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Re: Helix Match



Hi Richard , Gang

I have searched the contents of " Antennas by John Kraus 2nd edition "
for anything on a monofilar helix with separate reflectors.    I have not
found anything,  even in large  arrays ( 96 helix ) .   There are many
various arrays but all have a common reflector ( launcher ).    

The four helix array that folks are referring to here on the BB was
originated in 1948 by J. D Kraus " Helical Beam Antennas For wide-Band
Applications." Proc. IRE, 36,  1236-1242,  october 1948 .

This array is shown in the above 2nd edition with the beamwidth, axial
ratio and VSWR graphs  as a function of frequency .    It uses a single
reflector 2.5 lambda on a side.    With the centers of the helices at 1.5
lambda spacing.    The helices had a diameter of .3 lambda , 14 degree
and six turn .  The frequency band width was greater than 300 mHz .      
 The tapered matching lines were used to transform the 140 ohm impedance
of each helix to 200 ohms so that four helices in parallel would match a
53 ohm line.        The tapered lines are one lambda long.     The lowest
frequency had a gain of 18 db an the high end had a gain of 21 db
The axial ratio of the four was very reasonable ( 1.1:1 or so across the
band width ) .     Beam width became narrower ( couple of degrees ) as 
the frequency increased.      VSWR was also acceptable ( < 2:1)  across
the band.     

In conclusion I suppose I am still at the same place since your antenna
has separate reflectors. 
 
I do thank you for responding to my query.

73's   Joe  Murray  K0VTY

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