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A pink $16 pocket spectrum analyzer (ossmann.blogspot.com)
115 points by gourneau on Dec 13, 2010 | hide | past | web | favorite | 24 comments

What you can do with spectrum analyzers is pretty awesome. In my first year in a lab I built a program that scrapes the NIST spectral database, reads the data from a spectrum analyzer attached to the computer, and figures out which types of atoms the thing the spectrum analyzer is looking at contains. This is harder than it sounds. Essentially you're trying to match tens of thousands of sets of spectral lines of varying strength to a noisy spectrum measurement (something like this but noisier: http://upload.wikimedia.org/wikipedia/en/thumb/5/5d/Spectra-...).

The problem is that one element, say natrium, has many spectral lines of varying strength. You're trying to find a set of elements that best explains the measured spectrum. If you plotted all spectral lines from all elements on a spectrum, it would be completely black because there are so many. In the end it only worked well for fluorescent tubes, but it could tell you what's in them, even things a human would have a very hard time discovering by looking at the spectrum and manually comparing it to the NIST database (the university has all kinds of weird lamps like natrium lamps, blacklights, and fluorescent tubes in many colors all containing different stuff, and looking at computer monitor pixels is fun too).

My program output an element X who's name I forgot for many of the lamps, but when I plotted its spectral lines over the spectra I couldn't see the match clearly, so I added a parameter to the algorithm so that it would be more restrictive on the number of different elements returned. In the presentations of the lab the prof commented "many of these tubes also contain element X, but you can't see it with the spectrum analyzer you used, you need a higher quality one". Bummer.

The original posting describes a spectrum analyzer that shows the strength of radio-frequency signals. It's built by reprogramming a toy that uses the Texas Instruments CC1110F32 RF system-on-a-chip (http://focus.ti.com/docs/prod/folders/print/cc1110f32.html)

You (jules) are discussing a spectrometer, that shows the strength of optical spectral lines to identify materials (http://en.wikipedia.org/wiki/Spectrometer). These are two totally different things - radio-frequency vs optical. (Just want to keep the discussion from getting totally confused.) Also, Natrium == Sodium (Na)

You are completely right. Now that I'm reading it again they are repeating "radio" a lot of times and there are a ton of clues that this is radio frequency, but the picture of the device on the yellow peppers just triggered "oh they are measuring the light spectrum of yellow peppers". Sorry for the confusion.

    In my first year in a lab I built a program 
    that scrapes the NIST spectral database, reads the data 
    from a spectrum analyzer attached to the computer, and
    figures out which types of atoms the thing the spectrum 
    analyzer is looking at contains. This is harder than it 
No no, trust me, that sounds hard. :-)

It may sound hard but most of it is pretty mundane. Scraping the NIST database is just a program visiting pages for wavelength ranges 0-100, 100-200 etc. to get all the data. Then it parses the HTML tables into a hash table indexed by element name ("H", "O", "C", "Na") which gives for each element an array of pairs of floating point numbers (wavelength of spectral line, strength of spectral line).

Talking to the spectrometer is boring too: you have your program execute some other program that comes with the spectrometer, which talks to the spectrometer and saves a file containing a list of floating point numbers which describes a graph like this (http://upload.wikimedia.org/wikipedia/en/thumb/5/5d/Spectra-...) with data points. The floating point numbers come in a weird format that the standard floating point parsing function can't handle, so you munge it a bit with a regex.

Someone reversed the USB transceiver dongle too: http://blog.hodgepig.org/2010/10/22/im-me-usb-dongle-hacking...

Of course not forgetting the GPL drivers for the same: http://im-megpldrivers.sourceforge.net/

Also, $16? I paid £0.99 for mine on ebay :)

> The frequency ranges supported by my device are 281 - 361, 378 - 481, and 749 - 962 MHz. This is about 50% more than the chip is advertised to support and covers quite a bit of interesting activity in the US including ISM, LMR, television, amateur bands, pagers, and mobile phones.

Do hackers of this device risk running afoul of laws against intercepting mobile phone transmissions?

Quite possibly, but you would likely not get prosecuted. If you actually want to do online GSM decryption you need a lot fancier software radio than this thing, because GSM involves a lot of algorithmic frequency hopping/multiplexing.

Also there is no realistic practical way to passively detect a passive detector. Plus how would they distinguish you from someone on a normal mobile phone?

> Also there is no realistic practical way to passively detect a passive detector.

Is that true? I heard that the BBC license police used "receiver detectors" to find unlicensed TVs.

This is well known to be a a lie. The vans are fake. It's basically just extortion.

Just think of it as part of our eccentric british ways.

EDIT: just to add, I pay my license fee, happily, even though I dont have to because its not required to watch the iPlayer streaming service, which is how I watch almost all my TV. The fee is pretty cheap considering the sheer breadth of services the BBC provides. The UK would essentially fall apart without it culturally.

It may be fake, but it is possible. All televisions have a number of local oscillators for super-heterodyne reception. With sensitive equipment, the radiation from these oscillators can be detected because they are not well-shielded.

This is the case, but this technique will not allow you to distinguish between my television which I have paid for, and that of my nonpaying neighbour which is 12" away on the other side of an internal wall, on the 20th floor of a towerblock with hundreds of televisions in it, from the street. Which is what the Television Licensing Authority (the BBC dont actually have any involvement in collection or enforcement) claim they can do.

There was a television programme in Finland years ago, where they showed one of those "detectors" being used inside a building to find unlicensed televisions. What was visible of the device looked like an oven thermometer. It was the subject of much fun-poking, and there were screenshots floating around, but I can't find any of them now.

You do need a licence to watch 'live' programs via iPlayer:


I heard something about them working from CRT emissions, making them useless for LCDs, if they actually worked at all.

Edit: More broadly, you could say that just from the deterrent effect of their PR, they "work".

No. You aren't doing anything illegal unless you demodulate the signal.

Is this covered under DMCA? (Even though information is flying at your face, you not allowed to interpret it?)

Travis Goodspeed gave a talk at HOPE about the RFID badges, and touched on his work with the IM-ME. Smart (and neighborly!) guy.

For some reason this reminds me of ... http://megatokyo.com/strip/1107 (towards the bottom of the page)

Very cool mod, though.

How do you get them so cheap? Amazon lists them for $29.99.


I found mine for $15.99 and free shipping on eBay.

Where's my iPhone spectrometer!!!

But this is a frequency analyzer for finding overtones to determine broadcast frequency at close distance.

Why pink?

EDIT: I didn't see that the keys were alphanumeric and thought that was its intended purpose. I thought maybe they were going for the "science girl" demographic, which would have been cool.

It's a toy for little girls. It just happens to be easily hackable for other uses. Which is neat.

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