RTL-gopow: New heat map tool

Rtl_power is a tool that allows you to create wide band signal strength heat maps over a long length of time. It works by very quickly hopping across the spectrum, capturing the RTL-SDR bandwidth of about 2 MHz at a time, and then displaying it on a heat map. This is useful for seeing what frequencies are active and at what times. 

Usually to obtain a heat map with rtl_power you need to record the data first, and then pass it through a Python program called heatmap.py which creates the heat map image file. Now there is rtl_gopow which is a new program that directly creates a PNG heat map file from an rtl_power sweep. It is currently available for OSX, Linux, Linux ARM, and Windows.

You can download the binary releases here.

2.5 hour long heat map generated by RTL_GOPOW
2.5 hour long heat map generated by RTL_GOPOW

Uni-SDR Link: Control SDR Console V2 with Unitrunker

A new program called Uni-SDR Link has just been released. This software allows Unitrunker to control SDR-Console V2.

Unitrunker is software that allows you to follow trunked voice conversations, and SDR-Console V2 is a general purpose receiver, similar to other software such as SDR#. The authors write:

This applications sole purpose is to allow Universal Trunker (aka Unitrunker) to control the tuning frequency of individual VFO’s in SDR Console v2. This is achieved by translating Unitrunker Receiver Control commands into a format accepted by SDR Console. Communication occurs over virtual com / serial ports.

Uni-SDR Link has been tested on Windows 7 & Windows 8 and requires .NET Framework version 4.0 or greater.

Just download & launch. No installation required.

The Uni-SDR-Link.chm file contains help for the application should be placed in the same directory as the Uni-SDR-Link.exe.


International Space Station set to Transmit SSTV this Weekend (July 18 – 19)

To commemorate the 40th Anniversary of the Apollo-Soyuz mission the International Space Station (ISS) is set to transmit 12 Slow Scan TV (SSTV) images this weekend. The images are set to transmit Saturday morning, July 18 10:30 UTC and will run through until Sunday, July 19 21:20 UTC, but they note that the dates are tentative and could be subject to change. The images will be transmitted at 145.80 MHz and will probably be sent in the PD180 SSTV mode with 3 minute breaks between each transmission.

SSTV is a type of radio protocol that is used to transmit low resolution images over radio. An RTL-SDR with appropriate antenna can be used to receive these images from the ISS. The signal is usually quite strong, so even a simple whip or long wire antenna may receive these images if placed in a good unobstructed view of the sky. 

As with the last ISS SSTV event we suggest that to decode the images you use SDR# and pipe the audio into MMSSTV, a freeware SSTV decoding software program. We also suggest using the settings recommended by “happysat”, which are enabling “Auto slant” and “Auto resync” under Options->Setup MMSTV->RX.

To know when the ISS is overhead you can track it online using heavens-above.com or isstracker.com. If using heavens-above to predict pass times remember to set it to show all passes, not just the visible ones. Received SSTV images can be submitted to the ARISS Gallery.

This event is being discussed on Reddit here. Here is the official release from ariss.org:

40 years ago this week, the historic joint Apollo-Soyuz mission was conducted.   Apollo-Soyuz (or Soyuz-Apollo in Russia) represented the first joint USA-Soviet mission and set the stage for follow-on Russia-USA space collaboration on the Space Shuttle, Mir Space Station and the International Space Station.  The Soyuz and Apollo vehicles were docked from July 17-19, 1975, during which time joint experiments and activities were accomplished with the 3 USA astronauts and 2 Soviet cosmonauts on-board.  Apollo-Soyuz was the final mission of the Apollo program and the last USA human spaceflight mission until the first space shuttle mission in 1981.

To commemorate the 40th anniversary of this historic international event, the ARISS team has developed a series of 12 Slow Scan Television (SSTV) images that will be sent down for reception by schools, educational organizations and ham radio operators, worldwide.The SSTV images are planned to start sometime Saturday morning, July 18 and run through Sunday, July 19.  These dates are tentative and are subject to change. The SSTV images can be received on 145.80 MHz and displayed using several different SSTV computer programs that are available on the Internet. 

We encourage you to submit your best received SSTV images to:

The ARISS SSTV image gallery will post the best SSTV images received from this event at:

Also, as a special treat, on Saturday July 18 the ISS cosmonauts will take time out to conduct an ARISS contact with students attending the Moon Day/Frontiers of Flight Museum event in Dallas Texas.  This Russian cosmonaut-USA student contact is planned to start around 16:55 UTC through the W6SRJ ground station located in Santa Rosa, California.  ARISS will use the 145.80 MHz voice frequency downlink (same as the SSTV downlink) for the Moon Day contact. More details about these contacts are provided at Upcoming Contacts.

The ARISS international team would like to thank our ARISS-Russia colleague, Sergey Samburov, RV3DR, for his leadership on this historic commemoration.

An example SSTV image from the last ISS SSTV event
An example SSTV image from the last ISS SSTV event which was to commemorate first man to space Yuri Gagarin’s would be 80th birthday.

Detecting meteor radio echoes using the RTL-SDR USB dongle

At the recent 2015 Society of Amateur Radio Astronomers (SARA) Conference Ciprian Sufitchi (N2YO) presented a paper titled “Detecting meteor radio echoes using the RTL/SDR USB dongle” (pdf). His paper introduces the RTL-SDR, the theory behind forward scatter meteor detection as well as the practical application of the RTL-SDR to meteor detection. Ciprian summarizes meteor scatter as the following:

When a meteor enters the Earth’s upper atmosphere it excites the air molecules, producing a streak of light and leaving a trail of ionization (an elongated paraboloid) behind it tens of kilometers long. This ionized trail may persist for less than 1 second up to several minutes, occasionally. Occurring at heights of about 85 to 105 km (50-65 miles), this trail is capable of reflecting radio waves from transmitters located on the ground, similar to light reflecting from a mirrored surface. Meteor radio wave reflections are also called meteor echoes, or pings.

In the paper he explains how analog TV transmissions are the best for meteor scatter, but unfortunately these been discontinued within the USA. Instead he has been able to use analog TV transmitters from Canada, who still transmit this type of signal. He shows that about half of the USA could use the transmitter he is using for meteor scatter, which is based in Ontario, Canada.

Ciprian is also running a very cool live meteor detection stream on his website at livemeteors.com. His setup is located in the DC Metropolitan area and uses a directional Yagi antenna pointed at the Canadian analog TV tower which is broadcasting at 55.237 MHz. The receiver is an RTL-SDR dongle coupled with SDR# and the ARGO software.

Live meteor detection stream from livemeteors.com
Live meteor detection stream from livemeteors.com

Using a direct sampling enabled Airspy as a Panadapter for a Yaesu FTDX-5000

Tim Havens is an avid CW operator on the ham bands and primarily uses his Yaesu FTDX-5000 transceiver for this purpose. At the same time he also uses a software defined radio coupled with an upconverter as a panadapter by connecting the SDR to the 9 MHz IF output of the Yaesu.

However a problem Tim encountered was that the frequency drift of any SDR he tried was too large, even with a TCXO based software defined radio (like a modded RTL-SDR or the Airspy), and that it was a constant hassle to recalibrate. Furthermore, he noticed that the upconverters he used introduced their own drift which just added to the overall frequency drift.

To get around this Tim decided to use the Airspy in a special configuration. First he used the external clock input of the Airspy to connect to his Jackson Labs “Fury” GPSDO. This device uses GPS satellites to generate a very accurate 10 MHz clock, with almost zero drift. Secondly, to get around the need for an upconverter with it’s own frequency drift he used the ADC1 direct sampling input ports on the Airspy to connect to the 9MHz IF output of his FTDX-5000 through an extra band pass filter and LNA.

Tim writes that he will soon update his post with more images and a video.

Airspy with external GPS clock and ADC1 output connected.
Airspy with external GPS clock and ADC1 output connected.

Using a HackRF to convert ADS-B packets into Bluetooth packets for reception on your Smartphone/Tablet

HackRF experimenter Jiao Xianjun has recently posted about his new firmware which allows a single HackRF to receive an ADS-B data packet at 1090 MHz, and then retransmit it as a Bluetooth low energy (BTLE) packet at 2.4 GHz. A smartphone or tablet can then be used to view the ADS-B data. It appears that the system works by broadcasting several fake Bluetooth peripheral names as the received flight data, so there is no way to currently view the data on a map.

The firmware needs to be flashed into the HackRF RAM or ROM, and he provides instructions for this over on his post. The video below shows the HackRF and software in action on an iPad.

ADS-B to BTLE HackRF Relay
ADS-B to BTLE HackRF Relay

A new HackRF Compatible SDR: Rad1o

Every four years the Chaos Computer Club (CCC) in Germany organizes a special hacker themed camp. For this years upcoming September camp they have announced that all participants will be receiving a special software defined radio called the “Rad1o”

The Rad1o is inspired by the HackRF, but seems to have several additional features. It has an operating frequency range of 50 MHz – 4000 MHz, an ARM Cortex M4 CPU, a color LCD screen, a 2.5 GHz ISM band PCB antenna, an audio connector for headphone and microphone connections and an on board battery for portable use. It is also fully compatible with HackRF software.

They write that the Rad1o is not for sale at the moment, and that the only way to get one right now is to attend the camp. If there is enough interest after the camp they will consider producing a second manufacturing run. Despite that, all hardware design files appear to be open source and available at https://github.com/rad1o. More information about the Rad1o can be found here.

The Rad1o, a HackRF compatible software defined radio.
The Rad1o, a HackRF compatible software defined radio.

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.