I want to built an antenna to receive weather images. I have done this
before using a simple dipole antenna. This time I was thinking of using
a pair of crossed dipoles and wanted to know if it would be best to
configure them as a circular polarized antenna feeding them 90 degrees
out of phase or as a turnstile antenna with both elements fed in-phase.
I have an old vhf aviation band converter that I think I can optimize
for 137Mhz use. I think the only thing else I need is a PC with a sound
card and the right software. This is the first time my daughter has
ever asked me for help with a GS project so I had better do this right.

JIMMIE wrote:
This time I was thinking of using
a pair of crossed dipoles and wanted to know if it would be best to
configure them as a circular polarized antenna feeding them 90 degrees
out of phase or as a turnstile antenna with both elements fed in-phase.

A turnstile antenna has both elements fed 90 degrees
out of phase.
--
73, Cecil http://www.w5dxp.com

Make sure that your converter has wide enough bandwidth.
I built a turnstile antenna but found it almost useless. If you have
time, check out the web for quadrafilar helix designs. I used this one:

http://perso.wanadoo.es/dimoni/ant_qha.htm

73, Kevin


JIMMIE wrote:
I want to built an antenna to receive weather images. I have done this
before using a simple dipole antenna. This time I was thinking of using
a pair of crossed dipoles and wanted to know if it would be best to
configure them as a circular polarized antenna feeding them 90 degrees
out of phase or as a turnstile antenna with both elements fed in-phase.
I have an old vhf aviation band converter that I think I can optimize
for 137Mhz use. I think the only thing else I need is a PC with a sound
card and the right software. This is the first time my daughter has
ever asked me for help with a GS project so I had better do this right.

Here is another QFH antenna design:

http://www.askrlc.co.uk/

73 -- Dino KL0S/4


In article . com,
"ve1tv" wrote:

Make sure that your converter has wide enough bandwidth.
I built a turnstile antenna but found it almost useless. If you have
time, check out the web for quadrafilar helix designs. I used this one:

http://perso.wanadoo.es/dimoni/ant_qha.htm

73, Kevin


JIMMIE wrote:
I want to built an antenna to receive weather images. I have done this
before using a simple dipole antenna. This time I was thinking of using
a pair of crossed dipoles and wanted to know if it would be best to
configure them as a circular polarized antenna feeding them 90 degrees
out of phase or as a turnstile antenna with both elements fed in-phase.
I have an old vhf aviation band converter that I think I can optimize
for 137Mhz use. I think the only thing else I need is a PC with a sound
card and the right software. This is the first time my daughter has
ever asked me for help with a GS project so I had better do this right.

"JIMMIE" wrote in message
ups.com...
I want to built an antenna to receive weather images. I have done this
before using a simple dipole antenna. This time I was thinking of using
a pair of crossed dipoles and wanted to know if it would be best to
configure them as a circular polarized antenna feeding them 90 degrees
out of phase or as a turnstile antenna with both elements fed in-phase.
I have an old vhf aviation band converter that I think I can optimize
for 137Mhz use. I think the only thing else I need is a PC with a sound
card and the right software. This is the first time my daughter has
ever asked me for help with a GS project so I had better do this right.

Hi Jimmie

A turnstile antenna with reflectors is easy to build, and it works very
well for APT image reception from NOAA satellites.
If you build your weather satellite station from an aviation VHF receiver,
you wont be searching for perfection. So, I strongly suggest that you
avoid learning how to build a Quad helix.
If you have interest in learning about designing antennas for APT imaging,
I can show you how to construct an APT antenna that works better than a Quad
Helix . I have an "Internet buddy" who publishes alot of the information
I send him about the antenna concept that works a little better than a Quad
Helix. He (Patrik Tast) publishes the data at
http://213.250.83.83/~jerry/.

Jerry

"Jerry Martes" wrote in message
news:Z4Fah.13696$JQ.6142@trnddc06...

"JIMMIE" wrote in message
ups.com...
I want to built an antenna to receive weather images. I have done this
before using a simple dipole antenna. This time I was thinking of using
a pair of crossed dipoles and wanted to know if it would be best to
configure them as a circular polarized antenna feeding them 90 degrees
out of phase or as a turnstile antenna with both elements fed in-phase.
I have an old vhf aviation band converter that I think I can optimize
for 137Mhz use. I think the only thing else I need is a PC with a sound
card and the right software. This is the first time my daughter has
ever asked me for help with a GS project so I had better do this right.

Hi Jimmie

A turnstile antenna with reflectors is easy to build, and it works very
well for APT image reception from NOAA satellites.
If you build your weather satellite station from an aviation VHF
receiver, you wont be searching for perfection. So, I strongly suggest
that you avoid learning how to build a Quad helix.
If you have interest in learning about designing antennas for APT
imaging, I can show you how to construct an APT antenna that works better
than a Quad Helix . I have an "Internet buddy" who publishes alot of
the information I send him about the antenna concept that works a little
better than a Quad Helix. He (Patrik Tast) publishes the data at
http://213.250.83.83/~jerry/.

Jerry


Thanks Jerry, Interesting fact, I just noticed I already had this site as a
favorite.

Finally got to work on the antenna this weekend. My daughter sweated a
couple of the copper joints. I think she sees this a sculpture. Also she got
to hear some of the birds as they went overhead on the scanner. This was a
big kick knowing she was hearing signals from space. Nice to know she isnt
so jaded she cant appreciate something like this.

Jimmie


"ve1tv" wrote in message
ups.com...
Make sure that your converter has wide enough bandwidth.
I built a turnstile antenna but found it almost useless. If you have
time, check out the web for quadrafilar helix designs. I used this one:

http://perso.wanadoo.es/dimoni/ant_qha.htm

73, Kevin


JIMMIE wrote:
I want to built an antenna to receive weather images. I have done this
before using a simple dipole antenna. This time I was thinking of using
a pair of crossed dipoles and wanted to know if it would be best to
configure them as a circular polarized antenna feeding them 90 degrees
out of phase or as a turnstile antenna with both elements fed in-phase.
I have an old vhf aviation band converter that I think I can optimize
for 137Mhz use. I think the only thing else I need is a PC with a sound
card and the right software. This is the first time my daughter has
ever asked me for help with a GS project so I had better do this right.