- - The Quad Helix Array - -
This antenna can be scaled for use on 902 - 928 MHz.
Details for the 33 CM band and for other frequencies are below.

This design is from an article by W6UQH in the August 1963 QST.
The description above is from the 1967 ARRL Handbook.

The information in the following table is based on recommendations for helix design in the RSGB VHF/UHF Manual, 4th edition.  The axial-mode helix is quite broad-band and relatively non-critical in its dimensions.  Therefore the frequencies calculated are for the center of each band.  For these bands the helix conductor can be 3 - 6 mm diameter (1/8 - 1/4 inch) material.  Copper wire or tubing is recommended, and connections can then be readily soldered.  In the quad array shown above, the lines from the helix feedpoints  to the common feed point for the coaxial line must all be of the same length.

If designed for 1100 MHz, the array should work well for both the 902-928 and 1240-1300 MHz bands, IF you do not introduce some frequency-specific element in your design, such as a 'quarter-wavelength matching section in the feedline'.  Documentation for the helical antenna indicates that it is capable of covering to plus and minus 25% of the design center frequency.

Frequency  MHz Wavelength (L) cm Diameter  cm Pitch  cm Reflector  cm
915 32.8 10.5 7.2 82 X 82
1100 27.3 8.7 6.0 68 X 68
1270 23.6 7.6 5.2 59 X 59
General Case 30000/F 0.32L 0.22L 2.5L Square


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