Tag Archives: Android

Measuring the frequency of Androids NFC

Hey there,

Every blog has to start somewhere… I have some plans for projects I would like to put here. But a fews days ago I had an idea for a quick thing that should get me started.

I was wondering at what frequency Andrioids NFC is operating at. Sure I COULD ask the mighty Internet… but thats no fun. Lets measure it! Also I was wondering ‘Does NFC turn off when the phone goes into standby?’.

So I set up my analog Oscilloscope. Formed a simple antenna with my probe. Turned on NFC on my phone and placed it on top.

Easy! The scope shows a nice sine wave. Timebase is set to 20 ns per devision. And I get about 8.6 devisions per wavelength. That calculates to a frequency of about 14.5 Mhz (OK. Yes, I checked online. The “right” answer is 13.56 MHz). The signal disappears when I turn off the display and reappears when I unlock the phone. So I guess if you buy some of these cheap NFC tags, you need to unlock the phone and then put it on top. So i might as well turn on my bluetooth by hand rather than unlocking my screen and then put it on that NFC tag that I don’t have in my car.

The signal comes in bursts of about 5.4 ms every 265 ms. Which is not so easy to capture and measure with my analog scope. But I took some photos and made it work. The length of the burst is hard to see. So I edited the picture to make it appear more clearly. The last picture shows my attempt to measure the dead period between to bursts.

Thats it! Leave your comments below.