Time's Up for the Leap Second! A Historic Decision With Implications for Amateur Radio

After more than 50 years of occasionally adding an extra second to the world's clocks, international timekeepers have decided that the leap second has had its day. For radio amateurs, particularly those involved in digital modes, satellite communications and precision frequency measurement, the decision has some interesting implications.

On 15 October 2026, the General Conference on Weights and Measures (CGPM), meeting in Paris, adopted a resolution to move Coordinated Universal Time (UTC) to a continuous time scale.

The decision, made under the auspices of the International Bureau of Weights and Measures (BIPM), means the current practice of inserting leap seconds to keep atomic time closely aligned with the Earth's rotation will be discontinued.

The change takes effect on 20 May 2027.

It marks a significant development in international timekeeping and recognises the increasingly important role that accurate, continuous time plays in modern communications, computing, navigation and scientific measurement.

What Is a Leap Second?

We tend to think of a day as exactly 86,400 seconds, but the Earth doesn't rotate with the precision of an atomic clock.

Its rotation varies slightly because of factors including movements within the Earth's core, atmospheric circulation, ocean tides and changes in the distribution of mass across the planet.

Atomic clocks, meanwhile, measure time using extremely stable atomic transitions.

Since 1972, leap seconds have occasionally been inserted into UTC to keep it within 0.9 seconds of UT1, a time scale based on the Earth's rotation.

A positive leap second creates the unusual sequence:

23:59:58 → 23:59:59 → 23:59:60 → 00:00:00

Since the system began, 27 positive leap seconds have been introduced, with the most recent occurring on 31 December 2016.

The last one was captured by VK7TW - Link

However, recent variations in the Earth's rotation have raised the possibility that a negative leap second, where a second is removed rather than added, might eventually be necessary.

Such an adjustment has never been implemented and presents additional challenges for computer systems.

Why Get Rid of Leap Seconds?

What is the T Index?

Thank you to VK3FS 

If you spend a bit of time hunting or activating POTA or WFF stations, you’ll no doubt know that HF propagation can be fantastic one day, and terrible the next. One day, 10 metres is wide open, and you’re working stations thousands of kilometres away. The next day, the same band is completely dead.

We often look at sunspot numbers, solar flux, and geomagnetic activity to get an idea of what the bands might be doing. But there’s another number that’s particularly useful.

It’s called the T-index.

This Ionosonde image is used in calculating the T index.

So, what exactly is the T-index, what does it tell us, and how can it help us understand HF propagation?

First, a quick refresher, HF radio relies on the ionosphere to refract radio signals back towards Earth, allowing communication over hundreds or thousands of kilometres, but there’s a limit to how high in frequency we can go.

We call this limit the Maximum Usable Frequency, or MUF.

The MUF changes throughout the day, from season to season, and over the course of the solar cycle.

When solar activity is high, the ionosphere generally supports higher frequencies. That’s why bands like 15, 12 and 10 metres can perform so well around solar maximum.

At solar minimum, those higher bands are often much less useful, and we tend to rely more heavily on lower frequencies.

Maximum Useable Frequency

The familiar way of tracking the 11-year solar cycle is through the sunspot number. The solar cycle lasts roughly 11 years, from one minimum to the next. Generally speaking, more sunspots mean greater solar activity and increased ionisation in the upper atmosphere, and that often means better propagation on the higher HF bands. But there’s a catch…

Sunspot numbers don’t tell us exactly what the ionosphere is doing right now

The ionosphere responds to solar radiation, particularly extreme ultraviolet radiation, and that doesn’t always follow the sunspot number perfectly. Geomagnetic disturbances can also change propagation conditions dramatically. So, while the sunspot number is a useful guide, it doesn’t always reflect the actual state of the ionosphere. That’s where the T-index comes in.

To understand the T-index, we need an instrument called an ionosonde. Think of an ionosonde as a radar system for the ionosphere. It transmits radio signals vertically upwards, across a range of frequencies, and measures the echoes returning from different ionospheric layers. From those echoes, we can determine important characteristics of the ionosphere. One of these is called foF2.

Ionosonde vertical radar

foF2 is the highest frequency reflected vertically by the F2 layer

foF2 isthe highest frequency reflected vertically by the F2 layer, which is usually the most important layer for long-distance HF communication. foF2 isn’t quite the same as the MUF for a long-distance radio path, but it provides vital information for calculating that MUF. Ionosondes measure the ionosphere directly, they tell us what it’s actually doing, rather than what we might expect it to be doing.

Over many decades, scientists have collected ionosonde measurements and compared them with sunspot numbers. They’ve established relationships between solar activity and the frequencies supported by the ionosphere. Using those relationships, they can work backwards.

They look at the frequencies the ionosphere is supporting and calculate the sunspot number that would normally produce those conditions. That calculated value is the T-index.

In other words, the T-index is an equivalent sunspot number.

It’s not a count of sunspots. It’s a number that describes how the ionosphere is behaving, expressed on a scale similar to the sunspot number. And that’s an important distinction.

The T-index is an equivalent sunspot number

For example, imagine the actual sunspot number is 100, but ionosonde measurements indicate the ionosphere is behaving more like it would with a sunspot number of 65. The T-index might therefore be around 65. That tells us the ionosphere isn’t supporting frequencies quite as well as the sunspot number alone might suggest.

The reverse can happen too.

The T-index can be higher than the actual sunspot number when measured ionospheric conditions are better than expected.

T-index values commonly fall between minus 50 and plus 200. A low T-index generally indicates that lower HF frequencies are likely to be more useful. This might occur around solar minimum, or during a significant ionospheric disturbance. A high T-index suggests the ionosphere is capable of supporting higher frequencies, making propagation in the upper HF bands more promising.

But remember, the T-index doesn’t guarantee that a particular band will be open. It’s an input to propagation prediction models.

T index compared to sunspot number (SSN)

In Australia, the Bureau of Meteorology’s Space Weather Services operates ionospheric monitoring facilities. Measurements from these stations are used to calculate T-index values. The information feeds into propagation prediction systems.

These propagation prediction systems uses the T-index, along with information about the radio path, time of day and season, to estimate usable HF frequencies. And that’s where the T-index becomes particularly useful.

In conclusion, the sunspot number tells us about activity on the Sun. The T-index tells us how the ionosphere is responding to that activity. For HF communication, it’s the ionosphere that ultimately determines which frequencies will work. A higher T-index generally favours higher HF frequencies, while a lower T-index suggests looking further down the bands. It won’t tell you everything about propagation, but it provides a valuable indication of the ionosphere’s ability to support HF communication.

So, the next time you see a T-index reading in a propagation report, you’ll know what it means.

It’s effectively a sunspot number derived from what the ionosphere is actually doing.

That’s what makes it such a useful tool for HF radio operators.

End of an era

 
I'm really sorry to see Allan letting this go.  On the other hand, if I had a spare couple of mil lying around....

Praying for Pope Leo's Healing

As a cancer survivor myself and a person of faith, I am praying for Pope Leo's full healing as he faces his battle with the cancer demon.  I hope anyone who reads this will join me.  And please pray for cancer sufferers everywhere.

Anderson Powerpoles: There’s More. A Lot More.

by Chris  Warren in Off Grid Ham: My very first HF radio, a Heathkit SB-102 I bought used as a newly-licensed teen ham, had the same problem faced by nearly every radio operator of the era: proprietary power connectors. As I got more absorbed into amateur radio, I collected more equipment and every device had its own exclusive connector. If a cable broke or went missing, I could not simply swap it out or borrow one from elsewhere. Getting a replacement could be expensive or difficult and cause weeks of downtime. This problem was so common it was hardly even thought of as a problem. It was something operators almost unconsciously accepted and endured as the cost of participation. None of us knew it then, but a solution already existed. Anderson Powerpoles, connectors virtually unknown in the ham radio world at the time, would ultimately become the de facto standard.

Edison’s contemporaries.

In 1877, thirty-year-old Thomas Edison already had about 140 patents behind him and was on the cusp of bursting into international acclaim when he introduced the phonograph in December. That same year, two brothers, Albert and J.M. Anderson, founded the Albert & J.M. Anderson Manufacturing Company in Boston, which made electrical products. It started with bespoke machined parts. When electricity adoption took off in the 1880s, Anderson turned its attention to mass-produced switches for industrial applications and electric streetcars. In 1953 Anderson filed a patent for what would eventually become today’s Powerpoles. Ideal Electric bought Anderson in 2001 and ended Anderson’s 124-year run as a stand-alone corporation. The Anderson name and product line still thrive today as a subsidiary of Ideal.

The earliest ancestor of today’s Powerpole is the original 1953 SB connector. Industry was evolving quickly and needed DC power connectors that could satisfy what seems to be an unreasonable list of demands: genderless, solderless, capable of very high current, low resistance, hot-swappable, physically robust for harsh environments and rough handling, easy to install and work with, and cost-effective.

The “British Invasion” music movement. Johnson is President. The Powerpole is born.

The exact pedigree of Powerpoles is not very well documented. We do know Anderson first started using the name in 1965 and was granted a trademark by the U.S. Patent & Trademark Office in 1967. Between then and approximately 2000, the names “Anderson” and “Powerpole” were not in any radio amateur’s vocabulary. Anderson products were used almost exclusively in commercial and industrial applications. In the 1970s and 1980s, another company, Molex, became prominent as a major manufacturer of automotive connectors, and that carried over to ham radio. The term “Molex connector” evolved into a generic name for ham radio power plugs even when referring to other companies’ knockoff versions.

The seeds were planted.

Going into the 1990s Powerpoles were still virtually unknown in the ham universe. But the versatility of the device set it up to be a sleeper hit. Everything that made them excellent for industry also made them an obvious choice for amateur radio. So why wasn’t anyone using them? The answer is unsatisfactory: no one really knows for sure.

One possibility is that, in the 1990s, hams would likely turn to Molex for homemade projects because that was the traditional “go-to” product and any Radio Shack or neighborhood auto parts store sold them. Radio manufacturers in turn just kept doing what they had always been doing. Stasis is hard to break; the “holy grail” of standardization and interoperability was closer than ever, but no one realized it…yet.

The dam breaks.

 

The Solar Cycle Is Changing. Don’t Panic.

 by Thomas (K4SWL)

Several people have asked me lately what it’s going to be like as we move out of Solar Cycle 25 and eventually into the quieter years between solar cycles.

I understand the question and why so many ask.

There’re a lot of new amateur radio operators who came into the hobby during the pandemic. Many of them discovered amateur radio through things like Parks on the Air (POTA), Summits on the Air (SOTA), portable operating, and DXing. They’ve experienced a pretty active solar cycle in the past few years, and for some of them, this will be their first experience with the other side of the cycle.

So what happens when the Sun quiets down?

First, let me be clear, in Douglas Adams terms: Don’t Panic!

We’re not watching the end of amateur radio. We’re simply entering a different part of the cycle.

I’m not a solar physicist or a propagation expert, so I’m not going to even attempt to explain the science behind solar cycles here.

What I can do is talk about what I’ve experienced as an amateur radio operator since 1997, and especially what I’ve learned operating portable and QRP through different conditions.

And I think there’s some good news.

Solar Cycle 25 Wasn’t Always as Cooperative as It Looked

Solar Cycle 25 reached its maximum phase in 2024, according to NASA and NOAA, and we’re now moving into the declining phase of the cycle. We still don’t know exactly when we’ll reach the next solar minimum, but we’re talking years rather than months.

If I’m being honest here, I sometimes felt that we were a little cheated by this solar cycle.

The numbers were good. There were plenty of sunspots, and I experienced some of the best DX I’ve ever worked from the field. But there was also considerable instability, including geomagnetic storms that sometimes seemed to arrive just when conditions otherwise looked promising. I recall several Hamvention weekends in a row when conditions were so poor, groups of us struggled to make contacts even when there was a lot of spotted activity.

That’s one of the things I’ve learned over the years: no two solar cycles are exactly alike, and even within one cycle, conditions can vary enormously.

When I first became licensed in 1997, I remember some periods when 10 meters was absolutely spectacular–effortless, armchair copy transatlantic voice contacts at QRP levels. During the current cycle, I’ve certainly enjoyed 10 meters and the other higher bands, but I don’t feel that I’ve experienced the same consistently spectacular conditions I remember from those earlier years.

That’s just the way it is.

Sometimes the Sun cooperates. Sometimes it doesn’t.

How Did Police Scanners Become a Hobby?

reprinted from ScannerMaster Newsletter

Long before digital trunking, databases, and handheld scanners, curious listeners were already tuning in to hear their communities unfold over the airwaves.

For many scanner listeners, the appeal is easy to understand. You turn on a radio and, without knowing what will happen next, you can hear pieces of real life unfolding around you: a fire call, an aircraft approaching an airport, a railroad crew at work, severe weather reports, public works activity, or emergency responders handling an incident.

But how did listening to public-safety radio become a hobby in the first place? The answer starts decades before the modern police scanner existed. The hobby grew alongside police radio itself, then changed repeatedly as communications technology moved from early AM broadcasts to VHF and UHF, crystal-controlled scanners, programmable radios, trunked systems, digital communications, online databases, and today's sophisticated receivers.

In other words, the history of scanning is not simply a history of old radios. It is a history of people wanting to know what was happening around them, and technology gradually making that easier.

Uniden SDS200

Where are all the hams?