Tag Archives: Radio Astronomy

“Strange radio waves emerge from direction of the galactic centre”

(Source: University of Sydney)

Strange radio waves emerge from direction of the galactic centre

A signal from deep in the Milky Way is tantalising scientists

International student Ziteng Wang detected unusual signals from deep in the heart of the Milky Way using CSIRO’s ASKAP radio telescope. Now astronomers are on the search for more evidence of what type object could be emitting them.

Astronomers have discovered unusual signals coming from the direction of the Milky Way’s centre. The radio waves fit no currently understood pattern of variable radio source and could suggest a new class of stellar object.

“The strangest property of this new signal is that it is has a very high polarisation. This means its light oscillates in only one direction, but that direction rotates with time,” said Ziteng Wang, lead author of the new study and a PhD student in the School of Physics at the University of Sydney.

“The brightness of the object also varies dramatically, by a factor of 100, and the signal switches on and off apparently at random. We’ve never seen anything like it.”

Many types of star emit variable light across the electromagnetic spectrum. With tremendous advances in radio astronomy, the study of variable or transient objects in radio waves is a huge field of study helping us to reveal the secrets of the Universe. Pulsars, supernovae, flaring stars and fast radio bursts are all types of astronomical objects whose brightness varies.

“At first we thought it could be a pulsar – a very dense type of spinning dead star – or else a type of star that emits huge solar flares. But the signals from this new source don’t match what we expect from these types of celestial objects,” Mr Wang said.

The discovery of the object has been published today in the Astrophysical Journal.

Click here to read the full article at the University of Sydney.

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Radio Waves: Digital Audio via Vintage Radio, “10-Minute-ish” Transmitter, Why No Channel 37, and Inventor of the Audio Cassette Dies at Age 94

Image by Jon Tyson

Radio Waves:  Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers.  To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Ron, Valdo Karamitrov, Ronald Kenyon, and the Southgate ARC for the following tips:


‘I play digital music through my 1949 radio’ (BBC News)

When we think of technology our imagination usually takes us to images of the future. But for some, technology links us to the past – whether for nostalgia or for personal reasons

Following our recent feature on vintage technology, we asked you to share some of your collections with us – and people from around the world responded..

Rob Seaward, North Yorkshire, UK: 1949 Murphy A146 radio

I have a collection of older technology which I have collected throughout my life – including old cameras, calculators, hi-fis and radios. I had been interested in music from an early age, but it was really when my father purchased a Bang and Olufsen music centre that my interest in not only music, but style and function really took off.

To me, a lower middle-class grammar school kid living in Bradford, I suddenly had access to a world of real style and glamour.

My favourite piece must be the Murphy A146 console radio designed by Gordon Russell in 1949.

Its nickname is the “Batwing” because of the shape of the back panel. The sound is rich, slightly warm and typical of valve equipment. In its day, the radio cost the equivalent of an average monthly wage, it was built to last and the original valves are still working today.

However, as it pre-dates FM it is a little limited. I’ve had it restored and as part of the process we had a Bluetooth adapter installed which means I can now play my favourite digital music through this wonder from the 1940s – which really amazes people.[]

Getting on the Air With a 10-minute-ish Ham Transmitter (Hackaday)

Artificially constrained designs can be among the most challenging projects to build, and the most interesting to consider. The amateur radio world is no stranger to this, with homebrew radio designs that set some sort of line in the sand. Such designs usually end up being delightfully minimalist and deeply instructive of first principles, which is one reason we like them so much.

For a perfect example of this design philosophy, take a look at [VK3YE]’s twist on the classic “10-Minute Transmitter”. (Video, embedded below.)

The design dates back to at least the 1980s, when [G4RAW] laid down the challenge to whip up a working transmitter from junk bin parts and make a contact within 15 minutes — ten for the build and five for working the bands. [VK3YE] used the “oner” — one-transistor — design for his 10-minute transmitter, but invested some additional time into adding a low-pass filter to keep his signal clean, and a power amplifier to boost the output a bit.[]

Why Channel 37 Doesn’t Exist (And What It Has to Do With Aliens) (Vice)

Since the advent of analog TVs, channel 37 has always been static. Here’s why.

A version of this post originally appeared on Tedium, a twice-weekly newsletter that hunts for the end of the long tail.

I’m endlessly fascinated by stories of the quirks that were built into the TV system where the well-laid plans of the system simply fell apart because it was asked to do too many things.

Nearly five years ago, I wrote about one of them, the tale of how radio broadcasters were able to shoehorn an additional FM station into the radio because of the proximity of TV’s channel 6 to the rest of the radio feed.

So when I was informed that there was another oddity kinda like this involving the TV lineups, I decided I had to take a dive in.

It’s a tale that centers around channel 37, which was a giant block of static in most parts of the world during the 20th century.

The reason for that was simple: it couldn’t fend off its scientific competition.

1952

The year that the U.S. Federal Communications Commission opened up the television system to use UHF, or ultra high frequency signals. The practical effect of this addition of bandwidth was that the total number of potential TV stations increased dramatically, from 108 to 2,051, overnight. The first UHF applications were granted on July 11, 1952, according to The History of UHF Television, a site dedicated to the higher-frequency television offerings.

The radio telescope that became a headache for the television industry

Within a 600-mile radius of the city of Danville, Illinois, population 31,246, are numerous major cities—among them Chicago, Detroit, Milwaukee, Atlanta, Minneapolis, Pittsburgh, St. Louis, Toronto, and Washington, DC.

Nearly the entire length of the Mississippi River fits into that radius. If Danville was located just a little farther to the east, the radius would also include Philadelphia and New York City. For all intents and purposes, a 600-mile radius from Eastern Illinois covers basically the entire East Coast except the state of Florida and the Northeast.[]

Dutch inventor of the audio cassette tape dies aged 94 (Southgate ARC)

Lou Ottens, inventor of the cassette tape and a CD pioneer died aged 94 at his home in Duizel in Brabant on Saturday, Dutch media report.

Ottens, who studied to be an engineer, started working for Philips in 1952. Eight years later he became head of the firm’s recently introduced product development department. Within a year he and his team had developed the first portable tape recorder of which over a million were sold. Two years later he revolutionised the old reel-to-reel tape system by inventing the cassette tape.

‘I got annoyed with the clunky, user-unfriendly reel to reel system, it’s that simple’, Ottens said later. The new carrier had to be small enough to fit into his jacket pocket, Ottens decided, and he had a wooden model made to determine the ideal size. In 1963 the first plastic encased cassette tape was presented at an electronics fair carrying the slogan ‘smaller than a pack of cigarettes!’ The tapes were quickly copied by the Japanese but in different formats!

Ottens managed to make a deal with Sony to use the mechanism patented by Philips to introduce a standard cassette which was then rolled out globally. Over 100 billion were sold worldwide. Ottens went on to develop the CD, which again became a Sony-Philips standard and which sold over 200 billion.

In 1986 Ottens retired but he was often asked if he was proud of his inventions, which allowed millions to have access to music. ‘I have no ‘pride dial’’ Ottens said in an interview, stressing that both inventions were team efforts. His biggest regret was that that Sony, not Philips, invented what he considered to be the ideal application for the cassette tape, the Walkman. ‘That still hurts,’ he said. Dubious about the recent revival of the cassette tape Ottens said ‘nothing could beat the sound of a CD.’

Read more at DutchNews.nl
https://www.dutchnews.nl/news/2021/03/dutch-inventor-of-the-audio-cassette-tape-dies-aged-94/?


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Radio Waves: Australian Radio Stations Blocked on FB, Boomer Radio, Friedrichshafen 2021 Maybe a Go, and Ultra-Low Radio Frequencies Reveal Universe of Black Holes

Radio Waves:  Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers.  To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors William Lee, Sheldon Harvey, and Paul Webster for the following tips:


[Australian] Radio stations blocked from Facebook (RadioInfo)

Facebook has carried out its threat to remove news posts from its platform in response to the Australian Government’s mandatory bargaining code for digital media giants.

In a Faceboook post William Easton, Managing Director, Facebook Australia & New Zealand said:

In response to Australia’s proposed new Media Bargaining law, Facebook will restrict publishers and people in Australia from sharing or viewing Australian and international news content.

The proposed law fundamentally misunderstands the relationship between our platform and publishers who use it to share news content. It has left us facing a stark choice: attempt to comply with a law that ignores the realities of this relationship, or stop allowing news content on our services in Australia. With a heavy heart, we are choosing the latter.

Facebook has deemed radio stations as news publishers, along with newspapers and tv stations.

A check of radio facebook sites this morning shows most no longer contain any new content, with a message saying “no posts yet” on each page. All previous content also seems to have also disappeared.

When we checked shared posts to radio websites, the links were broken.

Read more at: https://radioinfo.com.au/news/radio-stations-blocked-facebook © Radioinfo.com.au

Meet the boomers taking on the BBC and launching a radio station for their generation (The Telegraph)

Baby boomers have found themselves increasingly dismayed when tuning into BBC Radio 2, the station that used to be theirs of choice. Time was when Terry Wogan would greet them in the morning with music from the likes of the Rolling Stones, Elton John and Queen. But Wogan gave way to Chris Evans, who in turn has passed the mic to Zoe Ball. And with each generation, there has been a change in sensibility. This month, the logic behind the move emerged: Radio 2 is trying to target ‘Mood Mums’, lower-income women in their 30s.

“Their playlist is full of Dua Lipa and Ariana Grande,” says David Symonds, 77, who is, incidentally, my grandfather. “I don’t want to listen to Justin Bieber, thank you very much. There’s a gap in the market left by Radio 2 in its continuous pursuit of youth.”

He has never been one to hold his tongue and his criticisms of Radio 2 are biting. “It is now full of D-list TV celebs who know nothing about music at all,” he continues. “Rylan Clark-Neal, for f**** sake, was a contestant on The X Factor singing badly, and now he’s everywhere.”

Grandad has been out of the radio establishment for decades – he was one of the original Radio 1 DJs and helped launch Capital Radio, but left the UK in 1995 to set up his own stations in Cyprus (Limassol FM) and then France (The Roolz). Then he received a call from fellow radio veteran David Lloyd asking if he wanted to be one of the first presenters on a new British station: Boom Radio.[]

Ham Radio in Friedrichshafen, Germany, Tentatively on for 2021 (ARRL News)

Ham Radio in Friedrichshafen, Germany, was canceled last year because of the pandemic. Organizers for Europe’s International Amateur Radio Exhibition this week expressed optimism that the 45th Ham Radio, sponsored by the Deutscher Amateur Radio Club (DARC), will be able to take place June 25 – 27.

“We are watching the situation closely, of course,” a message from Friedrichshafen Fairgrounds CEO Klaus Wellmann said. “At the moment, we are assuming that we will be able to hold Ham Radio in accordance with an extensive, tried-and-proven safety and hygiene concept and are looking forward to seeing everyone again at Europe’s most important trade fair for amateur radio.” []

A starry sky made of more than 25,000 supermassive black holes (Astron)

An international team of astronomers has produced the largest and sharpest map of the sky at ultra-low radio frequencies, using the Low Frequency Array (LOFAR) radio telescope. The map published in the journal Astronomy & Astrophysics reveals more than 25,000 active supermassive black holes in distant galaxies.

At a first glance, the map looks like an image of a starry night sky. However, the map is based on data taken by LOFAR and shows the sky in the radio band. Stars are almost invisible in the radio band, but instead black holes dominate the picture. With this map, astronomers seek to discover celestial objects that only emit waves at ultra-low radio frequencies. Such objects include diffuse matter in the large scale structure of the Universe, fading jets of plasma ejected by supermassive black holes, and exoplanets whose magnetic fields are interacting with their host stars. Albeit among the largest of its kind, the published map only shows two percent of the sky. The search for these exotic phenomena will continue for several years until a map of the entire northern sky will be completed.

The radio waves received by LOFAR and used for this work are up to six meters long which corresponds to a frequency of around 50 MHz. They are the longest radio waves ever used to observe such a wide area of the sky at this depth. “The map is the result of many years of work on incredibly difficult data. We had to invent new strategies to convert the radio signals into images of the sky, but we are proud to have opened this new window on our Universe.”, says Francesco de Gasperin, scientist at the Hamburg Observatory and leading author of the publication.

There is a reason why the Universe at these long radio wavelengths is almost uncharted: such observations are very challenging. The ionosphere, a layer of free electrons that surrounds the Earth, acts as a lens continuously moving over the radio telescope. The effect of the ionosphere can be compared to trying to see the world while being submerged in a swimming pool. Looking upwards, the waves on the water bend the light rays and distort the view. To account for ionospheric disturbances, the scientists used supercomputers and new algorithms to reconstruct its effect every four seconds over the course of 256 hours of observation.[]


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Radio Waves: NRAO Turns Scope System Into Planetary Radar, WBCQ Seeks Engineers, Deep Space Network Upgrades, and 2021 Propagation Summit

GBT-VLBA radar image of the region where Apollo 15 landed in 1971. The snake-like feature is Hadley Rille, a remnant of ancient volcanic activity, probably a collapsed lava tube. The crater at top, alongside the rille, is called Hadley C and is about 6 kilometers in diameter. This image shows objects as small as 5 meters across.
(Credit: NRAO/GBO/Raytheon/NSF/AUI)

Radio Waves:  Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers.  To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!


Successful Test Paves Way for New Planetary Radar (NRAO)

The National Science Foundation’s Green Bank Observatory (GBO) and National Radio Astronomy Observatory (NRAO), and Raytheon Intelligence & Space conducted a test in November to prove that a new radio telescope system can capture high-resolution images in near-Earth space.

GBO’s Green Bank Telescope (GBT) in West Virginia — the world’s largest fully steerable radio telescope — was outfitted with a new transmitter developed by Raytheon Intelligence & Space, allowing it to transmit a radar signal into space. The NRAO’s continent-wide Very Long Baseline Array (VLBA) received the reflected signal and produced images of the Apollo 15 moon landing site.

The proof-of-concept test, culminating a two-year effort, paves the way for designing a more powerful transmitter for the telescope. More power will allow enhanced detection and imaging of small objects passing by the Earth, moons orbiting around other planets and other debris in the Solar System.

The technology was developed as part of a cooperative research and development agreement between NRAO, GBO, and Raytheon.

“This project opens a whole new range of capabilities for both NRAO and GBO,” said Tony Beasley, director of the National Radio Astronomy Observatory and vice president for Radio Astronomy at Associated Universities, Inc. (AUI). “We’ve participated before in important radar studies of the Solar System, but turning the GBT into a steerable planetary radar transmitter will greatly expand our ability to pursue intriguing new lines of research.”

Using the information collected with this latest test, the participants will finalize a plan to develop a 500-kilowatt, high-power radar system that can image objects in the Solar System with unprecedented detail and sensitivity. The increased performance also will allow astronomers to use radar signals as far away as the orbits of Uranus and Neptune, increasing our understanding of the Solar System.

“The planned system will be a leap forward in radar science, allowing access to never before seen features of the Solar System from right here on Earth,” said Karen O’Neil, the Green Bank Observatory site director.

“Raytheon’s radar techniques could ultimately improve our ability to explore the Solar System,” said Steven Wilkinson, Principal Engineering Fellow at Raytheon Intelligence & Space. “Working with the astronomy community allows us to apply decades of radar know-how to a project that provides high-resolution images of near-Earth objects.”

“We are excited to be partnering with Raytheon and applying their radar expertise to transform our observatories’ telescopes in new science areas,” said AUI President Adam Cohen.

The National Radio Astronomy Observatory and the Green Bank Observatory are facilities of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.[]

WBCQ: Radio transmitter engineers wanted

WBCQ Radio is seeking radio transmitter engineers to work at our 500KW shortwave station. Come to northern Maine and get away from it all. Nice working environment, good pay, great people, fun work with BIG transmitting and antenna equipment. Contact Allan and Angela Weiner at 207-538-9180. Please send resumes to [email protected].

Deep Space Network upgrades and new antennas increase vital communication capabilities (NASA)

NASA’s Deep Space Network, commonly referred to as the DSN, has welcomed a new dish, Deep Space Station 56, to its family of powerful ground listening stations around the world.

The now-operational 34-meter antenna joins the network’s Madrid Deep Space Communications Complex located 60 kilometers west of Madrid, Spain while other dishes within the network undergo critical upgrades.

The new dish is part of an ongoing series of enhancements to the DSN, which traces its roots back to January 1958 when the U.S. Army’s Jet Propulsion Lab was tasked with standing up a series of communications stations in Nigeria, Singapore, and the U.S. state of California to support orbital telemetry operations for the Explorer 1 mission.

This precursor to the Deep Space Network was transferred to NASA along with the Jet Propulsion Lab on 3 December 1958. The DSN was then formally commissioned by the U.S. space agency as a way to consolidate the pending deep space communication needs through centralized locations to avoid each mission having to create its own ground listening station(s).

The three Deep Space Network ground locations are spaced roughly 120 degrees from each other in Canberra, Australia; Goldstone, California; and Madrid, Spain. The location of the three facilities ensures deep space missions with a line of sight to Earth can communicate with at least one of the locations at any time.

Updates throughout the decades have increased the network’s capabilities, most notably for the two Voyager probes that continue to operate and send back science data having both long-passed out of the heliosphere and into the interstellar medium.

The network, nonetheless, is showing its age, with upgrades and refurbishments needed to ensure continuous operations. Part of this initiative is the recent addition of the new dish, Deep Space Station 56 (DSS-56), at the Madrid complex.

“After the lengthy process of commissioning, the DSN’s most-capable 34-meter antenna is now talking with our spacecraft,” said Bradford Arnold, DSN project manager at the Jet Propulsion Laboratory.[]

2021 Propagation Summit Session Recordings Available (ARRL News)

YouTube recordings and PDF files from the 2021 Propagation Summit hosted on January 23 by Contest University are available. More than 1,000 logged in for the sessions. Each presentation begins approximately on the hour. You can advance the video to the presentation you wish to view.

  • 11 AM – “Update on the Personal Space Weather Station Project and HamSCI Activities for 2021” by Dr. Nathaniel Frissell, W2NAF
  • 12 Noon – “Solar Cycle 25 Predictions and Progress” by Carl Luetzelschwab, K9LA
  • 1 PM – “Maximizing Performance of HF Antennas with Irregular Terrain” by Jim Breakall, WA3FET
  • 2 PM – “HF Propagation: What to Expect During the Rising Years of Solar Cycle 25,” by Frank Donovan, W3LPL.

Slides decks are available for each presentation in PDF format: FrissellLuetzelschwabBreakall, and Donovan. []


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Video: Physicist reminisces about Arecibo Radio Telescope

Arecibo Observatory’s 305-meter telescope in November 2020 (Credit: University of Central Florida)

Many thanks to SWLing Post contributor, TomL, who shares the following:

I came across this youtube video about a physicist who worked there in his early years and gives this tribute to his time there. Maybe some others would like to see it too:

Amazing! Thank you, Tom!

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A Universe of Sound

This deep image from NASA’s Chandra X-ray Observatory shows the Vela pulsar, a neutron star that was formed when a massive star collapsed. (Source: NASA)

Many thanks to SWLing Post contributor, Roger, who writes:

Hello Thomas,

I thought you, along with some others in the SWLing community, might be interested in the musical renditions, or sonifications, that were released 9/22/2020 by NASA’s Chandra X-ray

Center Universe of Sound website.
https://chandra.si.edu/sound/index.html

I found it utterly fascinating, and hope you do too.

Source: ScienceNews, Vol. 198 ? No. 8 (November 7, 2020) p. 4.

Many thanks, Roger for sharing this! Below, I’ve copied one excerpt with one pulsar sound. I’d encourage you to check out the others by clicking here.

Listen to a Pulsar Clock

Turning a pulsar’s rotational data into sound makes it easier to observe patterns and make comparisons between different nebulous pulsar rotational speeds. as a pulsar ages it spins at a slower speed. listen to the different pulsar heartbeats. what can you guess about how fast these different pulsars rotate? Which pulsar is the oldest? How about the youngest?

Neutron stars are strange and fascinating objects. They represent an extreme state of matter that physicists are eager to know more about. Yet, even if you could visit one, you would be well-advised to turn down the offer.

The intense gravitational field would pull your spacecraft to pieces before it reached the surface. The magnetic fields around neutron stars are also extremely strong. Magnetic forces squeeze the atoms into the shape of cigars. Even if your spacecraft prudently stayed a few thousand miles above the surface neutron star so as to avoid the problems of intense gravitational and magnetic fields, you would still face another potentially fatal hazard.

If the neutron star is rotating rapidly, as most young neutron stars are, the strong magnetic fields combined with rapid rotation create an awesome generator that can produce electric potential differences of quadrillions of volts. Such voltages, which are 30 million times greater than those of lightning bolts, create deadly blizzards of high-energy particles.

These high-energy particles produce beams of radiation from radio through gamma-ray energies. Like a rotating lighthouse beam, the radiation can be observed as a pulsing source of radiation, or pulsar. Pulsars were first observed by radio astronomers in 1967. The pulsar in the Crab Nebula, one of the youngest and most energetic pulsars known, has been observed to pulse in almost every wavelength—radio, optical, X-ray, and gamma-ray.

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Radio Waves: Signals from Mars, Two More Hamstronauts, M17 Digital Voice Mode, and Climbing Trees for a Better Signal

Radio Waves:  Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers.  To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Troy Riedel, LG, Ron and the ARRL News for the following tips:


Radio Signals from Mars (Spaceweather.com)

How close is Mars? Close enough for radio reception. On Oct. 4th, amateur radio operator Scott Tilley picked up a carrier wave from NASA’s Mars Reconnaissance Orbiter (MRO) circling the Red Planet. Turn up the volume and listen to the Martian Doppler shift:

Tilley is a leader in the field of satellite radio. Dead satellites, zombie satellites, spy satellites: He routinely finds and tracks them. “But this was a first for me,” he says. “A satellite around Mars!”

It’s not easy picking up radio signals from distant planets. NASA does it using the giant antennas of the Deep Space Network. Tilley uses a modest 60 cm dish in his backyard in Roberts Creek, BC. This week’s close encounter with Mars set the stage for his detection.

“MRO’s signal is weak, but it is one of the louder signals in Mars orbit,” says Tilley. “The spacecraft has a large dish antenna it uses as a relay for other Mars missions. With the proximity of Mars these days, it was the perfect time to try.”[]

Two More Astronauts Earn Amateur Radio Licenses (ARRL News)

Although the lockdown of Johnson Space Center (JSC) postponed amateur radio training and licensing over the past 7 months, NASA ISS Ham Project Coordinator Kenneth Ransom, N5VHO, was able to work with all of the new astronaut-class graduates, as well as offer some refresher courses with already-licensed astronauts. Licensed astronauts on the International Space Station (ISS) may operate the on-station ham radio equipment without restrictions.

Astronauts often participate in Amateur Radio on the International Space Station (ARISS) contacts with schools and groups on Earth.

NASA Astronaut Kayla Barron, who completed her introductory course in June and received basic ham radio operations training in late September, recently tested and received the call sign KI5LAL.

European Space Agency astronaut Matthias Maurer passed his amateur radio exam on July 30, and he got his basic ham operations training in July. He now is KI5KFH.

Astronauts Shane Kimbrough, KE5HOD, and Shannon Walker, KD5DXB, completed the refresher course earlier this year. Two other new astronauts are in the queue to take the Technician license exam. — Thanks to Rosalie White, K1STO[]

M17 Aims to replace proprietary ham radio protocols (Hackaday.io)

While M17 might sound like a new kind of automatic rifle (as actually, it is), we were referring to an open source project to create a ham radio transceiver. Instead of paraphrasing the project’s goals, we’ll simply quote them:

The goal here should be to kick the proprietary protocols off the airwaves, replace DMR, Fusion, D-Star, etc. To do that, it’s not just good enough to be open, it has to be legitimately competitive.

Like some other commercial protocols, M17 uses 4FSK along with error correction. The protocol allows for encryption, streaming, and the encoding of callsigns in messages. There are also provisions for framing IP packets to carry data. The protocol can handle voice and data in a point-to-point or broadcast topology.

On the hardware side, the TR-9 is a UHF handheld that can do FM voice or M17 with up to 3 watts out. The RF portion uses an ADF7021 chip which is specifically made to do 4FSK. There’s also an Arm CPU to handle the digital work.[]

Armed with a radio, Cambodian girl climbs tree to access education (SE Asia Globe)

When Cambodian schools closed due to Covid-19, poor internet access and a lack of minority language materials made distance learning in rural communities near impossible. But armed with a simple radio, children are rising above these obstacles to their education

Jumping down from the tree near her home, Srey Ka assumes her spot in the shade underneath as she adjusts the dials on her radio. Her pet piglet remains asleep at her feet, twitching his nose as he dreams, his belly full of leftover rice. Around her, cows meander by, their ringing bells competing with the sound of static from her radio.

While her school is still closed due to Covid-19 regulations, she still wears her Grade 3 uniform as she attempts to locate a signal. She’s listening out for distance learning programmes – six hours of educational radio broadcasts per week for children in Grades 1-3, some of which are in her ethnic minority language.

It was August and Srey Ka had just received a radio from international nonprofit Aide et Action, two weeks before her school reopened as pandemic measures eased in Cambodia in early September.

From the Phnong ethnic minority group, Srey Ka struggled to find learning resources in her language during school closures. Eager to cram as much as she can before returning to school, Srey Ka tied the antenna of her radio to the highest point of a tree to get the best reception. Even a clear radio signal is hard to come by in the small fishing village of Pun Thachea, located along a remote stretch of the Mekong river in Cambodia’s northeast Kratié province.[]


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