Is my xLED too deep?

[Tuna.Fork]

Yup, and this thread, and this comment from @amal confirms that (and others). There are some things that do output a continuous field, because they’re plugged in, so power supply isn’t an issue. But cellphones only pulse to conserve energy, until they encounter a chip to read.

XLED implantable field detector

This is a commonly used tactic for battery powered applications to conserve energy. Because there is no chip in the xLED, the phone will keep checking for tags periodically. If you actually put a tag near the xLED, like held one on your skin near it, then the phone would detect the chip and keep the field on to talk to it, and the xLED should remain solid.