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I have noticed a common theme regarding propagation on the 10 meter band. There is a wide perception that when the band goes quiet and worldwide DX dries up in June or July, the solar cycle must be diving such that the frequencies become useless. Having written the propagation column in CQ Amateur Radio magazine since 2001, I have done much research into this topic.

The reality is that while the 11 year solar cycle certainly dictates overall band health, the dramatic differences we see between seasons on 10 meters are driven by complex changes in the Earth’s atmospheric chemistry and magnetic field.

The F2 Layer and the Winter Anomaly

During the autumn and spring months, 10 meters comes alive for long range global communication. To understand why this changes with the seasons, we have to look at the F2 layer of the ionosphere.

Complex Propagation Modes

The seasonal shift in thermospheric winds and the resulting chemical changes in the F2 layer are the true drivers of what we experience on the radio. This phenomenon is known in physics as the Winter Anomaly.

• The Summer Fade: During the summer months, intense solar heating creates upwelling wind patterns in the thermosphere. These winds pull heavier molecular gases, specifically molecular nitrogen (N₂) and molecular oxygen (O₂), higher into the F2 region. This drastically increases the recombination rate of ions. The extra nitrogen acts like a sponge, rapidly absorbing the free electrons we need to reflect 28 MHz signals. Because the electron loss is so high, the overall electron density drops, and transoceanic skip fades away.

• The Winter Peak: The opposite happens during the cooler seasons. As we move away from summer, the thermospheric winds shift and the heavy nitrogen settles back down. The F2 layer becomes dominated by atomic oxygen (O). Without the nitrogen there to absorb the electrons, the recombination rate slows down significantly. This allows a highly dense F2 layer to build up, reaching peak electron densities around November and February. This atomic oxygen rich environment creates the perfect reflective environment for global 10 meter communication.

Summer’s Silver Lining: Sporadic E

When summer arrives and the F2 layer thins out, the band brings its own unique conditions with the prevalence of Sporadic E propagation.

These intense, highly localized clouds of ionization form in the lower E layer of the ionosphere. Sporadic E provides incredibly strong short skip contacts. These openings typically range from a few hundred to a couple of thousand miles, temporarily replacing the global propagation we enjoy during the spring and fall. Most folks scrolling through social media just want a basic understanding of why they are suddenly making loud contacts into neighboring states instead of talking across the ocean, and Sporadic E is the answer.

Global Reach: TEP and Chordal Hop

For North American operators looking to communicate with places like Brazil or Australia, different propagation mechanics come into play.

For communication down into South America, you are dipping into a fascinating phenomenon called Transequatorial Propagation (TEP). TEP is deeply tied to the F2 layer conditions, but it is heavily driven by the structure of the Earth’s magnetic field near the equator.

Around the geomagnetic equator, the magnetic field lines run exactly parallel to the surface of the Earth. This causes the free electrons in the F2 layer to be pushed outward and downward, creating two massive, highly dense bands of ionization located about 15 to 20 degrees north and south of the magnetic equator. We call this the equatorial anomaly, and it is the engine for TEP.

When you transmit from North America down toward Brazil, your 10 meter signal hits that northern dense band. Instead of reflecting back down to the ground or ocean, the signal deflects horizontally across the equator high in the ionosphere. It then hits the southern dense band and reflects down into deep South America. Because the signal stays entirely in the upper atmosphere and avoids a lossy bounce off the Earth’s surface in the middle, the signals can be incredibly strong and clear. TEP is most reliable during the spring and autumn equinoxes, usually peaking in the late afternoon and early evening hours.

Talking to Australia from North America is slightly different because the path does not cross the magnetic equator at the perfect right angle needed for textbook TEP. However, working Australia often relies on a very similar principle called chordal hop propagation. Instead of bouncing between the ionosphere and the ocean all the way across the Pacific, the signal enters the F2 layer and skips along the underside of the ionosphere for thousands of miles. It stays trapped high up where there is very little absorption, eventually dropping down to receivers in Australia with surprising signal strength.

Regional Variances

Radio wave propagation is never a one size fits all experience. Your location on Earth plays a massive role in what you hear on 10 meters.

• The Coasts versus the Midwest: If you live on the East Coast of the United States, your signals have a relatively unobstructed single hop path over the highly reflective saltwater of the Atlantic Ocean to reach Europe. The West Coast enjoys a similar geographic advantage when working Japan and the Pacific Rim. In the Midwest and central USA, your signals must often make an extra hop over land. Because land absorbs radio waves much more than saltwater does, central USA operators might find global F2 paths a bit more challenging. However, Midwest operators are perfectly positioned to work both coasts simultaneously when intense summer Sporadic E clouds form over the continent.

• Equatorial Advantage: Operators located closer to the equator experience less of the severe Winter Anomaly shift. Because they sit under the equatorial anomaly, they enjoy much more consistent F2 and TEP openings year round compared to mid-latitude stations.

• High Latitude Challenges: Operators in high northern or southern latitudes, such as Alaska or northern Europe, must contend with auroral absorption. During periods of high geomagnetic activity, the auroral oval expands and can severely degrade or completely absorb 10 meter signals, shutting down paths that cross the polar regions.

If 10 meters feels like a completely different band right now, do not blame the sunspot numbers. It is simply the natural seasonal shift in atmospheric chemistry and radio wave propagation at work. Enjoy the loud Sporadic E contacts while they last, and get ready for the worldwide skip to return when the seasons change.

Addendum: From the Southern Hemisphere

I was asked how this looks, from the land of Down Under.

Thank you for bringing the Southern Hemisphere perspective into the conversation! You hit the nail on the head regarding the inclination of the Earth’s axis, and it is the perfect starting point to explain why our experiences are mirrored.

Because the Earth is tilted on its axis by 23.5 degrees, the hemispheres take turns leaning toward the Sun as we orbit. Right now, the Northern Hemisphere is tilted toward the Sun, giving us summer. The Southern Hemisphere is tilted away, resulting in your winter. This means the ionospheric effects we experience are exactly reversed on the calendar.

When you mention that the high bands shut down after dark during your current winter, you are experiencing the harsh reality of wintertime solar geometry. During the winter months in the Southern Hemisphere, the Sun is much lower in the sky and the daylight hours are significantly shorter. While the Winter Anomaly we discussed earlier means your daytime F2 layer can actually become quite dense and highly supportive of 10 meter skip during the daylight hours, that ionization is entirely dependent on active sunlight. The moment the Sun sets at 5:30 PM, the source of ionization disappears. Because the winter night is so long, the F2 layer rapidly depletes, shutting the band down until the Sun rises again the next morning.

Conversely, when you head into your summer months of November and December, two major things happen. First, your daylight hours increase dramatically, which keeps the ionosphere charged much later into the evening and extends your operating time. Second, just as the Northern Hemisphere experiences a massive peak in Sporadic E propagation during our summer, the Southern Hemisphere experiences its own Sporadic E season during your summer. This provides those loud, reliable regional contacts. Finally, as you move into mid autumn around March and April, the Earth reaches the equinox. During the equinoxes, the Sun is directly over the equator, providing optimal and balanced F2 layer ionization for both hemispheres. This is why global, long haul propagation is at its absolute peak for everyone at the same time.

Regarding your question about East to West paths: yes, communication between Australia and South America is fundamentally very similar to the path between North America and Europe. Both are mid latitude transoceanic paths that rely on multi hop F2 propagation.

However, the Southern Hemisphere actually has a distinct geographic advantage for these contacts. Radio waves lose a small amount of energy every time they reflect off the Earth’s surface between ionospheric hops. Saltwater is an excellent, highly efficient reflector of radio waves, while landmasses absorb much more of the signal. Because the path between Australia and South America is almost entirely over the highly reflective saltwater of the Pacific Ocean, your multi hop signals suffer far less ground absorption compared to Northern Hemisphere paths that must often cross large expanses of land. This makes those Southern East to West paths incredibly efficient when the F2 layer is cooperating!

Curious about what you can hear on shortwave ham radio? This video is a brief survey of the diverse world of communications on the shortwave spectrum. Expand your radio horizons and enhance your emergency communication preparedness by tuning in to the world of shortwave ham radio.

If you’ve started delving into radio communications beyond local stations and channels, like VHF and UHF, you’re in for a treat. Shortwave radio opens up a whole new realm of signals to explore, including emergency communications vital during natural disasters.

[embedyt] https://www.youtube.com/watch?v=pIVesUzNP2U[/embedyt]

Shortwave radio covers a range of radio frequencies from 3 kHz to 30 MHz. This spectrum is home to a diverse array of radio signals that cater to various communication needs, making it a hub of activity and connectivity.

Within these high frequencies, you can tune in to a multitude of transmissions, from transoceanic air traffic control communications to the chatter of ships navigating the vast seas. Imagine hearing the voices of fishermen, much like those on your favorite reality TV shows about high-seas fishing adventures, along with military communications and the vibrant world of amateur radio enthusiasts.

One of the remarkable features of high-frequency (HF) radio is its ability to propagate signals over long distances, transcending line-of-sight limitations. This means that HF radio enables communication between different regions and even continents, fostering connectivity across vast distances.

During times of crisis and natural disasters, shortwave frequencies become invaluable for emergency communications. When local infrastructure falters or is disrupted, shortwave radio serves as a vital lifeline, facilitating critical two-way communications in and out of disaster-stricken areas.

Explore the fascinating realm of shortwave radio, where distant voices blend with essential information, bridging gaps and connecting communities in times of need. Uncover the power of HF radio to transcend boundaries and provide lifelines when they are needed most.

In this video, I give you a glimpse of the voice and data transmissions I pick up on my high-frequency amateur radio transceiver (in this video, an Icom IC-7000). In later videos, I will dive deeper into specific types of HF communications, such as aeronautical trans-oceanic signals.

Turning back time to virtually witness a critical historic method of shortwave communication using the fundamental mode of continuous wave modulation. This is a film from 1944, teaching the basics of Morse code, for military comms.

What is the proper (and most efficient) technique for creating Morse code by hand, using a manual Morse code key? Ham radio operators find Morse code (and the ‘CW’ mode, or ‘Continuous Wave’ keying mode) very useful, even though Morse code is no longer required as part of the licensing process. Morse code is highly effective in weak-signal radio work. And, preppers love Morse code because it is the most efficient way to communicate when there is a major disaster that could wipe out the communications infrastructure.

[embedyt] https://www.youtube.com/watch?v=qmg1MlstxWM[/embedyt]

While this military film is antique, the vintage information is timeless, as the material is applicable to Morse code, even today.

Credits: National Archives and Records Administration

Department of Defense. Department of the Army. Office of the Chief Signal Officer. (09/18/1947 – 02/28/1964)

ARC Identifier 36813 / Local Identifier 111-TF-3697. PRINCIPLES AND BASIC TECHNIQUE FOR GOOD, RHYTHMIC SENDING 0F MORSE CODE BY OPERATING THE HAND KEY.

Made possible by a donation from Mary Neff.

This video is an introduction to an international public-service and technology hobby known as ‘amateur radio’ (or ‘ham radio’).

[embedyt] https://www.youtube.com/watch?v=K40HpIjDLRs[/embedyt]

Amateur radio (also called ham radio) describes the use of radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communication. The term “amateur” is used to specify “a duly-authorized person interested in radioelectric practice with a purely personal aim and without pecuniary interest;” (either direct monetary or other similar rewards) and to differentiate it from commercial broadcasting, public safety (such as police and fire), or professional two-way radio services (such as maritime, aviation, taxis, etc.).

The amateur radio service (amateur service and amateur-satellite service) is established by the International Telecommunication Union (ITU) through the Radio Regulations. National governments regulate technical and operational characteristics of transmissions and issue individual stations licenses with an identifying call sign. Prospective amateur operators are tested for their understanding of key concepts in electronics and the host government’s radio regulations. Radio amateurs use a variety of voice, text, image, and data communications modes and have access to frequency allocations throughout the RF spectrum to enable communication across a city, region, country, continent, the world, or even into space.

Amateur radio is officially represented and coordinated by the International Amateur Radio Union (IARU), which is organized in three regions and has as its members the national amateur radio societies which exist in most countries. According to an estimate made in 2011 by the American Radio Relay League, two million people throughout the world are regularly involved with amateur radio. About 830,000 amateur radio stations are located in IARU Region 2 (the Americas) followed by IARU Region 3 (South and East Asia and the Pacific Ocean) with about 750,000 stations. A significantly smaller number, about 400,000, are located in IARU Region 1 (Europe, Middle East, CIS, Africa).

Activities and practices

The expansive diversity found in the amateur radio hobby attracts practitioners who have a wide range of interests. Many hams begin with a fascination of radio communication and then combine other personal interests to make the pursuit of the hobby rewarding. Some of the focal areas amateurs pursue include radio contesting, radio propagation study, public service communication, technical experimentation, and computer networking. But, that is just a sampling of interest areas found in the hobby.

Amateur radio operators use various modes of transmission to communicate. The two most common modes for voice transmissions are frequency modulation (FM) and single sideband (SSB). The FM mode offers high-quality audio signals, while SSB is better at long distance communication when bandwidth is restricted.

Modern personal computers have encouraged the use of digital modes such as radioteletype (RTTY) which previously required cumbersome mechanical equipment. Hams led the development of packet radio in the 1970s, which has employed protocols such as AX.25 and TCP/IP. Specialized digital modes such as PSK31 allow real-time, low-power communications on the shortwave bands. More robust digital modes have been invented and improved, including such modes as Olivia, JT65, and WSPR.

NASA astronaut Col. Doug Wheelock, KF5BOC, Expedition 24 flight engineer, operates the NA1SS ham radio station in the Zvezda Service Module of the International Space Station. Equipment is a Kenwood TM-D700E transceiver.

Amateur radio operators, using battery- or generator-powered equipment, often provide essential communications services when regular channels are unavailable due to natural disasters or other disruptive events.

This video comes to us via Canada, and is used by permission from Bernard Bouchard – / ve2sms – The original video was published on Feb 28, 2013.- Website is https://www.ve2cwq.ca/amateur-radio-club-ve2cwq/

Voici maintenant, la version complète du documentaire «La radioamateur» d’une durée de 11 minutes. On y aborde toutes les activités sur le monde de la radioamateur. Ce vidéo a été produit par le Club Radioamateur VE2CWQ / Canwarn-Québec. Pour information: https://www.ve2cwq.ca/

Connect with me at https://NW7US.us

USA Amateur Radio information: http://ARRL.org

I had so many plans for my Hamvention 2023 visit on Friday and Saturday, May 19-20, 2023.  For example, I planned on many interviews including one with N3ZN, maker of great Morse code keys.  I also needed to visit the Card Checker Service of the ARRL DXCC program.  I had a handful of DX cards I was submitting toward DXCC credits.

NW7US, in ICU at the hospital, instead of attending Hamvention 2023.

But, I collapsed about 40 minutes after I got to the Hamvention, on Friday morning! I had just finished getting my DX QSL cards checked at the ARRL booth, then I collapsed. After only being at my first Hamvention for a brief 40-some minutes, I was taken by ambulance to an ER of a Xenia-area hospital.  My blood pressure was difficult to measure at the initial moments of being at the emergency room — it was about 60 over 40, and I had NO radial pulse.

After a CT scan of heart and neck, and blood lab work, I was transported again by ambulance to a hospital near Dayton. There, I was admitted to that hospital’s Intensive Care Unit (ICU) around 5:30 PM on Friday.

I’m writing this on Saturday, from my hospital bed, as I’m still in ICU in Dayton. I hope to be discharged tomorrow (Sunday, 21 May 2023).

The working diagnosis is Acute Kidney Injury (AKI), caused by a combination of issues starting with my parathyroidectomy surgery, a few months back. I had three of my four parathyroid glands removed because they were completely tumorous.  I wrote about that in my previous entry on this website.

Turns out my calcium levels were lower than they should be, causing problems throughout my body, but especially in my heart. Additionally, I was severally dehydrated due to two medications I had been taking because the VA doctors thought I should be on them.  But, these meds were working against me. One of those I don’t even need, but the VA had me taking. That one is FUROSEMIDE. The other is LISINOPRIL.  I don’t have high blood pressure, nor water retention.

At the ICU, I have stopped taking those meds.  I’m on an IV, getting hydrated, and getting calcium supplements.

My kidney function is improving but I’m going to spend another night in ICU until they feel confident I’ve made full recovery.  I hope to be discharged on Sunday, 21 May, 2023.

I hope all of you that were at this year’s Hamvention have enjoyed the fellowship of radio enthusiasts. Maybe I’ll meet many of you, next year!  I will make videos of Hamvention 2024, if all goes well in a year’s time.

If you were at Hamvention 2023, share some highlights in the comments!

UPDATE:  On Sunday, I was released from the ICU, and I am now home recuperating.  Monday is a bit rough, so am not at work, yet.  BP is normal, and I am on new medication for my heart so that I do not get dehydrated by the furosemide and lisinopril.  Here’s hoping for next year’s Hamvention, which I hope to attend.

73 de NW7US
https://nw7us.us
..

From the RAIN HamCast episode #57, 2021-XII-25 (used with permission):

RAIN’s Hap Holly/KC9RP spoke with Tomas recently about Solar Cycle 25. This is the second and final excerpt from their discussion.

From the introduction to The RAIN HamCast, Episode #57:

In this episode, we continue our discussion with Tomas Hood/NW7US, the author of many writings about space weather and effects of solar activity the past 20-plus years.

(Part 1 of 2 can be found here: Episode #56, https://www.youtube.com/watch?v=HnuSOXhFELQ)

Tomas has been a short wave enthusiast since 1973, a ham operator since 1990, and is a United States Army Signal Corps veteran today. He launched the first civilian space weather propagation website, HFRadio.org, in the mid 90’s; HFradio later spawned SunSpotWatch.com; at press time Sunspotwatch.com is being revamped for the new Solar Cycle 25.

Tomas has contributed to the Space Weather Propagation column in CQ magazine for over 20 years, and for The Spectrum Monitor magazine since 2014. A product of the Pacific northwest, Tomas resides now in Fayetteville, Ohio.

RAIN’s Hap Holly/KC9RP spoke with Tomas recently about Solar Cycle 25. This is the second and final excerpt from their discussion.​

Here is the second part of the two-part interview:

If you missed part one of this conversation, you’ll find it as RAIN Hamcast #56 both on therainreport.com and on the RAIN Hamcast page on YouTube, as well as here: Episode #56, https://www.youtube.com/watch?v=HnuSOXhFELQ.

RAIN Hamcast #58 will post January 8, 2022. Hap Holly/KC9RP edits and produces this biweekly ham radio podcast. It is copyright 1985-2021 , RAIN, all rights reserved. RAIN programming is made available under a Creative Commons license ; you are encouraged to download, share, post and transmit the RAIN Hamcast in its entirety via Amateur Radio. Your support and feedback are welcome on therainreport.com. Thanks for YouTube Technical Assistance from Tom Shimizu/N9JDI. I’m Will Rogers/K5WLR bidding you very 73 and 44 from the Radio Amateur Information Network.

KEEP ON HAMMING!

Footnote: Yes, NW7US misspoke about the time it takes sunlight to travel from the Sun to the Earth. He meant that it takes sunlight and radio waves just over 8 minutes to make that trip…