Foundations Of Amateur Radio

Foundations of Amateur Radio It broke and now what? Imagine you're a new amateur. You've woken up in the middle of the night because insomnia seems like a good way to use amateur radio as an excuse to get on air and make some noise. You turn on the radio, key up the transmitter and the next thing you know it's dark. The breaker that powers your radio popped and there's no more glow coming from the hardware that's warming up your shack. You get up, reset the breaker, tighten up your dressing gown and switch on your gear. You sit down and key up. Pop, darkness. What do you do next? The first thing to realise is that there is something wrong. That might sound obvious, the radio just tripped the breaker and it went off, but sometimes it's not that obvious, sometimes there's something wrong, but it's not nearly as clear as light and dark. For example, you might key up and the SWR goes high. You might not even notice if your radio is set to monitor the power output, or the automatic gain control that indicates

Foundations of Amateur Radio What's in a word? When you join a new community you learn very quickly that each community has its own language. A word in one community has a different or extra meaning in another. For example, the word "Snowflake" in one community might refer to a phenomenon related to water and freezing, in another community it refers to a person who is sensitive, easily hurt and offended. If you mix the two meanings all manner of misunderstanding ensues. In amateur radio, one of those words is the word gain. This word is used in many different aspects of our hobby, but today I'm going to focus on one specific use of it, in relation to antennas, antenna gain. This mythical property of an antenna is often used as a way to distinguish two different antennas and in advertising terms, bigger is better, more gain, more better. I'll skip over the marketing shenanigans related to artificially making the number larger by comparing apples and pears, or dBi and dBd and move on to how gain comes abou

Foundations of Amateur Radio How far can I talk on radio? A question that regularly hits the enquiring minds of people who are not (yet) radio amateurs is one about distance. For both amateurs and those who are not ye) inducted into our community the concept of distance speaks in ways that other parts of our hobby don't. It's a simple concept, between these two points, how far can you talk? The interesting thing to me about this phenomenon is that distance isn't a metric that we as amateurs use for anything other than calculating repeater coverage and then only for frequencies that are line-of-sight. If you're not an amateur then this might be unexpected or even illogical. Let me give you two questions: How far can you talk in amateur radio? - and - How far does light shine? If you're an amateur you'll know that those two questions are pretty similar, if not identical for certain frequencies, but if you're not, then these two questions appear completely unrelated to each other. Let me start with someth

Foundations of Amateur Radio Recently there was a discussion on social media about the legality of various types of transmissions. Before I get into the specifics, it's worth looking at some of the rules around this. I will point out that this isn't exhaustive, but it gives you an idea of what I'm talking about. In Australia, the rules about this are encapsulated in the Radiocommunications Licence Conditions Determination, referred to as the LCD. It essentially says that you must not operate an amateur station to transmit signals that are encoded for the purpose of obscuring the meaning of the signals, except for amateur satellite and repeater command and control purposes or emergency service operation and training. In the United States, the rules are covered under the FCC rules, Part 97 Amateur Radio Service. It says that you may transmit using a digital code who's technical characteristics have been documented publicly. It goes on to prevent such transmissions for anyone communicating with a country that

Foundations of Amateur Radio What would you do if you found that at random times your garage door opener didn't work, or the Wi-Fi network dropped out, or you couldn't switch off a light with an RF controller? That's the position I found myself in and the times at which this was happening were madly unpredictable. One moment everything would work fine and the next all things radio would just stop. As a radio amateur you're likely nodding your head and thinking, radio interference, there's some direction finding in your future. Sure enough, that's the case, but before that, I needed to know if the interference was random, if it had a particular pattern and how widespread it was, since it seemed to impact multiple different devices using different parts of the radio spectrum. Initially I focussed on getting a recording of it. I turned on my radio, tuned it to a 2m frequency and recorded the noise. Only one problem. There was no noise. All I could see was an extreme signal strength, but it wasn't showing up

Foundations of Amateur Radio For some time I've been explaining how some of the internal workings of a Software Defined Radio operate with a view to getting into the nitty gritty of the why and the how. This exploration is happening within the context of a world where there are countless choices for selecting a radio to match your budget. Increasingly that selection process starts with a simple question: Should I purchase a Software Defined Radio or a traditional radio? This is not a new question, previously it may have been: Should I select a radio with transistors or one with valves? Presumably the same happened when your ancestors faced a choice to buy a new car or update their horse and carriage. Of course I'm being flippant, but the point stands, as things evolve, choices change. Today we don't know what comes after the Software Defined Radio that we currently know, but it's likely to force the same selection on future generations of radio amateurs. So, if you're in the market for a new radio, what th

Foundations of Amateur Radio From time to time our hobby changes. While the idea that we're all a bunch of old men playing with spark gap transmitters, or using strange noises to the annoyance of others, the reality of amateur radio is markedly different from that stereotype. The changes we experience come from many different sources. As amateurs we're always trying something new, inventing things and building stuff. That type of change is integral to the hobby and in many ways it's why our community exists in the first place. Other changes are external. A new product arrives into the marketplace and we gleefully take possession of a new gadget. That in turn creates other changes which are incorporated into our day to day life as amateurs. A more structured change happens when the regulator makes a proposal, instigates a new rule, enforces an old rule or does something else that affects us. In the time I've been an amateur, I've seen changes happen that originate from the regulator that both benefit and

Foundations of Amateur Radio It seems my analogy with milk glasses hit a nerve when I explained some of the inner workings of a simple Analogue to Digital Converter, also known as an A/D Converter or ADC as part of my exploration into Software Defined Radio. Thank you for your comments, suggestions and corrections. I did make an error when I said, grab eight of them and you'll have a byte, I'll get into that. Thank you for pointing it out. With my milk glass analogy, if you missed it, without naming it, I drew a picture explaining how a flash or direct-conversion ADC works. Briefly, I said that if you were to pour milk into a glass and continued to do that until you ran out of glasses or milk, you'd have converted a signal into bits. I also covered how a partially filled glass was neither full nor empty and if you ended up with milk all over the desk you wouldn't know how much there was. In terms of electronics, how does this actually work? In essence you're comparing a reference voltage against your in

Foundations of Amateur Radio One of the unsung hero components of a Software Defined Radio is the A/D or Analogue to Digital converter. Its job is to convert the analogue signal that's coming in via the antenna into a digital signal that is processed by software. I've talked about the difference between analogue and digital before and many explanations talk about converting things into zero and one. There are a few steps before that. Imagine a row of identical glasses, let's say eight. Grab a jug of milk and pour it into the first glass. Keep pouring until it's full. Now do the same to the second glass, rinse and repeat until you either run out of milk, or run out of glasses. You now have either a row of glasses full with milk and some spilled all over your desk, or you have some full glasses and some empty ones. Now if you were to mark a one on your logging paper for every full glass and a zero for every empty glass, you'll end up with a row of zeros and ones. Essentially you've converted an analogue si

Foundations of Amateur Radio Today I'm going to go sideways to move forward. In amateur radio we consider circuits, components such as transistors, inductors, capacitors, crystals and how they're connected to each other. The framework in which that exists is embodied by the field of electronics and how these components can be mixed together to shape a radio that you can build or buy. In a software defined radio there are electronics and components to be sure, but the bulk of the work is done in the field of software and today I'm going to look at that. Computers surround us, in our work place, in our home, on the street, in our hospitals, across our society. Each of these devices is running a thing called software, as opposed to hardware - a physical thing, software is intangible, in much the same way as your date of birth is intangible. You cannot hold your birth date in the air and point at it. You could write it down onto a piece of paper and point at the piece of paper that has the date on it, but you'

Foundations of Amateur Radio Over the past few weeks I've been describing how some of the fundamental concepts of software defined radio work and how some of these operate and interact with each other. You might think of some of these ideas and technologies as unrelated to the hobby of amateur radio, or not relevant to traditionally built radios. Nothing could be further from the truth. Before I go on, I've been trying to find more elegant terms to distinguish between radios built with mostly software and those built with mostly hardware, and I use the word mostly, because a traditional radio like my Yaesu FT857D has software on board and similarly the software defined radio Flex 6600 has traditional components inside the box. For convenience, until I find a better distinction I'm going to refer to these as hardware radios and software radios. When I refer to a hardware radio, think Yaesu FT857D, when I say software radio, think Flex 6600. Back to the topic at hand. The techniques used in both disciplin

Foundations of Amateur Radio As a quick recap of what I've discussed before, a Software Defined Radio is a tool that essentially measures the voltage at the base of an antenna system and sends that to a computer for processing. The faster you measure, or sample, the better the representation of what's coming in via the antenna. The traditional view is that you need to sample at least twice as high as the highest frequency you want to represent. You may also recall that an antenna system doesn't just receive a single frequency, the one your radio is tuned to, but all frequencies. So, if you need to build a software defined radio from scratch, your first question might be: What do I want to listen to?, followed by: Which sample rate do I need? If we were to answer the first question with HF, say up to 50 MHz, the answer would be something like a sample rate of 100 MHz, so you can capture any signal up to 50 MHz. So, twice the highest frequency as the one you care about, that's the short way of waving your

Foundations of Amateur Radio If you were asked to make an image of the Sydney harbour bridge and only use four dots, the viewer might struggle to determine what was the bridge, the sky, the water and the Sydney Opera House. Regardless of the number of colours available to you, the number of dots would not be enough information for most people. You might have a nice piece of art on your hands, but it might be ineligible for the Archibald prize. Even if you were allowed many colours, and just four dots, figuring out if the blue dot was water, sky, or the background of the Australian flag on top of the bridge might be just as complicated. If you were asked to make the image with one hundred dots, and only use black and white, from the perspective of the viewer you'd have a result that was easier to understand. Use a thousand dots, even easier, even if you only used black and white. Now, if you were to use a hundred dots, with ten colours, your image might be just as easy to understand as if it was a thousand

Foundations of Amateur Radio If you measure the voltage at the base of an antenna and record the readings, you end up with a collection of numbers that represent the voltage over time. These numbers, or samples, can be used to represent the antenna signal inside a computer. An antenna system voltage is an example of an analogue signal, continuous over time, the recorded readings, the samples are an example of digital, discrete and intermittent. It's possible to reconstruct an analogue signal from digital samples and that's exactly what Software Defined Radio or SDR is all about. The process of sampling essentially converts a continuous signal into an intermittent one. As recording separate samples implies, there is loss of information in this conversion. For example, if you sample once a minute, you'd represent a continuous signal as 60 samples per hour, probably enough to reconstruct where you've driven in your car along the highway, but hardly enough to reconstruct the route through the middle of the c

Foundations of Amateur Radio We think of radio as operating on a specific frequency. We select an antenna resonant on a single band. We configure the radio for that same band and then turn the dial or the VFO, or Variable Frequency Oscillator to a particular frequency within that band. All of our language is geared towards this concept of tuning, of picking out, selecting one special tuned, resonant frequency and listening to it. I've said this before, but that's not actually what's happening. Your radio is receiving all RF frequencies, all of them, all at the same time, all the time. Your antenna is better at hearing some frequencies than others, but that doesn't stop it from hearing everything at once. Your radio is getting all that RF information at the antenna connector. After that, every step along the way is removing unwanted information, first it removes all the bands you're not listening to, then the VFO selects which part of what remains to let through to the decoder and the result finally arrive

Foundations of Amateur Radio If you've been around the hobby in the past decade, you may have come across the invention of a Software Defined Radio, or SDR. You might even own one and if you've looked into how it works, read the explanation that essentially describes it as a traditional radio where all the components are implemented in software. To me that's like explaining how a radio works by waiving your hands and saying: here is magic. How it actually works is something all together more interesting and thought provoking. If you think of sound, like my voice, coming from a speaker, you can imagine putting a volt meter on the speaker terminals and measuring every second what the voltage is. As my voice gets louder you might measure a large voltage, as I take a breath, it will be smaller. You could chart the different measurements and show a waveform that would represent the loud and soft parts of what I'm saying. The faster you measure, the more accurate the picture represents my voice. For comparison,

Foundations of Amateur Radio Previously I've spoken about the dynamic nature of your station. Even if from day to day use, nothing changes, things around you are always in flux. Propagation changes, power fluctuates and the environment in which your antenna operates is dynamic. Mobile stations even more so. A few days ago we had a gale come through, strong enough to do some major damage, rip off some roofs, break some trees, cause flooding, cause power outages, plummeting temperatures, the first of the Winter Storms. Obviously, checking out your antenna after such an event is expected. Better still, stowing your gear before the event is even better. Such extreme weather events are an obvious trigger to attending to antenna health and well being, not to mention, maintenance and repair. The thing is, it's not the only time you should check out your antenna. Every day it's subject to change. The sun rises in the East, follows its path along the sky and eventually sets in the West. The temperature and humidi

Foundations of Amateur Radio Our day to day life is full of communication. We listen, although less and less, to the radio for news and entertainment, sometimes mixed together as food and games for the masses. We can communicate with family, friends and the rest of the global population using a telephone. With the internet as a transmission medium, we exchange text, sound and vision with impunity to anyone who stumbles across it on a mind boggling collection of outlets, websites, social media, email, streaming services to name a few. The vast majority of this kind of communication is a commodity, that means that with little or no training most of the population has access to this. Another aspect of this commodification is that it's reliable. It works most of the time, it's generally good quality, with little or no loss, as in, you speak into your phone and there's an extremely high chance for the other party to hear your voice. While there are occasions that calls drop out, or the audio is chopped up, it'

Foundations of Amateur Radio When you get your amateur radio license you become part of a select group of humans who are required to notify authorities if you happen to hear an emergency transmission. Not only that, you're required to offer assistance. The regulator in Australia, the ACMA, says this about it: When a distress call is heard, you must immediately cease all transmissions. You must continue to listen on frequency. You must record full details of the distress message, in writing and if possible recorded by tape recorder. You must also wait for a short time to see if the message is heard by a station better placed to help. If the distress message is not acknowledged within a reasonable time, the amateur is obliged to assist. The regulator goes on to say that after acknowledging or attempting to acknowledge receipt of the distress message, you should immediately forward details of the distress situation to the nearest police station for land based distress situations or the Australian Maritime

Foundations of Amateur Radio If the thought of keying up a microphone has you break out in a cold sweat, or the notion of making a mistake sends you into fits of anxiety, the idea of performance in public makes your heart pound, this is for you. Amateur radio is a hobby of communication. The lowest barrier to entry is a hand held radio and making voice contacts with the rest of the community. There is an underlying assumption that this is likely to be the most common way that you'll start getting on air and making noise. Of course you don't have to do that. You could learn Morse Code and never have to open your mouth. You could get a license that's permitted to use a Digital Mode like JT65 or RTTY and let your fingers to the talking. Both those options are perfectly valid and if that's what you need to get on air, be my guest. If you do however want to actually get to a point where you can communicate with other amateurs using voice communication, then let's investigate what voice communication actually e