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.

banggood

Receiver Antenna Explained

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

The size of the antenna depends on the radio frequency, lower frequency such as 900MHz usually has a bigger antenna than 2.4GHz

Crossfire receiver antenna

ExpressLRS receiver antenna

 

Antenna Radiation Pattern

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

Dipole Antenna Radiation Pattern

Antenna Positioning vs Range

The alignment of transmitter and receiver antennas affects your range tremendously.

In example #1 in the following graph, it shows the optimal antenna alignment for maximum range where the antennas are parallel.

crossfire antenna alignment orientation effect range signal strength

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

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

How to Mount Receiver Antenna

The Lazy Way

If you don’t fly long range, it’s pretty common to just strap the antenna to one of the arms using zip ties. This is probably the easiest 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.

Another common solution is to use 3D printed mount, which makes a clean looking build.

Here is a bad example, as you can see, both ends of the antenna are touching the carbon fibre. It’s important to keep the active element of the antenna as far away from carbon fibre as possible if you want to get the best possible range. Carbon fibre is conductive and can block/attenuate radio signal.

The Best Way

For convenience and durability, most people would just mount their RX antenna horizontally, but the best way is to mount your antenna vertically so the receiver antenna is always align with the transmitter antenna.

You might be wondering why is the antenna tilted at an angle? Well, we have to compensate for the attitude of the aircraft when it’s flying forward.

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

I normally 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 as I showed you earlier, 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. If you are just flying around yourself in close range, this is usually fine, but this is not good for long range. It’s important to have both antennas be parallel to each other for the most consistent signal.

To address this, you could point your TX antenna side way to match the receiver antenna, but you will 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

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 might 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 should mount it for the best possible signal according to your flying style.

Monopole Antenna

Monopole antennas are basically just a piece of wire (sometimes with a grounded shielding), where the exposed wire is the active element. It has the most simple antenna construction.

Most modern receivers have switched over to dipole antennas, but older receivers tend to use 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 (after all it’s just a simple copper wire).

Monopole antennas have similar radiation pattern to dipole, it has the strongest signal on the side and weakest signal at the tip.

How to Mount Diversity Receivers Antennas

Single antenna receivers are aboslutely fine, but if you want more consistent/reliable radio signal I think diversity receivers are definitely the way to go. Check out the latest diversity receiver options for ExpressLRS. Make sure to get those with TCXO which has more accurate frequency.

Diversity receivers have two antennas, how you mount them depends on the application and how you fly.

Radiomaster Rp3 And Betafpv Superd Expresslrs Elrs Diversity Receivers Rx Compare

Usually, you would want to them mounted perpendicular to each other (at 90 degree apart), so you can always get a good alignment with at least one of the antennas at all time.

But if you are mostly just cruising (no freestyle moves and acrobatics), I have found in my testing that mounting both antennas upwards actually gives better RSSI and more consistent LQ. But for freestyle and acro, it’s probably safer to have one antenna pointing up and the other laying flat, which seem to perform better than having both at 45-degree to the horizon (90-degree apart).

Elrs Diversity Receiver Antenna Mounting Test Lq Rssi 45 Degree Elrs Diversity Receiver Antenna Mounting Test Lq Rssi One Up Flat Elrs Diversity Receiver Antenna Mounting Test Lq Rssi Both Up

For diversity receiver using monopole antennas, 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 for flying close range. The goal here is to have at least one of the two 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
  • Jan 2023 – Added data from diversity antenna mounting testing

Leave a Comment

By using this form, you agree with the storage and handling of your data by this website. Note that all comments are held for moderation before appearing.

28 comments

Laurent M. 3rd February 2023 - 1:16 am

Thank you so much for the diversity update. Was looking exactly for this information.
Have you tested different TX antenna orientation when antennas are at an angle?

Reply
Kernel Panic 18th November 2022 - 4:17 pm

Finally. I sure wish I’d stumbled across this article a long time ago. Electronics I understand, but I must admit antennas (antennae?) baffle me. I am currently experimenting with FPV transmission and have been forced to just purchase many types of antennas and use a dev board and serial monitor to report their RSSI. I now have a much better understanding, however, I wish you would have included some information on the “lollipop” antennas. So far, I’ve had the best RSSI readings with them, but looking back, it could be from my lack of orientation knowledge. Thanks for taking the time to post your research.

Reply
Markus 24th August 2022 - 1:14 pm

Hi,
how is the Radiation Pattern of the ceramic tower and flat Antenna and how is the best option to place them?

Reply
babipsylon 23rd July 2022 - 11:57 am

Your use of “side” and “ends” is confusing :)

Reply
MunchkinFPV 19th July 2022 - 1:46 pm

Thank you oscar!
Great article!
Could you share with us the stl for the vertical antenna mount?
Thanks

Reply
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

Reply
Oscar 10th May 2022 - 3:52 pm

No it doesn’t matter which side is up.

Reply
sofyan 4th January 2022 - 2:15 am

i m agree the mounting antenna refer to your picture
https://oscarliang.com/wp-content/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).

Reply
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

Reply
Oscar 3rd June 2020 - 12:19 am

Correct

Reply
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…

Reply
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?

Reply
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.

Reply
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

Reply
Charles 6th September 2019 - 7:28 pm

BEST VISUAL EXPLANATION ON THE INTERNET !

Reply
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!

Reply
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.

Reply
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

Reply
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.

Reply
Oscar 26th May 2019 - 2:45 pm

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

Reply
DIEDERIK THIERS 9th May 2019 - 3:45 am

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

Reply
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?

Reply
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

Reply
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