Beyond their love of radio, amateur radio operators and shortwave radio broadcasters have one thing in common: They rely on the ionosphere to refract or bend their signals back to Earth, so that they can travel beyond line-of-sight distances.

In turn, the ionosphere’s ability to refract radio signals depends on its level of ionization or charge. The more ionized the ionosphere is, the more likely it is to bend signals back to the ground rather than let them pass through.

Here’s where the sun comes in. The number of sunspots on the solar surface rises and falls over an 11-year period, during what is known as a solar cycle. The more sunspots, the more solar radiation comes to Earth. 

This radiation ionizes the ionosphere, improving the propagation of signals for transmitters and receivers alike. 

Right now is a good time for amateur operators and shortwave broadcasters (and listeners), because the world is just coming off the peak, or solar maximum, of Solar Cycle 25.

“Solar Cycle 25 refers to our current solar cycle, which began in December of 2019 and peaked in October 2024,” said Rob Steenburgh, the science and operations officer (SOO) at NOAA’s Space Weather Prediction Center (SWPC) in Boulder, Colo.

SWPC is the official source in the United States for space weather forecasts, watches, warnings and alerts. “The solar cycle refers to the naturally occurring maximum and minimum in the number of sunspots,” he told Radio World. 

A complete cycle lasts, on average, 11 years. The numbering began with Cycle 1 in 1755.

“The number of sunspots is an indicator of the amount of solar activity and emissions in the X-ray and Extreme Ultraviolet (EUV) wavelengths,” Steenburgh said. 

“Energy at these wavelengths drives the formation of the ionosphere, which is the critical atmospheric component for radio communication in the high frequency (HF; 3–30 MHz) bands. In addition to sunspots, radio users often follow the 10.7 cm wavelength solar flux, F10.7, which is also a proxy for solar activity.”

Sunspots are good

Gilles Letourneau is a respected radio enthusiast and the producer/host of the OfficialSWLchannel on YouTube. He is a big fan of more sunspots. 

In layperson’s terms, “That increased ionization changes the structure of the ionosphere making it thicker and denser and capable of bouncing shortwave signals of higher frequencies with more efficiency,” Letourneau said. “Without that extra energy, higher frequency signals simply go through and are lost into space.”

That said, not every band benefits equally from increased ionospheric ionization. 

“The largest influence of solar maximum is seen at bands above 20 meters (14 MHz), although you can still see some influence on 20m,” said Steenburgh. “Radio waves are refracted/reflected when their frequency is at/below the plasma frequency of the ionosphere. The plasma frequency is directly related to the electron density, and the electron density increases with the increased ionization occurring during solar maximum.”

Letourneau agreed: “The higher the sun’s output of energy in a solar cycle the higher the frequencies are capable of bouncing off the ionosphere. Thus higher frequencies are the first to show improvement in propagation, mostly above 20 MHz like the 15, 12 and 10 meter band and in extreme cases even the 6 meter amateur band (50 MHz).” He added that the increased energy “will improve the 19, 16 and 13 meter international broadcast bands also, making those more reliable.”

Shortwave boon

SW broadcasters are keenly aware of the solar cycles and use this to plan their transmission frequencies accordingly.

“Generally speaking, we need to use higher frequencies during the high points of the 11-year solar cycle, and lower frequencies during the low points, in order to provide the best reception quality for listeners,” said Jeff White, general manager of WRMI shortwave in Okeechobee, Fla., and chairman of the High Frequency Coordination Conference (HFCC). 

WRMI is the largest privately-owned shortwave station in the United States. The recent peak of Solar Cycle 25 is still delivering good results for WRMI. 

“We only use two very high frequencies (15770 and 17790 kHz), and we are finding that these frequencies are providing extremely good reception not only in the intended target areas, but all over the world,” White told us recently. 

“For example, 15770 is beamed primarily to Europe (with some coverage of North Africa and the Middle East), and we are getting reports of excellent reception of 15770 from listeners in places like Australia and South America.”

Other SW broadcasters have been enjoying similarly positive results. 

“Radio New Zealand was received in North America on their 17675 kHz frequency much more reliably last summer than years before,” said Gilles Letourneau. 

“BBC World Service even used the very seldom used 11-meter band on 25790 kHz that was giving an amazing signal due to higher solar activity. Radio France coming into Montreal was much more reliable on high frequencies like 17850 and 21690.” 

Letourneau also reported making amateur radio contacts on 10- and 12-meter bands with Europe and Asia “when it is usually dead in the low part of the solar cycle.”

“During solar maximum, listeners may be able to receive distant stations more reliably, while broadcasters and radio amateurs may find their signals travel farther. It’s a great time to be a DXer,” Steenburgh said. 

However, he cautioned that solar maximum is a double-edged sword. 

“In addition to fantastic propagation conditions, solar maximum sees large X-ray flares that result in periodic short-wave-fade events, and occasionally, radio bursts and noise storms. Solar particle events that can accompany flares lead to polar-cap absorption conditions. 

“Finally, flares can be associated with coronal mass ejections, which bring geomagnetic storms, noisy conditions and maximum usable frequency depressions.”

Useful resources

For those looking to take advantage of Solar Cycle 25 to improve their RF transmissions and reception, There are several websites that address radio propagation, Steenburgh said. 

“SWPC’s website, spaceweather.gov, provides a great deal of information of interest to radio operators and listeners, including the F10.7 solar flux, geomagnetic indices and output from our D-Region absorption.”

Letourneau recommended a similarly named, but distinct, resource for solar max enthusiasts. 

“Spaceweather.com is the first website anyone should know about to learn about and know what is happening with the sun and the solar cycle,” he said.

Which frequencies should we tune into, to exploit the solar maximum? 

Jeff White offered practical advice for the current environment. “Broadcasters can take advantage of the peak of the solar cycle by using higher frequencies (let’s say above 10 MHz), and listeners can look for these transmissions and enjoy better-than-usual reception on these frequencies, including reception well into the local nighttime,” he said. He recommended the HFCC website and the World Radio TV Handbook for station schedules, as well as The Spectrum Monitor for shortwave news.

Limited-time offer

The term “solar cycle” says it all: The peak of sunspot activity does not last, so the time to check out the amateur and SW bands for best performance is now.

“We appear to be moving past the peak of Solar Cycle 25, so the F10.7 numbers are expected to see a gradual decline over the next several years,” said Steenburgh, citing SWPC’s solar cycle progression plot. 

“It’s important to note that even though we’re on the ‘downslope’ of the solar cycle, impactful events can and do still occur. The most impactful storms of the last cycle (24) occurred in September 2017, more than three years after solar maximum in April 2014.”

Letourneau noted that the 11-year solar cycle is not set in stone, because a massive ball of fusing hydrogen is not committed to a firm schedule. In fact, “A solar cycle can last anywhere from 8 to 18 years in length,” he told Radio World. Still, 11 years has become the accepted length based on experience, so this is the standard that astronomers and broadcasters go by.

Now is the time to enjoy the plethora of sunspots and their effect on the ionosphere while you can.

“I expect they will diminish gradually over the next five-and-a-half years,” said White. “At that point, the lower frequencies will provide better reception and larger coverage areas.”

The post Solar Cycle 25 Gives Amateurs and Shortwave a Boost appeared first on Radio World.

From our “Who’s Buying What” page: Audacy will install synchronized boosters in New York City to solve “invisible coverage gaps” in local coverage for WCBS-FM and WXBK-FM.

The company will use MaxxCasting systems from GeoBroadcast Solutions, which deploys clusters of low-elevation, highly directionalized boosters. GBS called the agreement “a major expansion of proven FM signal-optimization technology into the nation’s largest and most complex radio market.”

According to GBS, even strong FM signals in dense urban markets may not reach their full potential audience.

“In New York, terrain effects and dense development in all directions can disrupt reception at street level, where most listening occurs, particularly in cars with antennas positioned roughly six feet off the ground,” it said in the announcement.

“For decades, broadcasters have assumed that top FM stations were engineered to the fullest extent possible and that additional reach was unlikely. In reality, natural terrain and dense development can create signal disruptions that traditional planning models do not fully account for.”

It said traditional planning assumes “ideal conditions and rooftop antennas,” but that real listening “happens at street level, in motion, in dense markets like New York.”

John Kennedy is Audacy senior vice president of technical operations.

MaxxCasting systems also are in use in San Diego, San Francisco and San Jose.

GBS also makes the ZoneCasting geotargeting technology.

The post Audacy Will Deploy MaxxCasting in New York appeared first on Radio World.

It is still difficult to qualify just how widely adopted AI voice use is across the radio industry.

We have come across quite a few implementations for services such as weather forecasts, particularly in smaller markets. On the other end of the spectrum is iHeartMedia’s recent “guaranteed human” pledge. 

A study from 2024 found that about one in five radio listeners think they’ve heard AI-generated content on the air. It’d be fascinating to see results today.

That said, with it being three years since the first wave of radio adoption of synthetic voices began, would you be able to even tell the difference if you heard AI on the air?

A recent study conducted by the University of Mississippi’s Jordan Center for Journalism Advocacy and Innovation inspired Radio World contributor and friend Dan Slentz to send us six underwriting announcements he produced for 105.9 WDOG(LP) in New Philadelphia, Ohio.

Slentz serves as the station’s consultant. The rock-formatted community station airs four underwriting announcements per hour, from the hours of 6 a.m. through midnight. That could, if “The Rock Dog’s” inventory is filled, total a maximum of 72 announcements per day.

“Sometimes getting a different voice in the mix is difficult,” Slentz said.

[Related: “What Happens When AI Shows Up on Your Station’s Social Media?”]

So, to enhance the station’s narrators, he has experimented with low-cost or free AI voice resources. Most recently, Slentz has used the free AI voice generator offered by QuillBot, which advertises speech that sounds “natural, expressive and human-like.”

Below are six different MP3s of WDOG underwriting announcements.

Three are recorded by humans. The other three are from AI.

Listen to them first, and then we’ll reveal their sources.

Human or AI?

1. Bear Carpet One Floor & Home in Sugarcreek, Ohio
2. Berner Trucking in Dover, Ohio
3. Better Banner Printing in New Philadelphia, Ohio
4. Dover Flea Market in Dover, Ohio
5. Dundee Marketplace in Dover, Ohio
6. Michael’s Restaurant in New Philadelphia, Ohio

Radio World’s performance

Before we reveal the answers — as Professor Slentz, also an instructor and director of John Carroll University’s Blue Streak Media, informed me — yours truly would have failed this test if it were being graded on an academic scale.

I had guessed that Berner Trucking, Better Banner and Dover Flea Market were AI. Just two of my six guesses were correct! 

Answers revealed

• Human: 3, 4 and 6
• AI: 1, 2 and 5

The Better Banner announcement, Slentz told us, is voiced by Steve Kelly.

Michael’s Restaurant is the voice of Dan’s wife, Gina.

Slentz himself is heard on the Dover Flea Market announcement.

The other three announcements? They are generated by AI.

“It’s pretty amazing how realistic AI can sound,” he told us.

Science backs the notion that we’re having a harder time distinguishing the difference between human and AI voices. A study conducted by Nadine Lavan, Mairi Irvine, Victor Rosi and Carolyn McGettigan that was published last September in the National Library of Medicine said that voice clones — similar to what WDOG uses — are labeled as human between approximately 58 and 70% of the time. AI voices, conversely, are labeled as human approximately 40% of the time.

The researchers concluded that “the widespread availability of human-like AI-generated voices as created by commercially available products has numerous implications for how humans evaluate the voices they hear around them.”

How did you do on the quiz? And have you deployed AI voice tools at your station? Let us know, as we’ll include it in a Radio World follow-up story.

[Read More Radio World Stories About Artificial Intelligence]

The post Time for Your “AI or Human?” Radio Announcement Quiz appeared first on Radio World.

A few years ago, as I was lining things up for a studio move in our Buffalo market, I found that the options for broadcast phone systems had changed significantly since I had last purchased one. 

After looking at all the available choices and with some reservation about the general concepts involved, I settled on a Telos VXs virtual VoIP system.

I had an integrator do the facility move, and they set up the VXs system there without issue, using our Avaya VoIP system as the SIP server. It all worked like the proverbial hose, and my reservations about using a virtualized on-air phone system diminished.

A short time later, I needed to replace a phone system in our Denver market. Again, looking at the available choices, the VXs virtualized system was the best fit, and since the Denver studios were just down the corridor from my office, it presented me with a way to get a firsthand look at such a system.

[Related: “How I Learned to Stop Worrying and Love the VLAN”]

We already had Telos VSet6 broadcast phone controllers, so all I needed hardware-wise was a server. I ordered up one from Dell, loaded Ubuntu and followed the instructions from Telos for spinning up a container and installing the VXs application. 

There were a few gotchas I had to work through, but it didn’t take long before I had it up and running, connected to our Avaya system as the virtual SIP server and working. It worked and sounded great, garnering praise from our afternoon talk host that very afternoon.

Since then, I have rolled out several other VXs virtualized systems across our company, and I plan to continue to go that route as our hardware-based systems wear out and reach end of life. 

The point of all this is not a product review of the Telos VXs system, although it’s a great choice that I would recommend. Rather it’s an example of the implementation of a new(er) and non-traditional technology in the broadcast environment. 

It represented for me a change in thinking, one that I am carrying forward in our facility planning.

Computers by another name

Since making that move, it has occurred to me that we already have a good number of virtualized components in our broadcast infrastructure. 

One example is our audio processors. All of our AM stations use Omnia.9 processors, and while those processors do have hardware, that hardware is used only for I/O and user control. Open the box and you’ll find a computer running software that’s doing all the heavy lifting. It’s an amazing processor.

Manufacturers are working on other virtualization, including PPM watermarking (available in several production audio processors even now), and there is a push underway to move EAS away from hardware and into the virtual environment. That makes all the sense in the world to me.

Major manufacturers offer virtualized mixing consoles that utilize the touch screen of your choice for operator controls. Sure, there is still some hardware — blades, nodes or whatever — to handle I/O, but even those devices are really computers with an OS running an application. 

In my company’s facilities, we still have traditional control surfaces with mechanical faders, pushbuttons, OLED screens and blinky lights, but even those are just user interfaces providing input to the application.

Shaking my Magic 8 Ball, the words “more virtualization” appear in the window. When you stop and think about it, the possibilities are just about endless for virtualization. 

I don’t think we’re going to see virtualized RF power amplifiers delivering many kilowatts to a transmission line, but everything right up to the PA hardware can be virtualized, and I predict we’ll see that kind of thing more and more.

Otherwise, what part of the broadcast infrastructure is not a candidate for virtualization? Our rack rooms have become server rooms and bear this out. We’re using less and less purpose-built hardware and relying more and more on computers and servers. 

Maybe it’s time for us all to stop worrying and love virtualization. I think it’s here to stay.

Comment on this or any story. Email radioworld@futurenet.com with “Letter to the Editor” in the subject field.

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