Tagged: rtl-sdr

Decoding HIRS Instrument Images from NOAA Weather Satellites

Thank you to Björn Schnabel who has written in to notify us about a website he's created for a program written by Zbigniew Sztanga called NOAA-HIRS-decoder which might be of interest to some RTL-SDR users. Most of us are familiar with the the ability to use an RTL-SDR to receive the APT signal on the NOAA 15/18/19 weather satellites. The APT signal provides a live image of the Earth. If you haven't tried to receive APT yet, we have a tutorial here.

Apart from APT there is also the HIRS instrument data which is transmitted in the Direct Sounding Broadcast (DSB) telemetry signal that is spaced at a slight offset from the APT frequency. According to NOAA, the HIRS instrument is "a discrete stepping, line-scan instrument designed to measure scene radiance in 20 spectral bands to permit the calculation of the vertical temperature profile from the Earth's surface to about 40 km". The SDR# screenshot below shows what the HIRS signal looks like, and to the sides you can see NOAA APT signals.

The NOAA HIRS Signal
The NOAA HIRS Signal (Center Signal)

NOAA-HIRS-decoder makes use of the Project-Dessert-Tortoise NOAA satellite telemetry decoder that we posted about previously which can be used to decode data from most of the other scientific instruments on the NOAA satellites. The HIRS decoder by Zbigniew uses the raw text data produced by the Project-Dessert-Tortoise decoder and converts it into images. Full instructions on setting up the decoder on Windows is provided on the NOAA-HIRS-decoder website, just click the menu icon on the top right of the page, and go to "usage".

The received data contains 10 channels of long wave infrared, 9 channels of medium wave infrared, and one visible light measurement. The software will plot the 20 channels as images that are 56 pixels wide. This is not a high resolution picture, but it is nevertheless valuable data that can be used for scientific or weather prediction purposes.

All 20 NOAA HIRS Channels (Image enlarged from 56 pixels)
All 20 NOAA HIRS Channels (Image enlarged from 56 pixels)

TETRA-Kit: A New Open Source TETRA Decoder

Thank you to Larry for submitting information about his latest project called TETRA-Kit. TETRA-Kit is an extensible open source TETRA downlink decoder for Linux that makes use of GNU Radio as the first stage, so it should be compatible with any SDR supported by GNU Radio, including the RTL-SDR. Larry writes:

[TETRA-Kit] is inspired by a lot of existing stuff (see 'Previous work' in the project page) but started from scratch with those following ideas:

  • Stays as close as possible to TETRA specification layers defined in ETSI EN 300 392-2 v3.4.1 (2010-08)
  • Transmit downlink informations (including speech frames) in Json plain text format to be recorded or analyzed by an external program
  • Reassociate speech frames with a simple method based on associated caller id and usage marker (save messages transmitted simultaneously in separated files)
  • KISS

The decoder implements a soft synchronizer allowing missing frames (50 bursts) before loosing synchronization.

It consists in 3 parts:

  • A physical layer transforming PI/4 DQPSK rf signal to bits (RF frontend is NESDR at 2MBPS)
  • A decoder, which is the actual TETRA stack reading bits and transforming it to Json text
  • A recorder, which read Json stack output and reorder speech frames into separate files

The ETSI codec is also provided so unencrypted speech can be played.

Software is written in C++ and licensed under GPLv3 and use few external softwares with compatible licensing.

TETRA is a type of digital voice and trunked radio communications system that stands for “Terrestrial Trunked Radio”. It is used in many parts of the world, but not in the USA.

TETRA-Kit Screenshot
TETRA-Kit Screenshot

Virtual Plane Spotting Livestream by Piping ADS-B Data into Flight Simulator

Over on YouTube we've recently discovered a live stream by channel Information Zulu that has created a virtual live 24hr view of LAX airport air traffic by piping ADS-B data into a flight simulator game. The stream also combines this with live air traffic audio and arrivals and departures information. Other videos on his channel show highlights like go arounds.

We're not sure what he's using to pipe ADS-B data into the simulator or exactly what simulator this is, but in the video description he notes that he uses a Pi 4, RTL-SDR blog V3 with ADS-B LNA, and an AirNav antenna to receive the ADS-B data. 

This reminds us of the Android ADSB Flight Tracker app which also has a 3D view, and the post about using ADS-B data to simulate what aircraft instruments would show on the real aircraft.

A 3D Printed Dual Screen Cyberdeck with Built in RTL-SDR

A Cyberdeck is a portable retro styled computer on the outside, but on the inside they typically consist of modern components like a Raspberry Pi. Having been inspired by the aesthetic of the Reviiser cyberdeck project, Reddit user u/dapperrogue set out to build his own version with a built in RTL-SDR.

In his Imgur post, dapperrogue documents the build process. The build consists of multiple 3D printed parts for the enclosure, as well as a really cool home made mechanical keyboard and dual LCD screens. Inside is a Raspberry Pi 4, with RTL-SDR Blog V3, as well as supporting components like a 12v to 5v step down converter, USB hub and four cooling fans. The RTL-SDR connects to a BNC port which is accessible from the outside.

CyberDeck with built in RTL-SDR
CyberDeck with built in RTL-SDR

YouTube Tutorial: Installing and Using CubicSDR on a Mac

Over on YouTube user RickMakes has uploaded a video showing how to install and use CubicSDR on a Mac computer. CubicSDR is a general purpose program compatible with multiple SDRs including the RTL-SDR and is one of the few SDR programs available for use on MacOS.

The installation is as simple as downloading the .dmg file from the CubicSDR GitHub page and running the automatic installer. Afterwards you can move the program to your Applications folder. Once opened CubicSDR should then automatically detect any RTL-SDR that is plugged in.

In the rest of the video RickMakes demonstrates CubicSDR and the RTL-SDR in action, receiving various broadcast FM and ISM band signals.

CubicSDR Basic Setup on Mac with RTL-SDR Blog V3

Using ADS-B Exchange to Track Police and Military Aircraft Monitoring the George Floyd Protests

During the recent George Floyd BLM protests police and military aircraft have been playing a large part in the surveillance of protestors. All these aircraft are required to transmit ADS-B which of course can be monitored with an RTL-SDR or other SDR. Many volunteers around the world use RTL-SDRs to upload ADS-B data to an online aggregation service, so flight data from all over the world can be accessed in one place. However, most ADS-B aggregation services like FlightAware and FlightRadar24 censor police and military aircraft from the raw ADS-B data received from the RTL-SDRs. ADS-B Exchange is the only service that has a policy to not censor any aircraft.

Buzzfeed recently ran an interesting article that used ADS-B Exchange to highlight the flight paths of various surveillance aircraft used during the protests, as well as the aircraft types used and who they are registered to. Most interestingly they saw that two military Black Hawk helicopters and a CBP Predator drone was used in Minnesota, and two military Lakota helicopters were using in Washington, DC.

As mentioned in a previous post, ADS-B Exchange recently updated their interface and backend, and they now run tar1090, which is a fully featured ADS-B mapping platform that can display the historical tracks of any tracked aircraft.

We also note that on Twitter John Wiseman @lemonodor also runs several "advisory circular bots" that make use of ADS-B Exchange data to automatically tweet a notification when aircraft are detected as having a circular flight path.

Police helicopter historical tracks over Minneapolis via adsb-exchange.com
Police helicopter historical tracks over Minneapolis via adsbexchange.com

Techminds: Building a V-Dipole for Weather Satellite Reception

A new video showing how to build a V-dipole for weather satellite reception has been uploaded over on the Tech Minds YouTube channel. A V-dipole isa dipole antenna arranged in a 120 degrees "vee" shape, and mounted horizontally. It was first popularized by Adam 9A4QV who realized that such a simple antenna would work well for low earth orbit satellites like the NOAA and Meteor weather sats.

The video shows how to use some steel rods, a plastic pipe and terminal block to build the v-dipole. After building and mounting the antenna in the required North-South orientation he shows how he's using Gpredict with SDR# and WxToImg to decode the NOAA satellite image.

How To Build A V Dipole For Receiving Weather Satellites

QO-100 Bullseye TCXO Ultra Stable LNB Now Available in our Store for $29.95 with Free Shipping

Back in March we posted about Othernet's release of their "Bullseye" TCXO ultra stable LNB for receiving QO-100 and other Ku-Band satellites. We have decided to now offer these for sale on our store as well.

They cost US$29.95 with free shipping to most countries. We are currently selling it over on our blog store and on our Aliexpress store. The Aliexpress store uses Aliexpress Standard Shipping which may be better for some countries like Poland, Ukraine, etc. As usual, please expect that there could be shipping delays at the moment due to the ongoing global pandemic. Since the US is not covered by QO-100 we will not be stocking Amazon USA.

QO-100 / Es'hail-2 is a geostationary satellite at at 25.5°E (covering Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia) providing broadcasting services. However, as a bonus it has allowed amateur radio operators to use a spare transponder. Uplink is at 2.4 GHz and downlink is at 10.5 GHz. Most SDRs do not tune all the way up to 10.5 GHz, so an LNB (low noise block) is typically used, which contains the feed, an LNA, and a downconverter which converts the 10.5 GHz frequency into a much lower one that can be received by most SDRs.

In order to properly monitor signals on QO-100 an LNB with a Temperature Compensated Oscillator (TCXO) or other stabilization method is required. Most LNBs have non-stabilized crystals which will drift over time with temperature changes.  This means that the narrowband signals used on QO-100 can easily drift out of the receive band or cause distorted reception. It is possible to hand modify a standard Ku-band LNB by soldering on a replacement TCXO or hacking in connections to a GPSDO, but the Bullseye LNB is ready to use and cheap.

The Othernet TCXO Ultra Stable LNB for QO-100 and Ku-Band Satellites
The Othernet TCXO Ultra Stable LNB for QO-100 and Ku-Band Satellites

The official product details read:

The Bullseye LNB is the world's most precise and stable DTH/consumer Ku-band down converter. Even a VSAT LNBF costing hundreds of dollars more is no match for the performance of the Bullseye 10K LNB. Each unit is calibrated at the factory to within 1 kHz of absolute precision against a GPS-locked spectrum analyzer. Under outdoor conditions, the stability of the LNB is well within 10 kHz of offset. As a bonus feature, the  Bullseye 10K provides access to its internal 25 MHz TCXO through the secondary F-connector. This reference output can be used to directly monitor the performance of the TCXO over time. 

Features

  • Bullseye 10 kHz BE01
  • Universal single output LNB
  • Frequency stability within 10 kHz in normal outdoor environment
  • Phase locked loop with 2 PPM TCXO
  • Factory calibration within 1 kHz utilizing GPS-locked spectrum analyzers
  • Ultra high precision PLL employing proprietary frequency control system (patent pending)
  • Digitally controlled carrier offset with optional programmer
  • 25 MHz output reference available on secondary F-connector (red)

Specifications 

  • Input frequency: 10489 - 12750 MHz
  • LO frequency 9750/10600 MHz
  • LO frequency stability at 23C: +/- 10 kHz
  • LO frequency stability -20 - 60C: +/- 30 kHz
  • Gain: 50 - 66 dB
  • Output frequency: 739 - 1950 MHz (low band) and 1100 - 2150 (high band)
  • Return loss of 8 dB (739 - 1950 MHz) and 10 dB (1100 - 2150 MHz)
  • Noise figure: 0.5 dB

We note that an external bias tee power injector is required to power the LNB as it requires 11.5V - 14V to operate in vertical polarization and 16V - 19V to operate with horizontal polarization. The bias tee on the RTL-SDR Blog V3 outputs 4.5V so it is not suitable.

There has also been an excellent review by @F4DAV and a video review by Techminds which we show below.

Ultra Stable Bullseye LNB For QO-100 Es Hail2 10 kHz