Sunday, November 4, 2012

RTLSDR in Virtualbox

To get rtlsdr working in Ubuntu 12.04 in virtualbox, just run the gnuradio build script and you can enable usb 2.0 (you'll need to install an extension pack).  It took it several minutes for the device to attach the first time (I was only using USB 1.1), so be patient (I thought it originally wasn't working).

While either USB 1.1 or USB 2.0 is chosen, the sample rate through virtualbox is still low enough that it's dropping packets at every sample rate I've tried, so I would not recommend it.  It does get enough valid data that you could probably work with it in many scenarios, so it's better than nothing, but I would not use rtlsdr in a VM if you can avoid it.

You will frequently need to disconnect and reconnect your rtlsdr since it seems to lock up every once in a while, just as it does on a physical machine, but it seems to happen more frequently.

Friday, November 2, 2012

GNURadio on Ubuntu 12.10 for RTLSDR

Very quick post.  I upgraded my Ubuntu laptop with gnuradio (built from script) from 12.04 and 12.10 and some of the dependencies seem broken.  I spent quite a while debugging it and rebuilt gnuradio from the script, but never resolved the issue.  I didn't try the gnuradio from apt, but I heard that was too old to support rtlsdr.  I couldn't find any discussions about this via google, so I thought I'd post this here in case someone was curious about upgrading.  I'm guessing this will be fixed at some point once smarted people run into this issue and fix it (in the build script?).

Update: I did a fresh install of 12.10 and reinstalled gnuradio from the build script and everything is working fine now.  My issue could be isolated, but my takeaway is to not upgrade ubuntu if you aren't willing to risk breaking your GNURadio install.

Saturday, May 5, 2012

Samsung TV Blown Capacitor - High Pitched Whine Sound

I had a Samsung TV that's known to have capacitor issues.  There is a capacitor settlement as a result of a class action lawsuit.  It was making a quiet but annoying high pitched whine sound.  This sound is normally from an inductor.

I couldn't find anything online about this, so that meant I was going to write this blog post when I fixed it to help others out.  I called the Samsung settlement line and they said this high pitched noise was not one of the symptoms of a blown capictor.

I took the back panel off and there was a popped capacitor, right next to an inductor, some transistors and a heat sink.  The capacitor is presumably used in an LC circuit before as part of a SMPS (switched mode power supply).  Initially, I tried hot gluing the inductor to quiet the oscillations down, because it didn't look too blown.  The sound changed in pitch, but remained.

The next day I replaced the capacitor and the sound went away.  I used my multimeter and the capacitor was measuring 0 farad.  I tested some known good ones, so I was using the multimeter it correctly.  I didn't have the right size capacitor handy, so I replaced the 2200uF 10v capacitor with a 220uF 50v capacitor.  It's not tuned to the right frequency (I think it's allowing the square root of 10 (3.16) higher frequencies than the initial design), but the sound went away entirely, so I'm happy.


I called the samsung line back and told them it was a blown cap and they said I'm still not eligible for anything because it wasn't exhibiting any of the known symptoms.  I dont know if it is worth pursuing, but it's annoying that there is a class action lawsuit to fix this issue, yet Samsung says I'm not covered.

The Fix
So in short, the fix (what you probably came here for) is to remove the back panel, look for a popped capacitor (the top will be lifted and there will be residue on it).  This capacitor will probably be in the position my screwdriver is pointing to, then replace the capacitor with one of the same size.  I only used a solder iron, solder, and a replacement capacitor.  You will probably want a 2200uF 10v (or greater) capacitor, which you can find thator something similar at RadioShack.

Let me know if you are having the same issue or if this helped.  Just curious how widespread this is.