Antenna Guide

This guide outlines what you should consider when selecting the appropriate antenna for your Blues Notecard- and/or Starnote-based prototype. Implementing the proper antenna in the prototype phase can reduce the risk of unforeseen problems later in your product development process.

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Key Takeaways

• Start with Blues-provided antennas—they're pre-tested and matched for Notecard impedance.
• Antenna selection depends on technology (cellular, satellite, LoRa, and/or WiFi), region, and deployment environment.
• Position matters: vertical orientation for most antennas, clear line-of-sight for best performance.
• Enclosure materials affect RF performance—test in your actual enclosure early.

In This Guide

This guide covers antenna selection, placement, and testing for Blues Notecard- and Starnote-based products:

• Antenna Terminology: Key RF concepts like wavelength, SWR, gain, and impedance matching.
• Practical Antenna Tactics: Enclosure selection, positioning, connectors, and feed line considerations.
• Practical Antenna Selection Examples: Scenario-based recommendations for common deployment types.
• Satellite Antennas (Starnote): Certified antenna requirements for Starnote for Skylo and Iridium.
• Indoor vs. Outdoor Deployment Considerations: Environmental factors, enclosure materials, and RF transparency.
• Antenna Testing and Validation: Signal strength measurement, field testing methodology, and what to look for.
• Antenna Selection Checklist: A checklist covering technology, integration, validation, and production readiness.

Antenna Terminology

This guide will not replace a textbook on RF or antenna theory — nor can it guarantee regulatory body certification. However, there are a few concepts you should at least have a passing understanding of before specing an antenna, so buckle up for a crash course on the terms you can expect to see when working on the antenna aspects of your smart connected product.

Wavelength is the speed of light divided by frequency. A 915 megahertz (US LoRa) signal, for example, has a wavelength equal to (3 x 10^8 meters/second / 915 x 10^6 waves/second) = 0.33 meters/wave—a wavelength of 0.33 meters (33cm). The higher the frequency, the shorter the wavelength. Fundamental antenna length is based on wavelength: quarter-wave antennas (antennas that measure 1/4 wavelength) are quite common and work well in many applications. The previously mentioned 915 MHz, 33cm LoRa signal could theoretically be transmitted and received with an 8.25cm (33cm/4) length quarter-wave antenna. In practice, this length will be around 5% shorter to account for electromagnetic effects.

The feed line is the wire that connects the transmitter (Notecard) to the antenna. SWR (standing wave ratio) measures how much of the signal is sent back to the feed line as a loss versus what is sent to the antenna. A 1:1 ratio would be perfect, while a 2:1 ratio is often considered acceptable, sending nearly 90% of the power to the antenna. SWR is related to impedance matching (see Practical Antenna Tactics).

Antenna efficiency, or radiation efficiency, is the ratio of power radiated from an antenna divided by the power input—this ratio will be between zero and one. Antenna gain indicates the maximum signal output versus a lossless isotropic (transmits spherically in all directions) antenna. Gain is a factor of the directionality of an antenna's signal: the total power isn't increased; it is simply focused in one direction or multiple directions.

Antenna alignment is especially important for high-gain (highly directional) antennas, where peak radiation may occur in a specific region. An antenna meant to stick upward to radiate along the earth's plane will work poorly on its side. While gain and directionality can be helpful, if the target isn't properly aligned—or if it intermittently moves in and out of range—this will instead be detrimental to transmission. When proper alignment can't be maintained, a greater focus on SWR and efficiency may be the best approach.

Antenna Types and Purpose

The basic function of an antenna is to take signals from a device and radiate them into the environment — and vice versa — for communication. Many antenna designs are available, but two of the most common are worth understanding.

A monopole is the simplest antenna design, consisting of a single conductor that radiates uniformly in a primarily axial orientation. A whip antenna is one type of monopole, consisting of a flexible wire or telescoping rods, often implemented in older vehicles and consumer radios. Dipole antennas implement two conductive arms, commonly positioned end-to-end. This type of antenna introduces greater directionality to a signal than a simple monopole, producing gain in certain regions with dropoffs in others.

Both types of antennas (and the vast array of other classes and variations) have their strengths and weaknesses. In some situations, it may be advantageous to employ two antennas together, combining their strengths. This RF concept is known as antenna diversity, or the secondary device can be referred to as a diversity antenna. The "wideband" Notecard Cellular and Notecard Cell+WiFi both feature “DIV” connectors for LTE Cat-1 diversity antennas.

Practical Antenna Tactics

With basic antenna concepts defined, how do you implement antenna technology on a more practical level?

Choose an appropriate enclosure: ideally, an antenna should be outdoors in an open area with nothing to interfere with the signal. While an enclosure around the antenna may be necessary in many cases, ensure that it's made of a material that RF signals can easily pass through—a metal box around your antenna is generally bad. This is especially important for PCB antennas (see Integrating Notecard into a Product), as an enclosure around the board, and thus the need to pass a signal through it, may be inherent to the design.

Positioning matters significantly. Consider the typical alignment of your installation: a typical monopole antenna should be pointed up, not lying on the earth or parallel to the horizon, which could lead to significant gaps in coverage. While flexible antennas can be bent, ensure that they're not creased. A note in the product's installation documentation or training materials may be appropriate to help ensure proper usage.

Impedance matching is critical. Antennas come spec'd with an impedance value in ohms, which should match the Blues device being used. A significant mismatch will result in a high SWR. For example, the Blues Flexible Dual LTE/Wi-Fi and GPS/GNSS Antenna has an input impedance of 50Ω, making it appropriate for use with the Notecard Cell+WiFi.

Keep the connection short: the feed line between the radio source and antenna should be as short as possible to avoid signal loss. What is acceptably short depends on the situation and frequency—typically, the shorter the wavelength, the shorter the connection needs to be.

Use the right connector: RF connectors are available in different standards that are not cross-compatible. Ensure that the board connector (e.g., u.FL IPX, MHF4 IPEX) and the antenna connector (e.g., RP-SMA female, RP-SMA male) both match and that male/female orientations are coordinated. While adapters can be used, they add inefficiency and an additional BOM item, and should be avoided in both prototype and final product stages. All Notecards and Starnotes use a u.FL IPX connector.

Remember that antenna technology is complicated. While an 8.25cm antenna can work well for LoRa, other lengths can be advantageous in some situations. A wide range of different designs and tricks can extract more gain from a signal—bigger and more complicated isn't always better, but it can be. Consider your situation, read antenna specs, and since you likely won't be designing your own antenna from scratch, ensure you're working with vendors that you can trust.

While no antenna situation or RF setup is perfect, keep improving and try to minimize problems. Note that the lack of antenna, or an improperly spec'd antenna, will negatively affect performance, and can even cause damage to your device in some situations.

Regional Considerations

Consider regional and environmental factors: local frequency restrictions must be satisfied. Choose the proper antenna for the region and for the chosen technology. Non-frequency concerns, like whether or not a large antenna can be used on certain types of buildings in a city or neighborhood, must also be accommodated.

For cellular, Notecard and antenna variations should be implemented for the intended region—North American variations of Wideband, Midband, and Narrowband would be appropriate for United States usage. For WiFi, the 2.4 GHz band is widely used in the United States and internationally, and Blues products exclusively use 2.4 GHz for its excellent range and throughput. For LoRa, a 915 MHz antenna meets United States regulations while 868 MHz is predominant in Europe. For satellite, Starnote for Skylo operates on S-Band and L-Band frequencies (B23, B255, B256) while Starnote for Iridium uses the L-band at 1616–1626.5 MHz. Both provide global coverage independent of terrestrial infrastructure, though each network requires its own certified antenna (see Satellite Antennas below).

Blues Wireless Tech Options

The most fundamental factor in antenna selection is the type of wireless technology implemented. Blues hardware can communicate via cellular, satellite, LoRa, and WiFi, and receive positioning data via GPS/GNSS. Since these technologies communicate on different wavelengths and in different locations, this will narrow down the appropriate options for your smart connected product antenna.

For example, consider that if you need a LoRa device in the USA, you'll need one of the many 915 MHz antenna options available. Your LoRa device destined for Europe would likely need to use an 868 MHz antenna, while the Asian version must function at 433 MHz. WiFi would inherently be different.

Blues Notecard datasheets are listed by RF technology here. Once the overall wireless tech is chosen, consider the following aspects to help select the appropriate antenna for your RF prototype, taking into account the factors listed above. The goal here is to use the optimum antenna in the correct position where it can stay connected and protected.

Start with an Off-the-Shelf Blues Antenna

Many Blues devices feature an onboard PCB antenna, which can simplify integration costs and BOM requirements. Blues products may also ship with external antennas which are already specified to work with our systems, either of which work very well in general use cases. The Blues Flexible Dual LTE/Wi-Fi and GPS/GNSS Antenna, as well as our Flexible LTE, Wi-Fi, or GPS/GNSS Antenna, are also available for purchase separately here.

While Blues does not explicitly recommend third-party antennas, our extensive partner network can help point you to the proper company for help as needed. After an appropriate antenna is chosen, the application will likely still need to be tested for RF interference and certified by the regulatory body where it will be used. A working prototype does not imply your device works within regulatory standards.

Even when a Blues product is used with a Blues antenna, we strongly advise comprehensive field testing in the final enclosure and deployment environment to ensure reliable connectivity and minimal RF interference.

Practical Antenna Selection Examples

Based on the factors and options listed above, your choice of prototype antenna for a particular smart connected product will come down to the technology, geography, user interaction, and planned deployment scale of the final product. Consider the following scenarios:

Scenario 1: Primary WiFi with Reliable Cellular Fallback

Situation: Your product typically has WiFi access but may occasionally move out of range or experience network outages — such as a portable asset tracker that's usually docked at a facility but occasionally transported.

Recommendation: The Notecard Cell+WiFi models provide the best of both worlds, automatically falling back to cellular when WiFi is unavailable. The Blues Flexible Dual LTE/Wi-Fi and GPS/GNSS Antenna is designed for this use case, covering wide cellular bands in a single antenna package. This is a solid general-purpose solution that works well across most deployment scenarios.

Scenario 2: Rural United States with Spotty Cellular Coverage

Situation: Your product will be deployed in rural or remote areas of the United States where cellular coverage is inconsistent — such as agricultural monitoring, wildlife tracking, or remote infrastructure.

Recommendation: This scenario requires more careful antenna selection. First, identify the specific Notecard variant you're using and consult its datasheet to determine which LTE bands the modem supports. Then, research and select an antenna specifically tuned to those bands, prioritizing the bands most commonly deployed by carriers in your target region.

This is a great example of when reaching out to Blues can be helpful to find the right antenna for your product.

For truly remote deployments where cellular may be unavailable entirely, consider pairing your Notecard with a Starnote as a satellite fallback. Starnote communicates via either Iridium or Skylo satellite networks, providing extensive coverage even in areas with no terrestrial cellular infrastructure. This hybrid approach ensures connectivity in even the most challenging environments.

Scenario 3: Cellular Deployment in Latin America (or Other Regions with Variable Coverage)

Situation: Your product will be deployed across one or more Latin American countries where cellular coverage varies significantly by region and carrier, with different carriers operating on different frequency bands.

Recommendation: Cellular band fragmentation is common in many international markets. Start by selecting the appropriate regional Notecard variant and reviewing its datasheet to identify all supported LTE bands.

Choose an antenna that covers the full range of bands listed in the Notecard datasheet for your region. Multi-band or wideband antennas are often necessary for deployments spanning multiple countries or areas served by different carriers. For wideband Notecards, consider using a diversity antenna (connected to the "DIV" port) to improve reception in challenging RF environments. Extensive field testing across your target deployment areas is strongly recommended before finalizing your antenna choice.

Scenario 4: LoRaWAN with Established Gateway Access

Situation: Your deployment has reliable, stable access to a LoRaWAN gateway (e.g., a Things Stack deployment in a warehouse, campus, or smart building).

Recommendation: Notecard for LoRa with the Blues-provided antenna is an excellent choice. LoRaWAN operates on well-defined regional frequencies (915 MHz in the US, 868 MHz in Europe), and the included antenna is already tuned for these bands. Since the gateway infrastructure is established and your devices remain within range, complex antenna considerations are minimal.

Scenario 5: Stable WiFi Access Point Coverage

Situation: Your product operates in a fixed location with consistent, always-available 2.4 GHz WiFi access — such as a smart home device, office sensor, or retail installation.

Recommendation: Notecard WiFi with its onboard PCB antenna works well for most indoor applications. For installations where the device is enclosed or positioned further from the access point, the Blues-provided external antenna offers improved range and signal quality. Since 2.4 GHz WiFi is standardized globally, regional frequency concerns are minimal.

Satellite Antennas (Starnote)

If your product uses Starnote for fallback satellite connectivity, antenna selection is straightforward but comes with strict certification requirements.

Starnote for Skylo

Starnote for Skylo communicates over NTN (Non-Terrestrial Network) using S-Band and L-Band frequencies on B23, B255, and B256 bands.

Starnote for Skylo is available in two antenna configurations:

• Starnote for Skylo (Antenna) includes onboard Ignion antennas integrated directly into the module, no external antenna connection is needed.
• Starnote for Skylo (u.FL) includes a certified dual-band flexible antenna that connects to the SAT u.FL connector on the device.

warning

Starnote for Skylo with u.FL connectors is certified on Skylo's network exclusively with the antenna provided in the kit. Replacing or modifying the antenna results in an uncertified device and may lead to network blocking by Skylo. If you need to use an alternative antenna, you must obtain a delta test lab report demonstrating the device-and-antenna combination doesn't exceed 30 dBm EIRP through a CTIA/OTA-authorized testing facility. Contact Blues for recommended test houses.

Starnote for Iridium

Starnote for Iridium operates in the Iridium L-band user link at 1616–1626.5 MHz and includes an Iridium-certified antenna that connects to the available u.FL connector.

warning

Starnote for Iridium is certified on Iridium's network exclusively with the antenna provided. Modifications result in an uncertified device with potential network blocking. Contact Blues for guidance on alternative antenna certification if your enclosure or deployment requires a different antenna configuration.

Satellite Antenna Placement Guidelines

Regardless of which Starnote variant you use, satellite connectivity requires clear sky visibility as obstructions between the antenna and the sky will degrade or prevent communication. When positioning satellite antennas:

• Mount with an unobstructed view of the sky. Satellite signals cannot penetrate metal, concrete, or dense building materials.
• Maintain at least 11mm clearance around the antenna to avoid detuning.
• Avoid permanent bends in antenna cables. Gentle curves are acceptable, but sharp creases damage the feed line and degrade performance.
• Route coaxial cables away from noisy traces on your PCB to minimize interference.

Indoor vs. Outdoor Deployment Considerations

The deployment environment significantly affects antenna performance and selection.

Indoor Deployments

Indoor deployments face several challenges: building materials attenuate signals (especially concrete, metal, and low-E glass), multipath interference from reflections off walls and objects can degrade performance, and interference from other wireless devices (WiFi, Bluetooth, microwaves) is common.

To address these challenges, position antennas near windows or exterior walls when possible. Avoid placing devices in metal enclosures or near large metal objects. Consider external antennas routed to better locations if internal placement is problematic. For WiFi, ensure line-of-sight to access points when possible. Most importantly, test in the actual deployment location—building construction varies widely and you can't assume one location will perform like another.

Outdoor Deployments

Outdoor deployments present different challenges: weather exposure (rain, ice, UV degradation) can damage equipment, temperature extremes affect antenna performance, physical damage from wind, animals, or vandalism is possible, and longer distances to base stations or gateways require more careful antenna selection.

To succeed outdoors, use weatherproof enclosures rated for outdoor use (IP65 or better). Select antennas rated for outdoor/industrial use that can withstand environmental stress. Consider antenna gain requirements for longer-range communication when base stations are distant. Mount antennas with clear sky view for GPS/GNSS and satellite connectivity. Protect antenna connections from moisture ingress with appropriate sealing.

Enclosure Material RF Transparency

Not all enclosure materials are equal when it comes to RF signals:

Antenna Testing and Validation

Before finalizing your antenna selection, validate performance in realistic conditions.

Signal Strength Measurement

Blues makes it easy to measure cellular signal strength. Use the card.wireless API to query connection quality. RSSI (Received Signal Strength Indicator) measures overall signal power—aim for -85 dBm or better. RSRP (Reference Signal Received Power) is LTE-specific—aim for -100 dBm or better. RSRQ (Reference Signal Received Quality) indicates signal quality—aim for -10 dB or better. See Diagnosing Cellular Connectivity Issues for detailed guidance on interpreting these values.

Field Testing Methodology

A thorough testing process progresses through several stages. First, bench test to verify basic connectivity in a known-good RF environment. Then test in enclosure to measure signal with the device in its final enclosure. Next, test at deployment sites—measure at actual or representative deployment locations. Test edge cases by checking worst-case positions, orientations, and environmental conditions. Finally, document results by recording signal strength, location, orientation, and environmental factors for future reference.

What to Look For

During testing, verify consistent connectivity where the device maintains connection over extended periods. Ensure acceptable signal strength within manufacturer recommendations. Monitor for reasonable retry rates since excessive retries indicate marginal signal. Confirm successful data transfer with events syncing reliably within expected timeframes.

Troubleshooting Common Antenna Issues

When you experience connectivity problems, work through these common issues:

Poor Signal Despite Good Antenna Spec

Symptoms: Device shows weak signal even with a quality antenna properly connected.

Possible causes include the antenna positioned inside a metal enclosure, antenna lying flat instead of vertical, feed line too long or damaged, enclosure material blocking signal, or deployment location in an RF shadow.

Solutions: Verify antenna orientation matches design intent and check that the u.FL connector is fully seated. Move the antenna outside a metal enclosure or use an RF-transparent window. Test with the antenna outside the enclosure to isolate whether the enclosure is the issue.

Intermittent Connectivity

Symptoms: Device connects sometimes but drops frequently or fails to sync.

Possible causes include marginal signal strength (works sometimes, not others), a loose antenna connector, antenna movement changing orientation, environmental interference from nearby equipment, or temperature-related expansion/contraction affecting connections.

Solutions: Measure signal strength to confirm marginal conditions. Secure the antenna connection and verify it doesn't move. Consider a higher-gain antenna or better positioning. Test at different times of day to identify interference patterns.

Performance Degradation Over Time

Symptoms: Device worked well initially but connectivity has worsened.

Possible causes include antenna connector loosened over time, corrosion on connectors (especially in outdoor deployments), antenna physical damage from UV or physical impact, environmental changes like new construction or vegetation growth, or carrier network changes.

Solutions: Inspect antenna and connections for physical damage. Clean and reseat connectors. Replace the antenna if degraded. Re-test signal strength and compare to initial measurements to quantify the change.

Enclosure Interference

Symptoms: Device works on bench but fails when enclosed.

Possible causes include metal enclosure blocking signal, conductive coatings or EMI shielding, internal components creating interference, or antenna positioned too close to the ground plane or metal.

Solutions: Use RF-transparent enclosure materials. Route the antenna outside the enclosure if necessary. Create an RF window in metal enclosures. Increase distance between the antenna and metal components.

Quick Reference: Antenna Selection by Use Case

Use this table as a starting point for antenna selection based on your deployment scenario:

Antenna Selection Checklist

Before finalizing your antenna selection, verify you've addressed these items:

Technology and Frequency

• Identified the wireless technology for your deployment (cellular, satellite, LoRa, and/or WiFi)
• Confirmed regional frequency requirements (e.g., 915 MHz LoRa for US, 868 MHz for EU)
• Selected Notecard variant appropriate for your region
• Verified antenna frequency bands match Notecard bands

Physical Integration

• Antenna connector type matches Notecard (u.FL IPX for all Notecards)
• Feed line length minimized
• Antenna position allows proper orientation (vertical for most)
• Enclosure material is RF-transparent or external antenna routing planned
• Mounting hardware appropriate for deployment environment

Performance Validation

• Bench tested with signal strength measurement
• Tested in actual enclosure
• Field tested at representative deployment locations
• Edge cases tested (weak signal, different orientations)
• Results documented with measurements

Production Readiness

• Antenna sourcing confirmed for production volumes
• Installation instructions include antenna positioning guidance
• Antenna protected from environmental damage (if outdoor)
• Spare antennas available for field replacements

Resources and Next Steps

Antenna selection can make or break your connected product's reliability. Start with Blues-provided antennas to validate your concept, test in your actual enclosure and deployment environment early, and use the checklist above to ensure nothing is overlooked before production.

Blues Resources

• Diagnosing Cellular Connectivity Issues
• Blues Design Review Program
• Starnote Best Practices
• Blues Antenna Guide

External Resources

• everythingRF RF Calculators
• SWR Discussion

Getting Help

If you have additional questions about antennas for your Blues-based product:

• Post questions on the Blues Community Forum
• Contact Blues sales for enterprise-level support