Self-phased quadrifilar helix antenna for 433MHz

Here is another one. Huge thing this time, designed for 433MHz, polarization RHCP. For dimensions etc. see design description below.

Self Phased QFH Antenna 433MHz

Outer dimensions are about 150mm diameter and 200mm height. Support tube diameter is 31.5-32mm, PVC, used for electrical installations. Radiating elements are made from 4mm brass tube.

Self Phased QFH Antenna 433MHzSelf Phased QFH Antenna 433MHz

Self Phased QFH Antenna 433MHz

433 MHz QFH Design description
433 MHz QFH Design description
Version: 1
1.8 MB
433MHz QFH Drill Template
433MHz QFH Drill Template
Version: 1
6.5 KB

6 thoughts on “Self-phased quadrifilar helix antenna for 433MHz

  1. Your designs are so impressive.

    Is possible with Antenna Magus having a design that is more like an iso-flux pattern (more radiation to the sides than vertical)


  2. Hi, I’m interested in constructing a similar antenna, but I’m kinda far from antenna construction theory. Does it need a balun? Can I swap the support tube for a smaller diameter (e.g. 25mm) without changing other dimensions?

    • It doesn’t require a balun. Support tube can be different in diameter with no problem.

  3. It is not clear to me how to connect the coax. Also what is meant by self-phased?

    • see Infinite baluns section. A&C are connected to ground while B&D to the coax hot end.

      Self-phased means, that because of mechanical design and feedpoint connection both antenna loops are out of phase by 90° which in turn is required to create a circular radiation pattern.

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