I have an RFID bus pass, and my phone case has an indent on the inside for a magnetic car mount plate. The indent is smaller than the bus pass card by around an inch on all sides. I'm wondering if I can safely cut some part of the plastic off my RFID card so it'll fit inside, but I'm not sure how to tell what's all inside. How would you go about doing this?

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    \$\begingroup\$ This is not a suitable question for an electrical engineering design forum. What kind of answer do yuu expect? If we tell you its okay to cut off a 1/4 inch, for example, and then the card is ruined, who would you blame? \$\endgroup\$
    – Barry
    Jan 2, 2021 at 18:39
  • \$\begingroup\$ I was hoping to find resources on typical antenna layout or how I could determine this card's antenna layout/internals. Is that relevant? \$\endgroup\$
    – bitmaker
    Jan 2, 2021 at 18:40
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    \$\begingroup\$ @bitmaker kind of. This platform is for engineering questions – and as RFID design differs between different card (to not so large surprise), it feels a bit like you've not done extremely much to research enough to elevate this to something that is really on the level of engineering. However: Have you tried holding your card up against a strong light source and looking "through it"? \$\endgroup\$ Jan 2, 2021 at 18:43
  • \$\begingroup\$ There are people who have tried this with bright light, solvents, probably someone ran one through an xray machine. But realistically you only do this if you can afford to sacrifice one. Regardless such a question is off topic here, because it is about the unknown details of a product, rather than about the application of engineering methods to information you are able to supply. \$\endgroup\$ Jan 2, 2021 at 21:17

1 Answer 1


RFID tags contain an embedded antenna (often a coil of wire). If this is damaged the tag will have its range reduced or cease to function. Unless you can clearly see where the antenna is trimming the enclosure is not recommended.

Three RFID tags Source: Grika/Wikipedia

  • \$\begingroup\$ Thanks, it seems like they're always right at the edges so there probably isn't much that can be done. \$\endgroup\$
    – bitmaker
    Jan 2, 2021 at 18:44
  • \$\begingroup\$ @bitmaker That's correct. \$\endgroup\$ Jan 2, 2021 at 18:45

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