On Thu, 14 Oct 2004 11:37:00 GMT, "G.Beat" wrote:

John Coppens ON6JC/LW3HAZ, posted a photo (NOAA 17) of a quadrifilar antenna
on his web page.
http://www.jcoppens.com/ant/qfh/index.en.php

g. beat
w9gb


"Walter Maxwell" wrote in message
.. .

the self-phasing characteristic the diameter of the radiating elements is
crucial in obtaining the 90-degree relationship between the two bifilar
elements, because the INDUCTANCE of the elements is the effective
parameter in
the phasing. The inductance of the short bifilar causes the current
flowing in
it to lead by 45 degrees, while the INDUCTANACE in the long bifilar causes
its
current to lag by 45 degrees. This phasing relationship requires the
diameter of
the radiating elements to be 0.0088 lambda in length for whatever
frequency is
used.

In the last sentence above the words 'in length' should be deleted. The
reference is only to the diameter of the radiator.

I also inadvertantely omitted reference to a photo of two QFH that uses self
phasing and infinite balun feed. In Chapter 22 of Reflections 2, appearing on my
web page at http://home.iag.net/~w2du.

See the photo in Fig 22-1 on Page 22-2. The QFH on the left is the wide-band
video 1.6 GHz antenna flying on all TIROS - N, NOAA polar orbiting wx
spacecraft.

Incidentally, the Astro Electronics Division of RCA designed and built all
TIROS spacecrafts 1 through 9, and all TIROS - N spacecrafts from 1973 thru
1986, when RCA was taken over by GE, and then sold to Lockheed, which has built
the TIROS-N's since the takeover. I was the lead engineer developing the QFH
antennas that are flying on all TIROS - N spacecrafts. I was also the sole
engineer who developed all the antennas flying on TIROS spacecrafts 1 thru 8,
and the 137 MHz 2-element phased array that transmitted the W XAPT signals on
TIROS 9.

Walt Maxwell, W2DU

I hadn't realized that when my GPS got me out of a bit of a jam on my
most recent backpacking trip, I had Walt to thank (among others of
course) -- the GPS receiver uses a quadrifilar helix antenna. Thanks, Walt!

Walt also gets credit for an important role in developing the weather
satellites which bring us such benefits as early warning of the
hurricanes that recently went through Florida. I hope your house in
DeLand came through ok, Walt!

Roy Lewallen, W7EL

Walter Maxwell wrote:

. . .
I performed the original research that led to the use of the QFH as the primary
radiators on all TIROS-N, NOAA polar orbiting satellites. As the lead engineer
at RCA Astro's antenna laboratory, I measured the radiation patterns and
terminal impedances on more than 1000 different electrical and mechanical
configurations of the QFH antenna. Of those many patterns one was chosen for the
NOAA satellites based on consistant, continous, solid contact with all ground
stations from the time the spacecraft was 10 degrees above the horizon.
. . .

Thanks, Roy, for the warm words about my connection with the QFH on the wx
spacecraft. My work in that area was a love affair, and I was just lucky to be
in the right place at the time the space exploration was just taking off.

I'm also lucky about the hurricane situation in Florida. My only damage was
losing one panel of screening around my pool. My son Bill, W2WM, has moved into
his new house, also in DeLand where I live, and he had no damage at all there.
But his house in W Palm Beach, that he is putting up for sale, suffered
extensive damage to the roof, causing leaks. However, FEMA came to his rescue by
placing a tarp over the house, covering the entire roof until it can be
repaired. I give FEMA a lot of credit for the terrific work they're doing to
help the survivors of those terrible storms.

Walt

On Thu, 14 Oct 2004 20:06:16 -0700, Roy Lewallen wrote:

I hadn't realized that when my GPS got me out of a bit of a jam on my
most recent backpacking trip, I had Walt to thank (among others of
course) -- the GPS receiver uses a quadrifilar helix antenna. Thanks, Walt!

Walt also gets credit for an important role in developing the weather
satellites which bring us such benefits as early warning of the
hurricanes that recently went through Florida. I hope your house in
DeLand came through ok, Walt!

Roy Lewallen, W7EL

Walter Maxwell wrote:

. . .
I performed the original research that led to the use of the QFH as the primary
radiators on all TIROS-N, NOAA polar orbiting satellites. As the lead engineer
at RCA Astro's antenna laboratory, I measured the radiation patterns and
terminal impedances on more than 1000 different electrical and mechanical
configurations of the QFH antenna. Of those many patterns one was chosen for the
NOAA satellites based on consistant, continous, solid contact with all ground
stations from the time the spacecraft was 10 degrees above the horizon.
. . .

I used to rx wx images off of the sat. USed a pair of crossed dipoles with a
reflector. Put it up on a pole high enough to clear the trees and you can
recive the sat from nearly horizon to horizon.
"Thierry" - wrote in message ...
Hi,

To pick up a 137 MHz signal from wx satellite (POES), are the discone and
quadrifilar helix antennas similar, I mean, they are different in design
but
for the rest ?
Are they both omnidirectional and are they both able to change
automatically
the elevation and azimuth to the satellite direction without interruption
and without requiring a rotator ? or only the helix provides this
capability
?

Thanks in advance

Thierry, ON4SKY
http://www.astrosurf.com/lombry