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..

"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

Jerry, if I came across a bit loud I apologize.. I usually skim down
the latest chatter and then just post to the group off the bottom
message, often having no direct bearing on the particular post it spins
off from... Also, I skim a number of groups and topics and I run a
business so I can miss a post that puts a different spin on things...
If I ruffled your feathers it was not intentional...
Let me comment that I absolutely agree with you that claiming a Yagi is
inefficient from the perspective of I2R losses shows a lack of basic
knowledge... Having said that, let me also note that closing the
spacing, i.e. tighter than the classical Yagi-Uda array, and putting
the beam into Supergain territory has consequences... Moxon has a non
mathematical discussion of the supergain antennas with a graph of
spacing v/s gain v/s impedence, and I Krauss mentioned that he designed
his flat top array stimulated from a paper by Brown (I think it was)
where he discussed arrays that have more than additive gain by tight
spacing... Anyway I digress; the point of all this mumble is that these
supergain "Yagi" arrays can have quite high I2R losses... But the
commercial Yagi-Uda today is not in that class...

Anyway, Cheers ... denny / k8do

Hi Denny

The fact is, I probably get "ruffled" too easily, probably because I'm
insecure. I'm not the sharpest antenna designer around.
My way of antenna design relies mainly on actual, measured data, so I am a
little short on convincing theoretical data. But, my approach to
determining relative efficiency would be based on measured data.
If *I* had made any statement on the efficiency of *any* antenna, you can
be sure I would include some measured data. Measuring Yagi antenna loss is
probably too mundane for Art. He already knows things that would require me
months of testing to 'check up on'.
If I wanted to know the "I squared R loss" efficiency of one antenna
compared to another antenna, I'd need to conduct time consuming experiments.

Jerry






"Denny" wrote in message
s.com...
Jerry, if I came across a bit loud I apologize.. I usually skim down
the latest chatter and then just post to the group off the bottom
message, often having no direct bearing on the particular post it spins
off from... Also, I skim a number of groups and topics and I run a
business so I can miss a post that puts a different spin on things...
If I ruffled your feathers it was not intentional...
Let me comment that I absolutely agree with you that claiming a Yagi is
inefficient from the perspective of I2R losses shows a lack of basic
knowledge... Having said that, let me also note that closing the
spacing, i.e. tighter than the classical Yagi-Uda array, and putting
the beam into Supergain territory has consequences... Moxon has a non
mathematical discussion of the supergain antennas with a graph of
spacing v/s gain v/s impedence, and I Krauss mentioned that he designed
his flat top array stimulated from a paper by Brown (I think it was)
where he discussed arrays that have more than additive gain by tight
spacing... Anyway I digress; the point of all this mumble is that these
supergain "Yagi" arrays can have quite high I2R losses... But the
commercial Yagi-Uda today is not in that class...

Anyway, Cheers ... denny / k8do

Jerry Martes wrote:
Hi Denny

The fact is, I probably get "ruffled" too easily, probably because I'm
insecure. I'm not the sharpest antenna designer around.
My way of antenna design relies mainly on actual, measured data, so I am a
little short on convincing theoretical data. But, my approach to
determining relative efficiency would be based on measured data.
If *I* had made any statement on the efficiency of *any* antenna, you can
be sure I would include some measured data. Measuring Yagi antenna loss is
probably too mundane for Art. He already knows things that would require me
months of testing to 'check up on'.
If I wanted to know the "I squared R loss" efficiency of one antenna
compared to another antenna, I'd need to conduct time consuming experiments.

Jerry






"Denny" wrote in message
s.com...
Jerry, if I came across a bit loud I apologize.. I usually skim down
the latest chatter and then just post to the group off the bottom
message, often having no direct bearing on the particular post it spins
off from... Also, I skim a number of groups and topics and I run a
business so I can miss a post that puts a different spin on things...
If I ruffled your feathers it was not intentional...
Let me comment that I absolutely agree with you that claiming a Yagi is
inefficient from the perspective of I2R losses shows a lack of basic
knowledge... Having said that, let me also note that closing the
spacing, i.e. tighter than the classical Yagi-Uda array, and putting
the beam into Supergain territory has consequences... Moxon has a non
mathematical discussion of the supergain antennas with a graph of
spacing v/s gain v/s impedence, and I Krauss mentioned that he designed
his flat top array stimulated from a paper by Brown (I think it was)
where he discussed arrays that have more than additive gain by tight
spacing... Anyway I digress; the point of all this mumble is that these
supergain "Yagi" arrays can have quite high I2R losses... But the
commercial Yagi-Uda today is not in that class...

Anyway, Cheers ... denny / k8do




Jerry:

I didn't really disagree with you, ALL antennas are 100% efficient
radiators (dummy loads are excellent too!), only a real fool would argue
that one!

But this is california, I don't need the infrared radiations all that
much; never had trouble with ice sickles on the 'tenna. grin.

Warmest regards,
JS

"John Smith" wrote in message
...
Jerry Martes wrote:
Hi Denny

The fact is, I probably get "ruffled" too easily, probably because I'm
insecure. I'm not the sharpest antenna designer around.
My way of antenna design relies mainly on actual, measured data, so I
am a little short on convincing theoretical data. But, my approach to
determining relative efficiency would be based on measured data.
If *I* had made any statement on the efficiency of *any* antenna, you
can be sure I would include some measured data. Measuring Yagi antenna
loss is probably too mundane for Art. He already knows things that would
require me months of testing to 'check up on'.
If I wanted to know the "I squared R loss" efficiency of one antenna
compared to another antenna, I'd need to conduct time consuming
experiments.

Jerry






"Denny" wrote in message
s.com...
Jerry, if I came across a bit loud I apologize.. I usually skim down
the latest chatter and then just post to the group off the bottom
message, often having no direct bearing on the particular post it spins
off from... Also, I skim a number of groups and topics and I run a
business so I can miss a post that puts a different spin on things...
If I ruffled your feathers it was not intentional...
Let me comment that I absolutely agree with you that claiming a Yagi is
inefficient from the perspective of I2R losses shows a lack of basic
knowledge... Having said that, let me also note that closing the
spacing, i.e. tighter than the classical Yagi-Uda array, and putting
the beam into Supergain territory has consequences... Moxon has a non
mathematical discussion of the supergain antennas with a graph of
spacing v/s gain v/s impedence, and I Krauss mentioned that he designed
his flat top array stimulated from a paper by Brown (I think it was)
where he discussed arrays that have more than additive gain by tight
spacing... Anyway I digress; the point of all this mumble is that these
supergain "Yagi" arrays can have quite high I2R losses... But the
commercial Yagi-Uda today is not in that class...

Anyway, Cheers ... denny / k8do




Jerry:

I didn't really disagree with you, ALL antennas are 100% efficient
radiators (dummy loads are excellent too!), only a real fool would argue
that one!

But this is california, I don't need the infrared radiations all that
much; never had trouble with ice sickles on the 'tenna. grin.

Warmest regards,
JS

Hi John

I didnt mean to imply that any antenna is 100 percent efficient. I would
suggest that the amount of power lost to I squared R losses in a well built
Yagi would be so low that they would be time consuming to evaluate.

I have even thought about how I'd try testing the I^2R losses in a Yagi,
as compared to another antenna design. But, that would be long learning
process for me.

I'd sure like to see Art's data before I'd start a test of yagi
efficiency.

Jerry