Category: Other

An RTL-SDR Comic Book!

We’ve recently been informed that the RTL-SDR has become so popular that is now has it’s very own Japanese Manga comic book! If you don’t know what Manga is, it a type of Japanese comic book. The manga appears to be a one off self published work in a continuing series about military radio interception. Other popular technical manga books have been released before, such as the manga guides to statistics, physics, calculus, electricity, linear algebra, biochemistry, the universe and relativity, but this is the first one we’ve seen on the RTL-SDR.   

The comic is written in Japanese and it looks like it explains what the RTL-SDR is as well as providing a tutorial on its installation and use. It is yet to be released but the release date is stated as mid August. The comic is sold on this Japanese web store (note that on the store it is possible to see some illustrated images that may be considered explicit by some so don’t click if you want to avoid that). It may be an interesting gift for RTL-SDR fans, or for Japanese readers who want a fun way to learn about radio. We’re not sure how to buy the comic if you reside outside of Japan, but this Japanese forwarding service might be able to buy it for you.

Below we’ve posted the cover image and the preview pages.

rtl_manga_1rtl_manga_2rtl_manga_3rtl_manga_4rtl_manga_5rtl_manga_6

Setting audio levels correctly when decoding with an RTL-SDR

When decoding a digital signal with an RTL-SDR the digital audio is usually piped from receiver software like SDR# via stereo mix or software like Virtual Audio Cable/VBCable into the decoding software. The decoding software expects a clean audio signal with the volume levels set not too loud, but also not too quiet. Usually this can be achieved by trial and error.

However amateur radio hobbyist K3RRR found that setting the audio level correctly was critical for maximizing decodes on his digital HF signals when using his RTL-SDR. To correctly set the audio levels he uses a program called Peak Level Meter and another called Soundcard Oscilloscope. Peak Level Meter is used to ensure that the audio levels are set correctly and Soundcard Oscilloscope is used to ensure that the audio is not being over driven into square waves.

Checking for over driven audio waveforms in Soundcard Oscilloscope.
Checking for over driven audio waveforms in Soundcard Oscilloscope.

Getting the RTL-SDR to work in Windows 10

The RTL-SDR is fully compatible with Windows 10. However with the recent release of Windows 10 some users have been having trouble using their RTL-SDR after upgrading. We thought that we'd announce that the simple solution to most problems is to reinstall the SDR drivers with Zadig. The latest version of Zadig can be downloaded from zadig.akeo.ie or if you use SDR# then it will already be in your SDR# folder. The process is:

  1. Plug in the RTL-SDR.
  2. Run Zadig as administrator by right clicking it and choosing run as administrator.
  3. Go to Options -> List all devices and make sure it is checked.
  4. In the drop down box choose Bulk-In, Interface (Interface 0). This may also sometimes show up as something prefixed with "RTL28328U". That choice is also valid.
  5. Make sure that WinUSB is selected as the target driver and click on Replace Driver.

If you need more help see the Quickstart Guide. (NOTE: If you have come across this post before the quickstart guide, be sure to use the quickstart guide as your first point of reference for installing RTL-SDR drivers and software!)

The Windows 10 upgrade process appears to replace the WinUSB drivers with the Windows DVB-T ones, so reinstalling the SDR drivers is necessary. It shouldn't be necessary, but one user also reported the need to log in to Windows with an administrator account and to uninstall the current drivers before running Zadig, so try that if you continue to have problems.

As in our previous post we can confirm that several popular SDR apps such as SDR#, HDSDR, SDR-Radio, CubicSDR and Unitrunker all work fine in Windows 10.

Skywave Linux: New Linux Ubuntu Distribution made for Software Defined Radio

Skywave Linux is a new Linux distribution based on Ubuntu 14.10. It is designed for users of software defined radio’s and comes with several useful SDR software packages preinstalled. It can be run from a bootable DVD, USB or SD card.

The author writes that Skywave Linux is currently compatible with the RTL-SDR and HPSDR hardware. At the moment it seems that the first version has only very few preinstalled software programs. These include: QT Radio, CubicSDR, Fldigi, and Dump1090. The authors write about Skywave:

Welcome to the first release of Skywave Linux! This is an operating system designed to provide access to a growing network of software defined radios all over the world. With global SDR access, shortwave listeners can access broadcast, utility, amateur radio, military, and other signals from almost anywhere in the world – from state-of-the art radio servers. All you need to do is boot Skywave Linux on a computer with internet access.

Why was Skywave Linux created? The developer of this system was plagued by a lack of access to quality radio broadcasts due to his residence in a country practising tight media control and censorship. In addition, software defined radio is an exciting way to experience the hobby of shortwave listening. By connecting to remote radio servers on the internet, it is possible to enjoy bleeding edge radio operation without large antennas or setting up a station on-site. Installing SDR software can be difficult for many computer users, and Skywave Linux eliminates the hassle of downloading, compiling, and configuring apps for the SDR servers on the internet.

If you’re instead looking for a distribution with GNU Radio preinstalled, then we note that other distributions such as KB1OIQ – Andy’s Ham Radio Linux, the GNU Radio live DVD, and Kali and Pentoo Linux also exist.

CubicSDR running in Skywave Linux
CubicSDR running in Skywave Linux

Wirelessly transmitting sound from a parabolic microphone with an FM Transmitter and receiving it with an RTL-SDR

Parabolic microphones allow listeners to clearly hear sounds from far away. They are often used by bird call enthusiasts and also probably by spies. A parabolic microphone works by using a dish to concentrate distant sound onto an amplified microphone and they have been commercially available since the 60’s as demonstrated by this old Radioshack ad.

An old parabolic micrphone advertised in a radioshack catalogue from the '60's
An old parabolic micrphone advertised in a radioshack catalogue from the ’60’s

Usually, the listener uses a pair of headphones directly tethered to the parabolic microphone and walks around with the dish in hand. However, this week electronics hobbyist Mario Fillipi wrote in to RTL-SDR.com to let us know about his project in which he created a wirelessly operated parabolic microphone.

To do this Mario connected a wireless FM transmitter to the headphone output of his home made parabolic mic, mounted the dish on a tripod, and then used his RTL-SDR to receive the FM transmission and demodulate the remote sounds. Of course reception can be done with any suitable radio, but the RTL-SDR provides the advantage of being able to easily manage, record and analyze the received audio.

The parabolic micrphone with FM transmitter
The parabolic microphone with FM transmitter

Mario used his wireless parabolic microphone to record the sounds of finches in a bird house that was about 70 feet (21 meters) away. Then he writes that in HDSDR he was able to analyze the finches calls in the audio spectrum waterfall. He noticed that the calls were in the 2300 – 6000 Hz audio range and that each call’s “imprint” or audio signature was very similar and could be easily recognized. You can listen to the finches calls that were recorded by the RTL-SDR in the audio file below.

Looking at the Finch calls' "imprints" in the audio spectrum waterfall in HDSDR
Looking at the Finch calls’ “imprints” in the audio spectrum waterfall in HDSDR

Mario writes that this can be done with any commercially available parabolic microphone, but if you want to know how to build your own wireless parabolic microphone then check out Make magazine’s article on Mario’s work. The article shows in detail how to build a parabolic microphone out of a squirrel baffle (a bowl shaped piece of plastic that prevents squirrels from eating bird feed), a Velleman Super Stereo Ear kit (microphone + amplifier kitset) and a standard wireless FM transmitter. Mario writes that the audio range of his home made parabolic mic is about 100 feet (30 meters). A video from Make magazine showing Mario’s home made parabolic mic is shown below.

Weekend Projects - Squirrel-Baffle Spy Microphone

A list of 5 Free Virtual Audio Cable Software Programs

The dxzone.com website has uploaded a post that lists five free virtual audio cable software programs. Virtual audio cable’s allow you to “pipe” or pass the audio from one application to another. For example, in order to pass the audio of a digital P25 signal received in SDR# into a decoding program such as DSD+, you need to use a virtual audio cable. The most commonly recommended software is Virtual Audio Cable, but this software is not free. See the dxzone.com post for their list of five alternatives for Windows, Linux and MaxOS.

virtualcablesdxzone

New Talk by Balint Seeber: Hacking the Wireless World with SDR

Balint Seeber is a researcher at Ettus, designers of the USRP line of software defined radios. Every so often he gives an interesting conference talk about his latest projects. This time he’s given a talk at Ruxmon Sydney in April of this year and it has just been uploaded to YouTube.

In the talk Balint overviews the projects that he’s working on or completed. His topics include:

  • His work with creating his own battery powered GSM base station including a live demo where members from the audience connect to and call him via the base station.
  • His work with FPV drones and creating an SDR based FPV digital video system.
  • Hacking restaurant pagers.
  • Attempting to communicate with and revive the ISEE-3 spacecraft using the large radio dish at Arecibo.
  • Gathering actual RADAR data from listening to a real airport active RADAR system and plotting the returns on a map.
  • Investigating RFID tags and attempting to unlock his car via an SDR.
Ruxmon Sydney (April 2015): Hacking the Wireless World with SDR

Monitoring Drone FPV Frequency Usage with a USRP Software Defined Radio

Over on YouTube balint256 (Balint), a researcher at Ettus (creators of the USRP line of software defined radios) has uploaded a video showing how he is using his USRP to help with frequency management at FPV time trial racing events. FPV a.k.a First Person View is a term used to describe the act of flying a remote controlled aircraft such as a quadcopter with an onboard camera that transmits live video down to the pilot. FPV racing is a new sport where pilots race FPV controlled drones around a track.

One important technical challenge at these events is frequency management. FPV drones use many frequencies at around 2.4 GHz for control and 5.8/2.4/1.3 GHz for video. With many drones in the air it is important that frequencies are managed appropriately so as to not jam each others signals.

To try and solve this problem Balint has been using GNU Radio coupled with a USRP X310 software defined radio to get very wide band RF spectrum waterfall views of the 2.4 and 5.8 GHz bands. In the waterfalls he is able to see when control signals and video signals are transmitted and at what frequency, and is able to tell if any are overlapping and jamming each other.

SDR Wideband Spectrum Monitoring for Drone FPV Frequency Management

In addition to this, Balint has also been working on his custom software defined radio based digital video downlink. Back in March we posted about his earlier work on this concept. In the video Balint demonstrates his drone with an on board USRP E310 which is used to send a custom 4.2 Mbps video downlink.

SDR digital video downlink (custom drone FPV) with E310 + webcam