What would be a good (free space, 1 GHz) antenna to achieve
circular polarizarion with a nearly spherical coverage?

Thanks,

Sam

"SamSvL" wrote in message
...
What would be a good (free space, 1 GHz) antenna to achieve
circular polarizarion with a nearly spherical coverage?

Thanks,

Sam


Hi Sam

If you want "half spherical" coverage for receiving a circularly polarized
signal, a turnstile is probably the easiest to build.
If your requirements for sensitivity are more stringent than the turnstile
provides, a quadrafilar helix is excellant circular polarization.

Jerry

"Jerry Martes" wrote in
news:Wgm9h.7725$9e.3808@trnddc02:


"SamSvL" wrote in message
...
What would be a good (free space, 1 GHz) antenna to achieve
circular polarizarion with a nearly spherical coverage?

Thanks,

Sam


Hi Sam

If you want "half spherical" coverage for receiving a circularly
polarized
signal, a turnstile is probably the easiest to build.
If your requirements for sensitivity are more stringent than the
turnstile
provides, a quadrafilar helix is excellant circular polarization.

Jerry

Hi Jerry,

Unfortunately I am looking for the full sphere :-(

Sam

"SamSvL" wrote in message
...
"Jerry Martes" wrote in
news:Wgm9h.7725$9e.3808@trnddc02:


"SamSvL" wrote in message
...
What would be a good (free space, 1 GHz) antenna to achieve
circular polarizarion with a nearly spherical coverage?

Thanks,

Sam


Hi Sam

If you want "half spherical" coverage for receiving a circularly
polarized
signal, a turnstile is probably the easiest to build.
If your requirements for sensitivity are more stringent than the
turnstile
provides, a quadrafilar helix is excellant circular polarization.

Jerry

Hi Jerry,

Unfortunately I am looking for the full sphere :-(

Sam


Hi Sam

You may have alot of difficulty locating a design for an antenna that
radiates a given "circular" polarization with "spherical" coverage. I
consider those requirements to be entirely beyond reality. Are you
planning to build this antenna or buy it *off the shelf*?

Jerry

"Jerry Martes" wrote in news:rOE9h.9036$9e.2359
@trnddc02:


"SamSvL" wrote in message
...
"Jerry Martes" wrote in
news:Wgm9h.7725$9e.3808@trnddc02:


"SamSvL" wrote in message
...
What would be a good (free space, 1 GHz) antenna to achieve
circular polarizarion with a nearly spherical coverage?

Thanks,

Sam


Hi Sam

If you want "half spherical" coverage for receiving a circularly
polarized
signal, a turnstile is probably the easiest to build.
If your requirements for sensitivity are more stringent than the
turnstile
provides, a quadrafilar helix is excellant circular polarization.

Jerry

Hi Jerry,

Unfortunately I am looking for the full sphere :-(

Sam


Hi Sam

You may have alot of difficulty locating a design for an antenna that
radiates a given "circular" polarization with "spherical" coverage. I
consider those requirements to be entirely beyond reality. Are you
planning to build this antenna or buy it *off the shelf*?

Jerry

Hi Jerry,

Buy if available, build otherwise ;-((

Sam

Two CP hemispheric antennas back to back feeding a Wilkinson adder.

Jim


"SamSvL" wrote in message
...
Hi Jerry,

Unfortunately I am looking for the full sphere :-(

Sam

"RST Engineering" wrote in news:THG9h.6
:

Two CP hemispheric antennas back to back feeding a Wilkinson adder.

Jim


"SamSvL" wrote in message
...
Hi Jerry,

Unfortunately I am looking for the full sphere :-(

Sam


Hi Jim,

Others suggested this solution, I will try.

Thanks,

Sam

On Thu, 23 Nov 2006 19:04:22 GMT, "Jerry Martes" wrote:


"SamSvL" wrote in message
. ..
What would be a good (free space, 1 GHz) antenna to achieve
circular polarizarion with a nearly spherical coverage?

Thanks,

Sam


Hi Sam

If you want "half spherical" coverage for receiving a circularly polarized
signal, a turnstile is probably the easiest to build.
If your requirements for sensitivity are more stringent than the turnstile
provides, a quadrafilar helix is excellant circular polarization.

Jerry

Hi Sam,

FYI, the quadrifilar helix comprises two bifilar helices fed in phase
quadrature. The result is hemispherical radiation in the radiation sphere. But
the hemispherical radiation results from the combined radiations from each
bifilar helix. Consequently, radiation from a single bifilar helix is spherical,
with the polizarization sense the same throughout the sphere, unlike the
radiation from a turnstile, which radiates one polarization sense above the
equator and the opposite sense below the equator, where the turnstile elements
lie on the equator.

You can find info on the bifilar helix in Chapter 22 of Reflections, eds 1 and
2. If you don't have a copy of Reflections available, Chapter 22 is available
for downloading from my web page at www.w2du.com. Click on "Read Chapters from
Reflections 2" and then click on 'Chapter 22, Quadrifilar Antenna'.

Fig 22-5 shows the radiation pattern for the quadrifilar, but the radiation in
the 180° direction is suppressed due to the effect of the second helix
positioned 90° from the first helix, and fed in quadrature (90°) relative to the
first. In the absence of the second helix the radiation from a single bifilar is
spherical.

Fig 22-8 shows a simple method of feeding the bifilar helix--it's called an
'infinite balun', because the current that would flow on the outside surface of
the coax when feeding a doublet dipole without a balun is now flowing on the
outside surface of the radiator, which is what we want.

If you're interested in further info on the helices used in quadrifilars or
bifilars, see the report on my R&D experiment on quadrifilars, in which I
measured radiation patterns and driving point impedances on more than a thousand
different configurations of the quadrifilar. The R&D report is available for
downloading on my web page. Click first on "Read Appendices from Reflections 2",
and then click on 'Appendix 13, RCA R&D Quadrifilar Helix Antenna'.

Hope this helps,

Walt Maxwell, W2DU

Walter Maxwell wrote in
:

On Thu, 23 Nov 2006 19:04:22 GMT, "Jerry Martes"
wrote:


"SamSvL" wrote in message
.. .
What would be a good (free space, 1 GHz) antenna to achieve
circular polarizarion with a nearly spherical coverage?

Thanks,

Sam


Hi Sam

If you want "half spherical" coverage for receiving a circularly
polarized
signal, a turnstile is probably the easiest to build.
If your requirements for sensitivity are more stringent than the
turnstile
provides, a quadrafilar helix is excellant circular polarization.

Jerry

Hi Sam,

FYI, the quadrifilar helix comprises two bifilar helices fed in phase
quadrature. The result is hemispherical radiation in the radiation
sphere. But the hemispherical radiation results from the combined
radiations from each bifilar helix. Consequently, radiation from a
single bifilar helix is spherical, with the polizarization sense the
same throughout the sphere, unlike the radiation from a turnstile,
which radiates one polarization sense above the equator and the
opposite sense below the equator, where the turnstile elements lie on
the equator.

You can find info on the bifilar helix in Chapter 22 of Reflections,
eds 1 and 2. If you don't have a copy of Reflections available,
Chapter 22 is available for downloading from my web page at
www.w2du.com. Click on "Read Chapters from Reflections 2" and then
click on 'Chapter 22, Quadrifilar Antenna'.

Fig 22-5 shows the radiation pattern for the quadrifilar, but the
radiation in the 180° direction is suppressed due to the effect of the
second helix positioned 90° from the first helix, and fed in
quadrature (90°) relative to the first. In the absence of the second
helix the radiation from a single bifilar is spherical.

Fig 22-8 shows a simple method of feeding the bifilar helix--it's
called an 'infinite balun', because the current that would flow on the
outside surface of the coax when feeding a doublet dipole without a
balun is now flowing on the outside surface of the radiator, which is
what we want.

If you're interested in further info on the helices used in
quadrifilars or bifilars, see the report on my R&D experiment on
quadrifilars, in which I measured radiation patterns and driving point
impedances on more than a thousand different configurations of the
quadrifilar. The R&D report is available for downloading on my web
page. Click first on "Read Appendices from Reflections 2", and then
click on 'Appendix 13, RCA R&D Quadrifilar Helix Antenna'.

Hope this helps,

Walt Maxwell, W2DU

Hi Walt,

Thanks for your reaction. And yes, I found your articles already some
time ago. I missed the notes on the bifilar, but will study them again
carefully.

Again, thanks,

Sam

"SamSvL" wrote in message
...
Walter Maxwell wrote in
:

On Thu, 23 Nov 2006 19:04:22 GMT, "Jerry Martes"
wrote:


"SamSvL" wrote in message
. ..
What would be a good (free space, 1 GHz) antenna to achieve
circular polarizarion with a nearly spherical coverage?

Thanks,

Sam


Hi Sam

If you want "half spherical" coverage for receiving a circularly
polarized
signal, a turnstile is probably the easiest to build.
If your requirements for sensitivity are more stringent than the
turnstile
provides, a quadrafilar helix is excellant circular polarization.

Jerry

Hi Sam,

FYI, the quadrifilar helix comprises two bifilar helices fed in phase
quadrature. The result is hemispherical radiation in the radiation
sphere. But the hemispherical radiation results from the combined
radiations from each bifilar helix. Consequently, radiation from a
single bifilar helix is spherical, with the polizarization sense the
same throughout the sphere, unlike the radiation from a turnstile,
which radiates one polarization sense above the equator and the
opposite sense below the equator, where the turnstile elements lie on
the equator.

You can find info on the bifilar helix in Chapter 22 of Reflections,
eds 1 and 2. If you don't have a copy of Reflections available,
Chapter 22 is available for downloading from my web page at
www.w2du.com. Click on "Read Chapters from Reflections 2" and then
click on 'Chapter 22, Quadrifilar Antenna'.

Fig 22-5 shows the radiation pattern for the quadrifilar, but the
radiation in the 180° direction is suppressed due to the effect of the
second helix positioned 90° from the first helix, and fed in
quadrature (90°) relative to the first. In the absence of the second
helix the radiation from a single bifilar is spherical.

Fig 22-8 shows a simple method of feeding the bifilar helix--it's
called an 'infinite balun', because the current that would flow on the
outside surface of the coax when feeding a doublet dipole without a
balun is now flowing on the outside surface of the radiator, which is
what we want.

If you're interested in further info on the helices used in
quadrifilars or bifilars, see the report on my R&D experiment on
quadrifilars, in which I measured radiation patterns and driving point
impedances on more than a thousand different configurations of the
quadrifilar. The R&D report is available for downloading on my web
page. Click first on "Read Appendices from Reflections 2", and then
click on 'Appendix 13, RCA R&D Quadrifilar Helix Antenna'.

Hope this helps,

Walt Maxwell, W2DU

Hi Walt,

Thanks for your reaction. And yes, I found your articles already some
time ago. I missed the notes on the bifilar, but will study them again
carefully.

Again, thanks,

Sam


Hi Sam

I dont want to discourage your study of them, but, bifilar has significant
nulls for CP.

Jerry


Jerry