Tagged: rtl2832

Gypsum: A Software-Defined GPS Receiver written in Python + A Writeup on How it Was Made

Thank you to RTL-SDR.COM reader Lee. who found a recently released program called "gypsum" which enables an RTL-SDR or HackRF to be used as a GPS Receiver when combined with a GPS antenna. Phillip Tennen, the author of Gypsum notes that Gypsum can obtain a fix within 60 seconds from a cold start and that it has no dependencies apart from numpy. We want to note that it appears that Gpysum has no live decoding ability yet, as it works from pre-recorded GNU Radio IQ files.

In the past, we've shown in a tutorial how GPS can be received and decoded with GNSS-SDRLIB and RTKLIB on Windows. The new Gypsum software should work on Linux and MacOS too.

What's more, Phillip has written an incredible 4-part writeup on how Gypsum was implemented from scratch. In the write-up, Phillip introduces GPS and explains how it can even work with such weak signals that appear below the thermal noise floor. He then goes on to explain how the detected signal is decoded and turned into positional information, and how challenging it was to propagate the accurate timing information that calculating a solution requires. The write-up is presented with clear visualizations to help readers intuitively gain an understanding of the advanced concepts involved.

Gypsum GPS Satellite Tracking Dashboard GUI
Gypsum GPS Satellite Tracking Dashboard GUI

The Latest Talks from the Society of Amateur Radio Astronomers

Over on YouTube a bunch of new talks from the Society of Amateur Radio Astronomers (SARA) have recently been uploaded from their recent SARA Western Conference that was held in April 2024. The talks typically involve small home-based radio astronomy setups that use small satellite or WiFi dishes and RTL-SDR or similar low-priced SDRs in their setup. Some of the latest talks include:

  • Nathan Butts: A Novice's Guide to Radio Astronomy (Link)
  • Dr Andrew Thornett: Detecting Cosmic Rays & Building your own version of the Large Hadron Collider (Link)
  • Dr Andrew Thornett M6THO: Lichfield Radio Observatory - Mapping Milky Way at 1420.405 MHz (Hydrogen) (Link)
  • Bruce Randall: IBT Eclipse and other Radio astronomy Failures (Link)
  • Felicia Lin: Mapping the Milky Way by Cross Section Data (Link)
  • Kent Britain WA5VJB: Antennas for Radio Astronomy (Link)
  • Charles Osborne: Eclipse Detection using a VLF Receiver (Link)
  • Rob Lucas - Eclipse Research (Link)
  • Dr Wolfgang Herrmann: Lunar Occultation Observation of Radio Sources (Link)
  • Keynote: Dr Linsay King - Gravitational Lensing (Link)

We note that the last talk was uploaded only a few hours ago at the time of this post, so we're not sure if more talks are yet to be uploaded. So please keep an eye on the SARA YouTube videos page.

Nathan Butts: A Novice's Guide to Radio Astronomy

New Tool to Convert Between SDR# and SDR++ Frequency List Formats

Thank you to 'thewsoftware' over on our forums who has shared with us his SDR# <-> SDR++ frequency list converter (sdrfc) software. SDR# and SDR++ are two popular SDR programs often used with the RTL-SDR, but each uses a different format for storing custom frequency lists.

The new sdrfc tool allows users to easily convert frequency lists between SDR# and SDR++ formats, so you don't need to manually type out a frequency list for both programs.

The sdrfc is a Windows command line tool and instructions for using it can be found on the GitHub Readme. A release zip file is available on the GitHub Releases page.

SDR# <-> SDR++ Frequency Converter Readme

Testing a WiFi Grid Antenna for L-Band Satellites

Over on YouTube dereksgc has uploaded a video where he tests out a 2.4 GHz WiFi Grid antenna for L-band weather satellite reception. WiFi grid antennas are typically repurposed in the SDR community for L-Band weather satellite reception because they are cheap and mostly work out of the box. They can also be used for hydrogen line radio astronomy. TV dish antennas are an alternative but with them, a custom feed needs to be built. 

In his video, dereksgc tests the WiFi dish on receiving various polar-orbiting L-band satellites including Metop, and Meteor M2. With the polar orbiting satellites the dish needs to point at the satellite as it passes over the sky and so dereksgc recommends using a mount if hand tracking them.

Later in the video he tests some geostationary satellites but finds that the dish is not tuned well enough to receive Elektro-LN3 properly without modifications. He was however able to receive a noisy image from FengYun-2H successfully.

We note that we also currently have our Discovery Dish product available for pre-order, which is similar to the WiFi grid dish, but smaller and lighter weight with a built-in optimized active feed.

I finally got a WiFi grid antenna for satellites

Saveitforparts: Receiving and Decoding L-Band Weather Satellites

Over on his YouTube channel 'saveitforparts' has uploaded a new video showing how he has been successful at receiving and decoding L-band weather satellites using his setup made from scavenged parts. He uses a custom-built helical feed on a scavenged dish, and an automatic pan-tilt rotator built from an old security camera mount. With this setup combined with an RTL-SDR and LNA and filter he is able to receive polar orbiting L-band weather satellites. 

In the video, he shows how his system works and what his software setup looks like. He uses SDR++ to record the pass initially, then SatDump to decode the data into images. We note that SatDump can be used to decode the images live, and can also record the raw radio files too, so SDR++ is not required.

How To Receive And Decode L-Band Weather Satellites

Flipper Zero Starts a Petition To Fight Canada Ban

Back in early February we reported about how the Canadian government is making plans to completely ban the Flipper Zero, and popular pentesting tool. The wording from Dominic LeBlanc, Canada's Minister of Public Safety, also implies that software defined radio devices could also be banned.

The reason for the ban is because the Canadian government claims that Flipper Zero and 'consumer hacking devices' are commonly being used as tools for high tech vehicle theft. However, as mentioned in the previous post, this has been debunked.

The team behind Flipper Zero have recently started a petition on change.org to stop the ban. At the time of this post the petition has already reached over 8,000 signature. The team have also penned a comprehensive "Response to the Canadian government" blog post, explaining why the ban makes no sense. In the post they debunk the myth of Flipper Zero being used for car theft, and show the real way high tech car theft is being done.

Doing 50 Things with RTL-SDR in One Week

Thank you to Blinry who recently wrote an article about how they set themselves a challenge to find 50 things to do with an RTL-SDR in one week. Blinry writes:

Last week, I attempted the challenge to try to find 50 things to do with an RTL-SDR device in a week!

It was quite an adventure: I received satellites and radio from the other side of the world, I went on a hunt for a radiosonde, and I invented a method to communicate using the NFC tag in a library book!

I used the RTL-SDR Blog V4 for everything, plus the antenna kit, plus a long piece of wire.

Congratulations Blinry for achieving your goal and taking us on a whirlwind ride through the different applications of RTL-SDR!

NOTE: We note that Blinry's website appears to be a bit slow to load, presumably because or the large image file sizes, and because his article has become quite popular. If you're having trouble loading the images and videos, maybe try again at a later time. Alternatively, thanks to user pbnjeh on Hackernews you can try loading directly from Archive.org or https://archive.is/ZHnfV.

Blinry Receiving and Tracking a Weather Balloon using SDRAngel and an RTL-SDR Blog V4

Meteor M2-4 has not failed – it is still in the testing phase

Thank you to Robin OK9UWU who wanted to point out that the recently launched Russian Meteor M2-4 weather satellite has not failed. There have recently been rumors and videos being spread online claiming that the satellite has already failed as the LRPT and HRPT signals are currently offline.

However, the satellite is still in a testing phase and was only briefly transmitting images for a few days after launch. It is difficult to find official updates from Roskosmos, the Russian space agency, but Robin explains his thoughts on what is happening:

The satellite in question, Meteor-M N°2-4 did not fail. The reason for both the LRPT and HRPT transmitters to be off is that the primary instrument (MSU-MR) is currently undergoing a routine cleaning process to get the IR channels up and running correctly.

It's completely normal.

Other reason why it's off could be that they are testing the MeteoSAR instrument (2-4 is the first sat of this series to have this), hence why unnecessary radios might have been taken offline.

It's important to understand that these satellites are being used to do actual science, weather forecasting etc. They require careful testing and calibration which might take some time. It's not just for "cool imagery".

For example, it took months to get the VIIRS instrument running onboard of the NOAA-21 satellite.

Keep calm and nerdy!

spaceintel101.com's infographic about the Meteor M2-4 Launch
spaceintel101.com's infographic about the Meteor M2-4 Launch