A simpler antenna that produces a similar pattern is the "eggbeater" Two
circles at right angles fed with a phase shift network. M2 sells one now,
KLM developed it in the 70-80s. It produces a satellite friendly circular
pattern skyward and a horizontal omni on the horizon. Neat
-----Original Message-----
From: Ford Peterson [mailto:ford@cmgate.com]
Sent: Sunday, June 10, 2001 10:29 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Quadrifilar antenna
I have been reading Walt Maxwell's new book Reflections II. He describes a
"Quadrifilar Helix" antenna used for satellite work. Anybody played with
these babies? I've been modeling the design and it looks quite promising.
180 degree az pattern over almost 175 degrees of elevation. Wow! It's a
cloud burner but just the ticket for LEO (Low Earth Orbit) satellite work.
I've been looking at making one but the materials are a problem. There was
an article in QST a while back that described making one but frankly, the
cheesy construction leaves a bit to be desired. In addition, there are
several aspects of the Maxwell paper that lead one to believe that the QST
version is a hoax (it can't possibly work at the top of a tower).
If somebody has experience with these antennas, I'd love to hear from them
direct. Perhaps we can share notes, models, etc.
Ford-N0FP
ford@cmgate.com
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