Your source for daily hacks

Published on: September 6, 2013 / Comments: None

Reducing the noise on your RTL-SDR

The guys over at SDR for Mariners put together a nice writeup on reducing the electrical interference on the good ol’ cheap RTL-SDR dongle.  When the signal you’re looking for is very faint, you need to remove all of unwanted noise or else your signal gets difficult to separate.  In their case the unwanted signal is in the form of FM radio.

Even if you aren’t a big RF nerd you know some of these remedies already like ferrite beads (you know those giant blocks on the ends of the expensive cables!).  But I’m actually surprised at some of the other ones.  I would have thought that the metal connector around a USB cable would help prevent noise, but according to their tests it was acting like a collector for their intrusive FM signal.  By removing the shield and just connecting the data pins they dropped the noise by 10db.  Not using the extension cable and just plugging straight in is even better.

So the winning combo appears to be all of their methods tested.  A stick wrapped in aluminum foil, touching the metal of the USB plug, connected by a USB extension cable, inside a metal housing.

I’d love to see a picture of the final setup.  Good tips to know when chasing down a faint signal.

Published on: August 27, 2013 / Comments: None

Decoding RF signals like keyfobs with HackRF SDR

Dragorn has a couple of tutorials up on his site about working with the HackRF SDR.  Just like decoding weather satellite signals, decoding wireless remotes and other signals is cool too.  If you’re familiar with the cheap RTL-SDR, then just know the HackRF is like that but more powerful (and can transmit).

Dragorn starts out with part 1: inspecting a pair of car keyfobs.  In this tutorial, he records the signals and inspects them using baudline.  You can see the different encoding mechanisms the 2 different keyfobs use.  Dragorn points out that actually decoding the data is pointless as the data transmitted uses a rolling key pair that constantly changes the data sent for security.


And thus he moves on to part 2: using GNU Radio this time with something that decoding the data might be useful.  For this one he is using a cheapo 433mhz transmitter you would use on an arduino like the ones use in this post.  GNU Radio is a little more complex than baudline.  You get to visually pipe inputs and outputs together for different modules until you achieve the proper filtering and decoding.

Published on: August 26, 2013 / Comments: 1

Receive weather satellite imagry with your SDR

Around 800 km / 500 miles above your head, weather satellites circle Earth, continuously sending back what they see.

You may or may not know, but there are weather satellites pushing un-encrypted images down to earth all the time.  With the right equipment and know-how you can capture these images and take a look.  The guys over at SDR for Mariners put up a little write up on how to do so.

They’re using the infamous cheap RTL-SDR dongle, but almost any SDR would work as long as you can capture the right frequency and have enough bandwidth.  This is being done on windows using SDR Sharp.  This is a great way to learn more about using your SDR, besides aren’t you tired of tuning FM with your SDR ?

Read the full post here.

Published on: August 14, 2013 / Comments: None

Spying on your neighbors with rtl-sdr

Unless you’re just upgrading from windows 3.1, you’ve seen the cheap SDR (software defined radio) rtl-sdr project.  SDR’s aren’t new but someone figured out how to turn a cheap sub-20$ dongle into a decent SDR bringing the entry price low enough for everyone to experiment with them.

Every electronic device you own is screaming its name into the infinite void

Melissa Elliott has put together a presentation titled “exploring the world of unintentional radio emissions” that was presented at DEF CON.    After talking about the concept itself, she shows you how almost everything that runs on electricity emits some sort of electronic signature.  That signature can be profiled and sometimes data can be decoded from it.

No it’s not time to break out the tin foil hats or anything but if you really are paranoid, Melissa gives some tips how to shield this information in the form of Faraday cages.  You don’t have to be an old ham radio buff or even a budding electronics engineer to appreciate how cool SDR’s are.




Published on: July 25, 2013 / Comments: None

PCB antenna design, for dummies… well almost

I love how this article starts out, the age-old saying about RF and analog being taboo… so true!  Anyhoo, Colin takes you on a quick rundown of antenna basics, focusing on tuning PCB antennas.  This is one of those articles you see AFTER you need it, personally I totally could have used this months ago.  So we’ve all seen these PCB antennas, those little squiggly lines on your board that do the voodoo RF magic, but what do you do when you need to tune it ?  Well start by reading this article.

With the recent boom of cheap SDR’s flooding the market, more people are getting back into RF design.  Although I wouldn’t recommend using a fixed-tune antenna for a SDR, the theory by its self is worth the read.  Of course the biggest hurdle here for a DIY’er is going to be having access to a spectrum analyzer.