Category: Applications

Receiving Signals from the Lunar Reconnaissance Orbiter with an RTL-SDR and WiFi Grid Antenna

Gat3way has recently posted on his blog an article showing how he was able to receive a signal from the Lunar Reconnaissance Orbiter (LRO) using only an RTL-SDR, WiFi grid antenna and a low noise block (LNB). The LRO is a NASA spacecraft which is currently orbiting and being used to create maps of the moon.

The LRO transmits a tracking, telemetry and control (TT&C) signal at 2271.125 MHz which is in the S band (2 to 4 GHz). Since the S band frequencies are commonly used for Indovision satellite TV, gat3way was able to find a cheap LNB which could downconvert the GHz level S band frequencies down into a frequency receivable by the RTL-SDR. For the antenna he used a high 22dBi gain motor controlled WiFi mesh parabolic grid antenna.

After aiming the antenna at the moon, gat3way was able to clearly see the LRO carrier signal in the RTL-SDR waterfall as shown in the image below.

WiFi Parabolic Mesh Antenna for the S Band
WiFi Parabolic Mesh Antenna for the S Band
LRO Signal Received by RTL-SDR, LNB and WiFi antenna.
LRO Signal Received by RTL-SDR, LNB and WiFi antenna.

Automatic Heatmap Logging on a Raspberry Pi using an RTL-SDR and RTL_POWER

Amateur radio hobbyist DE8MSH recently wrote in to let us know about a project he has been working on. His project involves using a Raspberry Pi B and RTL-SDR to automatically log a wide band heatmap using rtl_power. Rtl_power is a command line tool that will log signal strengths to a csv file using the RTL-SDR over a very large definable bandwidth.

To do the automatic logging the Raspberry Pi runs rtl_power for 23 hours constantly writing data to a mounted hard drive. After 23 hours the heatmap image is calculated and then uploaded to a webpage at The scheduling is performed by a cron job.

DE8MSH has also been working on a second related project over at The heatmap on this page shows various transmissions from weather balloons. As you mouse over those transmissions, the QTH (location) of those weather balloon transmissions is shown as well as the frequency and time of where the mouse pointer currently is.

Raspberry Pi Automatic Heatmap Logging with rtl_power
Raspberry Pi Automatic Heatmap Logging with rtl_power

Monitoring Multiple AM channels with RTL-SDR Airband

A new command line program for the RTL-SDR called RTL-SDR Airband has recently been released. The program can be used to simultaneously monitor multiple AM channels per dongle. It is intended to be used with online streaming services like which provide live audio streams of air traffic control communications around the world.

Its features include

  • Decode multiple AM channels per dongle (within bandwidth frequency range)
  • Auto squelch and Automatic Gain Control
  • MP3 encoding
  • Stream to Icecast or SHOUTcast server
  • Low CPU usage on Windows (<4% on i5-2430m) thanks to SSE and AVX instructions
  • FFT using GPU on Raspberry Pi (50-55% CPU with default clock)
Monitoring Multiple AM Channels with RTL-SDR Airband.
Monitoring Multiple AM Channels with RTL-SDR Airband.

RTL-SDR Based Coherent Multichannel Receiver

YO3IIU has written a post on his blog showing how he was able to create a coherent multichannel receiver using several RTL-SDR dongles all running on a single clock source.

To do this he used a CDCLVC1310-EVM board which provides up to 10 clock outputs and then connected four of the clock outputs to the clock inputs of four separate RTL-SDR dongles. He then uses a GNU Radio program to correlate the signals from each RTL-SDR stick.

Recently we have seen two applications of an RTL-SDR based coherent multichannel receiver used in passive a radar systems here and here.

Coherent Multichannel Receiver based on the RTL-SDR
Coherent Multichannel Receiver based on the RTL-SDR

Transmitting DVBT HDTV from a Raspberry Pi to an RTL2832U

Over on his blog, OZ9AEC has uploaded a post showing how he was able to create a live HDTV transmitter out of a Raspberry Pi, a Raspi Cam module and a UTC DVB-T Modulator adaptor. As he does not want to interfere with commercial DVB-T broadcasts, he sets the module to transmit at 1.28 GHz, aka the 23 cm licenced ham radio band.

On the RTL2832U dongle side, he modified the RTL2832U Linux DVB-T drivers (not the SDR drivers) to work on the 1.3 GHz band. The intention of this camera is for it to fly on a rocket mission. In the YouTube video below he has uploaded some sample footage with the RTL2832U dongle receiving the stream from 300 meters away.

Rocketcam 1 test 3 (20140531_142625)

Transmitting ADS-B with a HackRF and Receiving it with an RTL-SDR

Over on YouTube user Jiao Xianjun has uploaded a video showing how he was able to transmit an ADS-B signal from his HackRF One and receive it using an RTL-SDR with dump1090. He transmits a low power signal which shows a fake plane flying over the Senkaku islands.

Important Note: While this warning is also on the video we feel that we should re-emphasize that you should never transmit anything at 1090 MHz unless you are authorized to do so and are in a controlled RF environment.

ADS-B out by HACKRF and received by rtl-sdr + dump1090

Signal Mapping using RTLSDR Scanner and GPS on an iOS Device

Recently we posted how RTLSDR Scanner has been updated to allow interfacing with a GPS device. This allows you to make signal strength maps by driving around and recording both signal strength and GPS location together.

As most people don’t have a dedicated GPS device, Reddit user soooooil has put together a short guide on how he was able to use his iPhone as the GPS device and interface it with RTLSDR Scanner.

RTLSDR Scanner with iOS GPS device.
RTLSDR Scanner with iOS GPS device.

New RTL_POWER Based Wideband RTL-SDR Scanner GUI

Rtl_power is a command line program that can do a very wideband frequency scan by quickly tuning through 2 MHz chunks of bandwidth and recording radio power values.

Now a new GUI frontend for Windows rtl_power called rtl panorama has been released which simplifies the use of the command line tool. To use it download rtlpan.exe from the sourceforge page and then copy the rtlsdr.dll, libusb-1.0.dll and rtl_power.exe files from the official Osmocom librtlsdr download to the same directory as rtlpan.exe.

You can hover over each of the controls to see a tool tip explaining which each button does.

Recently a similar rtl_power GUI was released and shown in this post. There is also the more featured python based RTLSDR Scanner that is not based on rtl_power which does a similar job. However, the rtl_power based GUIs appear to be much faster at scanning.

New rtl_power GUI called rtl panorama.
New rtl_power GUI called rtl panorama.

RTL-SDR based Passive Multistatic RADAR used to Track Aircraft

Over on YouTube user Ben Silverwood has uploaded a video showing the results of his RTL-SDR passive radar. The passive radar works using two RTL-SDR dongles receiving a DAB radio tower’s radio waves that are reflected off the aircraft. On the video you are able to see the aircraft radar blip on the animated Matlab plots.

Previously we posted about another similar passive radar project in this post.

Low cost RTL-SDR passive multistatic DAB radar.

ScanEyes: Software for Visualizing, Listening to and Archiving Trunked Radio Traffic

Back in March we showed a beta version of Tyler Watts ScanEyes trunked call log recorder software. Now Tyler has released a more complete version of his ScanEyes software. A live version of the software can be found at ScanEyes works by using a software defined radio such as the RTL-SDR combined with trunking following software Unitrunker and optional P25 decoder DSD/DSD+ to archive all calls made on a trunked radio system. A user can then later go into the web interface and view and listen to archived calls.

ScanEyes Flow Diagram
ScanEyes Flow Diagram