Circular or Linear Polarized Antenna For FPV

by Oscar
Published: Last Updated on

Antennas for FPV can be categorized by their polarization: linear and circular. In this article we will discuss the differences between linear and circular polarized antennas.

To learn more about FPV antenna basics and our recommendations. If you are new to FPV, you should read up on this guide for FPV system.

Types of Polarization

Polarization means the way radio signal travels in space. It’s often mentioned in discussion of FPV antennas. In this section we will discuss the differences, pro’s and con’s of Linear and Circular Polarization to FPV system performance.

Linear Polarization

Linear polarized signal oscillates horizontally or vertically in one plane while travelling.

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Linear Polarization is used in some of the most basic antennas, such as the stock dipole antennas that comes with your VTX and VRX, or even in your home WiFi.

 

Pros and Cons of Linear Polarization

Linear polarized antennas are widely used due to its structural simplicity, which can be as simple as a piece of wire. The antennas tend to be smaller, cheaper and easier to build and repair.

In general linear polarization is great for long range as all the energy is focused on a single plane. The range advantage is seldom realized due to multipath interference which we will discuss shortly.

In order to get the best reception, both transmitting and receiving linear polarized antennas have to be aligned to ensure maximum radiation overlap.

The most extreme case is when the transmitter and receiver antennas are 90 degrees to one another, resulting in the least amount of signal overlap. This results in 30dB loss in signal strength and it’s referred to as cross polarization.

Our multirotor is moving constantly in the sky, it’s simply impossible to keep the antennas aligned at all times and therefore resulting in unstable FPV signal.

To solve this problem, we normally use circular polarized antennas.

Circular Polarization

In circular polarization, signal are transmitted on both horizontal and vertical planes with 90 degree phase shift that looks like a spinning corkscrew.

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Here are some of the common circular polarized antennas for FPV.

Skew-Planar Wheel antenna is circularly polarized and has excellent multipath rejection capability. This antenna is used for general purpose flying where aerodynamic drag (e.g. wind) is not a critical factor. While generally regarded as a receiver antenna, it works well as a transmit antenna too.

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The Cloverleaf antenna is more commonly seen on a transmitter. It can be coupled with a Skew Planar wheel for better range and signal penetration.

Pros and Cons of Circular Polarization

Circular polarized signal always overlap no matter what orientation or angle your mini quad is flying at relative to your receiving antenna. For this reason circular polarized antennas have become the standard in FPV flying.

Another advantage of circular polarized antennas is their ability to reject multipath interference.

Multipath interference is the most common reason for bad video quality, in the form of random color change, static, scrambled image and drop-outs. It happens when the signal is reflected from object and gets distorted with phase delay, and it interferes with the main signal.

VideoCrypt-signal

Circular polarized antennas are either left-hand (LHCP) or right-hand (RHCP). Transmitter and receiver need to have matching antennas otherwise it could result in significant signal loss.

CP antennas can benefit from this property against multipathing. Every time a CP signal bounces off object it changes its polarization direction. And LHCP antenna rejects RHCP signal and vice versa (cross polarization).

When to use circular polarization

  • When flying close to large objects such as trees, buildings, or in enclosed environment such as car parks and stadiums
  • Acrobatic flying where the aircraft orientation and angle are constantly changing
  • Low altitude flying (proximity flying)

When to use linear polarization

  • Long distance flying in the open without any obstacles
  • Stable flying without too much roll or pitch
  • When antenna size, weight and durability are the most important consideration

Can I Use Linear Antenna with Circular Antennas?

Yes, but with some signal loss as explained here:

The Best 5.8GHz Antenna for FPV Drone

Edit History

  • Oct 2013 – article created
  • May 2017 – article revised

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27 comments

kenan 21st September 2020 - 9:17 pm

hi..Which antenna can you recommend for parrot disco

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aaron d 14th July 2020 - 6:27 pm

Seems like a basic question, but can you use the standard dipole/linear VTx antenna with a RHCP receiver antenna? Or do you HAVE to use a linear receiver antenna?

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Vince 15th June 2020 - 6:50 pm

Hi, thank you for the nice article, beginner here!
I was having the impression from my research that the Cloverleaf(transmitter) was 3 lobes, and the Skewplanar(receptor) was 4 lobes, was that just a random thing from the one I checked? What is the difference in nature between the 2?

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Oscar 22nd June 2020 - 12:35 pm

slightly different specs, but not enough to be concerned about. Just follow its instructions if they are designed specifically for TX or RX, otherwise don’t worry about it :)

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Niek 4th February 2020 - 9:38 pm

Hi Oscar,
Very well done on the article!
I really understand this better now, but I have 1 more question: can I mix a linear polarized VTX with a circular polarized VRX?

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Oscar 18th February 2020 - 12:09 am

Yes, but you will have some signal loss.

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Kyle Griffiths 1st July 2018 - 4:41 pm

How about 3 blade vs 4 blade clovers? Which goes on which end? Often a 3 blade is fitted for the tx, while the rx is packin a 4 blade clover ive noticed. Is this coincidence?

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Oscar 24th July 2018 - 5:35 pm

I don’t think there is a rule that says you have to use 3 or 4 lobes for TX or RX, unless the manufacturer tells you so. They are just different designs. There are even 5-lobe antennas :)

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Todd 29th November 2017 - 9:38 pm

Hey Oscar, when you look at cloverleaf antennas, each “leaf” has two straight “legs”, if you will, and a curved section. DIY videos stress the importance of the length of the curved part. My question is, is the length of the “legs” less significant (or completely insignificant) because of the right-angle bends?

Thanks!

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Arun 11th August 2017 - 1:07 pm

Is it to use circular polarized antenna for vtx and linear polarised for vrx…?

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Oscar 11th August 2017 - 4:06 pm

It will work in short range, and there will be some signal loss.

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Yoann 17th May 2017 - 3:26 pm

In my experiences (without scientist facts), I’ve better reception with linear (simple wire) than with circular, specially in indoors conditions. Not having any range consideration but only glitches consideration

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Oscar 18th May 2017 - 12:51 pm

There are a lot of variables in this, such as the quality of the CP antenna you are comparing to, tuned frequency, the power of your VTX etc…

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shazzner 17th May 2017 - 3:18 pm

One question, I’ve been very curious about and maybe you could write a blog piece about is how to handle multiple transmitters on a single aircraft. I’m talking about a Video Transmitter (possibly even two), MavLink, perhaps Wi-Fi or Mobile. All I’ve seen so far is ‘keep them away as far as possible’ to prevent interference but this doesn’t seem the best guideline for something as relatively small as a drone. I’ve seen techniques such as beamforming, but I believe that only applies for signals all on the same frequency. Just curious on your thoughts!

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Jim eastep 24th May 2016 - 1:01 pm

Oscar:
Your explanations and diagrams are the BEST!
My question is regarding the facts, not hype on patch/planar antennas. I am seeing some providers claim they have patch antennas that are designed for circularly polarized signals, presumably from clover leaf or skew planar transmitter antennas.
Could you discuss and explain how a patch antenna would/could be adapted to circularly polarized signals and confirm/refute my belief that patch antennas have historically worked best with linearly polarized signals?
Thanks!
Jim

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Steven G 5th January 2016 - 8:46 am

Hi Oscar, I’m trying to improve the wifi link and rc link on my Q500 quad. The system I have is a Itelite DBS Phantom linear polarized antenna on my tx for both 2.4ghz and 5.8ghz, And on my quad I have externally mounted a RHCP cloverleaf for the 2.4ghz side and a skew planer RHCP for the 5.8ghz side. Is this setup totally wrong and if so what could I do to improve it ? I’m thinking that I have a mismatched antenna system. Thank you in advance. Steven

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Kelvin 30th August 2015 - 12:33 am

Hi Oscar
I am a physics graduate and I’d like to point out:
A cloverleaf (or a skew antenna) DOES NOT transmit circularly polarized waves! It only transmits mixed polarity signals (ie Horizontally + vertically polarized). Just like radio waves from your local radio stations.
it’s a common mistake. The term “circularly polarization” is often erroneously used to describe mixed polarity signals.

(To transmit circularly-polarized radio waves, you’ll need something like a helical antenna or something else clever. )
While a cloverleaf minimizes loss of signal, I doubt it maximizes range – as long as you are comparing it to a linear antenna with the same size.

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Oscar 30th August 2015 - 5:38 pm

Hi Kelvin, thanks for the info, i will look into this in more detail and come back to this :)
regards Oscar

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Francis 4th June 2015 - 9:23 pm

Can a skew planar antenna be used with a radio transmitter (Dx7, Taranis, etc.)? Will it increase the range of the radio link?

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Oscar 5th June 2015 - 1:57 pm

i don’t see why not! but most people never have any problem with weak radio link so it’s not very common i guess :)

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Keith 5th April 2015 - 6:59 am

Can’t find info I need on the net anywhere.
Please can some one help.

Fpv, circular polarised antennas.
Do right circular transmitter polarised antennas work with right or left polarised receive antennas?

That’s it. But hard to find the answer as I have found out.
Thanks in advance for any help you can give me.
Keith.

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Oscar 6th April 2015 - 1:07 am

no, both antennas need to be the same direction, right hand with right hand, left with left.

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dROb 31st March 2015 - 5:19 pm

Good stuff! Except that Cloverleaf is not larger than Skew-Planar Wheel, they are basically similar..

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Alex 29th January 2015 - 3:54 am

Thanks for the article but I have a question. What happens if you mix circular cloverleaf antenna on the transmitter with linear polarized on the receiver?

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Oscar 29th January 2015 - 9:58 am

it will work, but it just doesn’t give you the best range.

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Candelaria 27th May 2014 - 12:20 pm

Thanks for sharing such a nice opinion, paragraph is good, thats why i have read it
completely

Reply