Hello,
I am wondering what kind of antennas are there on the market that will work with the XIAO nRF52840? I tried to google nfc external antennas but I am getting confused as there are too many sizes and other specs. Could somebody please provide some specs for what antenna I may use? Or some links to such antennas?
p.s. the form factor is important, the smaller the antenna, the better it would be.
Hi there , So check this out, 
I read your post and thought Hmmm So I “Clicked” that magnifier" up in the corner and I entered “NFC ant” and hit the enter key, So it seems You are NOT the only one to look for this info or even ask this exact question. Good News. The fourth(4) entry in the list it provided has a link to what you seek…the list has a plethora of information but its contained in the virtual cornucopia of great posts.
I could paste the link here, but that would not allow you to Find “FOREVER”
“You can feed a man to FISH and he eats only that day. You can Teach a man to Fish and he can feed himself for a lifetime.”
HTH
GL 
P.S. 
it’s all about the support components you choose those based on what ANT YOU 
want and tune to.
Thank you very much. I have found the link. I admit it that I was too lazy or dump to search on seeed itself, I just googled external nfc antenna and found a lot of stuff that got me confused.
for future readers, here is the link
Nice … 
Yea I thought google should include those, IMO 