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.

"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.

"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

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

If a simple dipole is fed with 100 watts and radiates 95 watts, it is 95% efficient.

If a simple Yagi is fed with 100 watts and radiates 95 watts, it is 95% efficient.

If a full size 11 element Yagi is fed with 100 watts and radiates 95 watts, it
is 95% efficient.

What is your real question regarding efficiency?

/s/ DD

art wrote:

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!

Dave wrote:
If a simple dipole is fed with 100 watts and radiates 95 watts, it is
95% efficient.

How are you measuring the antennas "output" or "radiated power?"
--and--
How much of that 95 watts is spent in heating the dielectrics and metal
(or is that "missing" 5 watts the heating power? And, how did you
measure that?)

JS

RADIATED VERSUS LOSSES

John Smith wrote:

Dave wrote:

If a simple dipole is fed with 100 watts and radiates 95 watts, it is
95% efficient.


How are you measuring the antennas "output" or "radiated power?"
--and--
How much of that 95 watts is spent in heating the dielectrics and metal
(or is that "missing" 5 watts the heating power? And, how did you
measure that?)

JS

Dave wrote:
RADIATED VERSUS LOSSES

Hmmm. I am looking around for my "RADIATED VERSUS LOSSES" meter, can't
seem to find it, must have lost it. Too bad, have to run down to radio
shack and pick up another to double check you! Will get back to you then...

JS

Dave wrote:
If a simple dipole is fed with 100 watts and radiates 95 watts, it is 95% efficient.

David if you had a dipole that had inherrent directional capabilities
would you consider
that as a possible choice for better efficiency ? Where does the 95%
number come from and where did the 5% go so. Did turners post influence
your guess at that number? is he worth copying? Others can get an idea
what you are talking about ie. parameters of use for which you are
applying the 95% figure to. It is possible that we can at least one
negative from the discusion in search of the kernel of info. Does the
dipole become more or less efficient as it moves away from its design
frequency as it becomes "detuned" Give me some meat





snip/s/ DD

art wrote:

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!

art wrote:

Dave wrote:

If a simple dipole is fed with 100 watts and radiates 95 watts, it is 95% efficient.


David if you had a dipole that had inherrent directional capabilities
would you consider
that as a possible choice for better efficiency ? Where does the 95%
number come from and where did the 5% go so. Did turners post influence
your guess at that number? is he worth copying? Others can get an idea
what you are talking about ie. parameters of use for which you are
applying the 95% figure to. It is possible that we can at least one
negative from the discusion in search of the kernel of info. Does the
dipole become more or less efficient as it moves away from its design
frequency as it becomes "detuned" Give me some meat

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.