Foundations of Amateur Radio

Onno (VK6FLAB)
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Starting in the wonderful hobby of Amateur or HAM Radio can be daunting and challenging but can be very rewarding. Every week I look at a different aspect of the hobby, how you might fit in and get the very best from the 1000 hobbies that Amateur Radio represents. Note that this podcast started in 2011 as "What use is an F-call?".

  1. 5d ago

    What does I/Q have to do with anything .. time to poke the bear.

    Foundations of Amateur Radio More than seven years ago I first uttered the phrase: "I/Q", and palmed it off to future me with "we should look at that [at] some other time". Since then I've referred to it several more times and all but vaguely waved my hands about. Today I'm going to poke the bear called "I/Q" and to be clear, this is a signal term meaning "In-phase and Quadrature" not "Intelligence Quotient". Most explanations I've seen jump into the mathematics of this concept, but none ever spoke to me at any fundamental level. Ultimately, a simple phenomenon underlies all of the magic that hides behind the concept of an "I/Q" signal. So, let's explore. When you digitise a signal, you essentially record a voltage each time you take a sample, which can happen many millions of times per second. The aim of this process is to create a digital representation of an analogue signal for the purpose of doing something with it, like decode it. This process happens in billions of devices across the planet. In its simplest form a signal is a sine wave that starts at zero and oscillates between one and minus one. You might recall that a sine wave is associated with degrees in a circle and that each angle shares the same sine value with another. For example, the sine of 30 degrees and 150 degrees are the same, 0.5. This means that the value of 0.5 could represent 30 degrees, but it could also represent 150 degrees, which means that our digital representation of a sine wave is incomplete. A cosine wave has all the attributes of a sine wave. If you were to draw them together you'd notice that its shape is identical but shifted in time and because we're talking about angles, it's delayed, or phase shifted, by 90 degrees. What if you sampled both waves .. at the same time? Doing so removes all angle ambiguity. By convention, the I in "I/Q" represents the In-Phase or cosine signal and the Q in "I/Q" represents the Quadrature or sine signal. And while we're in the business of naming things, signals that are separated in phase by 90 degrees are "in quadrature". So, what does this buy you, or why does it matter? As it happens, you can represent any radio modulation as an I/Q signal. While until now I've talked about digital signals, all this applies to analogue signals, and it applies to transmitted signals as well. Final piece of the puzzle. To create any modulation from an I/Q signal, all you need is to vary the amplitude of each of the I and Q signals, which means that you can do this with analogue circuits as well as in software using cheap hardware. If you've looked at this phenomenon before, you might wonder why I haven't said anything about "complex numbers" yet and if you haven't, those words might scare you off. The concept of "complex" really refers to the idea of embracing two numbers within, for example, it can represent an arrow with a length and a direction. Our I/Q signal, which consists of two numbers for each sample, can also be represented as a complex number and it's one of several ways to represent an I/Q signal. One final comment. You can create an I/Q stream from an RF signal by mixing it with a so-called quadrature mixer, one that outputs two signals, 90 degrees out of phase. Now, I will add that I had porridge for breakfast and I'm operating on five and a half hours of sleep, but I'm fairly confident that I covered the foundations of an I/Q signal in less than four minutes and I even had time to tell you what I had for breakfast. For my next trick, I'm going to tell you how to make pancakes with just a banana and an egg. I'm Onno VK6FLAB

  2. Oct 10

    How to point an antenna without moving it?

    Foundations of Amateur Radio The radio telescope at Dwingeloo in the Netherlands recently promoted an Open Day where visitors were treated to tours and live demonstrations. One video caught my eye, a 2.4m dish on a remote controlled azimuth and elevation mount that scanned the entire sky every fifteen minutes and afterwards created a map of the captured radio signals. Having carried a dish that size around Australia for a couple of years, I was in awe. After I figured out how you'd create the map I was grinning. Essentially your program moves the dish through all the elevation and azimuth combinations while recording RF for each. Mapping becomes the process of drawing a representative dot at each location, and in doing so you have the basics of a radio telescope. It gets better. Imagine two identical antennas, side-by-side, receiving the same signal head-on. The combined antenna signals are said to be "in phase" and will reinforce each other, resulting in an amplified signal. However, if the source is off-centre, its signal arrives at the closest antenna slightly before the other and that delay, or phase, between the two will cause their combined signal to appear weaker or attenuated, because they're no longer entirely reinforcing each other. These signals are said to be "out of phase". If you were to add a slight delay to the earliest signal, or said differently, change its phase, the two would again appear to arrive at the same time, be in phase, and again reinforce each other. In doing so, you've essentially modified the focus of the antenna toward the off-centre signal by adding this delay or phase shift, and so by modifying the phase, you can shift the antenna focus. Just so we're clear, there's no actual moving parts here, we're electronically adding a phase shift to adjust the delay between antenna signals. In addition to changing the phase of any of the antenna signals, you can alter how much each antenna contributes to the combined signal and when you do that, you'll change the radiation pattern of the system. You might ask: "Does all this apply to receive or transmit antennas?", to which I'll say: "Yes". This arrangement of antennas is called a "phased array" and was first demonstrated as a three element array in 1905 by Nobel laureate Karl Ferdinand Braun, who shared the 1909 Nobel Prize in Physics with Guglielmo Marconi "in recognition of their contributions to the development of wireless telegraphy". While I've been talking about two antennas side-by-side, you can orient as many antennas as your budget allows in what ever shape you require. For example, the Square Kilometer Array being constructed around the corner from me, well about 550 km away, is planned to have a total 131,072 log-periodic-dipole antennas, arranged in 512 groups with 256 antennas each. Laid out in a grid, a phased array can change focus in any direction, and with it, the radiation pattern changes. By manipulating phase for different elements, you can create multiple points of focus from the same array, and while we're at it, since all this is done electronically, you can shift focus in nano even micro seconds, rather than multiple seconds associated with physical movement. I've been using the word "signal", because while this phased array phenomenon applies to RF, it also applies to sound, as-in sonar, and light, as in LiDAR. In addition to radio astronomy, it's used across plenty of other fields including weather radar, space communication, broadcasting and even amateur radio. You'll find phased arrays in autonomous vehicles and adaptive cruise control, even your Wi-Fi router and mobile phone. In amateur radio, we tend to use fixed rather than variable phase modification when we combine dipoles, Yagis, and even verticals in the venerable four-square antenna. If you want more detail in a thoroughly accessible form, I can recommend Marshall Bruner, who has a wonderful YouTube channel describing and animating many different fundamental aspects of radar technologies like this. You'll find his "Phased Arrays - Steering and the Antenna Pattern" on my YouTube channel in the "Videos for more inspiration" play list. I'm Onno VK6FLAB

  3. Oct 3

    Bald Yak 21: When you need to travel to Pluto and back

    Foundations of Amateur Radio I recently expressed the notion of using a PlutoSDR as a replacement for an oscilloscope, a spectrum analyser, and perhaps even a vector network analyser. I can add signal generator to that list and you get the notion that this one device might replace a bunch of tools in your shack. So .. I set out to come up with a minimum viable product to see what I might discover. There are days when you get out of bed with a spring in your step, only to end the day exhausted and thoroughly defeated. Given the chance, the next day, you get out of bed and try again. Fortunately for me, I have a full head of hair and my yak shaving barely made a dent and as a bonus, I learnt something, which is always nice. The short version is that you should use a USB Y-adaptor or splitter to ensure that your PlutoSDR has enough juice to power a USB Ethernet dongle. That statement alone is worth at least a combined fifteen hours of Yak Shaving. Without this turning into a PlutoSDR specific troubleshooting saga .. for reasons I don't understand, plugging the power supply into the Pluto power socket and a USB Ethernet dongle into the accessory port doesn't work, but plugging both into a Y-adaptor and that into the accessory port makes all the blinkenlights work, even those on your network switch. As I said, fifteen hours. So, what does this buy me, other than an appreciation for subtlety? It gives me network access to my PlutoSDR, which makes it possible to connect to it using GNU Radio running on a different computer, which then allows me to experiment. Before starting this side-quest into connecting to my Pluto, I went on the hunt for some example code. Jon Kraft, who is a senior staff Field Applications Engineer at Analog Devices, whom I came across first on YouTube, where he's been playing with beam-forming and other nifty RF phenomena, also has a GitHub repository with some PlutoSDR examples for use with GNU Radio. These examples are pretty straight forward, essentially connecting to a PlutoSDR, setting the centre frequency and extracting a bunch of RF and visualising it. Essentially what you'd want in some testing gear. After playing around for a bit with Jon's examples, I'm able to see radio spectrum, across the network, on my screen, using GNU Radio. Eagle eyed observers will note that I already achieved this with an RTL-SDR dongle and indeed I did. A few differences. I have access to a frequency range between 70 MHz and 6 GHz and I have the ability to transmit. Of course this doesn't yet get us to the point of replacing test gear, but I think it paves the way to a collection of experiments that will. If you're unfamiliar the Bald Yak project aims to create a modular, bidirectional and distributed signal processing and control system that leverages GNU Radio. It's called Bald Yak because by the time I'm done, the Yak is likely well and truly shaved. So, my oscilloscope and other tools adventure is an example of what Bald Yak might facilitate. In radio terms there's very little to distinguish this type of tool from a transmitter running your favourite mode, and it allows me to experiment with a different radio back-end. Full disclosure, I'm still trying to work out how to do this using SoapySDR, because if you remember, that will allow me to connect to any device, for now, this is using a PlutoSDR source and sink. While we're on the subject of Soapy, I did start digging into SoapyAudio and the idea of making a more universal module that will allow amateur radios for both receive and transmit using Soapy, but I came unstuck when I discovered that the example plug-in code is essentially an empty file with the programming equivalent of "here be dragons". I'll likely come back to it, but not today. Now, I do need to make some disclaimers because I know that there are plenty of caveats I've glossed over here. I think much of it is covered with the word "calibration". A PlutoSDR is not a laboratory grade device. It isn't calibrated in any way, it's likely unstable, connectivity across the network is likely to be choppy, and plenty more issues like this. In other words, if you come away from this thinking we're going to be building something to replace measuring gear you can buy for the price of a small car, you're going to be disappointed. However, if you're here for "Wow, cool, you can do that, for a couple of hundred bucks?", you've come to the right place. Also, I'm aware of the Analog Devices "IIO Oscilloscope", that it's extensible, and even has a plug-in specification, but what it doesn't have is GNU Radio, which is I want to use for a whole lot of reasons, least of which that it isn't hardware dependent. As I've said before, when I have something to show-and-tell, you'll be the first to know. In the meantime, you could do worse than look for Jon Kraft's GitHub or his RadioKrafter YouTube efforts and have some fun yourself, that's Jon, no "H" and Kraft with a "K". I'm Onno VK6FLAB

  4. Sep 26

    Getting Kitted Up with Amateur Radio

    Foundations of Amateur Radio Launched into your amateur radio adventure you're faced with figuring out what you need to fly. If you have a web browser, you can start listening to a massive array of online radio sources .. today. Beyond that, a handheld radio is often the first purchase for a new amateur, more often than not followed by the acquisition of a more advanced radio and associated paraphernalia, antenna, coax, power supply and the like. A video of forging the "Most Iconic Swedish Axe", by Torbjorn Ahman, a Swedish Blacksmith, started off with making several tools, before the axe forging itself got underway. It reminded me that in the amateur radio community we often talk about radio with rarely any mention of any toolkit. Spend six seconds thinking about this and you'll likely come up with a soldering iron and a multimeter as your next investment, but what happens after that? While not universal, truth be told, my soldering iron has very little use, though half a century ago it was probably essential. My multimeter gets more use, even though it really doesn't do any radio tricks. Its most used feature is continuity testing. One proper bit of test gear is an antenna analyser that we use most times anyone plays with antennas. Several years ago, I was given a lovely NanoVNA which gets a regular workout though calibration is a bit cumbersome. I was also given an inline power meter that provides all manner of battery health information. I take it to every portable operation. Gadgets aside, the tools I use more than all of these put together are a quality wire cutter and an Anderson Powerpole crimper with all the connector housing colours. There's also a comprehensive set of screwdriver bits, enabling access to more equipment than I have time to investigate. A 15 Watt dummy load, good to 150 MHz, gets regular use, and to complete the picture, underneath my desk is a HP 606A signal generator that I'm scared to restore. Last time I went near it, I managed to trip the house RCD for reasons I still don't understand. There's other stuff in boxes and drawers, but I clearly don't use them enough to come to mind. Unremarked is my computing infrastructure. Until a couple of years ago that consisted of a 27" iMac, vintage 2015. Expanded to 64 GB of RAM, it ran all my software using VMware, sometimes a dozen or so virtual computers simultaneously. It died in 2024 when the power cord managed to short itself on my portable desk, yes, that too tripped the RCD. Although I didn't lose any data, due to a perfect storm of incompatibility, it's been nearly two years before I found the beginnings of a replacement, a small form factor Lenovo IdeaCentre with 32 GB of RAM running Proxmox. If I was made of money, I'd probably find space for an oscilloscope and a signal generator, perhaps even a proper network analyser, but truth be told, most of my adventures these days are in the software realm. That's not to say that there is no place for such gear, just that I suspect that they'd feel overwhelming rather than something I'd grab to solve a problem. That said, regular posts by Ismo OH2FTG about resurrecting all manner of broken testing equipment revealed to me that a surprising number of these tools are essentially a computer with an operating system, running some custom application that presents itself to the user via a display. Apparently you haven't lived until you see a Windows boot loop on your Agilent oscilloscope. I suppose I shouldn't be surprised, the "HP 8920A RF Communications Test Set" that I played with a while back runs what looks like a version of DOS, which comes on ROM chips, according to HP taking 2 hours to replace for a firmware upgrade, and each of its in-built tests is a program written in HP Instrument BASIC. This morning I walked into my office and spotted my PlutoSDR on my desk. If you're unfamiliar, a PlutoSDR is a little box, blue, because of course colour matters, has two SMA coax connectors on one side and two USB sockets on the other side. One antenna port is marked "Rx", the other "Tx" and by connecting the two together, you can create a transmission and then receive it. While that sounds completely useless, it's the exact same set-up as any number of bits of test equipment, to be clear, normally you have something you're testing connected between the ports. Combine that with a connected computer and you have the makings of some fancy test gear, capable of 70 MHz to 6 GHz. Since it's all Open Source, you can write your code in your language of choice. Of course I'm not the first person to come to this point. There's tools around for making this reality, implementing oscilloscope, spectrum analyser and plenty more. I am already imagining what I might achieve with GNU Radio. While there's plenty of room for soldering irons in our community, I think it's also worth considering what software might help in your toolkit. I'm Onno VK6FLAB

  5. Sep 19

    Monitoring radio spectrum around you

    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

  6. Sep 12

    Global Ionospheric Maps

    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

  7. Sep 5

    It's all in the community

    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

  8. Aug 29

    Lightning in a bottle

    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

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About

Starting in the wonderful hobby of Amateur or HAM Radio can be daunting and challenging but can be very rewarding. Every week I look at a different aspect of the hobby, how you might fit in and get the very best from the 1000 hobbies that Amateur Radio represents. Note that this podcast started in 2011 as "What use is an F-call?".

Information

  • Creator
    Onno (VK6FLAB)
  • Years Active
    2015 - 2026
  • Episodes
    606
  • Rating
    Clean
  • Copyright
    ℗ & © 2015 - 2026 Onno Benschop
  • Show Website
    Foundations of Amateur Radio

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