I'd like to build an antenna for receiving 137 MHz signals from polar
orbiting NOAA weather satellites. I would like to get some information from
any of the readers of this group who might have thought about designing an
antenna for this application.

Jerry

Helical Beam is great at 400 MHz, could be too big for 137. Nasa, mil have
them. About 1 wavelength in circumference, 2.5 foot diameter, 5-6 turns,
circular polarization, and can be pointed at satellite. Circular pol needed
usually as most satellites tumble.

other signals out there at:
http://nssdc.gsfc.nasa.gov/spacewarn...diobeacon.html


"Jerry Martes" wrote in message
...
I'd like to build an antenna for receiving 137 MHz signals from polar
orbiting NOAA weather satellites. I would like to get some information
from
any of the readers of this group who might have thought about designing an
antenna for this application.

Jerry

Do a web search for "Turnstile Antenna".

Jim
N8EE
"Jerry Martes" wrote in message
...
I'd like to build an antenna for receiving 137 MHz signals from polar
orbiting NOAA weather satellites. I would like to get some information
from
any of the readers of this group who might have thought about designing an
antenna for this application.

Jerry

Jim

I'd like to get RHCP on the horizon so I could "pick up" the satelite as
early as possible.

Jerry



"JLB" wrote in message
.. .
Do a web search for "Turnstile Antenna".

Jim
N8EE
"Jerry Martes" wrote in message
...
I'd like to build an antenna for receiving 137 MHz signals from polar
orbiting NOAA weather satellites. I would like to get some information
from
any of the readers of this group who might have thought about designing
an
antenna for this application.

Jerry

Well, after I replied to you post I remembered another antenna type. The
reason I mentioned the Turnstile first is that it is easier to build. You
are right. The pattern does fall apart when you get into the same
horizontal plane as the antenna.

You have two choices. Either a highly directional antenna, for which you
would have to have a tracking system to follow the satellite, and the
appropriate software to run the thing (predicting when and where the bird
will appear).

The other choice, which is what I would recommend, is the quadrifilar helix.
It can be designed to have a hemispherical 180 degree beamwidth and still
have the same RHCP over entire beam. I would even suggest making it a bit
more than 180 degrees beamwidth, perhaps 200 degrees. The problem with the
quadrifilar helix is that it is harder to build than a simple turnstile, but
still easier than a directional antenna with two axis directional control.
A Google search gave 2860 hits for "quadrifilar helix". One I looked at was
http://web.ukonline.co.uk/phqfh/qfh.pdf . If you are not afraid of the
metric system, it gives detailed construction notes for a 137 MHz antenna
made from copper plumbing parts.

--
Jim
N8EE

to email directly, send to my call sign at arrl dot net

"Jerry Martes" wrote in message
...

Jim

I'd like to get RHCP on the horizon so I could "pick up" the satelite as
early as possible.

Jerry



"JLB" wrote in message
.. .
Do a web search for "Turnstile Antenna".

Jim
N8EE
"Jerry Martes" wrote in message
...
I'd like to build an antenna for receiving 137 MHz signals from
polar
orbiting NOAA weather satellites. I would like to get some
information
from
any of the readers of this group who might have thought about
designing
an
antenna for this application.

Jerry

The home page for this is
http://homepage.ntlworld.com/phqfh1/qfh_diy_guide.htm. Check it out. He is
doing WX satellite work like you are trying

--
Jim
N8EE

to email directly, send to my call sign at arrl dot net

Hi Jerry,
Here's a few more sites for building the quadrafilar antenna
http://www.qsl.net/kf4cpj/qha/,
http://www.jcoppens.com/ant/qfh/index.en.php,
and there's a nice article in QST, August '96, by W3KH.
Richard WB8KRN

Good sites.

Some may wonder why there are different geometries for the 'same' antenna'.
The reason is that the quadrifilar helix can be designed for practically any
beamwidth up to 300 degrees or so. This results in different lengths and
number of turns. Some designs are open at the bottom and some are closed at
the bottom. It all depends on what you want the antenna to do.

--
Jim
N8EE

to email directly, send to my call sign at arrl dot net

On Wed, 21 Apr 2004 22:32:44 GMT, "Jerry Martes"
wrote:
The QFH scares me. I dont understand whats going on within the QFH
anrenna.
....
I made one prototype turnstile and got marginal results. But the poor
signals were probably due to my building a faulty antenna.

Hi Jerry,

Odd, but one of the radio and antenna bibles of our group,
"Reflections," was written by Walter Maxwell who designed these QFHs
for the satellites - and yet no one has offered him as a resource or
reference. Try writing him at:


Try this link for formulæ:
http://www.askrlc.co.uk/

73's
Richard Clark, KB7QHC