When you look at a rooftop gateway installation for a smart city or a large agricultural network, you will almost certainly see a rigid, grey or white pole pointing towards the sky. It looks unassuming, perhaps like a standard radio mast, but this simple cylinder is a precision-engineered piece of hardware known as a LoRa fibreglass antenna.
For anyone deploying a LoRaWAN network, moving from the small, plastic “stubby” antenna that comes in the box to a proper outdoor fibreglass unit is the single most effective upgrade you can make. It is the difference between covering a single building and covering an entire town.
At Concept13, we understand that the reliability of your data depends entirely on the quality of your signal. This article explains what a LoRa fibreglass antenna is, why this specific material is the industry standard for outdoor IoT, and how to choose the right one for your specific environment.
The Quick Answer
A LoRa fibreglass antenna is a robust, outdoor-rated antenna designed to transmit and receive LoRaWAN signals over long distances. The internal copper element is housed inside a protective tube made of fibreglass (GRP). This material is chosen because it is RF transparent, meaning it lets radio waves pass through without interference, while being incredibly strong, rigid, and weatherproof. Unlike small indoor antennas, these are typically “collinear” designs, which stack multiple internal elements to flatten the signal beam and push it out towards the horizon, significantly increasing range.
Why Fibreglass? The Material Advantage
You might wonder why these antennas are not made of plastic, like a Wi-Fi router antenna, or metal, like an old car aerial. The choice of fibreglass is not aesthetic. It is purely functional.
Radio Frequency (RF) Transparency
The most important job of an antenna’s casing, or “radome,” is to protect the delicate metal parts inside without blocking the signal. Metal blocks radio waves entirely. Some plastics can absorb radio waves or degrade quickly under the sun.
Fibreglass is electromagnetically invisible to the radio frequencies used by LoRaWAN (868 MHz in the UK). This means that the signal generated by the copper core passes through the casing as if it were not even there. This maximises the efficiency of the transmission.
Rigidity and Stability
Imagine a thin, whippy antenna in a gale-force wind. It bends and sways wildly. As the antenna moves, the signal beam moves with it. This causes “signal flutter,” where the connection to distant sensors drops in and out as the beam swings up into the sky or down into the ground.
Fibreglass is incredibly stiff. A high-quality LoRa fibreglass antenna will barely move, even in high winds. This ensures that the signal beam remains perfectly horizontal and locked onto the horizon, providing a stable connection for critical applications like smart city technology.
Durability in British Weather
Outdoor IoT networks must survive for years without maintenance. They face freezing rain, scorching UV radiation in summer, and corrosive salt air in coastal regions. Fibreglass is non-corrosive and UV-stable. It does not rust, it does not become brittle and crack like cheap plastic, and it seals perfectly to keep water out of the connector.
Inside the Tube: How It Works
It is a common misconception that the entire grey stick is the antenna. In reality, the fibreglass is just the shell. Inside, suspended in the centre of the tube, is the actual antenna element.
The Collinear Array
Most fibreglass antennas are “collinear” arrays. Instead of a single piece of wire, they consist of several shorter copper or brass elements stacked vertically on top of each other, separated by phasing coils.
This stacking effect is what creates “gain.” By phasing the elements correctly, the antenna suppresses the energy that would normally be wasted going up into space or down into the roof. It forces that energy outwards in a flat disc.
An Analogy: The Doughnut
Think of the signal coming from a small, indoor antenna as a round balloon. It goes everywhere equally. Now, imagine squashing that balloon flat between two books. The balloon gets wider. It covers less vertical height, but it reaches much further out to the sides. This is what the internal structure of a fibreglass antenna does. It shapes the signal into a flat “doughnut” shape to maximise distance across the land.
Selecting the Right Gain (dBi)
When buying a fibreglass antenna, you will see a rating in dBi (decibels relative to isotropic). Common ratings are 3dBi, 5.8dBi, and 8dBi. It is a mistake to assume that “higher is always better.”
3dBi to 4dBi (The Round Apple)
- Beam Shape: Rounder, like an apple.
- Best For: Hilly terrain or dense urban cities. If you are in a valley or need to reach sensors that are higher or lower than the gateway, this is the best choice. It has a wide vertical reach.
5.8dBi (The Standard Doughnut)
- Beam Shape: Flatter, like a standard jam doughnut.
- Best For: General suburban use and mixed environments. This is the most common “all-rounder” for UK deployments. It offers a great balance of distance and vertical coverage.
8dBi and Above (The Flat Pancake)
- Beam Shape: Extremely flat and wide, like a pancake.
- Best For: Very flat, open countryside.
- The Risk: Because the beam is so thin, if you mount this high up on a hill, the signal might shoot right over the top of nearby buildings, creating a “dead zone” underneath. It is also harder to align.
The The Things Network (TTN) community provides excellent documentation on how these gain values affect real-world coverage maps.
Installation Best Practices
Even the most expensive fibreglass antenna will perform poorly if installed incorrectly.
Height and Line of Sight
Radio waves at LoRaWAN frequencies travel in straight lines. They can pass through some walls, but they cannot pass through hills or dense earth. The antenna must be mounted as high as possible, ideally clearing the roofline of surrounding buildings.
Vertical Mounting
Because of the “doughnut” signal shape, the antenna must be perfectly vertical. If you mount a fibreglass antenna at a jaunty angle, you are shooting your signal into the ground on one side and into space on the other. Use a spirit level when tightening the brackets.
The “Choke” Point: Connectors and Tape
The connection point where the coaxial cable screws into the bottom of the antenna is the most vulnerable spot.
- Connectors: Most fibreglass antennas use an N-Type connector. This is a rugged, weatherproof screw connector, much larger than the small SMA connectors found on indoor routers.
- Waterproofing: You must wrap this connection in Self-Amalgamating Tape. This is a rubbery tape that fuses to itself to form a solid, waterproof rubber lump. If water gets into this connector, it will travel down the inside of the coax cable and destroy your gateway.
Grounding and Lightning Protection
A tall fibreglass pole with a copper core mounted on a roof is, by definition, a lightning rod. While the fibreglass itself doesn’t conduct, the wire inside does.
A Lightning Arrestor should be installed between the antenna and the gateway. This is a small device that acts as a fuse. If high voltage hits the antenna, the arrestor diverts that energy to a ground wire (connected to the building’s earth) before it can travel down the cable and blow up your expensive gateway. Safety standards from bodies like the Radio Society of Great Britain (RSGB) offer guidance on proper earthing procedures.
Conclusion
The LoRa fibreglass antenna is the unsung hero of the Internet of Things. It transforms a fragile electronic signal into a robust, long-range communication link capable of connecting sensors miles away.
By choosing fibreglass, you gain a component that is transparent to radio waves yet tough enough to withstand a British winter. However, success lies in the details. You must choose the right gain for your terrain (avoiding the “bigger is better” trap) and ensure the installation is vertical, waterproof, and grounded. With the right fibreglass antenna standing guard on your roof, your LoRaWAN network will have the reach and reliability it needs to succeed.
