IoT Antenna Selection Guide: PCB, FPC, Spring, Rubber Duck, Magnetic, Fiberglass, and GNSS Antennas

Choosing an antenna for an IoT product is not simply a matter of matching a wireless frequency.

Two devices may both use the same radio module and still need completely different antenna structures.

A battery-powered sensor inside a plastic enclosure may work well with a PCB antenna. A compact tracker may need an FPC antenna because the available installation area is irregular. A smart meter may use a spring antenna when vertical internal space is available. An industrial gateway may require external rubber duck antennas, while an outdoor LoRaWAN gateway may use a fiberglass antenna mounted above the enclosure.

A tracking device may also need a separate GNSS antenna in addition to its cellular, WiFi, Bluetooth, or LoRa communication antenna.

This is why IoT antenna selection should begin with the complete product architecture.

The wireless standard tells you what frequency must be supported.

The device tells you what type of antenna can actually work.

Start With the Role of the IoT Device

Before comparing antenna types, determine where the device sits in the IoT network.

Typical IoT products can be divided into several roles.

Battery-Powered Sensor Node

Examples include temperature sensors, leak detectors, smart home devices, asset tags, meter nodes, environmental sensors, and LoRa terminals.

These products usually prioritize:

• compact size;
• low power consumption;
• low component count;
• low manufacturing cost;
• internal antenna integration.

PCB, FPC, spring, or compact ceramic antennas are common candidates.

Mobile or Tracking Device

Examples include asset trackers, fleet terminals, wearable devices, smart battery systems, and portable industrial equipment.

These products may require:

• cellular communication;
• GNSS positioning;
• Bluetooth;
• WiFi;
• several antennas inside one enclosure.

The antenna problem is therefore not only size. Isolation, orientation, housing material, battery position, and user interaction also become important.

Indoor IoT Gateway

A gateway may receive data from local sensor nodes through LoRa, Zigbee, Bluetooth, WiFi, or another wireless technology and then forward that data through Ethernet or cellular.

Gateways often have more space than sensor nodes, making external antennas practical.

Rubber duck antennas are commonly used where the product requires replaceable or adjustable external antennas.

Outdoor IoT Gateway

Outdoor gateways may need wider coverage and greater installation flexibility.

Fiberglass antennas can be mounted above the gateway enclosure and away from local obstructions.

This architecture is common in LoRaWAN, industrial telemetry, outdoor WiFi, remote monitoring, and smart infrastructure.

Industrial or Metal-Enclosed Device

A device installed inside a steel cabinet creates a different RF problem.

Even if the internal antenna performs well before installation, the metal cabinet can block or strongly alter radiation.

In these situations, an external rubber duck, through-wall, magnetic mount, or fiberglass antenna may be more appropriate.

RFLink’s Internal Antenna vs External Antenna guide provides additional background on this design choice.

IoT Antenna Types at a Glance

Antenna type	Typical IoT application	Main advantage	Main design concern
PCB antenna	Sensors, smart home devices, compact modules	Low cost and easy mass production	Needs PCB area and controlled ground/clearance
FPC antenna	Trackers, handhelds, compact IoT devices	Flexible placement	Sensitive to housing and installation position
Spring antenna	Smart meters, sub-GHz nodes, compact controllers	Uses vertical space efficiently	Nearby metal and ground structure affect tuning
Rubber duck antenna	Gateways, routers, terminals	Easy external installation and replacement	Connector, orientation and mechanical exposure
Magnetic mount antenna	Metal cabinets, temporary installations, vehicles	Flexible remote antenna position	Ground plane and cable routing matter
Fiberglass antenna	Outdoor gateways and fixed infrastructure	Suitable for elevated outdoor installation	Gain, height, cable loss and vertical beam
GNSS antenna	Trackers and positioning devices	Receives satellite navigation signals	Requires suitable sky visibility and low RF interference

No antenna type is universally superior.

The correct choice depends on the product.

PCB Antennas for High-Volume Compact IoT Devices

A PCB antenna is printed directly onto a circuit board or implemented on a dedicated small antenna PCB.

It can be attractive for high-volume IoT products because it eliminates a separate flexible antenna component and can be highly repeatable when the PCB structure is controlled.

Typical applications include:

• smart home sensors;
• Bluetooth devices;
• WiFi modules;
• smart meters;
• remote controls;
• compact LoRa or sub-GHz products.

However, PCB antennas are strongly dependent on the product ground plane and clearance area.

If the main board becomes smaller, the battery moves, a metal bracket is added, or the enclosure changes, the final RF performance may also change.

This is why a reference antenna copied from an evaluation board does not automatically perform the same way in a commercial device.

For more detail, see RFLink’s PCB antenna selection guide.

When PCB Is a Strong Candidate

Consider a PCB antenna when:

• the product has sufficient board area;
• the enclosure is mainly RF-transparent;
• the mechanical structure can preserve antenna clearance;
• the product will be manufactured in high volume;
• cost and assembly simplicity matter.

FPC Antennas When the Best RF Position Is Away From the Main PCB

FPC antennas are widely used in compact IoT equipment because the antenna does not need to remain on the main PCB.

A flexible antenna can be attached to a better position inside the housing and connected through a small coaxial cable.

This is particularly useful when the PCB is surrounded by:

• batteries;
• displays;
• cameras;
• metal shields;
• motors;
• connectors;
• dense digital electronics.

The antenna can sometimes be moved toward the edge of the housing where the RF environment is better.

Typical applications include trackers, smart locks, handheld devices, industrial sensors, compact gateways, and connected battery equipment.

RFLink’s FPC antenna guide explains placement, cable, connector, enclosure, and tuning considerations in more detail.

The main disadvantage is that FPC placement must be controlled during manufacturing.

Moving the antenna several millimeters, changing the adhesive position, or routing the cable differently can change RF behavior.

Spring Antennas for Compact Sub-GHz Devices

Spring antennas can be useful where the product has limited PCB length but some vertical internal space.

They are common in compact wireless controllers, metering products, alarms, sensors, and sub-GHz IoT equipment.

Instead of using a long PCB trace, part of the electrical length is formed in a three-dimensional spring structure.

This can help fit a lower-frequency antenna into a compact device.

However, a spring antenna is not independent of the product.

Its tuning can be influenced by:

• PCB ground;
• mounting position;
• nearby battery;
• enclosure;
• metal components;
• production tolerances.

A spring antenna should therefore be evaluated inside the final assembly.

Rubber Duck Antennas for Gateways and External Terminals

Rubber duck antennas are among the most familiar external antennas.

They are commonly used on:

• IoT gateways;
• wireless routers;
• industrial terminals;
• LoRa gateways;
• remote control equipment;
• test and development hardware.

They offer several practical advantages.

The antenna is outside the enclosure, can often be replaced, and may use standard connectors such as SMA or RP-SMA depending on the system.

For a gateway manufacturer, this simplifies some of the internal RF integration compared with an embedded antenna.

However, an external antenna still needs correct frequency coverage and orientation.

The product designer must also consider:

• connector strength;
• user rotation;
• clearance around the antenna;
• waterproofing where required;
• whether multiple antennas can collide physically;
• antenna spacing in multi-radio gateways.

Magnetic Mount Antennas for Metal Cabinets and Flexible Installation

A magnetic mount antenna moves the radiating element away from the radio enclosure and allows it to be positioned on a suitable metal surface.

This is useful for:

• industrial control cabinets;
• temporary monitoring equipment;
• field test systems;
• vehicles;
• vending or kiosk equipment;
• metal machinery.

The cable allows the antenna to be placed where the signal path is better.

But the mounting surface can become part of the RF system.

The size and shape of the metal surface may influence the antenna pattern or matching, depending on the antenna design.

Cable length also introduces loss.

A magnetic antenna should therefore be tested on a representative mounting surface rather than only in free space.

Fiberglass Antennas for Outdoor IoT Gateways

Fiberglass antennas are often used when an IoT gateway must provide coverage over an outdoor area.

They can be installed on poles, walls, towers, equipment shelters, or building roofs.

Typical applications include:

• LoRaWAN gateways;
• smart agriculture gateways;
• industrial telemetry;
• smart metering concentrators;
• remote monitoring;
• outdoor WiFi or 2.4 GHz IoT networks.

RFLink’s 868 MHz fiberglass antenna series is one example of an outdoor antenna format used for LoRaWAN, IoT gateways, smart meters, and industrial wireless systems.

A higher installation position can improve path clearance, but higher antenna gain is not automatically better.

For an omnidirectional fiberglass antenna, increasing gain often narrows the vertical beam.

This can affect coverage for nearby nodes or devices located at different elevations.

Cable loss must also be considered when the antenna is installed far from the gateway.

GNSS Antennas for IoT Tracking and Location

Many IoT systems need two completely different RF functions:

1. communication;
2. positioning.

A cellular antenna communicates with a terrestrial mobile network.

A GNSS antenna receives satellite navigation signals.

These antennas therefore have different jobs and different placement requirements.

GNSS is common in:

• asset trackers;
• fleet systems;
• smart battery packs;
• logistics equipment;
• portable industrial devices;
• outdoor monitoring terminals.

A GNSS antenna generally benefits from a location with a useful view toward the sky and sufficient separation from strong local interference sources.

In compact trackers, the GNSS antenna may need to share very limited space with cellular, WiFi, Bluetooth, a battery, and a display.

This makes device-level integration particularly important.

One IoT Device May Need Several Antennas

Modern IoT equipment increasingly combines several radios.

A gateway could contain:

• cellular MIMO;
• WiFi;
• Bluetooth;
• LoRa;
• GNSS.

A tracker may contain:

• cellular;
• GNSS;
• Bluetooth.

A smart meter concentrator may contain:

• sub-GHz communication;
• cellular backhaul;
• WiFi or Bluetooth service connection.

These antennas cannot be placed independently.

The design must consider:

• antenna-to-antenna isolation;
• cable routing;
• polarization;
• ground structure;
• nearby digital noise;
• available enclosure surfaces;
• RF connector location.

This is why multi-radio IoT products often require antenna planning early in the mechanical design process.

Frequency Comes Before Antenna Type

A beautiful FPC structure is useless if it does not cover the radio frequency.

A fiberglass antenna is not suitable merely because the product is outdoors.

The first technical question is always:

What frequency does the actual radio use?

This can depend on:

• wireless standard;
• module;
• regional regulation;
• operator;
• product market.

Sub-GHz IoT systems are especially region-dependent.

A product intended for several countries may require different antenna variants or a carefully designed wider-band solution.

RFLink’s frequency band guide explains the relationship between antenna frequency and wireless system requirements.

Do Not Select an IoT Antenna by Gain Alone

Gain is only one RF parameter.

An IoT antenna should also be evaluated for:

• operating bandwidth;
• VSWR or return loss;
• efficiency;
• impedance;
• radiation pattern;
• polarization;
• cable loss;
• isolation in multi-antenna systems.

A small internal IoT sensor may benefit more from good efficiency and balanced coverage than from a high peak-gain number.

An outdoor gateway may benefit from additional gain, but only if the resulting beam pattern matches the node distribution.

The Final Device Changes the Antenna

One of the most important lessons in IoT antenna design is that the antenna does not operate alone.

The final product may include:

• battery;
• display;
• PCB;
• ground plane;
• metal frame;
• shield can;
• cable;
• screws;
• sensors;
• connectors;
• enclosure;
• human body or installation surface.

All of these can influence RF behavior.

RFLink’s device-level antenna tuning guide explains why antennas can shift in resonance, lose efficiency, or change radiation patterns after final assembly.

Therefore, antenna validation should be performed in the real or representative final device.

A Practical IoT Antenna Selection Workflow

Step 1: Define the Wireless Systems

List every radio technology and frequency band.

Step 2: Define the Device Role

Is it a tiny sensor, wearable, tracker, meter, gateway, or fixed infrastructure device?

Step 3: Review the Mechanical Structure

Identify PCB area, battery location, metal, available housing surfaces, and cable paths.

Step 4: Decide Internal or External

Do not make this decision only for appearance.

Consider RF environment and installation.

Step 5: Select Candidate Antenna Types

Compare PCB, FPC, spring, external rubber, magnetic, fiberglass, or specialized GNSS options.

Step 6: Prototype in the Real Device

Measure after major components are installed.

Step 7: Validate Real Use Cases

Test the device in its normal mounting position and operating environment.

Step 8: Confirm Production Repeatability

Make sure assembly variation does not create large RF variation.

FAQ

What antenna is best for an IoT device?

There is no single best type. The right antenna depends on frequency, device size, housing, installation environment, range requirement, and whether the product is mobile or fixed.

PCB or FPC antenna for IoT?

PCB antennas are attractive for compact high-volume products with suitable board space and clearance. FPC antennas provide more placement flexibility when the best RF location is away from the main PCB.

When should an IoT device use an external antenna?

External antennas are especially useful for metal enclosures, gateways, outdoor equipment, and products that need flexible antenna placement or easier replacement.

Why use a fiberglass antenna for an IoT gateway?

A fiberglass antenna can be mounted outside and above the gateway enclosure, which can improve path clearance for wide-area outdoor networks.

Does an IoT antenna need custom tuning?

Not every product requires a fully custom antenna, but final device validation is important. Compact products, metal structures, multi-radio systems, and unusual enclosures often benefit from device-level tuning.

Conclusion

Effective IoT antenna selection begins with the device, not the antenna catalog.

PCB antennas can suit compact high-volume products.

FPC antennas provide flexible internal placement.

Spring antennas can fit certain compact sub-GHz devices.

Rubber duck and magnetic antennas provide external installation flexibility.

Fiberglass antennas are valuable for outdoor gateways.

GNSS antennas support positioning in trackers and connected equipment.

The correct choice depends on frequency, enclosure, ground structure, environment, network role, and production requirements.

When a standard antenna cannot meet the available space, frequency, connector, environmental, or performance requirements, RFLink’s custom antenna solutions can support device-level antenna development from evaluation and tuning through production.