Let’s talk about reading distances

Reading distance depends primarily on technology and frequency, and the size of a reader’s antenna. Passive UHF (Ultra High Frequency) can read transponders at distances out to 10 and even 15 meters. Conversely, in access control applications, 13,56 MHz and 125 kHz technologies, with detection ranges of a few centimeters are typical. Security features, i.e. encrypted data transfer can reduce ranges a little bit, but in applications where users have to bring their transponders near a reader anyway, a couple centimeters really doesn’t make a noticeable difference.

Actual onsite reading distances can differ from manufacturers’ specifications. That’s because, a site’s environment (radio-reflective materials) and other nearby powered readers can either extend or shorten detection ranges. There are also differences in how different readers and transponders work together, that can only be discovered by testing a reader’s performance with that transponder. Of course, here at Idesco, we test all transponders we sell to ensure they work fine with own readers.

Readers and tags in AVI applications: Download tutorial

EPC_rangeIn UHF applications that require long reading distances, the impact of the reflective surface environment on both readers’ and transponders’ performance can be even more profound. That’s because RFID waves can reflect off surfaces in the site environment, creating zones of either positive or negative interference that will either weaken or strengthen your reader’s effective range. Predictably, metal surfaces give the strongest reflections, but other materials may also have a similar impact. Furthermore, UHF transponders are typically designed to be installed on a specific material surface. For instance, transponders designed to install on metal surfaces tend to perform weakly on other surfaces, while other transponders are designed for windshields only, etc.

Successful UHF reading events, require more than overlap of the emission patterns of the reader and the transponder. The power, or amplitude and direction of the signal from the reader must also be enough at that position to bleed into the transponder’s antenna and power it’s reply. That’s why, for instance, horizontal or vertical placement of a windshield tag can make a big difference in the success of your planned AVI application.

Want to learn more about optimal siting of our readers and transponders for AVI applications? Check out our helpful tutorial about AVI readers and transponders and their optimal deployment in automated vehicle identification applications. We’re confident you’ll find it valuable for developing, deploying and testing your own AVI applications.


  • Reader and transponder factors
  • Emission patterns – Reader and Transponders
  • Installation of EPC Reader
  • Special windshields
  • Long Distance Read Error
  • Examples of Reader and Tag siting

Download Tutorial here!

Jyrki knows transponders

Jyrki_Almost all transponders Idesco delivers start their journey from Jyrki’s desk. Seven year Idesco veteran Jyrki’s primary responsibility is managing the vitally-important configuration process of transponders for numerous customers around the world. All Idesco transponders, with few exceptions, aren’t just labeled but also encoded then tested in a robotic process to authenticate transponders’ general functionality and reading distance. In addition to his responsibility for producing faultless encoded tags for Idesco’s numerous customers, Jyrki also oversees received materials within SCM while also contributing significantly to manufacturing processes for a variety of other Idesco products. While he enjoys and takes pride in the independence of his work, Jyrki still makes time for treasured, regular relaxing retreats to his cabin.