FPV Antenna Polarisation and Gain Explained: RHCP vs Linear
Key Takeaways
- Circular polarisation (RHCP) rejects multipath reflections, which is why it is standard for FPV video.
- A polarisation mismatch between RHCP and LHCP costs around 20dB – more than any antenna upgrade can recover.
- Gain comes from narrowing the beam, so a 12dBi Yagi must be aimed; an omni cannot be high gain.
- SMA and RP-SMA look identical but are not interchangeable, and forcing one onto the other damages the connector.
- Aomway’s 12dBi Yagi is VNA bench tested to SWR below 2.0 across 5500-6000MHz, rated to 60W.
Antenna choice affects FPV video quality more than almost any other component, and it is the one area where a single mistake — a polarisation mismatch — can cost you more than every upgrade you have made combined. This guide covers what polarisation actually does, what gain really costs, and how to avoid damaging connectors.
| Antenna | Frequency | Gain | Polarisation | Max power | Connector |
|---|---|---|---|---|---|
| 5.8GHz Directional Yagi | 5500 – 6000 MHz | 12 dBi | Vertical or horizontal | 60 W | SMA / RP-SMA male |
| 7G–9G RHCP Patch | 7 – 9 GHz | 13 dBi | RHCP | — | — |
| 7G–8.7G RHCP | 7 – 8.7 GHz | 4 dBi | RHCP | — | — |
| 3.3G RHCP | 3.3 GHz band | 4 dBi | RHCP | — | — |
What polarisation actually does
A radio wave has an orientation. Linear polarisation means the electric field oscillates in one plane, like a vertical or horizontal rod. Circular polarisation means the field rotates as the wave travels, either right-handed (RHCP) or left-handed (LHCP).
Two effects matter for FPV:
- Matching. Two antennas of the same polarisation receive each other well. Two of opposite handedness are almost blind to each other: an RHCP to LHCP pair loses in the region of 20dB. That is a factor of a hundred in power, and no amplifier or antenna upgrade recovers it.
- Multipath rejection. Every time a circularly polarised wave reflects off a surface, its handedness flips. So an RHCP antenna receives the direct RHCP signal strongly and rejects the LHCP reflections bouncing off the ground and buildings. That is why RHCP produces a cleaner image in real environments, not just a stronger one.
The rule: match both ends. RHCP on the aircraft, RHCP on the ground. It is the cheapest performance gain available and the most commonly missed.
Gain is not free: the beamwidth trade
An antenna does not amplify anything. It redirects energy. A 4dBi omni radiates in a broad doughnut; a 12dBi Yagi concentrates the same energy into a narrow beam.
That is excellent when you are pointing at the aircraft, and useless when you are not. Bank hard with a narrow-beam ground antenna and you drop out of your own beam. This is why diversity goggles pair one omnidirectional antenna with one directional antenna rather than running two high-gain panels: the omni covers manoeuvring, the directional covers distance.
Specifications that actually matter
Beyond gain and polarisation, these are the numbers to check:
- SWR / VSWR. Standing wave ratio measures how well the antenna matches the transmitter. Aomway specifies the 12dBi Yagi below 2.0 across the full 5500–6000MHz band, and every unit is VNA bench tested. A high SWR reflects power back into the amplifier as heat.
- Impedance. 50Ω is standard. Anything else will not match.
- Power rating. The 12dBi Yagi is rated to 60W, which comfortably covers even a 10W transmitter with margin.
- Frequency coverage. An antenna tuned for 5.8GHz is not suitable for 3.3GHz. Match the antenna to the band you actually transmit on.
- Connector gender and polarity. See below.
SMA versus RP-SMA: the mistake that damages hardware
These two connectors look nearly identical and are electrically different. SMA has the centre pin on the plug and the socket on the jack. RP-SMA (reverse polarity) swaps that: the plug has a socket and the jack has a pin. RP-SMA is the FPV standard on most video transmitters and goggles.
Screwing an SMA plug onto an RP-SMA jack will not make contact, and forcing it can bend or snap the centre pin. Always check the connector type before buying, and prefer a correctly specified antenna over an adapter, because every adapter adds loss.
Aomway antennas are available in both SMA male and RP-SMA male, and the full range is listed in the antenna selection documentation.
Matching antennas to your build
| Build | Airborne antenna | Ground antenna |
|---|---|---|
| Freestyle quad | RHCP omni (protects against any orientation) | RHCP omni on diversity goggles |
| Long-range quad | RHCP omni or low-gain directional | One omni plus one directional |
| Long-range fixed wing | Directional, aimed along the flight path | High-gain directional with tracking |
| Ground station | — | 13dBi patch or 12dBi Yagi with tracking |
The 12dBi Yagi and the 13dBi RHCP patch cover the two most common directional ground station configurations.
Frequently Asked Questions
What is the difference between RHCP and LHCP?
Both are circular polarisations, differing in the direction the electric field rotates. An RHCP antenna and an LHCP antenna are almost blind to each other, losing around 20dB. Both ends of an FPV link must use the same handedness.
Why is circular polarisation better than linear for FPV?
Because reflections flip the handedness of a circularly polarised wave, so an RHCP antenna receives the direct signal and rejects the reflected multipath. That produces a cleaner image in real environments, not just a stronger signal.
Does higher antenna gain always mean better range?
No. Gain comes from narrowing the beam, so a high-gain antenna must be aimed at the aircraft. If the aircraft manoeuvres out of the beam you lose the link entirely, which is why diversity goggles pair an omni with a directional antenna.
Are SMA and RP-SMA interchangeable?
No. RP-SMA reverses the pin and socket relative to SMA, and they will not make contact with each other. Forcing them together can damage the connector. Check which your transmitter and goggles use before buying an antenna.
What SWR should an FPV antenna have?
Below 2.0 across the band you transmit on is a reasonable target. Aomway’s 12dBi Yagi is specified below 2.0 across 5500 to 6000MHz and every unit is VNA bench tested. A high SWR reflects power back into the amplifier as heat.
Hardware Testing Application
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Product Specsheet Download
Full specification tables, frequency coverage and engineering reference notes for the hardware discussed here are published in the Aomway documentation centre. If you need a document that is not listed — a specific revision, a custom frequency table, or a manual for a discontinued model — contact our engineering team and we will send the correct document rather than have you work from a third-party copy.
About Aomway
Aomway has been developing and manufacturing video transmission and UAV radio hardware for over 15 years, producing equipment for any frequency band from 1 GHz to 9 GHz at power levels from 3W to 15W. We build high-power FPV video transmitters, directional and circularly polarised antennas, digital links, fiber-optic tether systems and detection hardware for pilots, integrators and commercial operators worldwide.
