Foundations of Amateur Radio

Foundations of Amateur Radio

Previously I've talked about using radio spectrum monitoring to detect lightning to potentially protect your equipment. This triggered an email from Nick VA3NNW, who pointed out that AM demodulation of "one point twenty-one jiggawatts", is really a red-herring, and indeed it is. Nick went on to point at another approach, which nudged things along.

So, let's start with the herring, not sure about red, I prefer mine fresh, raw, and covered in finely cut raw onion. If you know, you know. If you don't, think sweet fairy-floss. For extra culinary points, pair it with fresh crusty white bread, preferably still warm from the bakery, and slather it in butter. Yum! Beats bacon any day.

Oh, before I forget, pickled herring, lovely, fish aside, in terms of flavour and texture, not in anyway related to fresh herring, just so you know.

Where were we, ah, uh radio.

Before jumping back in, "squelch" is a radio term, it translates to "subdue forcibly", in our case, we're using it to describe a process where radio signals below a certain level, or volume if you like, are suppressed, so you'll hear nothing until the level reaches above the specified level.

This is useful in all manner of scenarios where there's background noise. In amateur radio, squelch is used on VHF and UHF repeaters, but on HF it often means that weak signals don't get heard, keep that in mind next time you start diagnosing a silent radio, ask me how I know.

Anyway, my initial choice of "rtl-airband" as the tool of choice for lightning detection was based on the idea that I could use it to receive a chunk of bandwidth, then automatically apply the in-built squelch to make everything silent when there was nothing but local noise, then when lightning was afoot, noise would suddenly increase above the threshold imposed by the squelch, and I could detect that.

Nick pointed out that there's a better tool for this, "rtl_power", written by Kyle Keen in 2013, which can continuously monitor a whole lot more frequencies, collect them over a set period and intermittently output the power values, which can then be processed.

The tool allows you to specify which frequencies to monitor, how long for and at what resolution. This is extremely useful for exploring activity on a new band. You can use the data to create images of band activity and see what's going on.

I have previously used it to find intermittent interference. Note that it doesn't decode anything as such. It reports relative power levels for the spectrum you're exploring.

As an aside, in the process of building a Docker container for rtl_power, because of course I did, it occurs to me that I often point at Docker as a solution, but I don't think I've ever detailed why.

For starters, it allows you to install and test software without disrupting your local machine, so if you want to remove your experimental installation, you can, and nothing on your computer will be affected.

It also helps with security and permissions, allowing you to define what is allowed and what isn't, helpful if you don't trust the software you're testing.

It allows you to run multiple versions of the same software side-by-side, something which otherwise would create a lot of hard work and head scratching.

If the software you're exploring doesn't exist on your version of operating system, there's a good chance that someone has it packaged elsewhere, Docker will allow you to use that package on your system, or you can build it from source inside the Docker container and not have all the libraries and dependencies clutter your system.

There's a thing called a "Dockerfile" .. essentially a list of commands that document how something is installed. This means that you have a record on how it's done. It means that when it breaks, you have a starting point for debugging, and because it's a text file, you can version control it.

Then there's the ability to automatically start a Docker container on reboot, so you don't have to futz around with "cron" or "scheduled tasks" if you're running that other operating system.

If that's not enough, there's thousands of Docker images just waiting for you to try. I will mention that I tend to build my own images, but you don't need to start there.

So, that's why I use Docker almost everywhere. I'd love for someone to figure out how to run Wayland applications over ssh, but I digress.

Back to rtl_power.

I realised that I don't yet have any data on what lightning looks like specifically. What power levels does an RTL-SDR dongle report when lighting happens, what frequencies should I monitor for the best result, how often should I check, how much data should I collate in each sample .. although we can check every second if we really want to, it seems to me that every minute or ten might be sufficient.

If you have opinions, or better yet, data, to share, feel free to get in touch.

I will end with a disclaimer.

I have only tasted North Sea herring fresh, so you're on your own if you go fishing in a different ocean.

I'm Onno VK6FLAB

Foundations of Amateur Radio

In the middle of the night when insomnia rears its head, there are occasions when an idea sprouts that is still with me the next day. I imagined a spinning globe that shows ionospheric propagation and allows you to navigate around the world and experiment. Think the ionospheric equivalent of windy.com in 3D.

To get to that point, I started off with the Australian Space Weather Forecasting Centre. I was on a roll when I discovered that under "HF Systems" it has a "Global HF" section with "Ionospheric Map", which, curiously enough, shows exactly what you'd expect.

What surprised me was that below the map is an animation viewer that allows you to see the last three days in half hour increments. Excitedly playing with this I found myself locked out and on the phone to the Bureau of Meteorology. I suspect that someone didn't tell the people who configured their content delivery network that users might be loading a gross of images from their website in short order, or two gross, if you also look at the "T-Index Map", like I did.

With no immediate solution on the horizon, I went on the hunt for other sources of maps and discovered the NASA/JPL-Caltech GUARDIAN project, described as near-real-time ionospheric monitoring software for natural hazards warning.

Their website has a limited archive of daily videos showing how the ionosphere changes, which was exciting until I discovered that my computer wanted to download each one, rather than play them in the browser, so making lemonade, I downloaded all of last month, thank you "curl", used my favourite video editing tool, "ffmpeg", to combine them, then uploaded the result to my VK6FLAB YouTube channel for our enjoyment.

What's fascinating to me is being able to see, for the first time, just how the ionosphere changes throughout the month. You can see where there's regular solar activity and where exceptions occur. I'll note that there's a few gaps, I suspect that the software behind the scenes at JPL had some outages, but what's there is what was available.

Now for the interesting stuff.

This data is not created by something monitoring in space at L1, or in orbit around Earth, it's created by ground stations scattered around the planet. GUARDIAN is based around the Global Navigation Satellite System or GNSS. The project, to give its full name, the GNSS Upper Atmospheric Real-time Disaster Information and Alert Network, uses the radio signals from the four navigation constellations, GPS, Galileo, BDS and GLONASS.

Name aside, the project has some really interesting goals; objective one, the result of which you can see in the video or on the website, is to allow users to explore ionospheric perturbations, in other words, you can see how the ionosphere changes over time.

This is achieved by some cool radio phenomena, specifically, two different GNSS carrier frequencies will show phase change as well as alter what's known as "pseudorange", the apparent distance between a satellite and a receiver, affected by among other things, the "Total Electron Content" or TEC along the signal path. What that means is that the satellite signal is directly and proportionally affected by what's happening in the ionosphere. As an aside, this phenomenon can impact your mobile phone navigation, more on that in a moment.

In other words, if you can measure how the radio signals from a navigation satellite change, you can calculate what the ionosphere is doing along a direct line between the transmitter and receiver, in response to natural and man-made events on Earth.

If that's not enough, remember, this is just the first objective, the second one is to automatically detect those changes, the third objective is to characterise potential natural hazards.

Lots of words to say that the aim is to detect events like geomagnetic storms, tsunamis, earthquakes, volcanic eruptions, thunderstorms, not to mention explosions and rocket launches.

You can explore some historic examples on the GUARDIAN website at JPL. You can also compare the current planetary geomagnetic index with what comes out of the GUARDIAN project.

At this point you might wonder what the ionosphere has to do with tsunamis? As it turns out, a whole range of natural and man-made hazards impact the ionosphere due to significant displacements of air at the surface, and the project used historic hazards and ionospheric data to link the two, and in July 2025, the magnitude 8.8 Kamchatka earthquake and associated tsunami was automatically detected 30 minutes before it reached the coast of Hawai'i.

If that doesn't hit you in the Wow spot, during my research I came across several projects that explore the use of mobile phone GPS receivers as sensors. There's billions of those, so potentially, planetary coverage. For comparison, in 2022 there were 80 Global Differential GPS ground stations powering GUARDIAN, today the network has over 200 sites.

Google Research published an article in 2024 using the same methodologies to measure the ionosphere using millions of mobile phone GPS receivers, effectively doubling coverage. Their article in Nature goes into detail which devices were used and how, essentially, using anonymised and privatised Android location data.

From an amateur radio perspective, it's interesting to note just how variable and dynamic the ionosphere is and what types of phenomena affect it. I also wonder if my PlutoSDR might be used to have a go, since we're talking about radio frequencies around 1.1 and 1.5 GHz.

All the more reason to get on-air and make some noise and excite the ionosphere and a receiver somewhere on Earth.

I'm Onno VK6FLAB

Foundations of Amateur Radio

Over the weekend I had the opportunity to participate in two completely different community events, one aimed at an amateur radio audience, the other at the general public.

Every year, several of the amateur radio clubs in my area hold their individual swap meet, where the aim of the event is to bring amateurs together and to use it as a social fund raising event.

Some jokingly refer to it as a junk library where one person's junk is the next person's treasure, only for it to turn up on their table the next year.

This particular event is held inside what can best be described as a large high school gymnasium. Mind you, my experience with high school facilities predates my amateur radio birthday by quite some decades, so, a building with a wooden floor, basket ball court and other sports markings on the floor.

Mind you, this building has a canteen, a foyer and a big parking lot, so it only resembles my reminiscing in abstract ways; I grew up with bicycles and snow - from time to time, not cars and sun.

Individuals and organisations can book and pay for one or more tables to display their wares. There's a raffle, growing in scope each year, the universal bloke yelling unintelligibly into a microphone, signal unreadable with an RST of 2 and 9, and there's food for sale with drinks, and tables to sit and chat.

It had been a while since I'd last attended and with it came memories of setting up the local news broadcast team so we could do a live edition of the weekly amateur radio news, hard work, lots of planning and very rewarding, also good practice.

This year the entry price went up, the event was down on numbers and there were half a dozen or so empty tables. I'm guessing these were booked and the participants didn't turn up, but I don't know. For the organising club this must have been heartbreaking. I know for me, it was disappointing.

That said, it offered the opportunity to catch up with plenty of friends and acquaintances, new and old amateurs, people who knew me before I knew them, the typical face to face experience that you might get from accidentally being in the same place at the same time.

If this description leaves you with the sense of longing, you know how I felt when I drove away to travel to the other side of the city to attend the second event.

Organised by a local council as an Open Day, it brings together a bunch of different organisations to a central location, augmented with food vans, sausage sizzle, ice-cream and coffee, the whole thing was outdoors.

One of the organisations represented was a different amateur radio club, based at the site, with a small display and the ability for people to talk, have a sticky beak and mosey on.

Interestingly, the kids attending were given a treasure hunt sheet with questions about each of the organisations there, including two questions about the amateur radio club. Funnily enough, a local community radio station is also on site and it too had questions in the treasure hunt.

This dynamic allowed kids and their parents to approach the club and ask silly questions and the confusion between "amateur" radio and "community" radio allowed for more information to be shared with more laughter to go around for all.

The sausage sizzle, a local Rotary club fundraiser, was a hit with a steady stream of people lining up for a bite.

This is the second time this event has been hosted and both times I spoke with many people who were not radio amateurs, people who had electronics projects in need of guidance, and the odd local politician, some more than others.

Over the years I've attended plenty of amateur radio events and while there's a place and need for each of them, I have to say, talking to an interested kid about a homebrew quadrifilar helix antenna has to my favourite experience.

So, why am I talking about this, you ask?

It's pretty simple. Ask yourself, does a particular amateur or amateur adjacent event spark joy, or does it represent an opportunity for reflection and renewal?

Do we need another swap meet, I think locally we have at least five across the year, or could you do a fundraiser with a bingo night in a pub? What about an exhibition, or an auction? A BBQ or a breakfast? A course or a camp out? Have you considered a shack open day or a school visit show and tell? What about joining forces with other community groups and clubs?

What could the ultimate event bring and who would you like to see there? What would they take away and what resources might you need to pull it off?

I'm Onno VK6FLAB

Foundations of Amateur Radio

The other day I heard a thunderclap and as is my Pavlovian response, immediately ran to my shack to disconnect the antennas from their respective transmitter and transceiver. I added a diary entry to my phone to note that I'd disabled my WSPR, or Weak Signal Propagation Reporter beacon, which generally runs 24/7. A few hours later I remembered that my beacon was off and I returned to put it all back in working order.

That's not always been the case. From time-to-time I've managed to turn off the beacon and forgotten to re-enable it, once for months. Same with my main radio, which at one point was disconnected from its antenna, taking a good half hour of stressful troubleshooting to discover one memorable Saturday morning, when I tried to set-up for my weekly net. Now it's the first step, before I turn on the power supply.

I've mentioned in passing that lightning protection and grounding requirements are not globally uniform and I'm purposefully refraining from advising you how to do this in your shack. When in doubt, talk to your local community and a licensed electrician, mainly because there's plenty of poor advice around that could result in your applicable household electrical regulations being breached.

Back to my shack.

Wouldn't it be cool if I could automate this, something like a remote controlled relay, preferably wireless so stray RF doesn't make it into the wrong circuit. Switching aside, it occurred to me that I'd also need some way of detecting lightning to trigger this system, you know, disconnect the antennas, turn off the beacon, then reverse the process when all is clear.

Speaking of automation, a few years ago I purchased a beautiful electromechanical coax switch. I'm still trying to discover how to drive it and I'm not game to power it with the risk of letting the magic smoke out, so if you have specific details for a K&L 6LMP-28-F-N-I-TTL six position coax switch, a data sheet would be wonderful, get in touch, cq@vk6flab.com is my email address.

Searching for lightning detectors reveals a boatload of circuits and tools. There's websites galore, an active community surrounding "blitzortung.org" with an absolutely mesmerising homepage, and plenty of other projects to play with. One thing I noticed was a distinct lack of SDR, or Software Defined Radio implementations. The number isn't zero, but I didn't find any turn-key solutions.

One recurring theme, other than arguing which frequency to tune to for the best result, was the notion that a simple AM radio receiver could be used. The idea often promulgated is to tune between stations and to listen for clicks and pops. It occurred to me that using an SDR as an AM receiver is pretty much the first thing you do after plugging it in.

Combining these ideas, it seems obvious, of course it's unlikely to be, but you know, why spoil the fun, to do this within the 2.6 MHz bandwidth of an RTL-SDR dongle which might actually detect some wideband RF, the signature of a lightning strike.

That started me down the path of splitting a signal in GNU Radio, routing it to multiple AM decoders, looking for peaks, all that fun, when I realised that I know of a tool that does pretty much all of that, "rtl-airband". With a simple text file to describe the frequencies you want to monitor, decode, apply squelch, mix, position and route, most of the job is done.

When it's running, you might have just created a lightning detector to start your journey on this road, using stuff you already have. I intend to create an example configuration file for exactly this purpose, perhaps even a script to generate it, and I'll publish it on GitHub.

Word of warning, based on the number of tools alone, the rabbit hole is deep.

I'm Onno VK6FLAB

Foundations of Amateur Radio

During the week I was shown a photograph of a chalkboard standing on the sidewalk with one of those "Thought of the Day" quotes on it. Credit aside, since I've been unable to confirm it, despite multiple reverse image searches and attempts at author attribution, the sentiment stuck with me and the more I think about it, the more it resonates and this being radio, that works on so many levels.

We proudly refer to our community as "amateur radio", hold it up as a badge of honour and tell everyone we know about it. Curiously, when you look in the dictionary, you see a litany of words with less than complementary connotations, like "freak", "dabbler", "crank", "neophyte", "inexpert", "unprofessional", "second-rate" and plenty more.

In essence the word "amateur" is contrasted with the word "professional" and our community comes out looking worse for wear.

I'm pointing this out because the experience is insidious. I've told the story of me attempting to report local radio broadcast interference to the regulator when I came upon an investigator who asked how I knew about interference. I explained that I was a licensed amateur. His response was: "I am a Professional". I can still hear the capital "P", now well over a decade later.

It's also interesting when you talk to people outside the community who don't really get what it is that we do. Often they'll think that you're not serious about this and will unthinkingly dismiss your interest and pursuit, because it has the word "amateur" in it.

So, what of this and the chalkboard?

Here's the quote.

"You say 'amateur' as if it's a dirty word. 'Amateur' comes from the Latin word 'amare' which means 'to love'. To do things for the love of it."

As you might imagine, I went hunting to confirm this sentiment.

It turns out that the word "amateur" comes from French "amateur", meaning, "person who cultivates an art or science for their pleasure", in turn that comes directly from Latin "amator", meaning "lover, one who loves", which stems from "amare", "to love". As an aside, "dilettante" from Italian "dilettare", comes from "to delight".

It appears that once respectable pursuits in arts and science lost ground against professionalism and we ended up with a growing gap between formal and informal which increasingly is understood as dangerous, rather than charming.

I think it's time to reclaim "amateur" and take "to love" to heart in our community.

So .. "radio, for the love of it". That's what we do, what we are. And to be honest, I think that really says everything we need to remember.

I'm Onno VK6FLAB