Category: Applications

RTL-SDR with GQRX Running on an Odroid C1 at 1 MSPS and Max FFT

Over on YouTube user neutron2025 has uploaded some videos showing GQRX running on an Odroid C1. The Odroid C1 is a low cost ($35 USD) mini computer with an Arm Cortex A5 quad core CPU and 1 GB RAM which runs Ubuntu 14.04 or Android KitKat. It is a much more powerful competitor to the Raspberry Pi which also goes for around the same price.

Despite its low cost, the video by neutron2025 shows that the Odroid C1 has enough processing power to run the relatively CPU intensive GQRX SDR software with the RTL-SDR at a 1 MSPS sampling rate and maximum FFT resolution.

To install GQRX, GNU Radio also needs to be installed. Installation of GNU Radio is a lengthy process containing many writes to the file system. The amount of writes that occur could destroy a SDCard. To get around this neutron2025 connected an external hard drive and used that as a swap file while installing GNU Radio. His installation notes can be found on pastebin. He writes that installation took around 8 hours.


RTL-SDR / Odroid C1 / GQRX / 2msps / Max FFT

Chaos Communications Congress Talks – Iridium Pager Hacking

A few days ago the Chaos Communications Congress (a technology and hacking focused conference) commenced. Among the talks there was one about reverse engineering the Iridium satellite paging system using software defined radio. Iridium satellites provide global communications via special satellite phones, pagers and other transceivers.

In the talk the speaker shows how they used a USRP radio together with a cheap active iridium antenna, a bandpass filter and an LNA to receive the Iridium satellite signals. They also mention that an E4000 RTL-SDR together with an LNA and appropriate home made antenna for frequencies in the ~1.6 GHz region can also be sufficient. Once they were able to receive signals they were then able to reverse engineer the signal and create several pieces of software to decode the pager messages. The code is available on their GitHub at https://github.com/muccc/iridium-toolkit.

Sec, schneider: Iridium Pager Hacking

Freqwatch – RTL-SDR Frequency Scanner and Recorder

Freqwatch is a new Linux based software program that has recently been released by programmer Joshua Davis. Freqwatch makes use of rtl_power to scan a wide swath of RF spectrum and then automatically records and stores in a database sound files of active signals by using rtl_fm.

The software is capable of making use of multiple RTL-SDR dongles in order to efficiently monitor larger bandwidths. After running the software for a while and generating a large database, you can then use a database analyzer like Splunk to find trends in the data or find out when something changes.

The software can be downloaded from its GitHub at https://github.com/covertcodes/freqwatch. Previously we featured some other software called ScanEyes which has a similar logging feature but focused on trunking radio channels and we also featured RTL Airband which monitors multiple airband frequencies simultaneously for logging and streaming.

Freqwatch Database Logs
Freqwatch Database Logs

Digital Ding Dong Ditch – Hacking wireless doorbells with Arduino and RTL-SDR

Over on YouTube user Samy Kamkar has uploaded a video showing how he was able to use an RTL-SDR to copy his friends wireless doorbell signal and prank him by replaying it using an Arduino and 433 MHz transmitter. His video goes through the entire reverse engineering process he used from recording the wireless doorbell signal with the RTL-SDR, to analyzing and understanding the signal and finally to programming the Arduino with the code to replicate the doorbell signal. If you don’t like video explanations, Samy has also done a write up of the same material on his website. 

Digital Ding Dong Ditch Prank - hacking wireless doorbells w/Arduino and RTL-SDR

SDR on TV: Using SDR to Break into Homes with Wireless Alarms

Earlier this year the American TV show Good Morning America featured a segment on software defined radios being used to break into houses with wireless alarm sensors. The story is based on a Defcon 2014 paper “Home Insecurity: No Alarms, False Alarms, and SIGINT” by Logan Lamb. In the TV segment Logan shows how he uses a USRP software defined radio to send a false alarm signal, jam a wireless sensor and finally to record sensor activation data from the alarm system.

Although Logan used a USRP, the same attack could be done with the cheaper HackRF.

SDR HackRf: Home Insecurity: No Alarms, False Alarms, and SIGINT

Characterizing the SWR of an Antenna with a Noise Source and an RTL-SDR

In our last post Adam Alicajic showed us on YouTube how to determine the frequency response of an RF filter using just a wideband noise source an LNA and an RTL-SDR dongle.

In his latest video Adam shows how the SWR of an antenna can be measured using almost the same low cost equipment. One additional piece of hardware required to measure the SWR is a directional coupler which can be bought on Ebay for about $10 USD.

SWR stands for "standing wave ratio" and is a measure that can be used to tune an antenna for a particular frequency. The closer the SWR is to 1:1 at the designed antenna frequency, the better the antenna will receive (and transmit).

In his video Adam shows how he measures the SWR of an ADS-B antenna which he has built and is selling. His results show that the antenna has an SWR of 1:1.02 at 1090 MHz which is quite good.

DIY Characterize the antenna Retrurn Loss / SWR with the DVB-T SDR

Characterizing RF Filters with a Noise Source and RTL-SDR Dongle

Over on YouTube RTL-SDR experimenter Adam Alicajic has uploaded a video showing how it is possible to use the RTL-SDR as a tool to measure the frequency response of an RF filter. To do this he uses a noise source circuit which produces wide band white noise connected to an LNA4ALL, connected to the RF filter and finally connected to the RTL-SDR. Then using the Touchstone spectrum analyzer software he does a 300 MHz bandwidth sweep over a section of the spectrum which shows the response of the filter.

The noise source can be built from a simple diode based circuit as shown in a previous post, or if you have the Ham-it-up upconverter you can buy the parts for the noise generator part of the circuit.

In his video he shows the frequency response of a 145 MHz helix filter, a coax notch filter and a 1090 MHz home brew bandpass filter.

http://www.youtube.com/watch?v=X_gd2gWyGi4
http://www.youtube.com/watch?v=UvdaURc01Ts

More filters and DVB-T dongle

Monitoring House Power Usage using an RTL-SDR

Home automation enthusiast Bruce Winter has recently posted on his blog about how he uses the RTL-SDR as part of his home automation system to automatically monitor his power (and solar power generation) usage. Many home power meters are now wireless which allows meter readers to gather power usage data from afar.

To gather the power usage data he used an RTL-SDR connected to a PC running rtlamr, which is software that can read data from ERT compatible power meters that transmit in the 900 MHz ISM band. He also uses some custom code he wrote that automatically plots the data over time and allows him to integrate it with his home automation system. In addition to his post he also uploaded a video shown below that shows his system in action.

Monitoring house power using a $20 RF RTLSDR USB stick