nd year EE student.

However, you need field theory and materials knowledge (among other
things)to design an antenna.

If you design an antenna only looking at ohm's law, you will never be
successful.

Yagi efficiency
 

art wrote:


Cecil Moore wrote:
Remember only R is of consideration for the addition of power from each
element which provides flux unless you can quantasize reaction for me
as producing the emmision of flux other than a indication of the
direction it takes .

I agree there are other losses but to prevent including losses that are
outside the E and H process change over such as ground reflections etc
is it not better to just accept The pure resistance only so there is no
need to characterize individual losses Once you go beyond the near
field it gets complicated as losses are created outside the EH
generation process.
Ii am not sure how the EZNEC thing functions but if you design the
array where all elements are driven you can then use the individual
element impedances to determine overall efficiency.i.e. power in versus
power out
Fortunately thats the way my program can operate
Art



Does this mean you are ignoring any interaction between elements?

Yagi efficiency
 

Re "it does not agree...".When you look at the main characteristic of a
yagi antenna which is the gain of the main lobe and then compare it
with the rest of the radiation field then I would say it is
inefficient. I sure wish I had a picture of all the radiation vectors
that go into the shaping of the field. I did a circular pattern array
the other day where a circular cone was radiated vertically and I
thought that was as close to a beam that I ever had seen but why it
formed that way is a mystery. Frankly I feel the major need nowadays is
a broard beam as possible for line of site use for wireless devices
where the gain is constant for excess of 90 degrees coverage plus
large bandwidth rather than a emphasis on gain itself
Art

Richard Fry wrote:
"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

Yagi efficiency
 

Ofcourse they are.They are both resonant and have the same "Q" which is
equivalent to half power. Isnt that why we talk of a half power width
of a main beam because of the assertion I just made. This is a
excellent candidate for a complex circuit analysis since the Q is the
same regardles of movement away from the resonant frequency and
coupling is not a factor!
Art
Art

Cecil Moore wrote:
art wrote:
Cecil Moore wrote:
Actually Art, adding reactance reduces the current in
the element thus *decreasing* losses below what a resonant
passive element would have. Pure reactance is lossless.

This current that you are referring to, I used P =I squared R
which leads to lower power. Where did I go wrong

Lower power results in lowering the loss due to heat.
That leaves more power available to be radiated by
the antenna system but not necessarily radiated by
this single element that we are discussing. I suspect
two driven elements are theoretically capable of
better performance than a two element Yagi given
equal total power input into the elements.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Ofcourse they are.They are both resonant and have the same "Q" which is
equivalent to half power. Isnt that why we talk of a half power width
of a main beam because of the assertion I just made. This is a
excellent candidate for a complex circuit analysis since the Q is the
same regardles of movement away from the resonant frequency and
coupling is not a factor!
Art
Art

Cecil Moore wrote:
art wrote:
Cecil Moore wrote:
Actually Art, adding reactance reduces the current in
the element thus *decreasing* losses below what a resonant
passive element would have. Pure reactance is lossless.

This current that you are referring to, I used P =I squared R
which leads to lower power. Where did I go wrong

Lower power results in lowering the loss due to heat.
That leaves more power available to be radiated by
the antenna system but not necessarily radiated by
this single element that we are discussing. I suspect
two driven elements are theoretically capable of
better performance than a two element Yagi given
equal total power input into the elements.
--
73, Cecil http://www.w5dxp.com

Yagi efficiency
 

Cecil Moore wrote:
The feedpoint impedance is 20 ohms and the current
induced in the passive element is 0.84 amps.


Cecil:

Does Roy's program allow you to insert a reflector made of
nickel-chromium wire. Stick one of those turkeys in there and see if
that doesn't cut that 0.84 amps down a bit! grin

Chuckling,
JS

Yagi efficiency
 

art wrote:
Tom Ring wrote:
art wrote:
They are of a group that everything is known about antennas and is
written in books. If you refer to something that is not in the books


Art:

If you refer to something that is "not in the books" one should take
great care. Why I do think evidence can be brought out and can be
demonstrated that some of the ways we "think" antennas are working is
not real, however, great men have developed thinking models and formulas
which are able to let us design and use WORKING antennas which are
PRACTICAL. I site that mysterious 377 ohms as an example, or for
another, incorporating the spin rate of the earth into antenna formulas
(time), ridiculous (but useful!) But, those "old books" contain methods
and means to develop antennas which do work and which do work well, we
owe much to those who have gone before us ...

I am only hoping that by refusing to allow "magic numbers" to be
embedded into equations without any suitable explanation of what those
numbers are "REALLY ABOUT" will one day awake the man who can form the
vision and see what the others have all been unable to, Tesla seemed to
have had an excellent ability which I hold as example of the type of
"vision seer" I mean.

I have an open mind, I guess you are as likely as the next guy to "be
the one!" Never hurts to try anyway ...

However, thank God practical antennas work and we have the tools to
design and build them.

Regards,
JS

Yagi efficiency
 

I figure that if it works ok on my program AO PRO and it is then
checked out OK on NEC4
independently,and I can produce the electrical laws that backs it up it
will get into the books tho for the present time it is not there now.
For a very long time I have tried to introduce this and others to those
who are experienced in that sort of thing but I could never get it off
the ground because the thread kept on being changed to suit somebodies
whim or it developed into a name calling setup that it was impossible
to procede. Actually I let one patent application drop during the
examination process because of the badmouthing that I got but my back
is now stiffer and this one is going all the way. I do it not for money
reasons but because antennas is my hobby despite my so called lack of
knoweledge I have had patents during my working years at G.E. and other
places so the idea of patents doesn't carry much with me any more. For
all the experts we have had over the years on this newsgroup I have
never been able to thrash out one of my ideas to fruition because of
various nebulous reasons. If I brought one up involving SWR, coupling,
baluns e.t.c. the thread will grow by leaps and bounds in minuits
because everybody has something to say about it. If a subject is
brought up that one cannot provide insight then that person feels
denied that he cant post so he will resort to firing bullets and
stones.
Art

John Smith wrote:
art wrote:
Tom Ring wrote:
art wrote:
They are of a group that everything is known about antennas and is
written in books. If you refer to something that is not in the books


Art:

If you refer to something that is "not in the books" one should take
great care. Why I do think evidence can be brought out and can be
demonstrated that some of the ways we "think" antennas are working is
not real, however, great men have developed thinking models and formulas
which are able to let us design and use WORKING antennas which are
PRACTICAL. I site that mysterious 377 ohms as an example, or for
another, incorporating the spin rate of the earth into antenna formulas
(time), ridiculous (but useful!) But, those "old books" contain methods
and means to develop antennas which do work and which do work well, we
owe much to those who have gone before us ...

I am only hoping that by refusing to allow "magic numbers" to be
embedded into equations without any suitable explanation of what those
numbers are "REALLY ABOUT" will one day awake the man who can form the
vision and see what the others have all been unable to, Tesla seemed to
have had an excellent ability which I hold as example of the type of
"vision seer" I mean.

I have an open mind, I guess you are as likely as the next guy to "be
the one!" Never hurts to try anyway ...

However, thank God practical antennas work and we have the tools to
design and build them.

Regards,
JS

Yagi efficiency
 

"art" wrote in message
ups.com...
Interesting Jimmy
Could you show me how me how a vector directed at a socalled reflector
behaves with respect to a constant plane without the implication of a
neutralising effect.
Now the reflector "works" only as a part of a particular plane so
please go on from there.
I often read of additive and subtractive radiation in books written by
the masters and I have seemed to have got the wrong idea about these
matters
Art

Then give a reference to what you are talking about if you are so familar
with the "masters".


Jimmie D wrote:
"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.