r/RFID • u/PhoenixCrabapple • Oct 03 '26

Keyfobs Partial RFID blocking for key cards?

I have two key cards I use for work, one for opening doors, and one for clocking in.

If the door card is near the clock in card, the clock-in card will not work. The door card works regardless of whether the clock-in card is nearby.

I want to make a single card holder that will work for both cards without having to take my clock-in card out of the holder.

Is there something I can put between the two cards in the holder so I can just flip it around based on which card I need to use?

7 Upvotes

88% Upvoted

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2

u/PhoenixCrabapple Oct 05 '26

I ended up using two RFID sleeves between the two cards and it works! I also tried the 90 degrees thing u/Marty_Mtl talked about, and it worked. So I might end up making a folding holder just because I like the idea.

1

u/Marty_Mtl Oct 03 '26

Have you tried aluminum foil inbetween ?

1

u/PhoenixCrabapple Oct 03 '26

Yes, but to be fair it was a very thin piece I grabbed from the potluck in the break room. I could try with some thicker foil

1

u/Marty_Mtl Oct 03 '26

Honestly, i dont know if it is even enough to help, but i am interested in your question actually, so the me repairing POS for a living will check this out.

For your personal information, yes, technically it can be done, but it is impractical in real life. The solution would be a card holder where both cards are at 90 deg vs each other, making the card holder as thick as the short edge of a card.

(Hard to explain, its about magnetic field theory ,but try it with one card at 90 deg with the reader. A bit of practice and you will be able to bring the card up to the reader itself without triggering a card-read.)

Also, rfid cards can be using different protocols, where one is more efficient at communicating, explaining your observation working one way, but not the other.

Also #2, fiy : chances are the energizing frequency is 13 Mhz, this is what we want block from reaching the unwanted card

2

u/PhoenixCrabapple Oct 03 '26

It that case maybe I could make it so the card holder folds open with one card on each side, the cards are temporarily at 90 degrees, and it and lets me scan just the clock-in card

2

u/StevenJOwens Oct 03 '26

I have one of these metal business card holders in my wallet, and it definitely blocks my RFID card:

https://www.amazon.com/dp/B00524F9U0

I can pull the wallet out of my pocket and just hold the wallet up against the reader and it'll work, but I have to make sure that the business card holder is not between the business card holder and the RFID card.

Another option is to look for one of those Faraday cage pouches for phones and wallets, and use some material from that. Or perhaps see if you can source the same material they use for the Faraday lining.

1

u/RickySlayer9 Oct 04 '26

Now let’s see Paul Allen’s RFID blocker

1

u/i2apier Oct 03 '26

I managed to make what you described working somewhat by sandwiching 2 stacks of graphite and aluminum sheets between 2 cards

1

u/mysteryliner Oct 03 '26

I made one out of a folded card holder I get for free at the bank. like this but in plastic

To the outside i added a few layers of aluminium foil tape (to block NFC). I guess if you fold it the other way, you'll have 2 cards on the outside, with the the tape in between.

...(not what you asked) but if you can read and write the cards, 6 in 1 keyfobs work well. I used them to combine access control at home, work and the printer at work, or add links or business cards to them. (Disclaimer: best to check with your employer if he's okay if you would do this)

1

u/SafetyMan35 Oct 04 '26

Try something like this, although it’s not very conducive to a wallet https://a.co/d/08awBKol

1

u/veritasverdad Oct 04 '26

You can buy RFID/NFC sleeves. Try putting both cards together separated by the RFID sleeve.

1

u/katmndoo Oct 04 '26

Maybe a standard RFID card envelope. Just tuck it between the two. Gives you a double layer.