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S helix antennas



The Olde Antenna Lab also offers an S band helix.  See
http://users.sgi.net/~hprice/c367.jpg
for a picture of OAL L and S helix antennas in use during P3D RUDAK testing
a couple of weeks ago.

Here is Dave's description of the L and S antennas:
Helix (General),  The Helix is an End Fire Array that exhibits the most gain
per element of any other array of its type, e.g. a ten turn Helix will exhibit
a gain of 10 dBiC.  The Axial Ratio of these antennas is approximately 1.0 and
therefore the E and H-plane beam widths will be equal. For the 10 turn Helix
the -3 dB beamwidth is 60 degrees in both E and H planes.  They can be
constructed for either Right Hand Circular (RHC) or Left Hand Circular (LHC)
polarization.  A solid reflector is employed measuring 0.8 wavelength in
diameter.  The slow wave structure of a ten turn Helix at "L" band will
measure  21" long and 3" in diameter.  The front to back ratio of this type of
array is on the order of 25 dB.  The slow wave structure (helix coil) is wound
on  PVC or Fiberglass tubing.  The first turn of the slow wave structure is so
constructed as to present a 50 ohm terminal impedance at the rear mounted type
"N" female connector of the reflector. O A L builds these so they will easily
handle a kilowatt of input power it you're so inclined.

Contact info for the Olde Antenna Lab is w6oal@aol.com

Standard disclaimers apply.

jw
jim@coloradosatellite.com
wd0e@amsat.org

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