Yagi efficiency
 

John Smith wrote:
art wrote:
...

Art:

You believe resonance of the driver is desirable? Have you plotted a
yagi with EZNEC and added reactance to make the director physically
shorter than the de, but the electrical length correct?

I have not; but would expect it to plot out as two identical de's
pattern with a reflector?

JS


.... sorry "... resonance of the driver ...", should have been resonance
of the director.

JS

Yagi efficiency
 

Jerry Martes wrote:
"art" wrote in message

Does that mean the Yagi gets hot when used to radiate RF? That is,
since the Yagi is less efficient than some other reference antenna, the Yagi
gets hotter than the other antenna when their input power is equal.

Jerry



Yes Jerry, if the radiation efficiency falls, the antenna should get
"hotter", where else would the lost power go? Harmonics? Psychic waves?

JS

Yagi efficiency
 

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

Yagi efficiency
 

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

Yagi efficiency
 

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.

Yagi efficiency
 

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

Yagi efficiency
 

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

Yagi efficiency
 

John Smith wrote:
art wrote:
...

Art:

You believe resonance of the driver is desirable? Have you plotted a
yagi with EZNEC and added reactance to make the director physically
shorter than the de, but the electrical length correct?
Yes I have done that lots of times if I have the question correctly
basically having resonant elements beside the driven element but of
different lengths

I have not; but would expect it to plot out as two identical de's
pattern with a reflector?
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

Yagi efficiency
 

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

Yagi efficiency
 

David, you are doing a lot of reading of different posters and then
placing them under my name. I have no idea of what you are trying to
project with this accumulation of various postings from various people
tho I cqan see that you are getting mad as hell over something.
cool down

Dave wrote:
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.