There are several well-known culprits behind RFID interference, and most of them come down to the environment where your tags and readers operate.

Metal Surfaces

Metal is one of the biggest enemies of RFID performance. When radio waves hit a metal surface, they reflect and scatter, which can block or distort the signal between reader and tag. Tags mounted directly on metal objects often become completely unreadable because the metal detunes the tag antenna, shifting its resonant frequency away from the operating band. The fix here is to use metal-mount tags, which include a spacer or specialised antenna design that accounts for the metal backing. Positioning tags so they face away from large metal surfaces also helps significantly.

Liquids

Water and other liquids absorb RF energy, particularly at UHF frequencies. This means tags attached to bottles, containers of liquid, or items stored in damp environments may suffer from reduced read range or complete signal loss. Using tags rated for liquid environments, or mounting them on the side of a container above the liquid line, can make a real difference. In warehouse settings, adjusting reader antenna angles to avoid sending signals directly through liquid-heavy areas is another practical solution.

Other RF Sources

RFID readers operate on radio frequencies that can overlap with Wi-Fi networks, Bluetooth devices, and other wireless equipment. When multiple RF sources compete for the same spectrum, the result is noise that drowns out the RFID signal. To reduce this kind of interference, try to separate RFID reader antennas from Wi-Fi access points and other wireless devices by at least a few metres. You can also use frequency-hopping spread spectrum (FHSS) readers that automatically switch channels to avoid congestion.

Dense Tag Populations

When large numbers of tags are packed closely together, they can interfere with each other. Readers may struggle to singulate individual tags from the crowd, leading to missed reads. Anti-collision protocols like EPC Gen 2’s Q algorithm help manage this, but physical spacing matters too. Spreading tags out even slightly, or using readers with advanced anti-collision features, will improve accuracy in high-density environments.

Tag Detuning

Detuning happens when a tag’s antenna performance is altered by nearby materials or objects. Even placing a tag on cardboard versus plastic can shift its tuning enough to reduce read range. The solution is to test tags in the exact environment and on the exact surface where they will be used. Many tag manufacturers offer application-specific models tuned for particular materials, which takes the guesswork out of the equation.

Practical Troubleshooting Steps

If you are experiencing interference issues, start by isolating the problem. Test individual tags in a clean environment to rule out faulty hardware. Move your reader away from walls, metal shelving, and other equipment to see if performance improves. Check for nearby wireless devices that could be causing RF noise. Adjust reader power levels, as running at maximum power is not always the best approach and can actually increase interference from reflected signals. Finally, review your tag placement and make sure tags are oriented correctly relative to reader antennas.

RFID interference is rarely a mystery once you know where to look. By understanding how metal, liquids, competing RF sources, dense tag populations, and detuning affect your system, you can take targeted steps to fix the problem and get back to reliable reads.

The post RFID Interference: What Causes It and How to Fix It first appeared on RFID News.

M&S started its RFID journey with a modest pilot project tagging men’s suits. The early results were promising enough to justify further investment, but progress was slow. The technology was expensive, with tags costing roughly five times what they do today, and the business case was still being built one department at a time.

The Beauty Product Problem

As M&S expanded RFID tagging across its non-food product lines, beauty and cosmetics products emerged as the most stubborn challenge. The physical properties of these items, including metal components in packaging, foil-lined containers, and liquid contents, created significant interference with radio frequency signals. Standard RFID tags simply could not deliver reliable reads when attached to products containing metal or liquids.

Working closely with longtime partner Avery Dennison, M&S invested years in developing specialised tag formats to overcome these obstacles. The collaboration produced 10 distinct tag formats and, because the retailer uses different colour codes for various product categories, a total of 70 tag variations. Some were designed specifically for apparel, others for beauty products, and still others for items containing metal or liquids. Each tag also had to meet the aesthetic standards demanded by cosmetic manufacturers, adding another layer of complexity.

Overcoming Senior Management Resistance

Perhaps even more challenging than the technical hurdles was the battle for internal buy-in. Richard Jenkins, M&S’s head of loss prevention and the driving force behind the RFID programme, has spoken candidly about the resistance he faced from senior leadership. There were individuals in senior positions who lacked understanding of the technology yet spoke with great confidence about its limitations. During particularly difficult periods, Jenkins and his team had to fight against active de-investment in the programme.

To counter this scepticism, M&S established a cross-functional steering committee that brought together representatives from corporate leadership, IT, store operations, and finance. Retail and store staff provided frontline feedback on deployment issues, while finance executives helped build a rigorous business case demonstrating clear return on investment for each phase of the rollout.

Testing, Validation, and Results

M&S took a methodical approach to validation, constructing a mock store at its headquarters to test tag performance across different materials before rolling out to live retail environments. This careful testing regime helped the team achieve consistent, accurate reads even on traditionally difficult product categories.

The results speak for themselves. SKU accuracy improved from just 68 per cent when the project expanded to a full product range in 2014, to an impressive 91.5 per cent by the second half of 2021. The retailer now uses approximately 350 million RFID tags per year across its stores.

Lessons in Persistence

The M&S story offers several valuable lessons for any organisation considering RFID adoption. First, technical challenges like metal and liquid interference are solvable with the right partnerships and sufficient investment in tag development. Second, internal resistance from senior management can be just as significant a barrier as any technical limitation. Building a cross-functional team with clear ROI metrics is essential for maintaining momentum. Third, bringing software development in-house gave M&S greater control and agility, helping the retailer adapt the technology to its specific needs.

M&S’s own-brand business model also proved to be a strategic advantage, enabling tagging at source rather than in-store. This simplified logistics and reduced costs, a benefit that retailers relying heavily on third-party brands may find harder to replicate.

Today, M&S continues to push the boundaries, exploring robotic tag reading in stores and planning new formats where automation can track every item entering and leaving in near real time. The retailer’s RFID journey is a testament to what persistence and strategic thinking can achieve, even when the odds and the boardroom seem stacked against you.

The post Case Study: Marks & Spencer – Navigating RFID’s Technical Challenges first appeared on RFID News.

An RFID site survey is a structured assessment of the physical environment where readers and tags will operate. The goal is to understand how radio frequency energy behaves in a given space before any hardware is permanently installed. This involves measuring ambient RF noise levels, mapping potential interference sources, evaluating structural materials, and testing preliminary reader and antenna positions to confirm that reliable tag reads can be achieved under real-world conditions.

Understanding RF Interference Sources

Radio frequency interference is one of the biggest threats to a successful RFID installation. Interference can originate from a wide range of sources including Wi-Fi access points, Bluetooth devices, cellular base stations, fluorescent lighting, electric motors, conveyor systems, and even other RFID readers operating nearby. In warehouse and industrial settings, variable frequency drives (VFDs) on motors and heavy electrical equipment are particularly problematic because they generate broadband electromagnetic noise that can drown out the relatively weak backscatter signal from passive RFID tags. A site survey identifies these interference sources early so that mitigation strategies, such as frequency hopping configuration, shielding, or adjusted reader power levels, can be planned before deployment.

Reader Placement Strategy

Where you mount RFID readers and antennas determines whether your system delivers consistent, accurate reads or frustrating gaps in coverage. Reader placement is not a guessing game. It requires careful analysis of read zones, tag orientation, movement speed, and the distance between antennas and tagged items. Overlapping read fields between adjacent readers can cause reader collision, where devices interfere with each other and miss tags entirely. Conversely, leaving gaps between read zones means items pass through undetected. A site survey uses test readers and reference tags to map coverage areas, measure read rates at various antenna angles, and confirm that the planned layout will achieve the required performance before permanent mounting.

Assessing the Physical Environment

The physical characteristics of a deployment environment have a direct and often dramatic impact on RFID performance. Metal surfaces reflect RF energy in unpredictable ways, creating multipath interference where signals bounce and arrive at the reader out of phase, causing destructive cancellation. Liquids absorb UHF radio waves, significantly reducing read range when tags are applied to bottles, containers, or products with high water content. Moving objects, including forklifts, conveyor belts, and personnel, create a constantly changing RF landscape that static testing alone cannot capture. Temperature extremes, humidity, and even the density of stacked inventory all affect signal propagation. A thorough environment assessment during the site survey accounts for these variables and informs decisions about tag selection, antenna type, mounting hardware, and reader configuration.

The Cost of Skipping the Site Survey

Organisations that bypass the site survey phase almost always pay for it later. The symptoms are predictable: inconsistent read rates, phantom reads from stray RF energy, blind spots in critical coverage areas, and reader collisions that degrade overall system performance. Troubleshooting these issues after installation is expensive and disruptive. Hardware may need to be relocated, additional readers purchased, or entire antenna configurations redesigned. In some cases, the wrong tag type was selected because nobody tested it in the actual environment, leading to a full re-tagging exercise. All of these costs dwarf the relatively modest investment of conducting a proper site survey upfront.

A well-executed RFID site survey typically takes between one and five days depending on the size and complexity of the facility. It should be carried out by experienced RF engineers who understand the physics of radio propagation and the practical realities of RFID deployments. The deliverable is a detailed RF plan that specifies reader locations, antenna types and orientations, power settings, frequency configurations, and any environmental modifications needed to ensure reliable operation. This plan becomes the blueprint for installation and the baseline for ongoing performance monitoring.

If you are planning an RFID deployment of any scale, treat the site survey as non-negotiable. It is the difference between a system that works on paper and one that works in practice.

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