From Deep Space To Hollywood: Unraveling RF Mysteries

By John Oncea, Editor

Let’s take a look at three RF stories: FRB 20220610A's distant origin, GPM J1839-10's puzzling behavior, and the complex history of frequency hopping, challenging Hedy Lamarr's invention claim.

Gather near, dear reader, for three RF stories guaranteed to delight and amaze you. The first is about a radio signal 8 billion years in the making, the second looks at a mysterious signal that’s baffled scientists for decades, and the third features actor Hedy Lamarr and her role in the frequency-hopping scheme.

FRB 20220610A

Fast radio bursts (FRB) are mysterious, fleeting, intense blasts of energy that can outshine a galaxy for as little as a few milliseconds, or up to three seconds. Capable of emitting as much energy in thousandths of a second as the sun puts out over three days, FRBs are incredibly difficult to spot.

According to Space.com, “FRBs come from all over the sky and have frequencies of around 1,400 megahertz, though some have been detected with frequencies as low as 400 to 800 hertz. Some scientists estimate that 10,000 FRBs could occur at random points in the sky over Earth each day. However, most FRBs last just milliseconds, and by the time their energy has reached Earth, it is 1,000 times weaker than a mobile phone signal would be if it were emitted from the moon and detected on Earth.”

Scientists don’t know what causes FRBs, but the list of possible sources includes white dwarf collisions, neutron star collisions, flaring stars, and plasma medium. There are repeating and non-repeating FRBs but it’s not clear if they share a common origin. They also have a characteristic profile, with high frequencies arriving before low frequencies.

The first FRD detection was made at the Parkes Observatory in Australia in 2001 “as it blasted out of the Small Magellanic Cloud, a satellite galaxy of the Milky Way,” writes Space.com. “However, this event would not be discovered until 2007, when astrophysicist Duncan Lorimer and colleagues found it in archival data from the observatory.”

Other discoveries followed and it was determined that studying FRBs could help astronomers map the universe because “as they travel, these short-lived radio-wave blasts can gather information about cosmic environments, like the clouds of interstellar gas they pass through.”

Enter FRB 20220610A is a remarkable FRB discovered on June 10, 2022, by the Australian Square Kilometer Array Pathfinder (ASKAP) radio telescope in Western Australia, according to NASA. This particular FRB has captured the attention of astronomers because it erupted halfway across the universe, making it the farthest and most powerful example detected to date.

“And if that's not strange enough, it just got weirder based on the follow-up Hubble observations made after its discovery,” NASA writes. “The FRB flashed in what seems like an unlikely place: a collection of galaxies that existed when the universe was only 5 billion years old. The large majority of previous FRBs have been found in isolated galaxies.”

The burst emitted an enormous amount of energy, equivalent to what our sun produces over 30 years, all within milliseconds, notes Earth.com. FRB 20220610A is unusually bright, challenging existing models of FRB emission mechanisms.

“Using ASKAP’s array of dishes, we were able to determine precisely where the burst came from,” said Dr. Stuart Ryder, an astronomer from Macquarie University. “Then we used ESO’s Very Large Telescope (VLT) to search for the source galaxy, finding it to be older and further away than any other FRB source found to date and likely within a small group of merging galaxies.”

The detection of FRB 20220610A demonstrates the potential of using these bursts to detect matter between galaxies and better understand the universe’s structure, writes ScienceAlert. Its extreme brightness and energy output are forcing astronomers to rethink current models of FRB formation and emission, and its dispersion measure doesn't quite match expectations, prompting a reconsideration of assumptions used when studying the universe through these phenomena.

In addition, the discovery of FRB 20220610A confirms the Macquart relation, which relates the dispersion measure of FRBs to their host galaxy's redshift, even for bursts halfway across the known universe. It also helps in measuring the “missing” matter between galaxies, providing a new way to estimate the mass of the Universe.

GPM J1839-10

A magnetar, writes NASA, is a type of neutron star with an extremely powerful magnetic field, considered to be the most magnetic object known in the universe, with fields thousands of times stronger than a typical neutron star and millions of billions of times stronger than Earth’s magnetic field. When the magnetic field rearranges, it can cause intense bursts of radiation, known as “starquakes,” releasing powerful gamma rays.

Located 15,000 light-years from Earth in the Scutum constellation is GPM J1839-10, a “remarkable object (that) challenges our understanding of neutron stars and magnetars, which are some of the most exotic and extreme objects in the Universe,” says Dr. Natasha Hurley-Walker.

Until recently, all known magnetars released energy at intervals ranging from a few seconds to a few minutes. GPM J1839-10 emits radio waves every 22 minutes, making it the longest period magnetar ever detected.

First detected in 2022 by the Murchison Widefield Array (MWA) radio telescope in Western Australia, GPMJ1836-10’s signal dates back to 1988 in archival data from various radio telescopes. It is different from other magnetars in several ways, including:

• Extremely Long Period: GPM J1839-10 has an unusually slow rotation period of approximately 22 minutes.
• Extended Radio Bursts: It emits bursts of radio waves lasting up to 5 minutes, much longer than typical pulsars or magnetars.
• Persistent Signals: The object has consistently been emitting signals for at least 35 years, showing remarkable longevity.
• Lack of X-ray Emission: Unlike typical magnetars, GPM J1839-10 does not produce detectable X-ray bursts.

As a result of this, GPM J1839-10 is challenging existing models as its behavior violates current theories about neutron stars and their emission mechanisms. Its slow rotation should place it in a “death valley” state where radio emissions cease, yet it continues to emit, meaning it may represent a new class of ultra-long period radio sources.

Due to its unique characteristics, some researchers have proposed that GPM J1839-10 might not be a magnetar at all, but rather an extremely magnetic white dwarf. This alternative explanation highlights how unusual this object is compared to known magnetars.

These distinctive features make GPM J1839-10 a highly enigmatic object that challenges existing models of magnetar behavior and neutron star physics, prompting astronomers to reconsider their understanding of these extreme cosmic objects.

Hedy Lamarr And Frequency Hopping

Frequency hopping, according to our friends at Rohde & Schwarz, is a wireless technology that transmits radio signals by rapidly switching between different frequency channels. It's also known as frequency hopping spread spectrum (FHSS).

In a nutshell, during frequency hopping the transmitter and receiver use a pseudo-random sequence to control the frequency switching. This reduces the impact of interference by switching between frequencies and improves security as the unpredictable frequency-hopping pattern makes it difficult for unauthorized parties to intercept or jam the signal.

Frequency hopping allows multiple devices to share the same frequency band with minimal interference and is used in wireless communications like Wi-Fi and Bluetooth. It also was invented by Hedy Lamarr, a Hollywood actor in the 1940s, along with composer George Antheil.

Or was it?

Lamarr, born in 1914 in Vienna as Hedwig Eva Maria Kiesler, was a fascinating figure who made significant contributions to both Hollywood and technology. Known for her beauty and roles in films like “Algiers” and “Samson and Delilah,” Lamarr had a keen interest in inventing and spent time experimenting with technology.

According to American Scientist, Lamarr collaborated with Antheil in 1941 to develop a #Secret Communications System,” which later became known as frequency hopping. The idea came from Lamarr’s desire to help the Allied war effort during World War II and was designed to prevent the interception of radio-controlled torpedoes by rapidly switching radio frequencies to prevent signal jamming.

The two received a patent for their invention in 1942 and donated the technology to the U.S. Navy which initially dismissed the idea, not implementing it until the 1960s. Over time, frequency hopping became the foundation for modern spread spectrum technology and is now used in various wireless communication systems, including Wi-Fi, Bluetooth, GPS, and mobile phones.

Lamarr’s contribution was largely overlooked during her lifetime but, in 1997, she received recognition from the Electronic Frontier Foundation. She also was inducted into the National Inventors Hall of Fame in 2014, posthumously.

Lamarr’s work on frequency hopping extended far beyond her acting career. Her invention, though not immediately appreciated, laid the groundwork for many of the wireless technologies we rely on today.

It also, technically, might not have been her invention.

American Scientist notes Hedley and Antheil’s patent for this radio-transmission method was not the first in this area. “It is further true that the earliest operational systems employing this technique were created after World War II independently of their patent, and the essential idea can be traced back nearly to the birth of radio itself. If Lamarr and Antheil’s attorneys had performed a more diligent patent search, different doodles might well have graced Google.”

As early as 1920, inventors were exploring concepts of frequency shifting for secure communications. Notable examples include Ellison Purington’s “frequency wobbling” patent in 1940, Willem Broertjes’ 1929 proposal for randomly varying transmission frequencies, and Emory-Leon Chaffee’s 1922 application describing erratic carrier frequency changes for secrecy.

Perhaps most significantly, a team from AT&T (Otto B. Blackwell, De Loss K. Martin, and Gilbert S. Vernam) filed a patent application in 1920 for a “Secrecy Communication System” that closely resembled later frequency hopping techniques.

Their system used randomly punched holes in telegraph tape to control frequency shifts, anticipating many features of subsequent inventions. This history demonstrates that the concept of frequency hopping evolved through multiple inventors and iterations, with each contribution building upon previous ideas in the field of secure wireless communication.

Frequency hopping’s origins involve a complex and interconnected history of innovation, highlighting that groundbreaking ideas often emerge through parallel and iterative processes rather than singular eureka moments. While Lamarr and Antheil are widely recognized for their 1942 patent on frequency hopping, the concept had been evolving for decades before their work.

This evolution demonstrates that the development of frequency hopping technology was a gradual process, with contributions from multiple inventors and researchers over several decades. It underscores the importance of building upon existing knowledge and the often-overlooked role of earlier innovators in shaping revolutionary technologies.

While Lamarr and Antheil’s work remains significant, particularly for bringing wider attention to the concept, it’s clear that they were part of a larger continuum of innovation in secure communication methods.