Tagged: rtl2832

NOAA-APT Decoder Updates: False Color, Pass Prediction and more

In the past we've posted a couple of times about the NOAA-APT decoder software as it is a worthy alternative to the now abandonware software WXtoIMG. However, it lacks certain features which makes WXtoIMG still the go to program for NOAA weather satellite decoding.

As NOAA-APT is open source it has recently seen a few new updates from another contributor, as well as the original author. These changes make it quite a bit more useful, although admittedly not perfect. Hopefully we'll see continued refinement over time. Regardless, this is still a great piece of software which is open source and multi-platform. Martin Bernardi, the original contributor writes:

Although I wasn't planning to continue working in my program, the quarantine happened so I worked on the program a little. Later, a person (Arcadie Z) added more features too, so I created a new version in case you want to add a blog post about it.

Added features since the last blog post:

- Redesigned GUI.
- Satellite prediction and map overlay (but has offsets I can't fix yet).
- False color images
- Histogram equalization (improves the contrast and brightness of images)
- Automatic image rotation depending on pass direction

In the end, the map overlay and false color does not work very well, but it is better than nothing I guess.

The NOAA-APT Decoder GUI

GQRX Updated to 2.13: Several Bug Fixes and Performance Improvements

GQRX is one of the most popular open source software choices to use with various SDRs on Linux and MacOS. Recently it was updated to version 2.13, bringing in a few new features and several bug fixes and performance improvements. From the GQRX news file, the changes include the following.

2.13.1: Released October 17, 2020

FIXED: Crash when invalid sample rate is specified.
FIXED: Decrease minimum size of FFT Settings panel.
FIXED: Typos.
IMPROVED: More Airspy HF+ sample rates added.

2.13: Released October 16, 2020

NEW: Stereo option for UDP streaming.
NEW: Script to generate AppImage.
NEW: Allow scroll wheel direction to be inverted.
FIXED: FM de-emphasis causing audio to be 20 dB quieter than it should be.
FIXED: FM de-emphasis applied incorrectly in WFM stereo receiver.
FIXED: Update waterfall time resolution when FFT settings are changed.
FIXED: Update waterfall time resolution when window is resized.
FIXED: Restore waterfall time span between sessions.
FIXED: FFT buffer overlap calculation.
FIXED: Crash when launching without device connected.
FIXED: Crash when setting invalid RF gains.
FIXED: Audio panadapter / waterfall slider direction.
FIXED: Clear FFT averages when changing FFT size.
FIXED: Crash when source block doesn't support IQ balancing.
FIXED: Bookmark labels in FFT draw over each other.
IMPROVED: DSP and FFT performance.
IMPROVED: Panadapter & waterfall performance.
IMPROVED: Smooth panadapter & waterfall redrawing.
IMPROVED: Better default values for various settings.
IMPROVED: Audio waterfall colormap matches I/Q waterfall.
IMPROVED: Use all available display space for panadapter & waterfall.
IMPROVED: Updated RDS decoder.
IMPROVED: More Airspy HF+ sample rates added.

The GQRX GUI (Older Version)

SDR# Updates: RTL-SDR Enhanced Mode, AM Co-Channel Canceller for MW DX

Over the past few days SDR# has been updated again adding several new great features. The first is an "RTL-SDR Enhanced" front end driver, which is actually Vasili's front end driver that was released a few years ago. This front end enhances the capabilities of the RTL-SDR as it exposes features like decimation and individual gain control. We note that the current version appears to have a bug preventing enhanced mode from starting, but we expect that it will be fixed again soon. Vasili's File Player has also been added, and this allows for easy playback of RTL-SDR IQ files.

The second feature added recently is an AM Co-Channel Canceller which is could be quite a big feature for medium wave (MW)/broadcast AM DXers. When DXing MW a problem is that you'll often encounter is two stations that are on or almost on the same frequency. This is either due to neighbouring countries not agreeing on frequencies, long range DX antennas picking up further than the intended broadcast range, or from malicious jamming as with the Chinese Firedrake. With a standard radio or demodulation algorithm such a situation makes either both stations impossible to listen to, or only the strongest station will be heard. However, the new AM Co-Channel Canceller plugin in SDR# uses clever DSP algorithms to allow one of those channels to be effectively removed, allowing you to listen to the other station clearly.

Over on the SWLing blog Guy Atkins has written up a comprehensive review and tutorial of the Co-Channel canceller plugin. We've also seen a few examples up on YouTube already, and the video posted below shows user "SDR-radio" in Japan experiencing a South Korean station blocking out a weak local Japanese station. Enabling the plugin allows the weaker station to be heard.

SDR# (SDRSharp): AM Co-Channel Canceller plugin

Easy-SDR: Open Source Designs for SDR Accessories

Back in 2018 we posted about Igor Yatsevich's Easy-SDR project which consisted of open source designs for a Mini-Whip antenna and upconverter. Igor has now added several new open source designs to the project including a bias tee, LNA, LNA with filtering, attenuator and SPDT antenna switch. On his Reddit post he notes:

The most interesting thing I've added so far:

  1. Most of the devices are now prepared for installation in a metal case measuring 80 x 50 x 20 millimeters.
  2. Completely redesigned LNA design. Now, Bias Tee powered amplifiers are housed in a 50 x 25 x 25mm metal case and have N-type connectors.
  3. Added an amplifier based on the PGA-103 microcircuit.
  4. Added the ability to install filters in final amplifiers (a separate printed circuit board, depending on the filter used).
  5. Added a new device - SPDT antenna switch for receiving antennas.
  6. The UP converter has been redesigned. Added intermediate buffer stage between crystal generator and mixer.
  7. RF lines in all devices were recalculated to correspond to the characteristic wave impedance of 50 Ohm.
  8. Reduced size of PI attenuator PCB.

In this project, I focused on the simplicity of self-assembly devices, which you can make at home. In the repository, you can find detailed assembly instructions, a list of necessary components for assembly, and GERBER files.

SPDT Antenna Switch from the Open Source Easy-SDR Project

Dictator Alert Fundraising

In the past we've posted about the Dictator Alert project a few times, as it makes use of ADS-B data contributed to ADS-B Exchange via volunteers who typically run an RTL-SDR as part of their ADS-B reception hardware. The project aims to track the movements of Dictators around the world via their use of private jets that can be tracked via ADS-B logging.

Over on Reddit the leader of the project Emmanuel has posted asking for donations. If you think this is a worthy project, please consider donating.

I'm raising some funds for our www.dictatoralert.org project which tracks aircrafts used by dictatorships all over the world (using SDR!). You can see all of the tracking for free on the website and several twitter bots (London, Paris, Geneva, EuroAirport).

The hosting costs me around $80 per month, which probably isn't a lot, unless you're a freelance journalist. I also hope to raise a bit more to make the project grow further with investigations (like this one on surveillance planes in Somalia or another on rich Frenchmen who used their jet to avoid COVID restrictions on travel.

You can give one-off donations or sign up to the Patreon, then I'll set you up with email alerts for your "favorite" dictators, airports, or any plane you like.

Patreon: https://www.patreon.com/dictatoralert

One-off donations: https://dictatoralert.org/donation/

Please don't hesitate to ask questions and let me know what you think!

Dictator Alert. A Twitter bot reporting on dictator movements via ADS-B data. dictatoralert.org
Dictator Alert. A Twitter bot reporting on dictator movements via ADS-B data. dictatoralert.org

Sanchez Scripting Examples For Post-Processing GOES, GK2A, Himawari, Elektro Satellite Images

Recently we posted about new updates to the Sanchez software. The updates allow users to combine images received from multiple geostationary weather satellites such as GOES 16/17, Himawari-8, GK-2A and Electro. The images can also be reprojected into a flat equirectangular image, and then optionally reprojected back into a disk view at any location on earth. Sanchez's original function is also still there which allows users to add a false color underlay image to grayscale infrared images received from the satellites.

Sanchez is a command line tool, so scripts are required to do anything interesting. Over on his page Carl Reinemann has uploaded a page with a number of Sanchez command line examples available. The page shows examples like how to stitch together multiple images, and how to create a stitched time lapse animation. The YouTube video below shows an example of an animation Carl created with Sanchez and GOES 16 and 17 images stitched together.

GOES 16-17 Composite imagery

And the image below is an example of an image of Himawari 8, GOES 16 and 17 he stitched together with Sanchez.

GOES 16 and 17 composite created by Carl Reinemann via Sanchez

Tech Minds: Portable RTL-SDR on Android

Over on his YouTube channel Tech Minds has recently released a new video demonstrating how to use an RTL-SDR portably via an Android tablet and an OTG cable. In the video he goes through the various Android software options available including general receiver software such as RF Analyzer (free) and SDR Touch (£5.99) as well as AVARE ADSB for ADS-B aircraft reception. He goes on to demonstrate each program in action.

Portable RTL - SDR Software Defined Radio with Android

Using an RTL-SDR to Measure the Basis for the Dark Matter Hypothesis

From calculations depending on the distribution of visible star mass in our galaxy, a certain galactic rotational velocity vs distance from center curve is expected. However, when scientists actually measure the galactic rotation, another curve is found - a curve which should result in the galaxy flying apart. This mismatch in expected vs measured data has given rise to the theory of "dark matter". The theory essentially states that in order to get the measured curve, the galaxy must have more mass, and that this mass must come from non-luminous matter scattered amongst the galaxy which is difficult or impossible to observe.

In the past we have posted about Job Geheniau's radio astronomy projects a few times on this blog. So far he has used an RTL-SDR and radio telescope dish to generate a full radio image of the galaxy at the Hydrogen Line frequency of 1.42 GHz. This project worked by pointing the telescope at one section of the galaxy, measuring the total Hydrogen line power with the RTL-SDR over a number of minutes, then moving the telescope to the next section.

Job's Radio Telescope + Laptop and RTL-SDR Setup

Using the same hardware and techniques to observe the Hydrogen Line frequency, he was now able to measure the rotational curve of our galaxy. When the telescope points to different arms of the galaxy, the Hydrogen line measurement will be doppler shifted differently. The measured doppler shift can be used to figure out the rotational velocity of that particular arm of the galaxy. By measuring the rotational velocity from the center of the galaxy to the outer edges, a curve is created. Job's measured curve matches that seen by professional radio astronomers, confirming the mismatch in expected vs measured data.

Job's document explaining his setup and measurement procedure can be found here (pdf file).

Job's Measured vs Expected Curve

If you'd like to get started with Hydrogen line radio astronomy with an RTL-SDR, we have a tutorial over here.