We do not recommend using the Track Box Passive with reusable transponders or the Disposable Triathlon Transponder. 

The Track Box Passive has been optimized to read RACE RESULT Bib Transponders, either worn on the chest or in free air (e.g. on MTB Number Plates). This means the Disposable Triathlon Transponder does not work as reliably as the Chip Race Number.  The main reason for this is the position at the ankle of an athlete as well as the non-vertical polarization of the transponder - even if in motion it is almost never perfectly aligned vertically.

The Track Box Passive can be used with ankle worn transponders, however, there are certain limitations which should be considered with these.

You can maximize read rates from a reusable transponder or disposable triathlon transponder when the following conditions are met:

• No mass passings - The Track Box is not at all suitable for a mass start, the optimal location is an isolated point with individual passings such as a trail run checkpoint. If participants are passing one at a time you will have better read rates. 
• Ensuring the Track Box antennas are pointed directly at transponders - In testing, we found the best read rates with a Track Box pointing downwards towards the feet of participants. The mounting position and the hanging angle depend on the expected distance between Track Box and Transponder.
• The maximum recommended distance between a transponder (either HuTag or Disposable Triathlon Transponder) is 2m (~6ft). Even with the reduced distance, you cannot expect read rates similar to a bib transponder. Beyond 2m you should expect severely reduced read rates.

Why are we making these recommendations?

Primarily, - pure physics - the position on the ground is not an option when a transponder is worn at the ankle if you look at the detection field of the antennas. The Track Box Passive has been tested extensively at a triathlon event with 1,300 participants all wearing HuTags yielding the following results.

At run splits where the maximum distance between participants and Track boxes was up to 4m the best setup (Track Box mounted at head height at an angle of 36 degrees) still only recorded ~70% of reads. Other setups at similar points yielded much worse results. 

At bike splits the Track Boxes were setup with a maximum distance of 2m between participants and Track boxes. Here we received >97% read rates with a Track Box mounted at 40cm looking out perpendicular directly at transponders, and >95% with a Track Box standing on the ground normally. 

Based on these results we do not recommend using the Track Box Passive with ankle worn transponders for timing, especially if the maximum read distance is greater than 2m.