"christofire" wrote in message
...
"Jerry" wrote in message
...

"Harry H" wrote in message
...

The Lindenblad has an overhead null that you might find anoying for
some high elevation passes of LEOs.
Are you open to trying to build a DCA (which is an antenna that I
developed)? I make the claim that there is no other hemispheric
coverage antenna design that performs better than a DCA. But, I sure
am open to being corrected.
The Feb 2008 QST contains an article on the DCA antenna design
concept.
It is my claim that a DCA is extreemely forgiving of construction
errors and uses 4 wire dipoles and 50 ohm coax with 5 RFI type ferrites
as "baluns'.

Jerry KD6JDJ
Given the fact I don't subscribe to QST, domicile Australia, would you
have a copy of the article?

HH


Hi HH

It would be my pleasure to disclose any/all the information I have
relating to the DCA antenna design concept. It is simple. It is two
pairs of crossed dipoles. Each pair is spaced 1/4 wave apart and fed in
phase. One pair is physically mounted 90 degrees from the other pair. All
four dipoles are tilted 30 degtrees from vertical. One pair is fed 90
degrees later than the other pair.
The concept is so simple and straightfoeward that it is probable that
the concept has been developed before I thought of it. But, I have been
unable to find anything published related to this simple "Double Cross
Antenna"
I told my *Internet buddy*, Patrik Tast, in Finland about the concept
and he found it to be exactly what he needed for reception of NOAA
weather satellite signals. Patrik publishes alot of what I send him
related to the antenna. Patrik shows a section of his web page to
describe the DCA to anyone interested. You can find the QST article in
the section Patrik identifies as ANTENNAS on the first page of his site
http://www.poes-weather.com/index.php.

If you have any questions about the DCA concept you are free to E-mail
me, anytime. Or, if you have any facts or data to show where I am wrong
about how well this antenna performs, or know of something that performs
better, please set me straight.

Jerry KD6JDJ


... but surely this is the same as a Lindenblad array? The tilt of the
dipoles was always a parameter in the Lindenblad, so I wonder how your DCA
differs from what N. E. Lindenblad described in the April 1941 edition of
'Communications'.

Chris


Hi Chris

Several, well educated, antenna experts insist that the DCA is actually a
Lindenblad. If you thought the DCA is a Lindenblad, you are not alone.
The DCA is not a Lindenblad. The array of four dipoles in a Lindenblad
are fed to produce an overhead null. The four dipoles in a DCA are fed to
produce no overhead null. The DCA is a hemispheric coverage CP antenna.
The Lindenblad is not.
Let me know if you have reason to consider the DCA to be the same as a
Lindenblad. I knew nothing about Lindenblad until after recognizing the
DCA concept.

Jerry m KD6JDJ

Jerry

"Jerry" wrote in message
...

"christofire" wrote in message
...
"Jerry" wrote in message
...

"Harry H" wrote in message
...

The Lindenblad has an overhead null that you might find anoying for
some high elevation passes of LEOs.
Are you open to trying to build a DCA (which is an antenna that I
developed)? I make the claim that there is no other hemispheric
coverage antenna design that performs better than a DCA. But, I sure
am open to being corrected.
The Feb 2008 QST contains an article on the DCA antenna design
concept.
It is my claim that a DCA is extreemely forgiving of construction
errors and uses 4 wire dipoles and 50 ohm coax with 5 RFI type
ferrites as "baluns'.

Jerry KD6JDJ
Given the fact I don't subscribe to QST, domicile Australia, would you
have a copy of the article?

HH


Hi HH

It would be my pleasure to disclose any/all the information I have
relating to the DCA antenna design concept. It is simple. It is two
pairs of crossed dipoles. Each pair is spaced 1/4 wave apart and fed
in phase. One pair is physically mounted 90 degrees from the other pair.
All four dipoles are tilted 30 degtrees from vertical. One pair is fed
90 degrees later than the other pair.
The concept is so simple and straightfoeward that it is probable that
the concept has been developed before I thought of it. But, I have
been unable to find anything published related to this simple "Double
Cross Antenna"
I told my *Internet buddy*, Patrik Tast, in Finland about the concept
and he found it to be exactly what he needed for reception of NOAA
weather satellite signals. Patrik publishes alot of what I send him
related to the antenna. Patrik shows a section of his web page to
describe the DCA to anyone interested. You can find the QST article in
the section Patrik identifies as ANTENNAS on the first page of his site
http://www.poes-weather.com/index.php.

If you have any questions about the DCA concept you are free to E-mail
me, anytime. Or, if you have any facts or data to show where I am
wrong about how well this antenna performs, or know of something that
performs better, please set me straight.

Jerry KD6JDJ


... but surely this is the same as a Lindenblad array? The tilt of the
dipoles was always a parameter in the Lindenblad, so I wonder how your
DCA differs from what N. E. Lindenblad described in the April 1941
edition of 'Communications'.

Chris


Hi Chris

Several, well educated, antenna experts insist that the DCA is actually a
Lindenblad. If you thought the DCA is a Lindenblad, you are not alone.
The DCA is not a Lindenblad. The array of four dipoles in a Lindenblad
are fed to produce an overhead null. The four dipoles in a DCA are fed
to produce no overhead null. The DCA is a hemispheric coverage CP
antenna. The Lindenblad is not.
Let me know if you have reason to consider the DCA to be the same as a
Lindenblad. I knew nothing about Lindenblad until after recognizing the
DCA concept.

Jerry m KD6JDJ

Jerry


Perhaps it's a rather fine distinction to say an antenna that has the same
physical form as the Lindenblad array is something different because the
elements are driven differently. The original version that he patented
didn't have rod elements at all (see, for example,
http://www.coe.montana.edu/ee/rwolff...B_antennas.pdf )
but it was the configuration of four slanted dipoles around a central pole
that appears to have borne his name since 1941. Henry Jasik's 'Antenna
Engineering Handbook' (now by John L. Volakis, Richard C. Johnson and Henry
Jasik, Chapter 29, Page 34) refers to the configuration as a Lindenblad
array, without being specific about the way the dipoles are driven.
However, applying new names to antennas that exploit well known
configurations seems fairly commonplace in the professional field,
particularly in broadcasting.

Of course you can name your antenna as you please, but there might be some
value in mentioning that it is a development of the Lindenblad array - you'd
certainly need to demonstrate awareness of, and distinction from, the prior
art if you were to seek a patent.

Chris

"christofire" wrote in message
...

"Jerry" wrote in message
...

"christofire" wrote in message
...
"Jerry" wrote in message
...

"Harry H" wrote in message
...

The Lindenblad has an overhead null that you might find anoying for
some high elevation passes of LEOs.
Are you open to trying to build a DCA (which is an antenna that I
developed)? I make the claim that there is no other hemispheric
coverage antenna design that performs better than a DCA. But, I
sure am open to being corrected.
The Feb 2008 QST contains an article on the DCA antenna design
concept.
It is my claim that a DCA is extreemely forgiving of construction
errors and uses 4 wire dipoles and 50 ohm coax with 5 RFI type
ferrites as "baluns'.

Jerry KD6JDJ
Given the fact I don't subscribe to QST, domicile Australia, would you
have a copy of the article?

HH


Hi HH

It would be my pleasure to disclose any/all the information I have
relating to the DCA antenna design concept. It is simple. It is two
pairs of crossed dipoles. Each pair is spaced 1/4 wave apart and fed
in phase. One pair is physically mounted 90 degrees from the other
pair. All four dipoles are tilted 30 degtrees from vertical. One pair
is fed 90 degrees later than the other pair.
The concept is so simple and straightfoeward that it is probable that
the concept has been developed before I thought of it. But, I have
been unable to find anything published related to this simple "Double
Cross Antenna"
I told my *Internet buddy*, Patrik Tast, in Finland about the concept
and he found it to be exactly what he needed for reception of NOAA
weather satellite signals. Patrik publishes alot of what I send him
related to the antenna. Patrik shows a section of his web page to
describe the DCA to anyone interested. You can find the QST article
in the section Patrik identifies as ANTENNAS on the first page of his
site http://www.poes-weather.com/index.php.

If you have any questions about the DCA concept you are free to E-mail
me, anytime. Or, if you have any facts or data to show where I am
wrong about how well this antenna performs, or know of something that
performs better, please set me straight.

Jerry KD6JDJ


... but surely this is the same as a Lindenblad array? The tilt of the
dipoles was always a parameter in the Lindenblad, so I wonder how your
DCA differs from what N. E. Lindenblad described in the April 1941
edition of 'Communications'.

Chris


Hi Chris

Several, well educated, antenna experts insist that the DCA is actually
a Lindenblad. If you thought the DCA is a Lindenblad, you are not
alone.
The DCA is not a Lindenblad. The array of four dipoles in a Lindenblad
are fed to produce an overhead null. The four dipoles in a DCA are fed
to produce no overhead null. The DCA is a hemispheric coverage CP
antenna. The Lindenblad is not.
Let me know if you have reason to consider the DCA to be the same as a
Lindenblad. I knew nothing about Lindenblad until after recognizing the
DCA concept.

Jerry m KD6JDJ

Jerry


Perhaps it's a rather fine distinction to say an antenna that has the same
physical form as the Lindenblad array is something different because the
elements are driven differently. The original version that he patented
didn't have rod elements at all (see, for example,
http://www.coe.montana.edu/ee/rwolff...B_antennas.pdf
) but it was the configuration of four slanted dipoles around a central
pole that appears to have borne his name since 1941. Henry Jasik's
'Antenna Engineering Handbook' (now by John L. Volakis, Richard C. Johnson
and Henry Jasik, Chapter 29, Page 34) refers to the configuration as a
Lindenblad array, without being specific about the way the dipoles are
driven. However, applying new names to antennas that exploit well known
configurations seems fairly commonplace in the professional field,
particularly in broadcasting.

Of course you can name your antenna as you please, but there might be some
value in mentioning that it is a development of the Lindenblad array -
you'd certainly need to demonstrate awareness of, and distinction from,
the prior art if you were to seek a patent.

Chris


Hi Chris

I wonder if you have any pictures of a Lindenblad and any radiation plots.
I also wonder if an end fire antenna is the same as a broadside antenna when
they look the same from a distance.

Jerry KD6JDJ

"Jerry" wrote in message
...

"christofire" wrote in message
...

"Jerry" wrote in message
...

"christofire" wrote in message
...
"Jerry" wrote in message
...

"Harry H" wrote in message
...

The Lindenblad has an overhead null that you might find anoying for
some high elevation passes of LEOs.
Are you open to trying to build a DCA (which is an antenna that I
developed)? I make the claim that there is no other hemispheric
coverage antenna design that performs better than a DCA. But, I
sure am open to being corrected.
The Feb 2008 QST contains an article on the DCA antenna design
concept.
It is my claim that a DCA is extreemely forgiving of construction
errors and uses 4 wire dipoles and 50 ohm coax with 5 RFI type
ferrites as "baluns'.

Jerry KD6JDJ
Given the fact I don't subscribe to QST, domicile Australia, would
you have a copy of the article?

HH


Hi HH

It would be my pleasure to disclose any/all the information I have
relating to the DCA antenna design concept. It is simple. It is two
pairs of crossed dipoles. Each pair is spaced 1/4 wave apart and fed
in phase. One pair is physically mounted 90 degrees from the other
pair. All four dipoles are tilted 30 degtrees from vertical. One
pair is fed 90 degrees later than the other pair.
The concept is so simple and straightfoeward that it is probable that
the concept has been developed before I thought of it. But, I have
been unable to find anything published related to this simple "Double
Cross Antenna"
I told my *Internet buddy*, Patrik Tast, in Finland about the concept
and he found it to be exactly what he needed for reception of NOAA
weather satellite signals. Patrik publishes alot of what I send him
related to the antenna. Patrik shows a section of his web page to
describe the DCA to anyone interested. You can find the QST article
in the section Patrik identifies as ANTENNAS on the first page of his
site http://www.poes-weather.com/index.php.

If you have any questions about the DCA concept you are free to
E-mail me, anytime. Or, if you have any facts or data to show where
I am wrong about how well this antenna performs, or know of something
that performs better, please set me straight.

Jerry KD6JDJ


... but surely this is the same as a Lindenblad array? The tilt of the
dipoles was always a parameter in the Lindenblad, so I wonder how your
DCA differs from what N. E. Lindenblad described in the April 1941
edition of 'Communications'.

Chris


Hi Chris

Several, well educated, antenna experts insist that the DCA is actually
a Lindenblad. If you thought the DCA is a Lindenblad, you are not
alone.
The DCA is not a Lindenblad. The array of four dipoles in a
Lindenblad are fed to produce an overhead null. The four dipoles in a
DCA are fed to produce no overhead null. The DCA is a hemispheric
coverage CP antenna. The Lindenblad is not.
Let me know if you have reason to consider the DCA to be the same as a
Lindenblad. I knew nothing about Lindenblad until after recognizing
the DCA concept.

Jerry m KD6JDJ

Jerry


Perhaps it's a rather fine distinction to say an antenna that has the
same physical form as the Lindenblad array is something different because
the elements are driven differently. The original version that he
patented didn't have rod elements at all (see, for example,
http://www.coe.montana.edu/ee/rwolff...B_antennas.pdf
) but it was the configuration of four slanted dipoles around a central
pole that appears to have borne his name since 1941. Henry Jasik's
'Antenna Engineering Handbook' (now by John L. Volakis, Richard C.
Johnson and Henry Jasik, Chapter 29, Page 34) refers to the configuration
as a Lindenblad array, without being specific about the way the dipoles
are driven. However, applying new names to antennas that exploit well
known configurations seems fairly commonplace in the professional field,
particularly in broadcasting.

Of course you can name your antenna as you please, but there might be
some value in mentioning that it is a development of the Lindenblad
array - you'd certainly need to demonstrate awareness of, and distinction
from, the prior art if you were to seek a patent.

Chris


Hi Chris

I wonder if you have any pictures of a Lindenblad and any radiation
plots. I also wonder if an end fire antenna is the same as a broadside
antenna when they look the same from a distance.

Jerry KD6JDJ


You could take a look at www.bbc.co.uk/rd/pubs/reports/1991-15.pdf which on
pages 9 and 10 has some details of a Lindenblad for 2.5 GHz, with patterns,
that was made from semi-rigid coax and brass tube. The aim in that work was
to achieve the best possible axial ratio in order to reject first-order
reflections from the ground and nearby objects. If I remember correctly,
phase rotation was tried but there really weren't enough variables to get
the axial ratio good enough over the whole sphere, so the dipoles were
driven in phase and the hole in the vertical radiation pattern at the bottom
was 'embraced' as a good thing! In this application, if good axial ratio
couldn't be achieved somewhere it was probably better to avoid radiating in
that direction.

Another Lindenblad, but also arrayed vertically in four tiers, was used at
High Hunsley transmitting station for FM radio. The older photos at
http://tx.mb21.co.uk/gallery/high-hunsley.php show it (at the top of the
structure) but they are rather distant. The modern replacements are
basically crossed dipoles in front of reflectors. A significant challenge
in the design of these (big) things is to get the horizontal radiation
pattern to hand over cleanly from one element to the next around the
structure, without lobes or nulls in either the vertical or horizontal
component. In UK Band II broadcasting, the polarisation is usually said to
be 'mixed' rather than intentionally circular. The Alan Dick company
http://www.alandick.com/broadcast_an...roduct_004.htm still offers a
Lindenblad array for Band II. Their 'FMAC' looks interesting!

As to your question, I'm not certain what you mean so perhaps you could
amplify a bit. Certainly if the paths of currents, their relative
amplitudes and their relative phases in time, appear the same from different
directions then the polarisation should be the same in those directions. A
short helix can operate as a broadside and end-fire antenna at the same time
and I know the quadrifilar helix is a popular option for small L-Band
satellite terminals. However, that radio-camera application imposed
stringent demands for axial ratio and, obviously, the requirements for
satisfactory reception of CP signals from satellites can be less demanding
when CP is used simply to avoid loss on account of mismatched linear
polarisations - when the other sense of CP isn't in use at the same
frequency by the same satellite.

Chris

"christofire" wrote in message
...

"Jerry" wrote in message
...

"christofire" wrote in message
...

"Jerry" wrote in message
...

"christofire" wrote in message
...
"Jerry" wrote in message
...

"Harry H" wrote in message
...

The Lindenblad has an overhead null that you might find anoying
for some high elevation passes of LEOs.
Are you open to trying to build a DCA (which is an antenna that I
developed)? I make the claim that there is no other hemispheric
coverage antenna design that performs better than a DCA. But, I
sure am open to being corrected.
The Feb 2008 QST contains an article on the DCA antenna design
concept.
It is my claim that a DCA is extreemely forgiving of construction
errors and uses 4 wire dipoles and 50 ohm coax with 5 RFI type
ferrites as "baluns'.

Jerry KD6JDJ
Given the fact I don't subscribe to QST, domicile Australia, would
you have a copy of the article?

HH


Hi HH

It would be my pleasure to disclose any/all the information I have
relating to the DCA antenna design concept. It is simple. It is
two pairs of crossed dipoles. Each pair is spaced 1/4 wave apart
and fed in phase. One pair is physically mounted 90 degrees from the
other pair. All four dipoles are tilted 30 degtrees from vertical.
One pair is fed 90 degrees later than the other pair.
The concept is so simple and straightfoeward that it is probable
that the concept has been developed before I thought of it. But, I
have been unable to find anything published related to this simple
"Double Cross Antenna"
I told my *Internet buddy*, Patrik Tast, in Finland about the
concept and he found it to be exactly what he needed for reception of
NOAA weather satellite signals. Patrik publishes alot of what I
send him related to the antenna. Patrik shows a section of his web
page to describe the DCA to anyone interested. You can find the QST
article in the section Patrik identifies as ANTENNAS on the first
page of his site http://www.poes-weather.com/index.php.

If you have any questions about the DCA concept you are free to
E-mail me, anytime. Or, if you have any facts or data to show where
I am wrong about how well this antenna performs, or know of
something that performs better, please set me straight.

Jerry KD6JDJ


... but surely this is the same as a Lindenblad array? The tilt of
the dipoles was always a parameter in the Lindenblad, so I wonder how
your DCA differs from what N. E. Lindenblad described in the April
1941 edition of 'Communications'.

Chris


Hi Chris

Several, well educated, antenna experts insist that the DCA is
actually a Lindenblad. If you thought the DCA is a Lindenblad, you
are not alone.
The DCA is not a Lindenblad. The array of four dipoles in a
Lindenblad are fed to produce an overhead null. The four dipoles in a
DCA are fed to produce no overhead null. The DCA is a hemispheric
coverage CP antenna. The Lindenblad is not.
Let me know if you have reason to consider the DCA to be the same as a
Lindenblad. I knew nothing about Lindenblad until after recognizing
the DCA concept.

Jerry m KD6JDJ

Jerry


Perhaps it's a rather fine distinction to say an antenna that has the
same physical form as the Lindenblad array is something different
because the elements are driven differently. The original version that
he patented didn't have rod elements at all (see, for example,
http://www.coe.montana.edu/ee/rwolff...B_antennas.pdf
) but it was the configuration of four slanted dipoles around a central
pole that appears to have borne his name since 1941. Henry Jasik's
'Antenna Engineering Handbook' (now by John L. Volakis, Richard C.
Johnson and Henry Jasik, Chapter 29, Page 34) refers to the
configuration as a Lindenblad array, without being specific about the
way the dipoles are driven. However, applying new names to antennas that
exploit well known configurations seems fairly commonplace in the
professional field, particularly in broadcasting.

Of course you can name your antenna as you please, but there might be
some value in mentioning that it is a development of the Lindenblad
array - you'd certainly need to demonstrate awareness of, and
distinction from, the prior art if you were to seek a patent.

Chris


Hi Chris

I wonder if you have any pictures of a Lindenblad and any radiation
plots. I also wonder if an end fire antenna is the same as a broadside
antenna when they look the same from a distance.

Jerry KD6JDJ


You could take a look at www.bbc.co.uk/rd/pubs/reports/1991-15.pdf which
on pages 9 and 10 has some details of a Lindenblad for 2.5 GHz, with
patterns, that was made from semi-rigid coax and brass tube. The aim in
that work was to achieve the best possible axial ratio in order to reject
first-order reflections from the ground and nearby objects. If I remember
correctly, phase rotation was tried but there really weren't enough
variables to get the axial ratio good enough over the whole sphere, so the
dipoles were driven in phase and the hole in the vertical radiation
pattern at the bottom was 'embraced' as a good thing! In this
application, if good axial ratio couldn't be achieved somewhere it was
probably better to avoid radiating in that direction.

Another Lindenblad, but also arrayed vertically in four tiers, was used at
High Hunsley transmitting station for FM radio. The older photos at
http://tx.mb21.co.uk/gallery/high-hunsley.php show it (at the top of the
structure) but they are rather distant. The modern replacements are
basically crossed dipoles in front of reflectors. A significant challenge
in the design of these (big) things is to get the horizontal radiation
pattern to hand over cleanly from one element to the next around the
structure, without lobes or nulls in either the vertical or horizontal
component. In UK Band II broadcasting, the polarisation is usually said
to be 'mixed' rather than intentionally circular. The Alan Dick company
http://www.alandick.com/broadcast_an...roduct_004.htm still offers a
Lindenblad array for Band II. Their 'FMAC' looks interesting!

As to your question, I'm not certain what you mean so perhaps you could
amplify a bit. Certainly if the paths of currents, their relative
amplitudes and their relative phases in time, appear the same from
different directions then the polarisation should be the same in those
directions. A short helix can operate as a broadside and end-fire antenna
at the same time and I know the quadrifilar helix is a popular option for
small L-Band satellite terminals. However, that radio-camera application
imposed stringent demands for axial ratio and, obviously, the requirements
for satisfactory reception of CP signals from satellites can be less
demanding when CP is used simply to avoid loss on account of mismatched
linear polarisations - when the other sense of CP isn't in use at the same
frequency by the same satellite.

Chris


Hi Chris

The Lindenblad antenna is fed to produce a null toward zenith. The
Lindenblad antenna as defined by Brown and Woodward in the mid 1940s for TV
transmission, has an omniazimuth radiation pattern.
The DCA has no zenith null.

If you consider an antenna with an overhead null to be the same as an
antenna with no null to be the same, I have no expectation that you and I
will agree.

The DCA offers little advantage over a Quad Helix when radiation pattern
is considered.
The DCA is slightly more sensitive toward the horizon than the Quad Helix.
..
The bandwidth of a DCA is far wider than a Quad helix.
The DCA is very insensitive to dimensional errors when built by an
amateur. The Quad Helix is extreemely demanding of prescission of
construction.

The original subject of this thread was related to building an antenna for
reception of Low Earth Orbiting satellites. I figured the OP could
appreciate knowing that a DCA will perform better than a Lindenblad and
needs no series matching transformors.

Jerry KD6JDJ

Jerry wrote:

Hi Chris

The Lindenblad antenna is fed to produce a null toward zenith. The
Lindenblad antenna as defined by Brown and Woodward in the mid 1940s for TV
transmission, has an omniazimuth radiation pattern.
The DCA has no zenith null.

If you consider an antenna with an overhead null to be the same as an
antenna with no null to be the same, I have no expectation that you and I
will agree.

The DCA offers little advantage over a Quad Helix when radiation pattern
is considered.
The DCA is slightly more sensitive toward the horizon than the Quad Helix.
.
The bandwidth of a DCA is far wider than a Quad helix.
The DCA is very insensitive to dimensional errors when built by an
amateur. The Quad Helix is extreemely demanding of prescission of
construction.

The original subject of this thread was related to building an antenna for
reception of Low Earth Orbiting satellites. I figured the OP could
appreciate knowing that a DCA will perform better than a Lindenblad and
needs no series matching transformors.

Jerry KD6JDJ



Just how good does this antenna have to be. It's not like it's being
used as a probe to measure randomly polarized signals, where AR=1 is
really important.

Quad helix antennas have a reputation for being demanding, but that's
where the performance requirements are demanding. Considering that quad
helix antennas are made by the millions for GPS and by the thousands for
WxSat use on boats, they aren't all that picky, because conventional
mass production tolerances are "good enough".

Relax the performance requirements and the helix is no more or less
difficult than a turnstile or Lindenblad or CP patch. Before the advent
of modern modeling tools, *designing* a quad helix was a huge chore,
especially if you didn't want to use a quad hybrid in the feed network,
but wanted to do the "one a bit long, one a bit short" to get the 90
degrees.

But, returning to the original question, why not a turnstile (crossed
dipoles fed 90 degrees out of phase)? For LEO satellites, you don't
really want a hemispherical pattern anyway. You want something with more
gain at the horizon where the slant range is much greater (thousands of
km) than at zenith (where the range is hundreds of km).

And, for that matter CP is probably not worth worrying about. The loss
from a perfect CP to a perfect linear is 3dB. If you're in a situation
where 3dB is going to kill you, you've got other problems to worry about.

Where CP is really, really nice is when you want to kill multipath from
close by reflectors. Or in deep space applications, where you don't
know the linear orientation of the transmitter/receiver (and you also
ARE worried about eke'ing out the last tenth or hundredth of a dB of
performance)


Jim, w6rmk

"Jim Lux" wrote in message
...
Jerry wrote:

Hi Chris

The Lindenblad antenna is fed to produce a null toward zenith. The
Lindenblad antenna as defined by Brown and Woodward in the mid 1940s for
TV transmission, has an omniazimuth radiation pattern.
The DCA has no zenith null.

If you consider an antenna with an overhead null to be the same as an
antenna with no null to be the same, I have no expectation that you and I
will agree.

The DCA offers little advantage over a Quad Helix when radiation
pattern is considered.
The DCA is slightly more sensitive toward the horizon than the Quad
Helix. .
The bandwidth of a DCA is far wider than a Quad helix.
The DCA is very insensitive to dimensional errors when built by an
amateur. The Quad Helix is extreemely demanding of prescission of
construction.

The original subject of this thread was related to building an antenna
for reception of Low Earth Orbiting satellites. I figured the OP could
appreciate knowing that a DCA will perform better than a Lindenblad and
needs no series matching transformors.

Jerry KD6JDJ

Just how good does this antenna have to be. It's not like it's being used
as a probe to measure randomly polarized signals, where AR=1 is really
important.

Quad helix antennas have a reputation for being demanding, but that's
where the performance requirements are demanding. Considering that quad
helix antennas are made by the millions for GPS and by the thousands for
WxSat use on boats, they aren't all that picky, because conventional mass
production tolerances are "good enough".

Relax the performance requirements and the helix is no more or less
difficult than a turnstile or Lindenblad or CP patch. Before the advent
of modern modeling tools, *designing* a quad helix was a huge chore,
especially if you didn't want to use a quad hybrid in the feed network,
but wanted to do the "one a bit long, one a bit short" to get the 90
degrees.

But, returning to the original question, why not a turnstile (crossed
dipoles fed 90 degrees out of phase)? For LEO satellites, you don't
really want a hemispherical pattern anyway. You want something with more
gain at the horizon where the slant range is much greater (thousands of
km) than at zenith (where the range is hundreds of km).

And, for that matter CP is probably not worth worrying about. The loss
from a perfect CP to a perfect linear is 3dB. If you're in a situation
where 3dB is going to kill you, you've got other problems to worry about.

Where CP is really, really nice is when you want to kill multipath from
close by reflectors. Or in deep space applications, where you don't know
the linear orientation of the transmitter/receiver (and you also ARE
worried about eke'ing out the last tenth or hundredth of a dB of
performance)


Jim, w6rmk


Hi Jim

It isnt clear to me that you read Howard Kowall's original post. He
intends to build his own antenna to communicate with low earth orbiting
satellites. I have information that will allow Howard to design and build
his own antenna that performs better than the design he chose (Lindenblad).
Do you disagree that a DCA will perform better than a Lindenblad?

I have read many of your post and recognize that you are a smart guy with
lots of information about antennas. Thats why I wonder why you'd write
something as stupid as " And, for that matter CP is probably not worth
worrying about". You know that 3dB *is* normally something to try to
achieve while building an antenna. The reason you write that the circular
polarization is minimally significant seems to be that you are attempting to
minimize the value of the DCA. I wonder if you have any facts or data,
measured or calculated, to demonstrate that you know of any antenna that
performs better than a DCA for ground based reception from LEOs

I agree with you that a Turnstile is a good antenna for LEO satellite
communication from Earth. But, I also claim that a DCA will perform better
than a Turnstile. Do you disagree?

Can you tell me more about why you wrote "For LEO satellites, you don't
really want a hemispherical pattern anyway. You want something with more
gain at the horizon where the slant range is much greater (thousands of
km) than at zenith (where the range is hundreds of km). That is precisely
what I tried to address in the QST article. That is precisely why the
DCA performs better than all others. Besides, the DCA is relatively easy
to build , unlike the Quad helix.

Again, do you know of any antenna design that performs better than a DCA
for communication with LEOs from earth and doesnt require pointing?

Jerry KD6JDJ

On Tue, 10 Feb 2009 18:12:26 -0000, "christofire"
wrote:


"Jerry" wrote in message
...

"christofire" wrote in message
...
"Jerry" wrote in message
...

"Harry H" wrote in message
...

The Lindenblad has an overhead null that you might find anoying for
some high elevation passes of LEOs.
Are you open to trying to build a DCA (which is an antenna that I
developed)? I make the claim that there is no other hemispheric
coverage antenna design that performs better than a DCA. But, I sure
am open to being corrected.
The Feb 2008 QST contains an article on the DCA antenna design
concept.
It is my claim that a DCA is extreemely forgiving of construction
errors and uses 4 wire dipoles and 50 ohm coax with 5 RFI type
ferrites as "baluns'.

Jerry KD6JDJ
Given the fact I don't subscribe to QST, domicile Australia, would you
have a copy of the article?

HH


Hi HH

It would be my pleasure to disclose any/all the information I have
relating to the DCA antenna design concept. It is simple. It is two
pairs of crossed dipoles. Each pair is spaced 1/4 wave apart and fed
in phase. One pair is physically mounted 90 degrees from the other pair.
All four dipoles are tilted 30 degtrees from vertical. One pair is fed
90 degrees later than the other pair.
The concept is so simple and straightfoeward that it is probable that
the concept has been developed before I thought of it. But, I have
been unable to find anything published related to this simple "Double
Cross Antenna"
I told my *Internet buddy*, Patrik Tast, in Finland about the concept
and he found it to be exactly what he needed for reception of NOAA
weather satellite signals. Patrik publishes alot of what I send him
related to the antenna. Patrik shows a section of his web page to
describe the DCA to anyone interested. You can find the QST article in
the section Patrik identifies as ANTENNAS on the first page of his site
http://www.poes-weather.com/index.php.

If you have any questions about the DCA concept you are free to E-mail
me, anytime. Or, if you have any facts or data to show where I am
wrong about how well this antenna performs, or know of something that
performs better, please set me straight.

Jerry KD6JDJ


... but surely this is the same as a Lindenblad array? The tilt of the
dipoles was always a parameter in the Lindenblad, so I wonder how your
DCA differs from what N. E. Lindenblad described in the April 1941
edition of 'Communications'.

Chris


Hi Chris

Several, well educated, antenna experts insist that the DCA is actually a
Lindenblad. If you thought the DCA is a Lindenblad, you are not alone.
The DCA is not a Lindenblad. The array of four dipoles in a Lindenblad
are fed to produce an overhead null. The four dipoles in a DCA are fed
to produce no overhead null. The DCA is a hemispheric coverage CP
antenna. The Lindenblad is not.
Let me know if you have reason to consider the DCA to be the same as a
Lindenblad. I knew nothing about Lindenblad until after recognizing the
DCA concept.

Jerry m KD6JDJ

Jerry


Perhaps it's a rather fine distinction to say an antenna that has the same
physical form as the Lindenblad array is something different because the
elements are driven differently. The original version that he patented
didn't have rod elements at all (see, for example,
http://www.coe.montana.edu/ee/rwolff...B_antennas.pdf )
but it was the configuration of four slanted dipoles around a central pole
that appears to have borne his name since 1941. Henry Jasik's 'Antenna
Engineering Handbook' (now by John L. Volakis, Richard C. Johnson and Henry
Jasik, Chapter 29, Page 34) refers to the configuration as a Lindenblad
array, without being specific about the way the dipoles are driven.
However, applying new names to antennas that exploit well known
configurations seems fairly commonplace in the professional field,
particularly in broadcasting.

Of course you can name your antenna as you please, but there might be some
value in mentioning that it is a development of the Lindenblad array - you'd
certainly need to demonstrate awareness of, and distinction from, the prior
art if you were to seek a patent.

Chris

Interesting article, it describes the Lindenblat array as a quartet of
coaxial horns. Not the same as a quartet of dipoles at all.

"JosephKK" wrote in message
...
On Tue, 10 Feb 2009 18:12:26 -0000, "christofire"
wrote:


"Jerry" wrote in message
...

"christofire" wrote in message
...
"Jerry" wrote in message
...

"Harry H" wrote in message
...

The Lindenblad has an overhead null that you might find anoying for
some high elevation passes of LEOs.
Are you open to trying to build a DCA (which is an antenna that I
developed)? I make the claim that there is no other hemispheric
coverage antenna design that performs better than a DCA. But, I
sure
am open to being corrected.
The Feb 2008 QST contains an article on the DCA antenna design
concept.
It is my claim that a DCA is extreemely forgiving of construction
errors and uses 4 wire dipoles and 50 ohm coax with 5 RFI type
ferrites as "baluns'.

Jerry KD6JDJ
Given the fact I don't subscribe to QST, domicile Australia, would
you
have a copy of the article?

HH


Hi HH

It would be my pleasure to disclose any/all the information I have
relating to the DCA antenna design concept. It is simple. It is two
pairs of crossed dipoles. Each pair is spaced 1/4 wave apart and fed
in phase. One pair is physically mounted 90 degrees from the other
pair.
All four dipoles are tilted 30 degtrees from vertical. One pair is
fed
90 degrees later than the other pair.
The concept is so simple and straightfoeward that it is probable that
the concept has been developed before I thought of it. But, I have
been unable to find anything published related to this simple "Double
Cross Antenna"
I told my *Internet buddy*, Patrik Tast, in Finland about the concept
and he found it to be exactly what he needed for reception of NOAA
weather satellite signals. Patrik publishes alot of what I send him
related to the antenna. Patrik shows a section of his web page to
describe the DCA to anyone interested. You can find the QST article
in
the section Patrik identifies as ANTENNAS on the first page of his
site
http://www.poes-weather.com/index.php.

If you have any questions about the DCA concept you are free to
E-mail
me, anytime. Or, if you have any facts or data to show where I am
wrong about how well this antenna performs, or know of something that
performs better, please set me straight.

Jerry KD6JDJ


... but surely this is the same as a Lindenblad array? The tilt of the
dipoles was always a parameter in the Lindenblad, so I wonder how your
DCA differs from what N. E. Lindenblad described in the April 1941
edition of 'Communications'.

Chris


Hi Chris

Several, well educated, antenna experts insist that the DCA is actually
a
Lindenblad. If you thought the DCA is a Lindenblad, you are not alone.
The DCA is not a Lindenblad. The array of four dipoles in a
Lindenblad
are fed to produce an overhead null. The four dipoles in a DCA are fed
to produce no overhead null. The DCA is a hemispheric coverage CP
antenna. The Lindenblad is not.
Let me know if you have reason to consider the DCA to be the same as a
Lindenblad. I knew nothing about Lindenblad until after recognizing
the
DCA concept.

Jerry m KD6JDJ

Jerry


Perhaps it's a rather fine distinction to say an antenna that has the same
physical form as the Lindenblad array is something different because the
elements are driven differently. The original version that he patented
didn't have rod elements at all (see, for example,
http://www.coe.montana.edu/ee/rwolff...B_antennas.pdf
)
but it was the configuration of four slanted dipoles around a central pole
that appears to have borne his name since 1941. Henry Jasik's 'Antenna
Engineering Handbook' (now by John L. Volakis, Richard C. Johnson and
Henry
Jasik, Chapter 29, Page 34) refers to the configuration as a Lindenblad
array, without being specific about the way the dipoles are driven.
However, applying new names to antennas that exploit well known
configurations seems fairly commonplace in the professional field,
particularly in broadcasting.

Of course you can name your antenna as you please, but there might be some
value in mentioning that it is a development of the Lindenblad array -
you'd
certainly need to demonstrate awareness of, and distinction from, the
prior
art if you were to seek a patent.

Chris

Interesting article, it describes the Lindenblat array as a quartet of
coaxial horns. Not the same as a quartet of dipoles at all.


Hi Joseph

I sent an E-mail to the address shown as yours in this group. I use
EZNEC and have lots of files on various sizes and shapes of the DCA and
other OmniAzimuth and Hemispheric coverage antennas. I'd be happy to share
them with you if you E-mail me directly.
I figure it will benefit me to see the facts and data that shows where I
am mistaken about how the DCA better than the other hemispheric coverage
antennas for LEO use. It is likely that I have overlooked something.
maybe the DCA can be improved.

Jerry KD6JDJ

Jerry KD6JDJ

On Mon, 16 Feb 2009 18:49:47 GMT, "Jerry"
wrote:


"JosephKK" wrote in message
.. .
On Tue, 10 Feb 2009 18:12:26 -0000, "christofire"
wrote:


"Jerry" wrote in message
...

snip

Chris

Interesting article, it describes the Lindenblat array as a quartet of
coaxial horns. Not the same as a quartet of dipoles at all.


Hi Joseph

I sent an E-mail to the address shown as yours in this group. I use
EZNEC and have lots of files on various sizes and shapes of the DCA and
other OmniAzimuth and Hemispheric coverage antennas. I'd be happy to share
them with you if you E-mail me directly.
I figure it will benefit me to see the facts and data that shows where I
am mistaken about how the DCA better than the other hemispheric coverage
antennas for LEO use. It is likely that I have overlooked something.
maybe the DCA can be improved.

Jerry KD6JDJ

Jerry KD6JDJ

I can retrieve the email. Thanks for the notice.

I have done a bit of gedanken after the slant range issue was raised.


A


B



o H
ooo
ooooo

Let the group of "o" represent a polar view of earth,
"A" represent satellite at azimuth (highest point in the sky),
"B" represent satellite between azimuth and horizon,
"Z" represent satellite very near the horizon,
nominal orbital height 1000 miles above mean surface,
and mean radius of earth of 4000 miles.
Then range to the satellite at A is about 1000 miles, at B may be
about 3000 miles and at H would be about 5000 miles. The arithmetic
for relative sensitivity versus elevation angle can even be solved
analytically, though 4 evenly spaced angles on either side of azimuth
would be quite sufficient to plot the most even EIRP curves.
Your DCA is notably more hemispherical than that. Can you tinker it
up to get about 16 dB more at the horizon than at the azimuth?