In this weeks video Rob from his Frugal Radio YouTube channel shows us how he's turned an old piece of scrap electrical extension cord into an effective HF antenna for his Airspy HF+ SDR. The scrap wire is combined with a US$15 NooElec 9:1 balun which helps improve the impedance match of the antenna. He then stretches the dipole out through his backyard and then hooks it up to his Airspy HF+.
The results show good reception across the 20m, 80m, 40m amateur radio bands, as well as on HF ATC aircraft communications, US coast guard weather information broadcasts and the AM broadcast band.
I made an HF Dipole for free! Reception was good on my AirSpy HF+ Discovery SDR!
Thank you to Jasper for writing in and letting us know about the release of his new open source software called "AIS-Catcher". AIS-Catcher is a MIT licensed dual band AIS receiver for Linux, Windows and Raspberry Pi. It is compatible with RTL-SDR dongles and the Airspy HF+.
AIS stands for Automatic Identification System and is used by marine vessels to broadcast their GPS locations in order to help avoid collisions and aide with rescues. An RTL-SDR with the right software can be used to receive and decode these signals, and plot ship positions on a map.
Jasper notes that his software was intended to be a platform for him to experiment with different receiving model algorithms. On the GitHub readme he explains how he's experimented with a coherent demodulation model that estimates the phase offset, a non-coherent model which is similar to what most existing decoders use, a modified non-coherent model with aggressive PLL, and an FM discriminator model which assumes the input is the output of an FM discriminator.
The readme goes on to show some comparison results indicating that the coherent model is the best although it uses 20% more computation time. He also compares AIS-Catcher against some other AIS decoders like AISRec and rtl-ais, showing that AIS-Catcher appears to be comparable or better than AISRec, which is one of the most sensitive decoders available for SDR dongles.
A Windows binary is provided on the releases page and compilation instructions for Linux are provided on the Github Readme.
Some results from AIS-Catcher. Different algorithms and different software compared.
Airspy is currently holding a 20% off summer promotion which runs from June 28th until Julty 4th 2021. The sale is active at all participating resellers, which includes our own store where we have the YouLoop on sale for US$27.96 including free shipping to most countries in the world, instead of the usual US$34.95. Please note that due to new EU VAT collection laws, EU customers must purchase the discounted YouLoop from our eBay or Aliexpress stores.
The YouLoop is a low cost passive loop antenna for HF and VHF. It is based on the Möbius loop design which results in a high degree of noise cancelling. However the main drawback is that it is a non-resonant design, which means that it works best when used with ultra sensitive receivers like the Airspy HF+ Discovery.
Back in early 2014 Crimea was annexed from the Ukraine by Russian forces. Recently we've heard news that a Crimean resident was arrested by the Russian Federal Security Service under the suspicion of being a Ukrainian informant who was intending to transfer, or was transferring military data abroad using RTL-SDRs.
A video of the arrest has been uploaded to YouTube, and RTL-SDR dongles running with the Airspy SDR# software on his laptop can clearly be seen as having been photographed. The photos of the SDR# screen appear to show that he was monitoring the commercial aviation band with a scanner plugin.
The YouTube description is translated below:
Today it was reported about the arrest of a Crimean resident, either intending to transfer, or transferring military data abroad.
The FSB has published footage of the arrest. The time on the laptop caught on the video during the search of housing 07:40 date 06/22/21. The laptop is turned on, the AIRSPY radio frequency scanning program is running, the laptop is in the dust - only traces of pressing some keys are visible, and the touchpad was not used. There are many icons in the room, books on radio engineering, a Ukrainian flag, aircraft models, several pennants "Tavria 1958", an ICOM IC-R6 radio, maps.
The detainee transferred the information received to Ukraine on one basis, collected it on the other and intended to transfer it.
The court sent the man to the pre-trial detention center for 2 months. If his guilt is proven, then high treason "shines" and does not shine to see the will for 25 years.
According to an article on RadioFreeEurope, the man was detained as he was "collecting data on the flights of Russian military planes for Ukrainian intelligence".
It is unclear if the man was knowingly providing intelligence services, or is simply an aviation hobbyist caught up in politics. If anyone has more information about his story, please let us know in the comments.
UPDATE 29 June 2021: More information on the story at this link.
Украинский осведомитель был футбольным фаном. Болел за «Таврию»
Crimean resident arrested for using RTL-SDRs to monitor the airbandCommercial Aviation Frequencies Monitored
We recently came across the LibreCellular project which is aiming to make it easy to implement 4G cellular networks with open source software and low cost SDRs. The project appears to be in the early stages, and seems to be focusing on deploying and modifying existing open source 4G basestation software known as srsRAN which will be used with a particular combination of hardware in order to create a reliable and easy to set up 4G basestation solution.
The reference hardware that they are recommending consists of an Intel NUC single board computer ($699), LimeSDR ($315), LimeRFE front end filtered power amplifier ($699), and Leo Bodnar Mini Precision GPS Reference Clock ($140). All together you can create a 4G basestation for around $1850.
LibreCellular Components for a 4G Basestation: LimeRFE, Leo Bodnar GPS Clock, LimeSDR, Intel NUC.
Thank you to Egor for writing in a sharing his work on modifying dump1090 in order to support the HackRF on Windows. dump1090 is software that is often used with RTL-SDR dongles for decoding ADS-B data for aircraft tracking. He writes:
Some time ago I was looking for dump1090 version with HackRF support that could work on Windows. But I have not found such version.
So I forked Malcolm Robb's version of dump1090 that could be built on Windows around 7 years ago. :) I've updated it and have added HackRF support from Ilker Temir's fork.
Now my version is available here https://github.com/esuldin/dump1090. The main difference from the others that it supports HackRF One device on Windows.
Over on Reddit we've seen that SDR4Space, a provider of a satellite ground station receiver hardware and software has released a free feature limited lite version of their embedded software over on their GitHub page. In the Reddit comments the software is explained as follows:
It's a command-line tool using scripts, for SDR users. You can write your own scripts to: record IQ samples, predict satellite passes, start a record for a specific satellite and correct doppler at the same time.
It's also useful to record narrow subband IQ streams ( example: 48kHz wide instead of 2.048 MHz on rtlsdr, a single signal on HF is only few kHz wide).
You can work on IQ files: cut, resample, merge, convert formats and so on.
Having said that you can recognize features from predict, rx_sdr/rtl_sdr ,rtl_power/rx_power.
Regarding installation, a Debian package is provided, installing application and some examples in /opt/vmbase directory. Most of dependencies are installed by the package. But you should install SoapySDR and Soapy drivers for your SDR device first by yourself if not yet done !
To understand how it works, the best is perhaps starting download TLE and print a passes list, using scripts in ./sat/ directory.
For the next SSTV event I'd try to run unattended reception of ISS (from ./sat/sat_receiver directory).
From the examples, it appears that you can script a fully automated doppler corrected satellite signal receiver with the SDR interface connecting through Soapy, and all the DSP handled by the SDR4lite library.
In the latest episode of his YouTube series on Aviation monitoring Rob explores how to decode L-band satellite ACARS (Aircraft Communication Addressing and Reporting System) and CPDLC (Controller Pilot Data Link Communications) messages using JAERO, an SDR like an RTL-SDR, and a appropriate L-band antenna such as our RTL-SDR Blog Active L-Band Patch (currently out of stock).
In the video Rob shows examples of what you might receive such as CPDLC ATC instructions, digital ATIS information, arrival information and suggested landing data configuration instructions. He goes on to show satellite coverage maps, what hardware is required to receive these signals, and finally how to setup the receiving and decoding software.
How To Decode L band Satellite ACARS and CPDLC messages with JAERO and your SDR
