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.
Antenna Positioning vs Range
The alignment of transmitter and receiver antennas plays a huge role in your range.
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.
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.
If you have a moxon antenna on the TX, the same principle applies.
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.
That’s because the signal is the weakest when the tips of the antennas are pointing at each other.
For example, this is bad.
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.
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.
- 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