NFC antenna tuning without a VNA

RE: NFC antenna tuning without a VNA

Luka851 — Mon, 11 May 2026 21:32:02 GMT

Hi, lot of time has passed. Have you ever tried to measure impedance of a hand winded copper coil? I have an nfc keyfob, blue ones that usually come with the reader, I wanted to measure its impedance for learning purposes, and then to tune it fo it matches the rc5180 reader module matching circuit. Do you know if it is possible to measure it without VNA, and then what shall I use and how? with just a coild be enough, should it have an nfc chip on it, or resistors and capasitors? thank you

RE: NFC antenna tuning without a VNA

Fred27 — Mon, 30 Dec 2019 15:00:23 GMT

I've updated the guide as I've since discovered that cheap VNAs exist. The $50 NanoVNA is great for NFC antenna matching.

RE: NFC antenna tuning without a VNA

mpandrews — Thu, 12 Dec 2019 03:25:15 GMT

Why must the impedance of the antenna be 50 Ohms and how is the value of the imaginary part calculated from the inductance?

RE: NFC antenna tuning without a VNA

DAB — Sat, 08 Dec 2018 19:47:44 GMT

Nice post and solution to the problem.

A little research always pays off with a simple solution.

DAB

RE: NFC antenna tuning without a VNA

shabaz — Sat, 08 Dec 2018 00:29:00 GMT

Hi Fred.

This is a great piece of work, achieving a match for the NFC antenna without a VNA! The project looks great and the capacitive buttons look very responsive from the video too!

By the way you've got a typo, you've used uF but I'm guessing you mean pF : )

RE: NFC antenna tuning without a VNA

genebren — Fri, 07 Dec 2018 23:52:07 GMT

Nicely done! So how are the range and sensitivity post modification?

Gene

RE: NFC antenna tuning without a VNA

14rhb — Fri, 07 Dec 2018 21:59:11 GMT

Hi David,

This is a really good and should help others get into RF design with minimal cost, I like your approach to this and the software you highlight.

Rod

RE: NFC antenna tuning without a VNA

fmilburn — Fri, 07 Dec 2018 20:54:48 GMT

It really looks nice and thanks for the link to impedance matching and reporting results. I am unable to see the video currently.

Frank