UHF Tags Enter the Timing Race

By Mary Catherine O'Connor

Oct. 18, 2007—Since its founding in 2004, Swedish race organizer Racetimer has sought to differentiate itself from the sports-timing pack, where using low-frequency (LF) RFID tags to track racers' times is commonplace. Instead, the company has employed passive ultrahigh-frequency (UHF) tags made by Alien Technology (based in Morgan Hill, Calif.) to track runner times. While LF tags are less susceptible than UHF tags to RF interference from liquids—in this case, blood and fluids inside each racer's body—LF tags also have a very short read range (just a few centimeters), whereas UHF tags can be read from upwards of 60 feet away, according to Alien.

Ronnie Skoeld, Racetimer's international sales manager, says the company has used Alien's tags and interrogators since its inception, but after Alien switched to its own EPC Gen 2 chip, the Higgs (or H2), instead of the Impinj chip it initially used, Racetimer began timing large races with many thousands of. Skoeld says the tags containing the H2 chip are not impacted by the high liquid content carried in packs of racers, and that compared with earlier Alien UHF tags, they produce more consistent reads—even when large groups of racers run through read zones simultaneously.

The tags remain attached to the race bibs, which most racers keep as mementos.

Racetimer creates read zones at a course's beginning and end, and at split-time zones in between, by suspending a line of antennas above and along the side of the course. An Alien tag is affixed to the top of each racer's bib, extending at a 90-degree angle from the chest to keep the tag away from the runner's RF-absorbing body. To pinpoint the exact times at which each racer passes the start and finish lines and each split-time read zone (for example, at the 5K mark on a 10K course), Racetimer utilizes proprietary software that associates the time each tag signal is picked up in a read zone with a break in a laser beam transmitted across that zone.

The break in the beam, detected by a sensor, is caused when a racer's body passes through the zone and blocks the light. This sensor, Skoeld explains, is similar to the electronic eye mounted at the entrance to many convenience stores that triggers a bell when a customer passes through the door, alerting employees to that person's arrival.

To date, Racetimer has managed timing only for running races, the largest consisting of 8,000 entrants. However, it is under contract to provide its service to cycling races, triathlons and horse races as well.