Regarding antenners, thats right,antennas.
Plenty of listings for various gains achieved with antennas
but I have not seen any similar listings for F/R and F/B.
Is there any around so I can see what can be or has been attained or
is blocking of rear signals of little consequence for todays hams. I can see
that being true
for when the band has just opened and propagation has not opened to the rear
or
with net operations so perhaps gain is every thing after all.
It is my opinion that if interest/efforts are increased first in deflecting
the rear action to the
front first and thereby INCREASING the front lobe width there will be more
opportunities
for increasing gains without the side lobes and narrow forward lobes that
accompany Yagi's.
as well as shorter booms. ( more deflectors/reflectors perhaps)
( no religeous, porno or genocide preaching please, fighting to see which is
best
could take place on boat anchor nets to see which has taken position of the
lowest level)
Regards
Art

Hi Art

In my experience (or maybe its just anecdotal) F/B ratios are very
frequency dependent for high dB numbers. You might for example get 28dB
F/B on 14.100 but it may drop to 15dB 100kHz away. The forward gain in
this case doesnt change much at all. How would you then advertise this
except by a graph?

Keep in mind also that F/B is expressed in a specific direction. 5-10
degrees off that and you will see the numbers fall off.

Max F/B rarely occurs at max forward gain...

Front to side is also good for attenuating signals you dont want.
(Assuming horiz polarisation)

If I was tackling this as a project I'd start defining some parameters
like 3dB beamwidth and the maximum unwanted lobe figures. Then plug it
into a modeling program (like 4nec2) I havent played much with modelling
but I assume that the optimising tools could do the trial and error
calcs for you. You are aiming for an antenna with moderate forward gain
but as low as possible radiation/reception in other directions..

In fact if you havent tried modelling it is well worth it just to see
the effect on the patterns.

You can also tune a (yagi/quad) reflector remotely if you want to peak
the F/B

Probably not what you were after sorry...

Cheers Bob VK2YQA (In Oz...)


wrote:
Regarding antenners, thats right,antennas.
Plenty of listings for various gains achieved with antennas
but I have not seen any similar listings for F/R and F/B.
Is there any around so I can see what can be or has been attained or
is blocking of rear signals of little consequence for todays hams. I can see
that being true
for when the band has just opened and propagation has not opened to the rear
or
with net operations so perhaps gain is every thing after all.
It is my opinion that if interest/efforts are increased first in deflecting
the rear action to the
front first and thereby INCREASING the front lobe width there will be more
opportunities
for increasing gains without the side lobes and narrow forward lobes that
accompany Yagi's.
as well as shorter booms. ( more deflectors/reflectors perhaps)
( no religeous, porno or genocide preaching please, fighting to see which is
best
could take place on boat anchor nets to see which has taken position of the
lowest level)
Regards
Art

It should also be mentioned that the front/back ratio is different at
various elevation angles. You won't get the free-space f/b ratio in
practice at most elevation angles. This is easily seen with modeling
software.

Good nulls also depend on a precise balance of strong fields, which all
have to be just right in order to add to zero. If any of the various
fields is just a little off, the null won't be what you expect -- it'll
be shallower and/or in a different direction. It takes only a small
difference to change the depth of a deep null by 20 dB or more. That
means you can't expect deep nulls to be exactly what a computer program
or other calculations predict, because there will inevitably be small
differences between the model and the real antenna. Or, for that matter,
from one antenna to the next one of the same type, even when built as
close to exactly the same as possible. You have the best chance of
achieving deep and repeatble nulls with the simplest antennas, like a
carefully built and balanced small loop. The larger the number of
elements, the larger the number of fields which all have to add together
to a value of zero, and the more opportunity there is for variation.

Roy Lewallen, W7EL

Bob Bob wrote:
Hi Art

In my experience (or maybe its just anecdotal) F/B ratios are very
frequency dependent for high dB numbers. You might for example get 28dB
F/B on 14.100 but it may drop to 15dB 100kHz away. The forward gain in
this case doesnt change much at all. How would you then advertise this
except by a graph?

Keep in mind also that F/B is expressed in a specific direction. 5-10
degrees off that and you will see the numbers fall off.

Max F/B rarely occurs at max forward gain...

Front to side is also good for attenuating signals you dont want.
(Assuming horiz polarisation)

If I was tackling this as a project I'd start defining some parameters
like 3dB beamwidth and the maximum unwanted lobe figures. Then plug it
into a modeling program (like 4nec2) I havent played much with modelling
but I assume that the optimising tools could do the trial and error
calcs for you. You are aiming for an antenna with moderate forward gain
but as low as possible radiation/reception in other directions..

In fact if you havent tried modelling it is well worth it just to see
the effect on the patterns.

You can also tune a (yagi/quad) reflector remotely if you want to peak
the F/B

Probably not what you were after sorry...

Cheers Bob VK2YQA (In Oz...)


wrote:

Regarding antenners, thats right,antennas.
Plenty of listings for various gains achieved with antennas
but I have not seen any similar listings for F/R and F/B.
Is there any around so I can see what can be or has been attained or
is blocking of rear signals of little consequence for todays hams. I
can see that being true
for when the band has just opened and propagation has not opened to
the rear or
with net operations so perhaps gain is every thing after all.
It is my opinion that if interest/efforts are increased first in
deflecting the rear action to the
front first and thereby INCREASING the front lobe width there will be
more opportunities
for increasing gains without the side lobes and narrow forward lobes
that accompany Yagi's.
as well as shorter booms. ( more deflectors/reflectors perhaps)
( no religeous, porno or genocide preaching please, fighting to see
which is best
could take place on boat anchor nets to see which has taken position
of the lowest level)
Regards
Art

Roy allow me to be a bit more directive regarding my pursuit.
I am trying to see what methods that can be used for maximum gain.
Having made many a long boom yagi 80 feet and 13 elements I have
come to the cinclusion that thinking must move away from Yagi's.
If one starts with a balloon squeezed in the center we get the figure 8
pattern.
I think we all can agree on that
My logic is that we must find a way to move all the volume at the rear to
the front thus increasing
the front diameter before we begin to massage it. The present thinking is
one sqeeze at the rear
is the best that one can do. It is here that I part company with the norm.
If we move all the volume to the front then talk of gain/boom length becomes
moot.
There are other points that I am not happy with regarding antennas in that
if we have reprocity
how is it that radio rays can arrive at angles as low as 3 degrees?
Deflection of radio waves jump right out at you
I model quite a bit but models tend to follow the input thinking so I
intentially put Yagis aside and mainly revolve around close coupling and
clustering of elements
but at the same time I am interested in what
aproaches have been made with the yagi in removing the rear volume as it
were.
I am aware that antennas have been studied to death over the years but it is
my belief
that all these studies started around yagi phillosophy which made them all
interdependent.
I believe I have arrived at a turning point in my quest and should know in a
few days
when the weather has cleared up.and I can get on the air for trials.
There we have it , no deviation from antennas just one hams thinking

who is loathe to follow others.
Regards
Art



"Roy Lewallen" wrote in message
...
It should also be mentioned that the front/back ratio is different at
snip

Art, all you need to do in order to convince me is to produce
quantitative evidence that supports your theories.

Roy Lewallen, W7EL

wrote:
Roy allow me to be a bit more directive regarding my pursuit.
I am trying to see what methods that can be used for maximum gain.
Having made many a long boom yagi 80 feet and 13 elements I have
come to the cinclusion that thinking must move away from Yagi's.
If one starts with a balloon squeezed in the center we get the figure 8
pattern.
I think we all can agree on that
My logic is that we must find a way to move all the volume at the rear to
the front thus increasing
the front diameter before we begin to massage it. The present thinking is
one sqeeze at the rear
is the best that one can do. It is here that I part company with the norm.
If we move all the volume to the front then talk of gain/boom length becomes
moot.
There are other points that I am not happy with regarding antennas in that
if we have reprocity
how is it that radio rays can arrive at angles as low as 3 degrees?
Deflection of radio waves jump right out at you
I model quite a bit but models tend to follow the input thinking so I
intentially put Yagis aside and mainly revolve around close coupling and
clustering of elements
but at the same time I am interested in what
aproaches have been made with the yagi in removing the rear volume as it
were.
I am aware that antennas have been studied to death over the years but it is
my belief
that all these studies started around yagi phillosophy which made them all
interdependent.
I believe I have arrived at a turning point in my quest and should know in a
few days
when the weather has cleared up.and I can get on the air for trials.
There we have it , no deviation from antennas just one hams thinking

who is loathe to follow others.
Regards
Art



"Roy Lewallen" wrote in message
...

It should also be mentioned that the front/back ratio is different at

snip

On Mon, 21 Feb 2005 17:10:00 GMT, "
wrote:

Roy allow me to be a bit more directive regarding my pursuit.
I am trying to see what methods that can be used for maximum gain.
Having made many a long boom yagi 80 feet and 13 elements I have
come to the cinclusion that thinking must move away from Yagi's.
If one starts with a balloon squeezed in the center we get the figure 8
pattern.
I think we all can agree on that
My logic is that we must find a way to move all the volume at the rear to
the front thus increasing
the front diameter before we begin to massage it. The present thinking is
one sqeeze at the rear
is the best that one can do. It is here that I part company with the norm.
If we move all the volume to the front then talk of gain/boom length becomes
moot.

This sounds like a place for the horn antenna similar to what we use
in microwave communications.

You have an interesting approach.

I am sure you have considered this, but how well do the multiple
reflectors work with the yagi? not so much those in line with the
elements as those that form a wall behind the driven element or the
first reflector.

Buck



--
73 for now
Buck
N4PGW

Understood and that is what I am trying to do but I do not want to go thru
the
same rigor remole that happened last time
where I could not open any minds to even start thinking of it
Regards
Art

"Roy Lewallen" wrote in message
...
Art, all you need to do in order to convince me is to produce quantitative
evidence that supports your theories.

Roy Lewallen, W7EL

wrote:
Roy allow me to be a bit more directive regarding my pursuit.
I am trying to see what methods that can be used for maximum gain.
Having made many a long boom yagi 80 feet and 13 elements I have
come to the cinclusion that thinking must move away from Yagi's.
If one starts with a balloon squeezed in the center we get the figure 8
pattern.
I think we all can agree on that
My logic is that we must find a way to move all the volume at the rear to
the front thus increasing
the front diameter before we begin to massage it. The present thinking is
one sqeeze at the rear
is the best that one can do. It is here that I part company with the
norm.
If we move all the volume to the front then talk of gain/boom length
becomes moot.
There are other points that I am not happy with regarding antennas in
that if we have reprocity
how is it that radio rays can arrive at angles as low as 3 degrees?
Deflection of radio waves jump right out at you
I model quite a bit but models tend to follow the input thinking so I
intentially put Yagis aside and mainly revolve around close coupling and
clustering of elements
but at the same time I am interested in what
aproaches have been made with the yagi in removing the rear volume as it
were.
I am aware that antennas have been studied to death over the years but it
is my belief
that all these studies started around yagi phillosophy which made them
all interdependent.
I believe I have arrived at a turning point in my quest and should know
in a few days
when the weather has cleared up.and I can get on the air for trials.
There we have it , no deviation from antennas just one hams thinking

who is loathe to follow others.
Regards
Art



"Roy Lewallen" wrote in message
...

It should also be mentioned that the front/back ratio is different at

snip

The idea of 'reflectors' is perhaps the wrong approach, I prefer the term
deflectors
as one sees when rays hit a knife edge. Also close coupling enables elements
to
be current heavy and others voltage heavy such that it would appear that a
element was doing nothing when in fact it is the link for more current
loaded elements
in cluster form. A wall that you suggest can indeed reflect and absorb radio
waves but a
wall is beyond my means thus resonance remains a important function of
change.
But then close coupling of elements together with the deflection aproach has
been
dissed many times over the years with me and always ends in derision of the
author
Time will tell but experimentation can be enjoyable especially when a trail
of past results
suggests that my rubicon is at hand and close to submission to RADCOM where
experimentation is still valued.

Heh, no politics here or religeon so all can join in without fear especially
those who are willing
to consider and pursue 'outside of the box' ideas that others distain., in
order to gain better
understanding
Regards
Art


"Buck" wrote in message
...
On Mon, 21 Feb 2005 17:10:00 GMT, "
wrote:

Roy allow me to be a bit more directive regarding my pursuit.
I am trying to see what methods that can be used for maximum gain.
Having made many a long boom yagi 80 feet and 13 elements I have
come to the cinclusion that thinking must move away from Yagi's.
If one starts with a balloon squeezed in the center we get the figure 8
pattern.
I think we all can agree on that
My logic is that we must find a way to move all the volume at the rear to
the front thus increasing
the front diameter before we begin to massage it. The present thinking is
one sqeeze at the rear
is the best that one can do. It is here that I part company with the norm.
If we move all the volume to the front then talk of gain/boom length
becomes
moot.

This sounds like a place for the horn antenna similar to what we use
in microwave communications.

You have an interesting approach.

I am sure you have considered this, but how well do the multiple
reflectors work with the yagi? not so much those in line with the
elements as those that form a wall behind the driven element or the
first reflector.



If you look at current flow in a corner reflector antenna you will note
that rear elements individually carry little current! Food for thought
Art




Buck



--
73 for now
Buck
N4PGW

" wrote in message
news5bSd.33636$tl3.9146@attbi_s02...
Regarding antenners, thats right,antennas.
Plenty of listings for various gains achieved with antennas
but I have not seen any similar listings for F/R and F/B.
Is there any around so I can see what can be or has been attained or
is blocking of rear signals of little consequence for todays hams. I can
see that being true
for when the band has just opened and propagation has not opened to the
rear or
with net operations so perhaps gain is every thing after all.
It is my opinion that if interest/efforts are increased first in
deflecting the rear action to the
front first and thereby INCREASING the front lobe width there will be more
opportunities
for increasing gains without the side lobes and narrow forward lobes that
accompany Yagi's.
as well as shorter booms. ( more deflectors/reflectors perhaps)
( no religeous, porno or genocide preaching please, fighting to see which
is best
could take place on boat anchor nets to see which has taken position of
the lowest level)
Regards
Art


Art

Excuse me if I misunderstand your post above. It reads to me that you
have an interest in building an antenna that minimizes "side lobes" to the
rear of the main beam.
In my experience with directional antennas I have not been able to
corelate minimum side lobes with maximum gain.
I'd suggest that the sidelobes will probably never be held lower than the
same level as the forward gain. That is a 20 db gain antenna will have
side lobes no lower than - 20 db with respect to the main lobe. Or, another
way to put it is; there will always be a side lobe that gets up to or above
isotropic level somewhere in the pattern.

I think I'm misreading your post because I read it to say that main lobe
could be increased in width while increasing the antenna sensitivity. That
doesnt make sense, so I guess I'm not understanding.

And, I submit that, with yagis, there is so little energy radiated in the
sidelobes of a 15 db gain Yagi antenna that *all* the sidelobe radiation
redirrected to be included in the main lobe wont add significantly to the
Practical Useability of the antenna. I write Practical Useability because
I want to distinguish that from scientific exploration of antenna gain,
which accounts for fractions of one db.

Jerry

"Jerry Martes" wrote in message
news:XJqSd.17298$uc.14470@trnddc01...



" wrote in
message news5bSd.33636$tl3.9146@attbi_s02...
Regarding antenners, thats right,antennas.
Plenty of listings for various gains achieved with antennas
but I have not seen any similar listings for F/R and F/B.
Is there any around so I can see what can be or has been attained or
is blocking of rear signals of little consequence for todays hams. I can
see that being true
for when the band has just opened and propagation has not opened to the
rear or
with net operations so perhaps gain is every thing after all.
It is my opinion that if interest/efforts are increased first in
deflecting the rear action to the
front first and thereby INCREASING the front lobe width there will be
more opportunities
for increasing gains without the side lobes and narrow forward lobes that
accompany Yagi's.
as well as shorter booms. ( more deflectors/reflectors perhaps)
( no religeous, porno or genocide preaching please, fighting to see which
is best
could take place on boat anchor nets to see which has taken position of
the lowest level)
Regards
Art


Art

Excuse me if I misunderstand your post above. It reads to me that you
have an interest in building an antenna that minimizes "side lobes" to the
rear of the main beam.

Correct..minimise or remove
..
In my experience with directional antennas I have not been able to
corelate minimum side lobes with maximum gain.

Oh I fully agree with that observation and that is another part of my
thinking
as it should never be so UNLESS you are captive to Yagi thinking.

I'd suggest that the sidelobes will probably never be held lower than the
same level as the forward gain. That is a 20 db gain antenna will have
side lobes no lower than - 20 db with respect to the main lobe.


20 db gain would not be rotatable at HF which represents a huge drawback,
better to stay with a rombic thinking and cancel the energy complely to the
rear of the
feed point.

Again that is true if you are captive to the Yagi
Make no mistake the Yagi is as about as simple a thing to make that works
well,
it is doubtfull with respect to simplicity it can be beat.

Or, another
way to put it is; there will always be a side lobe that gets up to or
above isotropic level somewhere in the pattern.

Then think what actualy generates a lobe whether directional(frontal)
or at the rear.



I think I'm misreading your post because I read it to say that main lobe
could be increased in width while increasing the antenna sensitivity.
That doesnt make sense, so I guess I'm not understanding.

Yes you misunderstood. Bank to the ballon if all the volume to the rear
of the figure 8 ahat the new diameternd placed in the front of the feed
point it is obvious will be wider and with more gain and if I might adde NO
sidelob.
You have to return to basics to understand that it is energy to the rear
that
generates side lobes at the rear.


And, I submit that, with yagis, there is so little energy radiated in the
sidelobes of a 15 db gain Yagi antenna that *all* the sidelobe radiation
redirrected to be included in the main lobe wont add significantly to the
Practical Useability of the antenna. I write Practical Useability
because I want to distinguish that from scientific exploration of antenna
gain, which accounts for fractions of one db.

Well that is the essence of my disagreement with the masses which I admit
I have not yet released my findings. Think about it, I could have a single
directive lobe
that has twice the energy of a standard dipole in unidirectional form
and with a broader lobe.and I have yet to discuss yagi type manipulations
that
narrow the lobe ,which can be unhelpful, and start from a new datum line if
one
wants to determine gain per unit length type thinking that goes with
Yagi,s.
..Maybe some experts can add some view points, after all it is a general
discussion group on antennas where many believe all is already known
and in a book....... grin
Regards
Art ........KB9MZ

Jerry