Tagged: radio astronomy

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

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.

Discovery Dish Updates and Some Cool Hi-Res Images

We have recently posted an update on our Discovery Dish crowd funding campaign over on Crowd Supply. Check it out on the update page, or on the repost down below.

Discovery Dish Teardown Session Livestream Recording

Thank you to Helen Leigh and Crowd Supply for featuring us on one of their Teardown Sessions live streams a few days ago. If you missed it, feel free to watch the recording below. On the livestream we discussed the Discovery Dish and talked a bit about the journey we took to get to the final product design.

Teardown Session 38: Discovery Dish

Enclosure Glands and Vents

We have decided to include a few cable glands and vents with the Discovery Dish Enclosure, as these will ensure that the bottom of the enclosure is protected against water jets and any splash back from the ground, as well as allowing the electronics inside to breathe a bit. Allowing waterproof enclosures to breathe is important in many environments to avoid condensation build up inside.

The glands and vents will be metal to ensure that RF tightness of the enclosure is maintained as much as possible.

The electronics inside can be passively cooled via thermal pads that sink all generated heat to the metal enclosure which acts as a large thermal mass and heatsink.

In the image below you can also see the mounting board. We are still planning to reduce the hole spacings on the board.

Rotator Timelapse

We’ve been testing an early prototype design of our upcoming antenna rotator for the Discovery Dish, and have created a quick preview timelapse of it running overnight. With mechanical designs like this it’s important to do some long-term testing, so we’re going to be running prototypes non-stop for several months while tracking many more satellites than would be typical.

DD Rotator Preview

 

Example Weather Satellite Images Downloaded

Some people have asked for high resolution examples of what can be received from satellites with the Discovery Dish. Below are a few samples.

GOES 18 Full Disk

Discovery Dish GOES 18 Full Disk Blend

 

GOES 18 Mesoscale

GOES 18 EMWINN

GOES 18 NWS

Metop AVHRR (Advanced Very High Resolution Radiometer)

Metop IASI (Infrared Atmospheric Sounding Interferometer)

GK-2A Full Disk

FengYun 4A Full Disk

Meteor MSU-MR (Multispectral Scanner Unit - Medium Resolution)

NOAA AVHRR (Advanced Very High Resolution Radiometer)

Crowdfunding Goals

We just wanted to clarify a point regarding how crowdfunding works. If the goal isn’t reached then everyone who ordered won’t be charged. We have had a few concerns from potential customers wondering if we will keep the money if the goal isn’t reached, but this is certainly not the case! In fact, credit cards will only be charged if we hit our funding goal. You can learn more in the Crowd Supply Guide.

The goal is set relatively high as this product requires a number of molds to be created for the dish and the various plastic parts, and molds typically have a high fixed initial cost. There is also a high minimum order quantity that we need to commit to in order to do a production run.

But the campaign is currently over 70% to its funding goal and we are expecting some large reseller orders to come in during the last few days of the campaign, so please don’t worry as the goal will almost certainly be reached with the help of just a few more individual supporters. If you have been on the edge, please consider supporting us to get this product started!

Customer Questions

In my environment temperatures get down to -20 to -30 degrees C. Will the electronics in the feed hold up?

The components used in the feed all have ratings down to at least -40 degrees C. In very cold environments, the one thing we would suggest considering is if a dish heater is required. These are heating strips that can be placed on the dish and can help melt snow/ice buildup.

What is the hole pattern on the dish?

The hole pattern on the dish has no specific function, the holes are simply used for reducing wind loading and weight. The manufacture of the prototype dish requires that the holes be cut by laser cutter, but the laser cutter we have available was not large enough to do the entire dish at once. So it was manually rotated around, and this caused an uneven pattern.

The production version of the dish will split into three petals, and each petal will be manufactured via a stamping process. Stamping is when a sheet of metal is placed under a heavy molded block of metal, and then that block of metal is pressed down on the sheet metal to create a desired shape. With this stamping process we will have perfectly neat hole patterns.

I suggest that the S-band version of the feed not use a downconverter, and just use an SDR that can receive S-band instead.

We currently have a similar opinion.

To explain this customer question/comment, we note that as mentioned in the previous update, we are planning to soon test an S-band version of the feed which should be able to receive S-band satellites.

However, the typical software defined radio used is an RTL-SDR, which cannot reach S-band frequencies like 2.2 GHz where most S-band satellites transmit. To get around this, we could add downconversion circuitry to the S-band feed, which would increase complexity and cost. This would convert the 2.2 GHz frequencies down to a frequency that the RTL-SDR can receive (below 1.766 GHz). Alternatively, we could simply recommend that customers interested in S-band reception instead use another SDR such as the HackRF, PlutoSDR, or LimeSDR Mini 2.0.

Once we have tested the S-band version of the feed, we will make a decision on if we should add a downconverter or just recommend the use of other SDRs that can reach the S-band.

Can any of the feeds be used for 1296 MHz EME (earth-moon-earth bounce communications)?

Sorry no, the feeds will not be suitable for EME, as that requires transmission which our feeds do not support.

I would like to use the dish on an astronomical mount. What is the expected weight of the dish and feed?

The dish itself weighs less than 1 kg (2.2 lbs). Together with the feed and mount we expect it to weigh a total of less than 1.5 kg. This is significantly lighter than a Wi-Fi dish which is already 1.6 - 2 kg (depending on the brand) for just the dish by itself.

Are weather satellites encrypted?

No, most weather satellites like this are not encrypted. Although these satellites come from various countries’ governmental space and/or military agencies, weather satellite data is generally considered public science. If it’s not necessary, adding encryption is undesired as it adds complexity to the system and increases the amount of data that needs to be transferred.

Obviously high-end military and commercial satellites are encrypted and we cannot receive data from those. It’s possible that future weather satellites could be encrypted, but given the current trend of new weather satellites being unencrypted this seems unlikely.

 

Crowd Supply Discovery Dish Teardown Session: Thursday 30 November Noon PST

Crowd Supply is hosting Teardown Session 38 on Thursday 3- November at Noon PST time which will feature the Discovery Dish. Join us for this livestream where I will be talking about and showing the Discovery Dish prototype.

Discovery Dish is currently being crowd funded over on Crowd Supply. It is designed to be an easy entry to the world of L-band weather satellites, hydrogen line radio astronomy, and Inmarsat reception. The Discovery Dish aims to be the start of an ecosystem of hardware designed to get users set up with satellite reception, including a planned companion light-duty antenna rotator.

Remember to click on the “Notify me” button on the YouTube link in order to be reminded about the stream!

Teardown Session 38: Discovery Dish

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

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

Recent Talks from the Society of Amateur Radio Astronomers 2023 Conference

Over on their YouTube channel there have been numerous talks uploaded over the past few months from the 2023 Society of Amateur Radio Astronomers (SARA) conference. Some of these talks are quite useful for beginner radio astronomers who are getting started with small dishes and software defined radios like the RTL-SDR.

One talk by Alex Pettit describes how to build a radio telescope from a an umbrella and some "Faraday fabric" which is copper cloth. The results show more than adequate performance for the cost, making this an affordable and easy entry to radio astronomy.

Alex Pettit - Umbrella Antennas

Another video presented by Dr. Wolfgang describes building small to medium sized radio telescopes. He explains how small radio telescopes less than 3 meters in size can work well for receiving the 21cm Hydrogen line, and how SDRs are the best choice of receiver for them. Many examples of small dish installations are shown.

Dr. Wolfgang Herrmann: Building Small/Medium Size Radio Telescopes

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