Building a spectrum analyzer

Discussion in 'Technical' started by gunbunny, Apr 16, 2015.

  1. gunbunny

    gunbunny Never Trust A Bunny

    Since we got on the topic of spectrum analyzers, I did a little digging around to see just what is involved. I found this nifty little nugget: An RTL-SDR Spectrum Analyzer | Hackaday
    Unfortunately, It uses Linux. I don't have anything that runs Linux. I'm not in the mood to get one, either. I'm just now trying to figure out Android, for Pete's sake.

    I am intrigued by the possibility of a small, inexpensive unit made from select parts. The plans call for an Elonics E4000 dongle (a usb powered and pluggable unit, if I am correct) that has an RTL2832U EEPROM chip in it.

    That part I can understand, but the problem is, trying to find this device. I've been lead astray on more than one occasion buying a POS that did not function as the description says it should. The next problem will be a software one. Where do I find a program that will work on Android or Win7?

    I've looked for Android apps under Spectrum Analyzer, but all it comes up with is a fancy decibel meter. It is nice to have a decibel meter, but it wasn't what I was looking for. BTW, my Android tablet (DigiLand DL701Q) does actually have a radio tuner in it- an actual tuner, not a webcast app. I can put the tablet in airplane mode with the wi fi and bluetooth off, and it will pick up the local radio stations.

    That being said, how do I find out whether or not I have an RTL2832U EEPROM chip living aboard? If it does, how can I exploit that to make a spectrum analyzer...
  2. DarkLight

    DarkLight Live Long and Prosper - On Hiatus Site Supporter

    Can't speak to getting a device with the correct EEPROM, but will throw my hat into the ring on the Linux issue.

    Have you ever run a Virtual Machine? If you need a primer, let me know and I'll walk you through it. There are a couple of good free ways to "get 'er done". The point is you can set up a Linux VM and pass the USB device through into the VM. Et Voila, running your Linux app on your Windows 7 box.

    The other alternative is, if you have a machine that can run Windows 7, you already have a machine that can run Linux. Dual Boot is always an option.

    I promise I'm not (and I won't) trying to convert you to Linux, just trying to think of a way to allow you to do both.
    sec_monkey, kellory and gunbunny like this.
  3. gunbunny

    gunbunny Never Trust A Bunny

    I don't have anything against Linux per se, it's just that it is yet another thing I have to spend time on and learn about, and it doesn't seem to do anything any better than C:. I believe the reason there aren't any viruses for Linux is that there aren't enough people running Linux to bother making one.

    Here's a comment from a scathing review about the DL7 I have. I know it's a crappy tablet, I just wanted something cheap to play with Android on. $49 at Best Buy made this particular tablet interesting. I really like the radio function, and along with a few select other apps (inclinometer, dash command), will find a place on my Jeep dash in a few months.

    Anyway, here's what someone said about my tablet:

    "I’m not sure I’d write this thing off, quite so fast: I just purchased one today, and found out that it’s in “Developer mode”. In other words, there’s a full, usable Linux Command line available (though not “rooted”, there are articles out there, suggesting that it’s not hard to do).

    Also, the “Owner’s Manual” is almost worth the price, in comedy value. For example, on the first, inside page, #13 reads: “When CPU in high-speed operation, especially in 3D games or in long time playback high-definition video, the fuselage will have the phenomenon of fever”.

    I picked #13, because someone complained about how slow this is. In the “Accessibility” option, there’s a selection for “High Speed Mode”, that’s unchecked, by default.

    By the way, I like this, as an Android Geek. I REALLY don’t recommend it for an Andorid novice! Seriously!"

    So, do you think there might be hope for it to become a mobile Spectrum Analyzer?
  4. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    I like monkeys helping monkeys.:)
    Tully Mars likes this.
  5. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Do a Goggle search on SDR ( Software Defined Radio) and then read up on Spectrum Analyzer Software that will run on that SDR, and the OS of your choice....
    Ganado likes this.
  6. gunbunny

    gunbunny Never Trust A Bunny

  7. gunbunny

    gunbunny Never Trust A Bunny

    It looks like I found one: SDR Touch for Andriod. SDR Touch - Software Radio for Android

    I downloaded the app, but it looks like two things: 1) it doesn't recognize the internal SDR chip. My el cheapo DigiLand DL7 has to have an internal SDR, or I wouldn't be able to listen to the radio with the wi fi and bluetooth off in airplane mode. You have to plug in a headset so it has an antenna, it's not web-based.

    2) You have to pay for the full version spectrum analyzer. If I have to pay a little bit to get the full software so be it, I'd just like to be able to use the spectrum analyzer. It just seems a little inefficient to attach a dongel when I may be able to use the internal chip. I sent an email to the FAQ on the site asking them about it.

    Anyway, I'll keep you posted of the results.
  8. Ganado

    Ganado Monkey+++

    I feel stupid asking this but..

    what are you using this for?
  9. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    Ganado likes this.
  10. Ganado

    Ganado Monkey+++

    What u laughing at Willis?
  11. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    Spectrum analyzer - Wikipedia, the free encyclopedia
    They get used for many things, but my guess would be ham radio.

    @BTPost could give you a complete rundown, without breaking a sweat. (If you asked him nicely;)) they are a useful lab tool, and often used interchangeably with an oscilloscope.
    Last edited: Apr 16, 2015
  12. ghrit

    ghrit Bad company Administrator Founding Member

    Really not interchangeable at all. O'scopes operate in the time domain, spectrum analyzers operate in the frequency domain. There are some common features, but they do not interchange that I know about.
  13. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    "The display of a spectrum analyzer has frequency on the horizontal axis and the amplitude displayed on the vertical axis. To the casual observer, a spectrum analyzer looks like an oscilloscope and, in fact, some lab instruments can function either as an oscilloscope or a spectrum analyzer"
    This is what I meant.
    Witch Doctor 01 and ghrit like this.
  14. gunbunny

    gunbunny Never Trust A Bunny

    You could call it modern urban survival. Not the typical fire making fare, but more like an esoteric exercise in discovering the wavelengths of energy flowing around my location. I.E.- seeing what's going on around me in the electromagnetic spectrum.

    Possibilities include listening to HAM radio if the equipment is upgraded, possibly RF direction finding with more equipment.
    Ganado likes this.
  15. gunbunny

    gunbunny Never Trust A Bunny

    big grin.
    It's just really cool, just think if you would have tried to do this 15 years ago, you would have spend $1000's. Now they have the technology to do it with a $49 tablet and less then $40 worth of peripherals, and it fits in the palm of your hand.
    Ganado and kellory like this.
  16. Tully Mars

    Tully Mars Metal weldin' monkey

    I just need a functioning Flux capacitor then all is possible..
    kellory and gunbunny like this.
  17. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    easy, just fall off your toilet.[winkthumb]
  18. fmhuff

    fmhuff Monkey+++

    So what you are up to is a broad spectrum RF sniffer? An omni-directional antenna might be good for detection but for locating a uni-directional antenna will prove useful.

    Clever Monkey. (y)
    Tully Mars and gunbunny like this.
  19. gunbunny

    gunbunny Never Trust A Bunny

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  20. madmax

    madmax Far right. Bipolar. Veteran. Don't push me.

    Wow. A foreign language to learn...

    The world is full of endless things to explore.
    gunbunny and kellory like this.
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