Tagged: hydrogen line

A Tribute to Amateur Radio Astronomer Job Geheniau (Job’s Radio Telescope)

Job Geheniau was someone whose amateur radio astronomy projects were often featured on RTL-SDR Blog (often referred to as Job's Radio Telescope). It with great sadness that we have recently learned that Job Geheniau passed away from cancer in late December 2023. We would like to take the time share this post to highlight some of his achievements in the amateur radio astronomy field.

Back in 2020 Job first surprised us with one of his first radio astronomy results (Part 1, Part 2) where he was able to image the Milky Way in neutral hydrogen by using a 150cm dish, RTL-SDR, LNA and motorized mount. Over eight nights he recorded hydrogen line readings throughout the Milky Way and ended up creating a 2D Excel sheet that showed an image of the Milky Way at the 1420 MHz hydrogen line frequency. 

Job would go on, rapidly evolving and each time showing us that low cost hardware set up in a backyard could be used to unlock many of the secrets of the universe. Using a satellite dishes less than two meters in diameter, RTL-SDRs, LNAs and filters he was able to:

Job's Radio Astronomy website remains up at https://jgeheniau.wixsite.com/radio-astronomy, and many results and writeups of his other experiments can be found there. We will sorely miss posting about Job's achievements, but we hope that his life has inspired you to take a closer look at the amateur radio astronomy hobby.

A tribute to Job will also be published in the next membership journal from the Society of Amateur Radio Astronomers.

TotalPower: Windows Program for Hydrogen Line Detection and Analysis with an RTL-SDR

Thank you to Mario A. Natali (I0NAA) who wrote in an wanted to share his Windows software called TotalPower which is designed for mapping the galactic Hydrogen line and works with RTL-SDR dongles.

The Hydrogen Line is an observable increase in RF power at 1420.4058 MHz which is created by Hydrogen atoms. It is most easily detected by pointing a directional antenna towards the Milky Way as there are many hydrogen atoms in our own galaxy. This effect can be used to measure the shape and other properties of our own galaxy.

Mario writes:

[TotalPower] was originally designed to measure total power of received spectrum and that, thanks to the input of many users, is now able to perform many other tasks including the 3D mapping of selected sky areas and HLine detection with the ability to estimate the speed of rotation of galaxy arms ( respect to our position )

TotalPower is available from the downloads section on Mario's website. Mario has uploaded a manual which explains how the program works, which we have mirrored here.

TotalPower measuring the rotational speed of galactic arms
TotalPower measuring the rotational speed of galactic arms

Wok-The-Hydrogen: A Low Cost Wok Based Hydrogen Line Radio Telescope

In addition to the last Hydrogen Line radio astronomy post from a few minutes ago, we've also recently seen a post on Hackaday about a research paper (PDF) that describes a Hydrogen Line Radio Telescope made from a cooking Wok, LNA and RTL-SDR dongle.

In the paper Leo W.H. Fung et al of Hong Kong University of Science and Technology uses a 61cm cooking Wok with a custom made dipole feed at the calculated focal point. A filtered LNA sits after the feed, and is connected to an RTL-SDR Blog V3 dongle enclosed within a metal cookie box for additional shielding.

The results show that the Hydrogen Line was indeed detected, and measurements of the galactic rotational velocity were possible.

Again we note that we will soon by crowdfunding for a product called the 'Discovery Dish' that will be fairly similar in size and shape. It is designed for receiving L-band weather satellites, but can also be used as a Hydrogen Line telescope too.

The Wok Hydrogen Line Telescope Setup

TechMinds: Using a Software Defined Radio as a Radio Telescope

Back in 2020 we released a tutorial about how to use a 2.4 GHz WiFi Grid Dish antenna as a radio telescope which can detect and measure the Hydrogen line emissions in our Milky Way galaxy.

Recently matt from the TechMinds channel has uploaded a video showing this same project but using the NooElec mesh antenna that has been slightly modified for improved performance on 1.7G and 1.4G.

In his video Matt sets up a drift sky scan, where the rotation of the earth drifts the Milky Way through the beamwidth of the dish. Matt uses Stellarium to virtually visualize the live sky map, SDR# and the IF average plugin to average the spectrum, and an Airspy software defined radio.

We note that we will soon be crowdfunding for our 'Discovery Dish', which we believe will be a superior solution for detecting and measuring the Hydrogen Line on a budget.

Using Software Defined Radio As A Radio Telescope

Video Demonstrating Hydrogen Line Detection with an RTL-SDR and WiFi Dish

Back in January 2020 we posted a tutorial showing how it's possible to detect and measure the galactic Hydrogen line using a simple 2.4 GHz WiFi dish, RTL-SDR Blog V3 and a filtered LNA. Since then many people have used the same setup with great results.

Over on YouTube user stoppi who is one such person who is using the same steps from our tutorial, and he has uploaded a video showing his setup and results. If you're thinking of getting started with Hydrogen Line reception, his video slide show tutorial would be a good complimentary overview to go along with our text tutorial.

Detection of the galactic hydrogen - the 21 cm radiation - Wasserstoffstrahlung der Milchstrasse

Detecting Interstellar High-Velocity Clouds with a Radio Telescope and an RTL-SDR

Over on Facebook Job Geheniau has recently described his success in detecting interstellar high-velocity clouds with his telescope consisting of a 1.8 meter dish, amplifiers, band pass filters, and an RTL-SDR.

High-velocity clouds or HVC's are areas of interstellar gas that are moving at very high velocities relative to that of the galactic rotation.

Job has been ticking off some amazing amateur radio astronomy milestone results recently with his radio telescope and RTL-SDR. So far he has managed to image the Cygnus star forming region, complete a Hydrogen line survey of the northern sky, measure the galactic rotational curve, and create a radio image of the milky way.

His latest post about detecting high velocity clouds reads:


CIII High Velocity Cloud detected with 1.8 meter JRT.

The receiver was a RTLSDR connected to some amplifiers, band pass filter and a 1.8 meter dish.

HIGH VELOCITY CLOUD CIII with JRT (Job’s Radio Telescope)

“High-velocity clouds (HVCs) are large collections of gas found throughout the galactic halo of the Milky Way. These clouds of gas can be massive in size, some on the order of millions of times the mass of the Sun and cover large portions of the sky. They have been observed in the Milky Way's halo and within other nearby galaxies.

HVCs are important to the understanding of galactic evolution because they account for a large amount of baryonic matter in the galactic halo. In addition, as these clouds fall into the disk of the galaxy, they add material that can form stars in addition to the dilute star forming material already present in the disk. This new material aids in maintaining the star formation rate (SFR) of the galaxy.

The origins of the HVCs are still in question. No one theory explains all of the HVCs in the galaxy. However, it is known that some HVCs are probably spawned by interactions between the Milky Way and satellite galaxies, such as the Large and Small Magellanic Clouds (LMC and SMC, respectively) which produce a well-known complex of HVCs called the Magellanic Stream. Because of the various possible mechanisms that could potentially produce HVCs, there are still many questions surrounding HVCs for researchers to study.”

My detection:

For JRT the High Velocity Clouds are pretty hard to detect.

The Anti Center Complex is the easiest which I detected earlier last year.

This week I tried C III. It’s at Galactic Coordinates 120 50 and has a Vlsr of -140 km/s. You can find it on the chart:

In the simulation it looks like this:

Pay attention the low Brightness Temperature (0.3 Kelvin) compared for instance with Deneb (80 Kelvin)! Pretty hard to detect with my dish.

With JRT I did a 4 hour exposure (also 4 hours of Darks in the neighborhood) at 1420.405 MHz.

The new Feed I built is very good and has a perfect ‘pitch’ at gain 25 dB.

The final result for High Velocity Cloud CIII with my 1.8 meter dish:


SDRAngel Features Overview: ADS-B, APT, DVB-S, DAB+, AIS, VOR, APRS, and many more built-in apps

SDRAngel is a general purpose software defined radio program that is compatible with most SDRs including the RTL-SDR. We've posted about it several times before on the blog, however we did not realize how much progress has occurred with developing various built in plugins and decoders for it.

Thanks to Jon for writing in and sharing with us a demonstration video that the SDRAngel team have released on their YouTube channel. From the video we can see that SDRAngel now comes stock with a whole host of built in decoders and apps for various radio applications making it close to an all-in-one SDR platform. The built in applications include:

  • ADS-B Decoder: Decodes aircraft ADS-B data and plots aircraft positions on a map
  • NOAA APT Decoder: Decodes NOAA weather satellite images (in black and white only)
  • DVB-S: Decodes and plays Digital TV DVB-S and DVB-S2 video
  • AIS: Decodes marine AIS data and plots vessel positions on a map
  • VOR: Decodes VOR aircraft navigational beacons, and plots bearing lines on a map, allowing you to determine your receivers position.
  • DAB+: Decodes and plays DAB digital audio signals
  • Radio Astronomy Hydrogen Line: With an appropriate radio telescope connected to the SDR, integrates and displays the Hydrogen Line FFT with various settings, and a map of the galaxy showing where your dish is pointing. Can also control a dish rotator.
  • Radio Astronomy Solar Observations: Similar to the Hydrogen line app, allows you to make solar measurements.
  • Broadcast FM: Decoding and playback. Includes RDS decoding.
  • Noise Figure Measurements: Together with a noise source you can measure the noise figure of a SDR.
  • Airband Voice: Receive multiple Airband channels simultaneously
  • Graves Radar Tracker: For Europeans, track a satellite and watch for reflections in the spectrum from the French Graves space radar. 
  • Radio Clocks: Receive and decode accurate time from radio clocks such as MSF, DCF77, TDF and WWVB.
  • APRS: Decode APRS data, and plot APRS locations and moving APRS enabled vehicles on a map with speed plot.
  • Pagers: Decode POCSAG pagers
  • APRS/AX.25 Satellite: Decode APRS messages from the ISS and NO-84 satellites, via the built in decoder and satellite tracker.
  • Channel Analyzer: Analyze signals in the frequency and time domains
  • QSO Digital and Analog Voice: Decode digital and analog voice. Digital voice handled by the built in DSD demodulator, and includes DMR, dPMR and D-Star.
  • Beacons: Monitor propagation via amateur radio beacons, and plot them on a map.

We note that the video doesn't show the following additional features such as an analog TV decoder, the SDRAngel "ChirpChat" text mode, a FreeDV decoder and several other features.

Imaging the Cassiopeia A Supernova Remnant with an RTL-SDR and Amateur Radio Telescope

Just a few days ago we posted about Job Geheniau's success at radio imaging the Cygnus-X star forming region at 1424 MHz with a 1.9m radio telescope, an RTL-SDR and some additional filtering and LNAs.

Now in his latest post on Facebook Geneniau has also shown that he has successfully imaged Cassiopeia A with the same equipment. Cassiopeia A is a supernova remnant known for being the "brightest extrasolar radio source in the sky at frequencies above 1 GHz" [Wikipedia]. Geheniau writes:

A new observation from JRT. These are driftscans of Cassiopeia A to make a radio plot. Several driftscans are made last week and combined. Always nice to see whats possible with a 1.5-1.9 meter dish. 2 LNA's and a bandpass filter, connected to a RTL-SDR at 1424 MHz. Happy that I got Cygnus complex and now Cassiopeia A which is the second radio source which is possible to receive with this dish.

The dish is fully remote controlled 50 km away.

Job Geheniau - The Netherlands

Cassiopeia A Radio Imaged with an RTL-SDR and 1.9m dish
Job's Radio Telescope