RHCP vs LHCP: The Complete Guide to Circular Polarization in FPV Systems

Introduction to Antenna Polarization

In FPV drone systems, antenna polarization is one of the most critical yet frequently misunderstood aspects of RF signal transmission. Whether you’re a racing pilot needing reliable video through tight courses or a long-range enthusiast pushing distance limits, understanding polarization – particularly circular polarization – can mean the difference between crystal-clear video and frustrating signal breakup.

This comprehensive guide will explain:

  • The fundamental differences between RHCP and LHCP
  • Why circular polarization dominates FPV applications
  • How reflections affect your signal (including the truth about parabolic dishes)
  • Real-world antenna recommendations from ProDrone.pl
  • Advanced setup tips for optimal performance

Understanding Polarization Basics

Linear vs Circular Polarization

All radio waves have polarization – the orientation of their electric field oscillation:

Linear Polarization:

  • Electric field oscillates in a single plane (vertical or horizontal)
  • Examples: Dipole antennas, Moxon antennas
  • Advantages: Simple design, good for control links
  • Disadvantages: Sensitive to antenna orientation changes

Circular Polarization:

  • Electric field rotates as the wave propagates
  • RHCP (Right Hand Circular Polarization): Clockwise rotation
  • LHCP (Left Hand Circular Polarization): Counter-clockwise rotation
  • Advantages: Maintains signal integrity during drone maneuvers

Why FPV Systems Favor Circular Polarization

FPV video systems overwhelmingly use circular polarization because:

  1. Orientation Independence: Drones constantly change attitude – circular polarization maintains signal regardless of roll/pitch/yaw
  2. Multipath Rejection: Naturally filters out reflected signals (more on this later)
  3. Interference Reduction: Allows multiple pilots to fly simultaneously with less crosstalk

RHCP vs LHCP: Key Differences

There’s no performance difference between RHCP and LHCP when used correctly.

While RHCP and LHCP are functionally identical in performance, their opposite rotation has important implications:

CharacteristicRHCPLHCP
Rotation DirectionClockwiseCounter-clockwise
Common ApplicationsStandard FPV, GPSAlternate channel systems
After ReflectionBecomes LHCPBecomes RHCP
CompatibilityMust match RX/TXMust match RX/TX

Critical Rule: Your video transmitter and receiver must use the same polarization type (both RHCP or both LHCP) for optimal performance.

The Reflection Paradox: How Surfaces Affect Polarization

This is where many pilots get confused – especially regarding parabolic dishes.

The Fundamental Principle:

All reflections reverse circular polarization:

  • RHCP → LHCP when reflected
  • LHCP → RHCP when reflected

This occurs because the reflection inverts the wave’s rotation direction.

Flat Surface Reflections:

When your signal bounces off the ground, buildings, or trees:

  1. Direct signal maintains original polarization
  2. Reflected signal reverses polarization
  3. Matching RX/TX polarization automatically rejects reflected signals

Parabolic Dish Truth:

Despite common misconceptions:

  • Parabolic dishes DO reverse polarization just like flat surfaces
  • The curved shape focuses the signal but doesn’t prevent polarization reversal
  • You must account for this in your antenna selection

Dish Setup Rule:
If using a parabolic reflector:

  • VTX antenna: RHCP
  • Dish receiver antenna: LHCP (to match the reflected signal)

ProDrone.pl Antenna Recommendations

RHCP Solutions (Standard FPV)

  1. ProDrone PRO 12T (RHCP)
    • Premium omnidirectional antenna
    • Optimized axial ratio for clean signal
    • Ideal for freestyle and racing
  2. Helix PRO 18 (RHCP)
    • High-gain directional antenna
    • Perfect for long-range applications
    • 18dBic gain for extreme distances

LHCP Solutions (Specialized Applications)

  1. LHCP Crosshair 5.8GHz
    • Rejects RHCP interference
    • Excellent for group flying
    • Works with dish reflector systems
  2. LHCP Helical Array
    • Custom ground station solution
    • Pairs with parabolic reflectors
    • 14dBic gain for weak signal reception

Linear Antenna Options

  1. Moxon 2.4GHz (Linear)
    • Highly directional
    • Ideal for control links (ELRS/Crossfire)
    • Not for video transmission

Advanced Setup Considerations

Group Flying Protocol

When multiple pilots fly together:

  • Alternate polarizations between pilots
  • Example: Pilot 1: RHCP, Pilot 2: LHCP
  • Reduces video crosstalk and interference

Polarization Purity Matters

Not all RHCP/LHCP antennas are created equal. Key specifications:

  • Axial Ratio: Measures how “pure” the circular polarization is (closer to 0dB is better)
  • VSWR: Indicates how well the antenna is tuned (under 1.5:1 ideal)

ProDrone.pl tests all antennas for optimal performance in these metrics.

Special Case: Dual-Polarization Systems

Some advanced systems use:

  • Simultaneous RHCP/LHCP reception
  • Diversity combining for maximum signal robustness
  • Requires specialized receivers and antennas

Troubleshooting Common Issues

Problem: Video breakup when flying behind obstacles
Solution: Ensure matched polarization and consider higher-gain antennas

Problem: Interference from other pilots
Solution: Switch to opposite polarization scheme

Problem: Weak signal with dish system
Solution: Verify you’re using opposite polarization on receiver

Conclusion and Key Takeaways

  1. RHCP and LHCP are equally effective – consistency matters most
  2. All reflections reverse polarization – including parabolic dishes
  3. Dish systems require opposite polarization on receiver
  4. Group flying benefits from mixed polarization
  5. Antenna quality (axial ratio, VSWR) significantly impacts performance

At ProDrone.pl, we offer professionally tuned antennas for every FPV scenario. Our technical team can help you select the perfect polarization solution for your specific needs.

You can find more detailed information on wikipedia:
https://en.wikipedia.org/wiki/Circular_polarization