<p>A dipole antenna is linearly polarised, which means it radiates most of its energy in one 'plane' relative to the antenna. For maximum efficiency, the transmit and receive antenna should be orientated such that their plane of radiation is the same, or very close to.</p>

<p>It is important to note that as the aircraft flies around, the orientation of the antenna changes with the aircraft. The reason a vertical orientation is recommended is that aircraft - particularly multirotors - generally<sup>1</sup> fly with one side 'up'; therefore, for whichever direction the aircraft is travelling the antenna is still vertical (or, mostly so) compared with the transmitter.</p>

<p>With a horizontally orientated antenna, when the aircraft turns through 90° relative to the transmitter, the antenna is now 90° out of alignment to the transmitter; it may help to think of/visualise this as "North/South" and "East/West", and the loss of signal will be comparable to vertical vs. horizontal as the angle difference is the same. Some receivers have multiple antennas and recommend orientating them at 90° to each other to mitigate this scenario.</p>

<p>What you may consider, if your transmitter permits it, is to have the antenna at a 45° angle as a compromise for signal strength. Most drones have a built-in lost comms failsafe so a loss of signal should not be a huge concern; for a fixed-wing model aircraft, I would be more concerned about matching antenna orientations.
<hr />
[1] The main exceptions probably being stunt aircraft</p>

CC BY-SA 4.0
2021-06-11T14:15:13.927Z
@DronesandWhatnot:
About every antenna has nulls (i.e. directions in which the antenna has about zero gain). Every antenna also has cross-polarization attenuation. These factors are separate but both present. 
So a linear antenna will reject signals of any polarization coming along its axis, and it will _also_ reject signals that are linearly polarized perpendicular to its axis.
Circular polarization is great in that it stays the same from the antenna's perspective no matter the direction from which the signal is coming, so only directionality remains. This is not so for linear antennae.
FlashCactus
CC BY-SA 4.0
2021-06-11T14:18:19.067Z
@FlashCactus this is what I was saying with regards to the polarisation being independent of orientation but signal reception being dependent upon null zones in the antenna’s reception. Thank you for succinctly putting the discussion into a single comment.
Drones and Whatnot
CC BY-SA 4.0
2021-06-11T14:27:33.100Z
But (linear) polarisation __is__ dependent on orientation: it is the same orientation as the transmitting antenna, and the CP attenuation is dependent on how the receiving antenna is oriented relative to that.
To be fair, the effect @Kralc is referring to in his first paragraph indeed stems from directionality and not polarization, and what he discusses later seems to also relate more to nulls than polarization as well.
To summarize, for the best signal you need to both have the antennae always oriented the same _and_ pointing their sides at each other.
Maybe I should edit the answer...
FlashCactus
CC BY-SA 4.0
2020-04-14T21:34:06.130Z
Good answer, however I don’t think the orientation has to do with polarisation. For example, a dipole antenna is not polarised and accepts RHCP and LHCP signals equally, however there is a dead region running parallel through the long axis of the antenna.
Drones and Whatnot
CC BY-SA 4.0
2020-04-14T21:36:47.317Z
@DronesandWhatnot You are correct about circular polarisation, however I refer to linear polarisation where orientation does make a difference. (I am not familiar with the Crossfire range specifically, but my searches online have not indicated this uses circular polarisation; and, the pictures generally show dipoles.)
Kralc
CC BY-SA 4.0
2020-04-14T21:54:31.490Z
I’m not an RF expert, however as far as I am aware that is the directional gain, not the polarisation. For example, if I have an RHCP patch receiver antenna and an RHCP omni TX antenna, if I face the patch away from the TX, the orientation is different and it’s gain is lower, however the polarisation of both the EM waves and the antenna is the same. Again, I’m not an RF expert by any means, this is just how I have always understood polarisation.
Drones and Whatnot
CC BY-SA 4.0
2020-04-14T21:56:07.350Z
I see what you are saying, and I agree that the type of polarisation isn't changing when you change the angles, just the relative orientation. I've probably oversimplified by referring to the angles as discrete 90° segments; as linear polarisations are commonly horizontal or vertical, I've extended my answer from this. I'll have a go at rewording to try and make this clearer, but still keep it accessible.
Kralc
CC BY-SA 4.0
2020-04-14T21:57:03.680Z
ah okay, thank you. Sorry if I came across as confrontational.
Drones and Whatnot
CC BY-SA 4.0
2020-04-14T22:00:45.447Z
Not at all; it's good to have another view and it means a better answer. It is difficult to critique your own writing, as you know what it 'should' mean!
Kralc
CC BY-SA 4.0
2020-04-14T22:02:29.373Z
good point! And I hope that our discussion will be useful for someone in the future trying to gain a better understanding! :)
Drones and Whatnot
CC BY-SA 4.0
2020-04-14T21:31:51.140Z
2020-04-21T22:12:09.987Z
2020-04-21T22:12:09.987Z
Kralc
<p>In theory, both vertical is the best way to go. However, I've got over 2 miles with both antenna's being horizontal without any issues.  Crossfire is such a robust signal that, if you are not pushing serious range, you can get away with putting your antennas any orientation and still be ok.</p>

CC BY-SA 4.0
2020-04-14T21:49:46.907Z
2020-04-21T04:33:27.150Z
2020-04-21T04:33:27.150Z
tavis
<p>I've always heard that you should orient the antenna on the Crossfire transmitter vertically, with the ends pointing up and down. I've also heard that you should do the same with the receiver antenna (immortal T), but on many builds that is difficult or less durable, so I mount the antenna horizontally on the drone (under an arm, for example).</p>

<p>For the best signal when flying a drone that has a horizontally mounted Crossfire antenna, should I also rotate the transmitter antenna horizontal to match, or is it better to keep it vertical regardless?</p>

<p>It would be great to understand the logic either way as well. Thanks!</p>

<crossfire><antenna><immortal-t>
Should Crossfire transmitter antenna orientation match receiver antenna orientation?
Yorb
# Should Crossfire transmitter antenna orientation match receiver antenna orientation?

(Asked by: username_0 on 2020-04-14)

I've always heard that you should orient the antenna on the Crossfire transmitter vertically, with the ends pointing up and down. I've also heard that you should do the same with the receiver antenna (immortal T), but on many builds that is difficult or less durable, so I mount the antenna horizontally on the drone (under an arm, for example).

For the best signal when flying a drone that has a horizontally mounted Crossfire antenna, should I also rotate the transmitter antenna horizontal to match, or is it better to keep it vertical regardless?

It would be great to understand the logic either way as well. Thanks!

**Tags:** crossfire, antenna, immortal-t

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## 2 answers

### Answer by username_1 on 2020-04-14. Score: 4 | Accepted answer

A dipole antenna is linearly polarised, which means it radiates most of its energy in one 'plane' relative to the antenna. For maximum efficiency, the transmit and receive antenna should be orientated such that their plane of radiation is the same, or very close to.

It is important to note that as the aircraft flies around, the orientation of the antenna changes with the aircraft. The reason a vertical orientation is recommended is that aircraft - particularly multirotors - generally1 fly with one side 'up'; therefore, for whichever direction the aircraft is travelling the antenna is still vertical (or, mostly so) compared with the transmitter.

With a horizontally orientated antenna, when the aircraft turns through 90° relative to the transmitter, the antenna is now 90° out of alignment to the transmitter; it may help to think of/visualise this as "North/South" and "East/West", and the loss of signal will be comparable to vertical vs. horizontal as the angle difference is the same. Some receivers have multiple antennas and recommend orientating them at 90° to each other to mitigate this scenario.

What you may consider, if your transmitter permits it, is to have the antenna at a 45° angle as a compromise for signal strength. Most drones have a built-in lost comms failsafe so a loss of signal should not be a huge concern; for a fixed-wing model aircraft, I would be more concerned about matching antenna orientations.

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[1] The main exceptions probably being stunt aircraft

> **Comments:**
> **username_3**: Good answer, however I don’t think the orientation has to do with polarisation. For example, a dipole antenna is not polarised and accepts RHCP and LHCP signals equally, however there is a dead region running parallel through the long axis of the antenna.  
> **username_1**: @DronesandWhatnot You are correct about circular polarisation, however I refer to linear polarisation where orientation does make a difference. (I am not familiar with the Crossfire range specifically, but my searches online have not indicated this uses circular polarisation; and, the pictures generally show dipoles.)  
> **username_3**: I’m not an RF expert, however as far as I am aware that is the directional gain, not the polarisation. For example, if I have an RHCP patch receiver antenna and an RHCP omni TX antenna, if I face the patch away from the TX, the orientation is different and it’s gain is lower, however the polarisation of both the EM waves and the antenna is the same. Again, I’m not an RF expert by any means, this is just how I have always understood polarisation.  
> **username_1**: I see what you are saying, and I agree that the type of polarisation isn't changing when you change the angles, just the relative orientation. I've probably oversimplified by referring to the angles as discrete 90° segments; as linear polarisations are commonly horizontal or vertical, I've extended my answer from this. I'll have a go at rewording to try and make this clearer, but still keep it accessible.  
> **username_3**: ah okay, thank you. Sorry if I came across as confrontational.  
> **username_1**: Not at all; it's good to have another view and it means a better answer. It is difficult to critique your own writing, as you know what it 'should' mean!  
> **username_3**: good point! And I hope that our discussion will be useful for someone in the future trying to gain a better understanding! :)  
> **username_2**: @DronesandWhatnot: About every antenna has nulls (i.e. directions in which the antenna has about zero gain). Every antenna also has cross-polarization attenuation. These factors are separate but both present.  So a linear antenna will reject signals of any polarization coming along its axis, and it will _also_ reject signals that are linearly polarized perpendicular to its axis. Circular polarization is great in that it stays the same from the antenna's perspective no matter the direction from which the signal is coming, so only directionality remains. This is not so for linear antennae.  
> **username_3**: @FlashCactus this is what I was saying with regards to the polarisation being independent of orientation but signal reception being dependent upon null zones in the antenna’s reception. Thank you for succinctly putting the discussion into a single comment.  
> **username_2**: But (linear) polarisation __is__ dependent on orientation: it is the same orientation as the transmitting antenna, and the CP attenuation is dependent on how the receiving antenna is oriented relative to that. To be fair, the effect @Kralc is referring to in his first paragraph indeed stems from directionality and not polarization, and what he discusses later seems to also relate more to nulls than polarization as well. To summarize, for the best signal you need to both have the antennae always oriented the same _and_ pointing their sides at each other. Maybe I should edit the answer...  

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### Answer by username_4 on 2020-04-14. Score: 1

In theory, both vertical is the best way to go. However, I've got over 2 miles with both antenna's being horizontal without any issues. Crossfire is such a robust signal that, if you are not pushing serious range, you can get away with putting your antennas any orientation and still be ok.


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