Category: Applications

Transmitting ggwave Sound Encoded Messages with a HackRF SDR

Thanks to Rado for submitting his news about the release of his project called "ggwave-fm" which allows transmitting of ggwave encoded messages with an SDR. The idea behind the original ggwave is to allow data transfer between devices using audio tones. This is useful for things like serverless one to many data broadcasts, device pairing, IoT devices and audio QR codes. Many products such as wireless security cameras already uses a similar audio data transfer system for automatically sending WiFi login data from a smartphone to the camera. Rado writes:

Ggwave is an open-source library that allows you to communicate small amounts of data between air-gapped devices using sound. You can find some technical details and a lot of examples on the project page: https://github.com/ggerganov/ggwave.

I thought it'd be cool to somehow extend the range of transmission for ggwave and this is how ggwave-fm was born. It modulates ggwave encoded messages with NBFM, interpolates the signal and produces a complex sampled IQ file which is ready for transmission with an SDR. 

In the video shown below Rado demonstrates ggwave-fm working with a HackRF and uses a Baofeng FM radio as the receiver, with the "Waver" mobile app for decoding. He notes that the demo script (demo.sh) used in the video is availalbe in the Git repository.

Transmit ggwave messages with HackRF

A Hi-Z to 50 Ohm Impedance Matching Transformer for Improving HF/SW Reception

Thank you to Mitsunobu for writing in and sharing news about the release of his new product which is a Hi-Z (high impedance) to 50 Ohm matching transformer. This transformer allows you to use small antennas such as short telescopic whips for HF/SW reception on software defined radios.

Generally for HF reception you would want to use a full sized antenna, which can be many meters long and certainly not portable. However, by using an high impedance transformer it becomes possible to use smaller portable antennas. Reception with a small antenna and transformer will still be suboptimal compared to a full sized HF antenna, however, if the signals are strong enough the transformer will allow you to receive them decently.

In the tests shown on his blog (in Japanese, use Google Translate) he shows how the transformer adapter can be connected to a small telescopic whip and Malachite DSP SDR for portable use. Later he also shows how the adapter can make our Dipole Kit antenna work well for HF on a RTL-SDR Blog V3 with direct sampling.  

The product is only available via Amazon in Japan. However, Mitsunobu notes that Amazon.jp offers international shipping. He offers the transformer by itself, and a version including a short telescopic whip antenna.

Hi-Z to 50 Ohm Antenna Transformer for HF/SWL

Frugal Radio: Monitoring HF Aviation Voice Communications with your SDR Radio or a WebSDR

Rob from Frugal Radio has recently uploaded the next episode in his excellent YouTube series on Aviation monitoring. In this episode Rob covers HF aviation communications. Rob writes:

Whether you are using a Software Defined Radio (SDR), an old school HF receiver, or utilizing a WebSDR, there is plenty to monitor when you know where to look.

This video will give you the basics of where to find the Aviation Communications that take place from 3-30 MHz (HF / Shortwave).

This episode covers VOLMET broadcasts, the Major World Air Route Areas (MWARA), and Military Nets like the US Global Communications System (HFGCS).

Remember, these signals travel thousands of miles. It can be quite exciting to receive them over such great distances. When editing this video I was listening to a VOLMET station in Auckland, New Zealand - a distance of over 7500 miles (12,200km) away!

Monitoring HF Aviation Voice Communications with your SDR Radio or a WebSDR

Building an Automated NOAA and Meteor Weather Satellite Image Collector with RTL-SDR

Over on his YouTube channel saveitforparts has uploaded a video showing how he has built an automated weather satellite image collector for the NOAA APT and Meteor M2 LRPT satellites. The video shows a time lapse of him building a QFH antenna, and how he's mounted a Raspberry Pi and RTL-SDR inside a waterproof enclosure attached to the antenna mast. He goes on to show how he's automating the system with the Raspberry-NOAA V2 software. 

Automated Home Weather Station (Satellite Image Collector)

Exploring 433 MHz Devices in the Neighborhood with RTL-SDR and rtl_433

Over on his YouTube channel CWNE88 has posted how he has been using and RTL-SDR with the rtl_433 software to explore the data coming in from various 433 MHz ISM band devices in his neighborhood. In the video he explains how he has set up rtl_433 on his Raspberry Pi, and what sort of data he is receiving. Some examples of devices he's received include various weather stations, doorbells, remotes and car tyre pressure monitors.

He also mentions how these signals are unencrypted, noting that in a future video he will show on GNU Radio how a false signal could be synthesized.

Decoding 433 MHz Devices With SDR

yellowShoes: A Browser Based HD Radio / NRSC-5 User Interface

Thank you to Evuraan for writing in and sharing his new browser based HD Radio / NRSC-5 interface for the nrsc5 decoder which he has called yellowShoes.

NOTE: We have been informed by some users that yellowShoes may contain a Trojan virus. This is likely to be a false positive which is a very common problem with antivirus software falsely detecting viruses on newly released niche software via heuristics. We have removed the above link out of an abundance of caution, however if you wish to continue the yellowShoes Github is here. If you want the software, but are concerned you can check the code compile it yourself.

NOTE UPDATE: The author of the software has contacted us regarding the virus concerns and written "I wanted to write in clarify that it is indeed a false positive, please see https://groups.google.com/g/golang-nuts/c/Au1FbtTZzbk and also https://golang.org/doc/faq#virus - this false positive occurs when you cross compile go binaries - This is a common occurrence, especially on Windows machines. Commercial virus scanning programs are often confused by the structure of Go binaries, which they don't see as often as those compiled from other languages." 

HD Radio is a digital broadcast protocol replacement for analogue broadcast FM. It is only used in North America and is easily recognized as the two rectangular blocks on either side of a broadcast FM station signal on a spectrum analyzer/waterfall display. Together with an RTL-SDR and theori's command line nrsc5 decoder, the HD Radio signal can be decoded and listened to. Evuraan writes:

I wrote yellowShoes - an nrsc5 player which you can control from your browser. (Should work on Windows, Linux etc. Player F/E also works on Android Phones.)

Its sole dependency is that the nrsc5 binary must be available in the path.

A discussion thread on Reddit has also been created.

Screenshot of the yellowShoes browser based UI for the NRSC5 decoder.

Cloning A Garage Key with RTL-SDR, Universal Radio Hacker and an Arduino

Over on YouTube Adam Łoboda has uploaded a video showing the full steps that he's taken to reverse engineer and clone a wireless garage door key using an RTL-SDR and Arduino.

He starts by using the Universal Radio Hacker software to record a copy of the wireless signal generated by the garage key. Using the software he can then analyze the signal, and determine the preamble data, payload data and pulse width which he can then input into some Arduino code. The Arduino can then generate an identical signal, and transmit it via a cheap FS1000A 433 MHz RF module. Finally, at the end of the video Adam shows the cloned Arduino based garage key working as expected. 

hacking & clonning my garage key with URH ( Universal radio Hacker ) and ARDUINO DIGISPARK + FS1000A

Raspberry-NOAA V2: Raspberry Pi Automated NOAA and Meteor Weather Satellite Capture

Raspberry-NOAA is open source code and a set of scripts that allows you to set up a Raspberry Pi as an automated NOAA and Meteor weather satellite station with an SDR like an RTL-SDR. The software makes use of the Raspberry Pi version of WXtoIMG and meteor_decoder for decoding the satellites, a program called predict for predicting satellite passes, and various automatically generated cron scripts to schedule recording and processing.

Recently V2 has been released by Justin Karimi who builds on the work of the original creators. It seems that the webpanel has been upgraded and made mobile friendly, as well as many more enhancements that can be seen on the Release page notes.

Raspberry-NOAA V2 Web Panel