When one looks at a.radiating array pattern one can see that the yagi
is very inefficient. Does anybody know of the relative volume
contained in the main radiation lobe versus the total volume of the
entire pattern? I know there are a lot of different type antenna gains
and
arrangement but I am trying to determine in an informal way the
efficiency ratio and compare it to what would appear to be a very
efficient
antenna such as a dish.

I think the parameter that you are searching for is GAIN !!!!

An antenna only has gain by compressing power more into one direction more
than another. It is a case of robbing Peter to pay Paul, the more power you
have in the main lobe the less you have in other directions.

73
Jeff

I'm not sure I understand the question, but a large fraction of the
total power is typically in the main lobe of a Yagi. You won't increase
the power in the main lobe significantly by reducing or eliminating
other lobes, because there just isn't much power there. If you want more
power in a narrower range of directions, you need more directionality,
which means a longer Yagi, stacked Yagis, or some other type of antenna
which will probably be larger. The methodology for and tradeoffs
involved in increasing directionality are well known. And because Yagis
(ones not having lossy traps or loading components) are very efficient,
directionality and gain are inextricably linked.

Roy Lewallen, W7EL

It occurs to me that by art's definition, all antennas are
"inefficient". When you're talking with someone, only a teeny, tiny
fraction of the radiated power is going precisely in the right direction
to be collected by his antenna, so the remainder is wasted. Shucks, I'd
be amazed if the "efficiency" of the best HF antenna is better than
0.001% by this criterion.

Roy Lewallen, W7EL

The other point I note is that he wants enhanced HF radiation between
10 and 4 degrees elevation and apparently beamed to a specific point
on the globe... The cubic size and the towers and the arrays that it
will take to accomplish this are not efficient in time, money, and
effort... He is chasing a unicorn...
As has been pointed out already, the percentage of time that the major
portion of the arriving HF EM wave is below 10 degrees can be
enumerated on the fingers of one hand... Besides, who is going to have
the array on the other end with comparable response?

denny / k8do

"art" wrote in message
ups.com...

Richard Clark wrote:
On 21 Sep 2006 19:09:38 -0700, "art" wrote:

Notwithstanding that the
upper half of the major lobe serves no usefull purpose to what the
antenna is required for there is a mass of radiation in many directions
and levels that have no connection to the required purpose of the
antenna, thus we have a lot of wasted radiation that if we harness it
so that it is used for the antennas primary use the efficiency of the
antenna would increase immensly.

Hi Art,

The classic solution is to stack yagis vertically. This draws down
the higher radiation lobes and puts their gain in the forward
direction.

Well you are getting closer to the question at hand. You have now
doubled the
power input but only slightly gained directionality(2db) efficiency I
would also suspect that you have flattened the lower lobe only into a
pancake shape. But again I go back to the desirable radiation which can
be said in this case to be the lower half of the major lobes half power
envelope which for a directional radiated array is very small compared
to the total radiated field.True propagation can play games but the
ARRL
give the average arrival angles over a 11 year period so it is not a
hopeless task to get a ball park figure regarding usefull radiation
knowing where the target is
I suppose I could make a model and slice out the half power lobe
portion and compare the two volumes for myself, I just thought that it
had already been looked at
Oh well back to the drawing board
Art

what you are missing is the variability in that arrival angle. if you are
interested in a specific path you must be able to receive all the possible
arrival angles, which with yagi's requires mounting several of them at
different heights. for instance consider a path from w1 to western europe
at the sunspot peak on 10m... it is not uncommon for the band to open at a
very low angle, say where a single yagi at 120' is the best antenna, then as
the day progresses the angle increases so much that the 120' antenna is
almost worthless but one at only 30' is working great. if you put
everything into getting that 10-12 degree angle you lose out by mid morning
when the arrival angle is up to 30 degrees or more... but at the same time
that top antenna may be working great into siberia!

what you are looking for is not normally called 'efficiency', but
'directivity'. unfortunately horizontally polarized yagi's vertical
radiation pattern is very dependent on height and the terrain so increasing
the directivity is seen mostly in the width of the pattern. and as noted
above, controlling the vertical pattern is normally done by changing the
antenna height, usually by stacking multiple antennas on the tower and
selecting them one at a time or in combinations to give the desired vertical
coverage. There have been some experiments with variable phasing of stacked
yagis, but it is not a common capability in amateur installations.

Gentlemen let me reiterate
I am building an antenna for this winter and my target is the UK Thus
I submit that the main lobe is the area of radiation contact and which
comprises of a certain volume ( and I am looking for a ball park
figure)
compared to the radiation emmitted from the whole array.
What is so wrong with that question,? It seems that people are avoiding
the main question and diverging into other areas for the sake of an
augument
There is nothing wrong in not knowing the answer and you do not have to
post
or respond but you can always start a new post where a facet of your
choice
can be discussed
Art


...

Richard Clark wrote:
On 21 Sep 2006 19:09:38 -0700, "art" wrote:

Notwithstanding that the
upper half of the major lobe serves no usefull purpose to what the
antenna is required for there is a mass of radiation in many directions
and levels that have no connection to the required purpose of the
antenna, thus we have a lot of wasted radiation that if we harness it
so that it is used for the antennas primary use the efficiency of the
antenna would increase immensly.

Hi Art,

The classic solution is to stack yagis vertically. This draws down
the higher radiation lobes and puts their gain in the forward
direction.

Well you are getting closer to the question at hand. You have now
doubled the
power input but only slightly gained directionality(2db) efficiency I
would also suspect that you have flattened the lower lobe only into a
pancake shape. But again I go back to the desirable radiation which can
be said in this case to be the lower half of the major lobes half power
envelope which for a directional radiated array is very small compared
to the total radiated field.True propagation can play games but the
ARRL
give the average arrival angles over a 11 year period so it is not a
hopeless task to get a ball park figure regarding usefull radiation
knowing where the target is
I suppose I could make a model and slice out the half power lobe
portion and compare the two volumes for myself, I just thought that it
had already been looked at
Oh well back to the drawing board
Art

what you are missing is the variability in that arrival angle. if you are
interested in a specific path you must be able to receive all the possible
arrival angles, which with yagi's requires mounting several of them at
different heights. for instance consider a path from w1 to western europe
at the sunspot peak on 10m... it is not uncommon for the band to open at a
very low angle, say where a single yagi at 120' is the best antenna, then as
the day progresses the angle increases so much that the 120' antenna is
almost worthless but one at only 30' is working great. if you put
everything into getting that 10-12 degree angle you lose out by mid morning
when the arrival angle is up to 30 degrees or more... but at the same time
that top antenna may be working great into siberia!

what you are looking for is not normally called 'efficiency', but
'directivity'. unfortunately horizontally polarized yagi's vertical
radiation pattern is very dependent on height and the terrain so increasing
the directivity is seen mostly in the width of the pattern. and as noted
above, controlling the vertical pattern is normally done by changing the
antenna height, usually by stacking multiple antennas on the tower and
selecting them one at a time or in combinations to give the desired vertical
coverage. There have been some experiments with variable phasing of stacked
yagis, but it is not a common capability in amateur installations.

You are right... You are so far ahead of this group that we can not
even comprehend the question...


denny

art wrote:
Gentlemen let me reiterate

Thank you for those kind words but I will keep trying
Art

Denny wrote:
You are right... You are so far ahead of this group that we can not
even comprehend the question...


denny

art wrote:
Gentlemen let me reiterate

Right on Jeff
Obviously I would like to rob Peter of everything he
stole and give it to Paul because he is doing something constructive
with his energy where as Peter is robbing energy and just throwing it
away
If Paul had posession of that energy then his half power beam width
would
increase as opposed to decreasing in the pursuit of gain using the
small amount
of radiation available to him
Art



Jeff wrote:
When one looks at a.radiating array pattern one can see that the yagi
is very inefficient. Does anybody know of the relative volume
contained in the main radiation lobe versus the total volume of the
entire pattern? I know there are a lot of different type antenna gains
and
arrangement but I am trying to determine in an informal way the
efficiency ratio and compare it to what would appear to be a very
efficient
antenna such as a dish.

I think the parameter that you are searching for is GAIN !!!!

An antenna only has gain by compressing power more into one direction more
than another. It is a case of robbing Peter to pay Paul, the more power you
have in the main lobe the less you have in other directions.

73
Jeff

It is unintelligible and displays no practical understanding of antenna theory.

The Man in the Maze
QRV at Baboquivari Peak, AZ