80 meter Circular Polarization Antenna Comparison
EZNEC+ simulation condition: 3.7 MHz, antenna height 14 meters, good ground conductivity 0.03 S/m, dielectric constant 20.

Turnstile, two 1/2 wave dipoles in 90º phase

4-phase Turnstile RF current

 Full Wave Loop, single loop fed in 90º phase

4-phase Full Wave Loop RF current
 Tripole, three 1/4 wave wires fed in 120º phase

3-phase 1/4 Wave Tripole RF current
 Tripole, three 1/2 wave wires fed in 120º phase

3-phase 1/2 Wave Tripol RF current

4-phase Turnstile 3D Plot
Symmetrical 3D radiation pattern
4-phase Full Wave Loop 3D Plot
Symmetrical 3D radiation pattern
3-phase 1/4 Wave Tripole 3D Plot
Symmetrical 3D radiation pattern
3-phase 1/2 Wave Tripole 3D Plot
Asymmetrical 3D radiation pattern

4-phase Turnstile 2D Plot. NVIS circular gain 7.31dBi
Biggest opposite circular gain -10dBi at 30º
4-phase Full Wave Loop 2D Plot. NVIS circular gain 7.76dBi
Biggest opposite circular gain -10dBi at 30º
3-phase 1/4 Wave Tripole 2D. NVIS circular gain 7.08dBi
Biggest opposite circular gain -7dBi at 35º
3-phase 1/2 Wave Tripole 2D Plot. NVIS circular gain 7.95dBi
Biggest opposite circular gain 2dBi at 45º

Verdict
  • All of these circular polarization antennas provide a clean polarization at 90º takeoff angle.
  • Half wave tripole doesn't provide clean circular polarization for lower takeoff angles. See more here.
  • Half wave end fed wires need a huge impedance ratio ununs which is challenging for QRO power.
  • The phasing and the impedance matching is most simple for turnstile (two half wave dipoles in 90º angle).
  • Turnstile (two dipoles) and full wave loop provide the cleanest circular polarization in all takeoff angles.
See the takeoff angle calculator in this link

Update 2021-09-28 OH7SV

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