ADS-B antenna and location guide
We’ve put together the following guide and tips to help you to get the best out of your ADS-B equipment. Learn about choosing the best location, mounting guidance, antenna selection and picking the right antenna position.
Table of contents
Location selection
There are two main things to consider when locating your antenna; direct line of sight (LOS) and vertical alignment. When mounting and positioning the ADS-B antenna, it is critical that in the immediate vicinity, any masts, other antennas, and metal parts of neighboring objects are at a horizontal distance.
Good position
Bad position
roofline blocking antenna
Bad position
inside
Cables can also be a source of interference in the immediate vicinity as the cable’s sheathing acts like a metal part. The higher the antenna in relation to the environment, the larger the area from which it can receive signals. Obstacles such as buildings and topography can also play a role. These include mountains, buildings, settlements, forests, and even the foliage of nearby trees. At greater distances, the completely natural course of the terrain up to the curvature of the earth can also cause disturbance.
Indoor positions, even if only behind a coated window pane or under a roof, will always compromise the signal. An internally positioned antenna will not produce good results. Your antenna must be aligned vertically. The more perpendicular to the horizontal the position is maintained, the better the radio connection will be (if an antenna is mounted at an angle, half of this radiates into the ground and not to the horizon, or it does not receive any signals from the horizon).
Antenna mounting guidance
Mounting on the top of a mast
1 antenna
2 antennas
If you can not mount on the top of a mast
"Placing the antenna outside, as high as possible, is essential. An internally positioned antenna will not produce good results."
Picking the right atenna position
Bad position
as high as possible
Bad position
as high as possible
Bad position
buildings blocking antenna
as high as possible
good reception of ADS-B signals
Incorrect antenna placement with blockage
bad or no ADS-B signal reception
Choosing the right antenna
Within the radio frequency (RF) range, radio performance depends on the antenna – regardless of whether you use the antenna for transmitting or receiving. The antenna is the best amplifier and its selection should be prioritized over anything else. This means, for example, an amplifier cannot compensate for an antenna that is too small. More is more! A doubling of the mechanical dimensions brings a maximum gain of almost +3 dB. A FLARM antenna of 8 cm, for example, cannot reach a real 8 dB. That said, you should be mindful when checking the marketing information of manufacturers.
As for the type of antenna, narrow-band antennas usually have higher gain than broad-band antennas. If you’re considering adding an amplifier to the antenna of the right size, consider an active antenna with a built-in amplifier first. Finally, depending on your location, consider whether you can or must rely on the durability of the antenna. Weather resistance is a must for outdoor use, and high-quality products can also withstand extreme heat, high humidity, or, for example, seawater.
You should also be prepared for potential issues: What happens if the glued areas break? Does water then run into the antenna and maybe even further into the cable? If you notice any weathering effects on the antenna, it is good practice to clean any algae buildup off to inspect the top cap for any damage or breaches and the silicone seal around the base. Any moisture build-up or cuts may allow water or condensation to build up inside. This has a high probability of reducing reception performance.
Antenna accessories
With masts and mastheads, the most important factor is antenna placement. The only thing that will ruin the range of a well located, powerful antenna is the wrong accessories. The most used hardware here is filters and amplifiers. Filters are used when interference from other transmitters cannot be avoided when choosing the location – such as the LTE/GSM mobile antenna on the neighbour’s roof.
We advise against filters because they can lead to an attenuation of the signal. Receiver preamplifiers are a means of compensating for a lack of sensitivity in the receiving device or the attenuation caused by a long cable that is absolutely necessary. A reception preamplifier will not be able to work in the vicinity of strong transmitters because the strong signals from the transmitters overload it. It may be better or even necessary to use a filter so that the receiver is not overloaded by the transmitters.
Regardless of the use of a receiver amplifier, it is worth using as few adapters as possible and cables as short as necessary. Use high-quality adapters and the shortest possible, low-attenuation cables. And last but not least, please don’t forget to ground during installation: direct lightning strikes are unpredictable and protection against electrostatic discharge needs to be considered. The higher the antenna, the better the reception. If the receiver can be located close to the antenna, there will be less signal degradation from the coax cable which loses data over a long cable run.
Summary
An antenna that is freestanding and placed as high as possible usually covers most of the surrounding area in direct line of sight. In a city, the immediate surroundings are the limiting factor. Houses and trees, especially those with a lot of foliage in the summer months, limit the range and strength of the signal. Other obstacles, such as near mobile phone masts, should also be avoided or compensated for.
Next on the list of priorities is antenna gain. You can recognize a good omnidirectional antenna by the fact that it achieves maximum gain for its physical size. If you then mount the antenna correctly and choose cables with low attenuation, almost nothing can go wrong. Finally, depending on the cause of your setup’s performance degradation, you can significantly improve the performance of the antenna with an amplifier or a filter.
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