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