How to Mount/Position Transmitter and Receiver Antenna on FPV Drone

by Oscar
How To Point Transmitter Tx Antenna Rx Receiver Vertical Zorro

By properly mounting and positioning your radio transmitter and receiver antennas, can optimize signal quality and range. In this post I will show you the the best ways to point antennas in various RC systems including Crossfire, ExpressLRS and Frsky.

Dipole Antenna Explained

Most modern radio receivers use dipole antennas, such as ExpressLRS and Crossfire. There are two ends in a dipole antenna – one end is the antenna element and the other is ground. Both ends are equally important, if either end is damaged it will have an impact on performance.

The size of the antenna depends on the radio frequency, lower frequency usually has a bigger antenna.

 

Antenna Radiation Pattern

The radiation pattern of a dipole antenna is a doughnut shape, it has the strongest signal on the side and worst on both ends.

Dipole Antenna Radiation Pattern

Antenna Positioning vs Range

The alignment of transmitter and receiver antennas plays a huge role in your range.

crossfire antenna alignment orientation effect range signal strength

Example #1 shows the optimal antenna alignment for maximum range where the antennas are parallel.

Now imagine your quad just rotates 90 degree, and we have example #2, where the RX antenna’s tip is pointing at the TX antenna, and your range will be reduced.

The worst case scenario is example #3, where the tips of both antennas are pointing at each other.

How to Mount Dipole Receiver Antenna

The Lazy Way

For non-long range rigs, I usually just strap the antenna to one of the rear arms with zip ties. This is probably the easiest and most common way to install RX antenna.

For “loose” dipole antennas, you can use two zip tie wrapped around the arm pointing at the opposite direction, and strap the antenna wires to the ziptie with heatshrink tubes.

You can also use 3D printed mount.

Here is a bad example, as you can see, both ends of the antenna are touching the carbon fibre. Keep the antenna active element as far away from carbon fibre as possible if you want to get good range. Carbon fibre is conductive and can block/weaken radio signal.

The Best Way

For convenience and durability, most people would just mount their RX antenna horizontally. Although it’s not always possible, my preferred way is to mount it vertically so the sides of the antenna are always facing the transmitter antenna.

Note that the RX antenna is mounted with a tilt angle to compensate for the attitude of the aircraft when flying forward.

Receiver Antenna Mounted Vertically Fpv DroneThe Best Way to Point TX Antenna

I always point the transmitter antenna up, so it would be parallel to the receiver antenna which I also normally have it mounted vertically. This is due to the radiation pattern (same as the receiver antenna radiation pattern), signal comes out from the side of the antenna and not from the tip of the antenna. This minimizes the chances of having both your antenna’s tips line up and results in the worst possible signal.

How To Point Transmitter Tx Antenna Rx Receiver Vertical Zorro

If you have a moxon antenna on the TX, the same principle applies.

How To Point Transmitter Tx Antenna Rx Receiver Vertical Tx16s

However, if you have your RX antenna mounted horizontally, this is actually not such a good idea as you will get something called “cross polarization”, where signals are at 90 degree to each other, and this can result in a pretty big signal loss. For short range flying, this is usually fine, but for longer range flying, it’s best if you can have both antennas in parallel for the most consistent signal.

To address this, you could also point your TX antenna side way, but you have to make sure you don’t fly to your sides and always have the model stay in front of you.

How To Point Transmitter Tx Antenna Rx Receiver Horizontal

That’s because the signal is the weakest when the tips of the antennas are pointing at each other.

For example, this is bad.

How To Point Transmitter Tx Antenna Rx Receiver Horizontal Tip To Tip Side

Be Smart

You might need to change how you point your antennas depending on the situation.

Let’s say if you were going to dive a building, you would be flying directly above yourself, then pointing the antenna side way would be beneficial in this scenario.

But if you are just flying around yourself, then it’s probably better to point the antenna upward, and this is usually the case for most people.

If you are using other types of antenna on your transmitter rather than the usual dipole antenna, you might want to check its radiation pattern and determine how you mount it for the best possible signal according to your flying style.

Monopole Antenna

Older receivers used to have monopole antennas, such as the Frsky R-XSR. Sometimes it’s also used in weight-critical applications, such as tiny whoop receivers where every gram counts (they just use a simple copper wire).

It’s basically just a piece of wire (usually with a grounded shielding), where the exposed wire is the active element.

It has similar radiation pattern to dipole, strongest signal on the side and weakest signal at the tip.

Mounting Diversity Receivers Antennas

Diversity receivers usually use two monopole antennas. Ideally, these antennas should be mounted perpendicular to each other (at 90 degree).

Simply mount the two antennas at 90-degree apart, ideally pointing them upward for the reasons mentioned above.

It’s also pretty common to lock a zip tie to each arm and to heat shrink each antenna to one of the protruding zip ties, this is easy and usually works fine if range isn’t a concern.

The image below demonstrates my mounting method.

The goal here is to have at least one of the antennas stays in line of sight to the transmitter antenna.

That’s it. Happy flying!

Edit History

  • Oct 2018 – Tutorial created
  • May 2022 – Changed URL, updated post to include ExpressLRS receivers, added diversity receiver antenna mounting, added some more images for demonstration

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23 comments

Joris 9th May 2022 - 8:32 pm

maybe a strange question.. But does it matter wich of the 2 sides of the dipole is up? Im using the frsky r9 module with the super 8 antenna. the super 8 I use vertical and the 2 dipoles in a small angle from vertical to adapt to the banking of the wing. There are (EU freq) yello rings on the dipoles but does it matter if they stick up or down?
Cheers!! J

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Oscar 10th May 2022 - 3:52 pm

No it doesn’t matter which side is up.

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sofyan 4th January 2022 - 2:15 am

i m agree the mounting antenna refer to your picture
https://oscarliang.com/ctt/uploads/2019/02/frsky-r9m-r9mm-antenna-mount-mini-quad-racing-drone-1024×683.jpg
this methodology in theoretically will give the possible signal strength about 50% to 100% according to the movement of the quad,,,

Reply
Mark 26th November 2020 - 4:08 am

Thank you Oscar for all your hard work and efforts.

A quick question, I understand carbon fiber is a NO-NO for antenna placement, how about foam, battery and electronic (FC / ESC excluding VTx).

Thanks.

Reply
MIchael Bibby 18th September 2020 - 2:04 pm

Its probably already been in the comments section already, but in the example you gave for how not to mount a crossfire dipole, probably the worst factor is the metalwork of the motors themselves, more than the proximity to the carbon fibre. The radiation pattern and SWR of a dipole is effected by nearby metal more than anything, especially when its in the same orientation as the elements themselves (but a dipole wont really be effected by, say, the metal poll that it is mounted on, because its orientated 90 degrees to its axis).
One question I have (being quite new to longrange FPV), is: does anyone make a good 1/2 wave, ground-independent, end-fed vertical antenna for use with crossfire that could easily be mounted on a drone? I guess it would have to be ground-indepedent because of the lack of metal on a drone, but maybe not. I’m pretty sure, if it was to be efficient, it would need a matching circuit to balance the impedence at the feed point, but then again it is only a receiving antenna, so maybe not. Anyway, there are plenty of 800/900 mhz antenna’s out there (for various applications), but I don’t see anyone adapting them for use on drones (yet).

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Steffen 4th May 2020 - 4:21 pm

Hey there. Since Frsky R9 and CRSF are on 868MHz in Europe, I presume the antennas are interchangeable, right?

Cheers Steffen

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Oscar 3rd June 2020 - 12:19 am

Correct

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Randy 16th February 2020 - 10:31 pm

do you (or anyone here) have the .stl file (or know where to get it) for that 3D printed mount? looking to upgrade my quads…

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Jorge 15th January 2020 - 10:28 am

I have a 868Mhz immortal T antenna, if i go to the US and change my frequency to 915Mhz but keep the same antenna will my performance go down significantly?

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Oscar 24th January 2020 - 4:47 pm

As far as I know their antennas are made to work for both frequency, so you shouldn’t notice too big of a difference.

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Jan Demant 12th October 2019 - 1:24 pm

:) Ty for UL and all your great work
Where did case #3 go, in antenna positions? :)

LOolz

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Charles 6th September 2019 - 7:28 pm

BEST VISUAL EXPLANATION ON THE INTERNET !

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Dennis 18th June 2019 - 4:00 pm

Does it matter if the antennas are rotated relative to one another while still being parallel (i.e. parallel, but not in the same plane)? Thx!

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Oscar 27th June 2019 - 5:42 pm

Yes, you get some signal reduction when turning one antenna away from the other even when they are parallel.

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Kenn Elliott 7th June 2019 - 5:39 am

What about the R9 with two flat antenna on the ends of two wires? What’s their best orientation Oscar?

Kenn

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Andreas 4th June 2019 - 9:38 am

Hey,
how do I recongize if I have a 915 MHz or a 868 MHz T Antenna? They look similar and I don’t know how to discern.
Thank you!

Reply
Oscar 6th June 2019 - 5:58 pm

From Frsky, they should be have a color heatshrink indicating the frequency. Not sure how TBS differentiate it as I no longer use their system.
But anyway when you buy any receiver or antenna, there should be an option where you can select which frequency you want.

Reply
Jens J 24th May 2019 - 11:01 am

Have you had a prop-strike on that contraption? The reason I’m wondering is that it’s easy to underestimate just how destructive they can be: just the other day I had a worn out prop nut which came lose (my bad for not checking it) at takeoff – the throttle was at maybe 20% – this made the prop detach from the motor shaft, cleanly cut through both antenna tubing and antenna and take off a chunk of the XT60-connector before launching into space, never to be seen again. I’ve had prop strikes damage pretty much anything but the actual carbon fiber on other occasions. So it seems to me, the only real protection from strikes is a tube of carbon fiber or steel, neither being a very good idea… Me, I just make sure to mount things where there is as slim chance as possible of a prop ever getting to them.

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Oscar 26th May 2019 - 2:45 pm

Well, maybe try to avoid having a loose prop? That’s never happened to me.

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DIEDERIK THIERS 9th May 2019 - 3:45 am

Any suggestions on how to mount the wire “floppy” antenna’s?

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Jarrett 19th October 2018 - 3:24 am

In the L rx configuration, i assume the active element is in the vertical position, and ground out back, correct?

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Jon 16th October 2018 - 11:51 pm

I mount the crossfire immortal T antennas in the vertical (y axis) plane out of the back of the quad, I have found this gives consistently the best link quality. (I have 3 x 250 and below crsf quads using the crsf nano rx) The downside of this is that it takes more effort during the build. To stiffen up the pigtail section and reduce the likelihood of prop strikes I cut a 6mm OD PU tube along the axis then hot glue and heat shrink in place. I also 3D print a support out of something light weight like HIPs or PLA that I can hot glue three antenna into; this reduces any rotation force being put onto the ufl connector and helps keep the antenna in position – the total additional weight of the pu, 3D printed part and dabs of glue is 1 to 2grams depending on the quad, insignificant on a 4 or 5” quad

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zak 16th October 2018 - 2:00 am

you can turn the stock antenna into a ‘ghetto’ T using 2 pieces of antenna tube and some heat shrink

Reply