RTL SDR As A Spectrum Analyzer

November 19, 2014 by Brian Benchoff 24 Comments

RTL-SDR, the USB TV tuner turned software-defined radio is an amazing device, capable of listening to nearly anything from 25MHz to 1750MHz, fits in your pocket, and costs about $20. Even more astonishing is that it’s also a kinda-okay spectrum analyzer. [Kerry D. Wong] tested out one of these USB TV tuner, and the results are exactly what you would expect: it lacks a little precision, and sampling bandwidth is only a tiny bit terrible, but it does work.

A stock USB TV tuner doesn’t come with a connector that would normally be used for spectrum analysis. A BNC connector can be easily attached, as can a terminator to match the 75Ω impedance of the SDR. This isn’t really necessary; the frequencies being measured are low enough that you can get away without one.

As far as software goes, [Kerry] first pulled out the usual suspects of the SDR world; rtlsdr-scanner distorted the measured spectrum, as did a lot of other SDR receivers. Gqrx SDR was the first one that worked well, but the king of this repurposing of USB TV tuners was OSMOCOM. There’s a huge number of tools for spectrum analysis right out of the box with this package.

How did the RTL SDR fare as a spectrum analyzer? Feeding some stuff in from a signal generator, [Kerry] discovered the LO in the RTL SDR was off by a hair. Also, OSMOCOM only measures amplitude in dB, not the dBm found in every other spectrum analyzer ever made. By measuring a 0 dBm signal whatever value displayed can be shifted up or down.

So, does it work? Yes, it does. If, for some reason, you need a spectrum analyzer now, can you use this? Yep. Pretty cool.

Hackaday Prize Finalist: A Portable SDR

November 5, 2014 by Brian Benchoff 74 Comments

No other project to make it to The Hackaday Prize has people throwing money at their computer screen hoping something would happen than [Michael Colton]’s PortableSDR. It’s a software defined radio designed for coverage up to 30MHz. Amateur radio operators across the world are interested in this project, going so far as to call this the first Baofeng UV-5R killer. That’s extremely high praise.

[Michael] was kind enough to sit down and answer a few questions about how his entry to The Hackaday Prize has gone. You can check that out below, along with the final round video of the project. Anyone who wants their own PortableSDR could really help [Michael] out by taking this survey.

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THP Hacker Bio: Michael R Colton

September 7, 2014 by Brian Benchoff 6 Comments

With many hackers out there realizing how much you can do with a few RF blocks connected to a computer, it’s no surprise software defined radio would make a showing in the semifinalists for The Hackaday Prize. [Michael]’s project is the PortableSDR, a small, self-contained unit that handles just about everything below 30MHz. No, [Michael] isn’t dealing with gigahertz accessible with fancier SDRs, but that’s not the point: PortableSDR is meant to do everything – vector analysis, a neat waterfall display, transmit and receive – in a small, portable package you can take anywhere. It’s also fairly cheap to build, and of course completely open source.

This isn’t [Michael]’s first rodeo; he’s built a number of equally cool projects before. He was kind enough to send in a short bio, available below.

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Hackaday Links: August 30, 2014

August 31, 2014 by Brian Benchoff 18 Comments

Adafruit did another Circuit Playground, this time concerning frequency. If you’re reading this, no, it’s probably not for you, which is great because it’s not meant to be. If you have some kids, though, it’s great. Not-muppet robots and oscilloscopes. Just great.

The Hack42 space in Arnhem, Neterhlands recently got an offer: clean out a basement filled with old computer equipment, and it’s yours. Everything in the haul had to fit through an 80cm square door, and there are some very heavy, very rare pieces of equipment here. It’ll be a great (and massive) addition to their museum. There’s a few pics from the cleanout here and here.

[Mike] has been working on a project to convert gerber files into SVGs and it’s great.

[Carl] did a roundup of all the currently available software defined radios available. It’s more than just the RTL-SDR, HackRF, and BladeRF, and there’s also a list of modifications and ones targeted explicitly to the ham crowd.

This is a Facebook video, but it is pretty cool. It’s a DIY well pump made in Mexico. A few rubber disks made out of an old inner tube, a bit of PVC pipe, and a string is all you need to bring water to ground level.

What can you do with a cellphone equipped with a thermal imaging camera? Steal PIN codes, of course. Cue the rest of the blogosphere sensationalizing this to kingdom come. Oh, what’s that? Only Gizmodo took the bait?

About a year ago, we saw a pretty cool board made by [Derek] to listen in on the CAN bus in his Mazda 3. Now it’s a Kickstarter, and a pretty good one at that.

Your connectors will never be this cool. This is a teardown of a mind bogglingly expensive cable assembly, and this thing is amazing. Modular connectors, machined copper shields, machined plastic stress relief, and entire PCBs dedicated to two caps. Does anyone know what this mated to and what the list price was?

DEFCON 22: The HackRF PortaPack

August 17, 2014 by Brian Benchoff 12 Comments

What do you get when you combine one of the best (and certainly one of the best for the price) software defined radios with the user interface of a 10-year-old iPod? The HackRF PortaPack, developed by [Jared Boone], and demonstrated at DEFCON last weekend.

[Jared] is one of the original developers for the HackRF, a 10MHz to 6GHz software defined radio that can also transmit in half duplex. Since the development of the HackRF has (somewhat) wrapped up, [Jared] has been working on the PortaPack, an add-on for the HackRF that turns it into a portable, ARM Cortex M4-powered software defined radio. No, it’s not as powerful as a full computer running GNU Radio, but it does have the capability to listen in on a surprising amount of radio signals.

Because [Jared] is using a fairly low-power micro for the PortaPack, there’s a lot of tricks he’s using to get everything running smoothly. He gave a lightning talk at the Wireless Village at DEFCON going over the strengths and weaknesses of the chip he’s using, and surprisingly he’s using very little floating point arithmetic in his code. You can check out the video for that talk below.

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Hackaday Links: July 27, 2014

July 27, 2014 by Brian Benchoff 14 Comments

Taking apart printers to salvage their motors and rods is a common occurrence in hacker circles, but how about salvaging the electronics? A lot of printers come with WiFi modules, and these can be repurposed as USB WiFi dongles. Tools required? And old printer, 3.3 V regulator, and a USB cable. Couldn’t be simpler.

The Raspberry Pi has a connector for a webcam, and it’s a very good solution if you need a programmable IP webcam with GPIOs. How about four cameras?. This Indiegogo is for a four-port camera connector for the Raspi. Someone has a use for this, we’re sure.

The one flexible funding campaign that isn’t a scam. [Kyle] maintains most of the software defined radio stack for Arch Linux, and he’s looking for some funds to improve his work. Yes, it’s basically a ‘fund my life’ crowdfunding campaign, but you’re funding someone to work full-time on open source software.

Calibration tools for Delta 3D printers. It’s just a few tools that speed up calibration, made for MATLAB and Octave.

[Oona] is doing her usual, ‘lets look at everything radio’ thing again, and has a plan to map microwave relay links. If you’ve ever seen a dish or other highly directional antenna on top of a cell phone tower, you’ve seen this sort of thing before. [Oona] is planning on mapping them by flying a quadcopter around, extracting the video and GPS data, and figuring out where all the other microwave links are.

PowerPoint presentations for the Raspberry Pi and BeagleBone Black. Yes, PowerPoint presentations are the tool of the devil and the leading cause of death for astronauts*, but someone should find this useful.

* Yes, PowerPoint presentations are the leading cause of death for astronauts. The root cause of the Columbia disaster was organizational factors that neglected engineer’s requests to use DOD space assets to inspect the wing, after which they could have been rescued. These are organizational factors were, at least in part, caused by PowerPoint.

Challenger was the same story, and although PowerPoint didn’t exist in 1986, “bulletized thinking” in engineering reports was cited as a major factor in the disaster. If “bulletized thinking” doesn’t perfectly describe PowerPoint, I don’t know what does.

As far as PowerPoint being the leading cause of death for astronauts, 14 died on two shuttles, while a total of 30 astronauts died either in training or in flight.

A GSM Base Station With Software Defined Radio

July 5, 2014 by Brian Benchoff 40 Comments

gsm If you’re wondering how to get a better signal on your cellphone, or just want to set up your own private cell network, this one is for you. It’s a GSM base station made with a BeagleBone Black and a not too expensive software defined radio board.

The key component of this build is obviously the software defined radio. [Julian] is using a USRP B200 radio for this project. It’s not cheap, but it is a very nice piece of hardware capable of doing just about anything with GNU Radio. This board is controlled by a BeagleBone Black, a pretty cheap solution that puts the total cost of the hardware somewhere around $750.

The software side of the build is mostly handled by OpenBTS, the open source project for the software part of a cell station. This controls the transceiver, makes calls and SMS, and all the backend stuff every other cell station does. OpenBTS also includes support for Asterisk, the software of choice for PBX and VoIP setups. Running this allows you to make calls and send texts with your SDR-equipped, Internet-enabled BeagleBone Black anywhere on the planet.