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

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

Thanks,

Near 1.5 Ghz the "Patch" antenna works well for me and my GPS receiver. I
THINK it is CP but which rotation??? Some sources indicate you have to nick
alternate corners of the radiating element to achieve CP. I don't know.

Google .com tells me the GPS patch is available at
http://users.bart.nl/users/plundahl/...e/patchant.htm

or a 2.4 GHz version at http://www.rc-cam.com/gp_patch.htm#GPP_faq

You scale it to your approximate center freq. Good luck

"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

"Sal M. Onella" wrote in
:


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

Thanks,

Near 1.5 Ghz the "Patch" antenna works well for me and my GPS
receiver. I THINK it is CP but which rotation??? Some sources
indicate you have to nick alternate corners of the radiating element
to achieve CP. I don't know.

Google .com tells me the GPS patch is available at
http://users.bart.nl/users/plundahl/...e/patchant.htm

or a 2.4 GHz version at http://www.rc-cam.com/gp_patch.htm#GPP_faq

You scale it to your approximate center freq. Good luck


Thanks. But the patch covers only hemisphere (and a little bit more)
and 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

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

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

"SamSvL" wrote in message
...
"Sal M. Onella" wrote in

snip

... the "Patch" antenna works well for me and my GPS
receiver. I THINK it is CP but which rotation??? Some sources
indicate you have to nick alternate corners of the radiating element


snip

Thanks. But the patch covers only hemisphere (and a little bit more)
and I am looking for the full sphere!

Sam


Well how about building two of them, mounting them back-to-back and
combining the outputs?

"Sal"

"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