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Foundations of Amateur Radio

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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?".


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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?".






Accolades in Amateur Radio?

Foundations of Amateur Radio Today I'd like to start with saying thank you to the Wireless Institute of Australia for awarding me the Brenda Edmonds Education Award "in recognition of outstanding service in the education of the Amateur Radio Community and advancement of licensees." It's an unexpected honour and a thrill that leads me to a question about how we recognise the people around us. Over the years I've been a member of around a dozen radio amateur clubs and associations. To my recollection, the only one who has ever said thanks, and in my case, more than once, is the Wireless Institute of Australia. What of the other clubs? What about the clubs you're a member of, or the groups you meet-up, either for lunch or on the local repeater? What about when you go out on a field-day and set-up a barbecue? I look around me and I see activity that goes back more than a century. It's fair to say that every member of the community benefits from that effort. Memes on social media notwithstanding, there is real labour and toil, love and heartbreak, success and failure all around you. What process do you have in place to say thanks? Now before you start handing out participation trophies to everyone who turns up, mind you, they did when others didn't, consider what saying thanks might look like in your community? It could be a special QSL card, or a certificate sent in the mail that someone could hang on their wall. I'm not advocating for sending out monetary awards or trophies, or other such paraphernalia, I'm just asking you to consider who in your group is worthy of a thank you and what that might look like. You should also think about what you're saying thank you about. Is it for output, for the number of laughs, the level of participation, how many new club members were signed up, how many contacts someone made, how much fund raising they achieved, how many radios they fixed or how many nets they hosted, or something else? You can think about who in your community might serve as an example to strive for and name the award after them. It might be someone who is active right now, or it might be someone who has attained mythical status in the stories you tell each other around the campfire during an overnight activity. No matter what you call it, what it's for, how often you award it, what you present and whom you present it to, consider that it's a formal way of saying thank you, from the group to the individual, from all of you to one person in particular. Since starting F-troop, I've now hosted more than 600 weekly nets for new and returning amateurs, a feat which we recently celebrated with a morning breakfast on the local aptly named Wireless Hill, but I couldn't have done it without the local repeater group who maintains the repeater we use. I also couldn't have done it without the countless individuals who join in every week, or who quietly sit on the sidelines making sure that the various nodes scattered around the globe are up and running, or the people who did the catering and logistics for the event. Looking back, for me that event represents a missed opportunity to say thank you, something which I intend to do something about in the near future. So, ask yourself. When was the last time someone in your community received a thank-you for their contribution? I'm Onno VK6FLAB


A Linux contest logger ...

Foundations of Amateur Radio As you might know I'm in the process of building a cross-platform, open source, contest logger. Right now that project is at the stage where there is a proof of concept that you can use and install as a progressive web app on any web browser. It's intended as a starting point for discussion. Note that this is a long way from the stage where you might want to actually use it for any contest, it's not feature complete and if it breaks you get to keep both parts. It's currently cunningly named "contest-logger". No doubt that will change. I'm collecting suggestions for features using the GitHub issue tracker, which you're welcome to contribute to. Behind the scenes, I'm writing the documentation that describes how I want to actually develop and design this application. What kinds of things are important, what will drive the process, all the planning stuff that sets up the project. Of course I'm doing this whilst writing articles, looking for work and dealing with the health-care fun and games associated with being alive. While my project is nowhere near finished, truth be told, it really needs to start first, I've come across a different tool written by a fellow amateur Michael K6GTE. This tool is written for Linux only in Python and is in Beta release at this point. This means that you can install and run the application and most of the functionality works. The application is called Not1MM. Here's what Michael has to say about his efforts: Not1MM's interface is a blatant ripoff of N1MM. It's NOT N1MM and any problem you have with this software should in no way reflect on their software. If you use Windows you should run away from this and use some other program. I personally don't. While it may be possible to get N1MM working under Wine, I haven't checked, I'd rather not have to jump through the hoops. Currently this exists for my own personal amusement. Something to do in my free time. While I'm not watching TV, Right vs Left political 'News' programs, mind numbing 'Reality' TV etc... Michael goes on to say that: The current state is "BETA". I've used it for a few contests, and was able to work contacts and submit a cabrillo at the end. I'm not a "Contester". So I'll add contests as/if I work them. I'm only one guy, so if you see a bug let me know. I don't do much of any Data or RTTY operating. This is why you don't see RTTY in the list of working contests. The Lord helps those who burn people at the... I mean who help themselves. Feel free to fill in that hole with a pull request. You can find Not1MM on Michael's GitHub repository ready for your testing and experimentation. It's also available as a PyPi package if you're already familiar with Python. In my opinion, one thing that this tool does well is consider how contest logging can be customised for individual contests and likely it will serve as inspiration for how I intend to implement the plugins in my own project. I've also submitted a patch to Not1MM so you can use Docker to install it on your own machine or at least see what the requirements are to make it run in your environment. I'm thrilled to have discovered this tool and hope that it solves some of your contest logging issues on your Linux workstation. What features are you hanging out for in your contest logging adventures? Feel free to share your bug reports and feature requests to either Michael's project, or mine, or both. I'm Onno VK6FLAB


Considering the language of our community ...

Foundations of Amateur Radio A curious thing happens when you become part of the amateur community, you start to talk like an amateur. This phenomenon isn't specific to being a radio amateur, it happens whenever you join any community. Lead by example, one word at a time, you start to inherit a vocabulary that represents that community. Amateur radio, rife with acronyms and so-called Q-Codes, a standardised set of three-letter codes that start with the letter "Q", does this in spades. If you've been around amateurs for more than 30 seconds, it's likely that you have already heard QSL, QTH and QRM, colloquially short for "Yup", "Home" and "Noise". There's an official meaning if you're keen. You can use the three letters as both a question and an answer, so QSL can mean "Can you acknowledge receipt?" and "I am acknowledging receipt." Similarly, QTH means "What is your position in latitude and longitude (or according to any other indication)?" and QRM means "Is my transmission being interfered with?" In those cases, used either with Morse code or Voice, they can make getting the message across simpler, faster, and more accurate, all important aspects of communication. It's easier to get QTH across to an amateur who doesn't speak English as their first language than it is to ask the whole question. Other letter groups also creep into common language of an amateur. You've likely heard the letters: "XYL", but if you haven't, let me explain. Given that amateur radio is an activity dominated by men, "YL" refers to Young Lady and "XYL", refers to eX-Young Lady, a less than complimentary way of referring to one's wife. I'd like to point out something curious. In Morse code, XYL is sent using: -..- -.-- .-.. It's intended to represent the word WIFE which is sent in Morse code as: .-- .. ..-. . Now, if you know anything about Morse, you'll know that a dit is one unit, a dah is three. Individual elements are spaced by one unit. The space between letters is three units and the space between words is seven units. Armed with that knowledge, XYL takes 39 units and WIFE takes 31 units to send. So, sending the shortcut actually takes longer and it's clear that this choice is not about efficiency. Describing someone as an eX-Young Lady to refer to your Significant Other seems very 1950's to me. In the situation where you are the female amateur operator, the apparently appropriate way to refer to your Significant Other is as Old Man or "OM". Are female operators supposed to refer to themselves as YL or XYL? Really? Sexism aside, this is extremely offensive in a same-sex and gender fluid community. Then there's the symbol "88", apparently meant to refer to "Hugs and Kisses", not something I'd feel comfortable sending to anyone other than my partner who is emphatically not an amateur, let alone the idea that it would be appropriate to send it to any random station or the connotations around males sending such a message to a random female operator. So, given that we now live in the 21st century and we're no longer in 1950, perhaps it's time to consider what language we teach new amateurs. One proposal by Chris M0YNG is to refer to the Operator as "OP" and the Significant Other as "SO". Seems like a good start. I will point out that this conversation was brought to my attention by Andreas DJ3EI who was participating in a conversation with Tim N7KOM who started the thread. I think it's a worthwhile thing to discuss such an evolution of our language, it goes to the heart of our community, you are what you say you are, and words matter. So, what words, acronyms and symbols do you use in your amateur community and what are you teaching new amateurs? I'm Onno VK6FLAB


Measuring the Solar Flux Index at home ...

Foundations of Amateur Radio Recently the Australian Space Weather Forecasting Centre issued an alert for a Coronal Mass Ejection or CME expected to impact Earth within 24 to 36 hours. This was presented within the context of seeing the resulting Aurora, but as a user of the HF radio spectrum, I'm subscribed to their email list, not for the pretty pictures, though I would be delighted to actually see them with my mark one eyeball, I'm on the list for the impact on propagation for my hobby. As a good citizen I shared the alert with my community both via email and social media and as a result I received some questions and comments. One question was, "What does this mean?", one comment was "it's not going to impact the United States." My response was to point out that HF propagation and the impact of the Sun is a very deep rabbit hole and encouraged further research by supplying several links, including a very detailed video by Rohde and Schwarz titled "Understanding HF Propagation", very, highly, recommended. Whilst watching that video I discovered that the Solar Flux Index is measured using a receiver tuned to 2800 MHz or 2.8 GHz. Being in the business of having receivers scattered around my shack, I asked myself if I had something that was able to receive on that frequency. My RTL-SDR dongle doesn't cut it without extra hardware, it tops out at 1.75 GHz. However, my PlutoSDR has a standard frequency range that goes up to 3.8 GHz out - of the box - and with some tweaks can make it to 6 GHz, so well and truly within range. Now, before I move on, I should mention that an RTL-SDR is a cheap, as-in $20, USB computer accessory that looks like a thumb-drive and is ostensibly built to receive digital television, or DVB-T signals. I've spoken about this previously. It can be used to receive radio frequencies outside the purpose it was built for. The PlutoSDR, or to give its official name the ADALM-PLUTO, on the other hand, something which I've also spoken about, is a single board Linux computer made by some smart people at Analog Devices, specifically for the purposes of learning and experimentation with receiving and transmitting RF. It comes with all manner of documentation and software and to be honest, I'm a little bit in love with mine. Back to measuring stuff. In this case I'm attempting to measure the power levels of radio frequencies at 2.8 GHz. I know of a simple tool called rtl_power that can measure RF power over time and started investigating if that tool had been hacked to be able to use the PlutoSDR, rather than the RTL-SDR dongle. It might have been, but I've not yet discovered it, however, that in turn led me to several other tools, most of which I'm still investigating. What it does tell me is that I'm not the first person to tread these paths, much has happened and been documented in the analogue sphere, some has been done using digital I/Q data and a transverter, a device that can multiply radio frequencies to make them appear in a different part of the radio spectrum, but I'm not yet sure if anyone has made a Solar Flux Index device out of a PlutoSDR. I recalled a wonderful little tool that I've also talked about before, there's a theme here, I'm sure, but the tool, "csdr", written by Andras HA7ILM, which allows you to do all manner of interesting things to a stream of raw data, specifically RF raw data. It has a function called logpower_cf which Andras describes as "useful for drawing power spectrum graphs", which is precisely what I'm looking for. Armed with that I'm now in the process of building a compiled version using Docker, so I can run csdr on my PlutoSDR and perhaps generate a power spectrum graph for 2.8 GHz. Of course that will now require that I learn how to extract raw data, known as I/Q data from the PlutoSDR command-line, process it through the logpower_cf function, output an image and hopefully show the result as a web-page. At the moment I'm still in the weeds with a Makefile, but that's...


Propagation during the 2023 Solar Eclipse

Foundations of Amateur Radio On Thursday the 20th of April, 2023 at 04:17:56 UTC the world was subjected to a rare event, a hybrid solar eclipse. In Perth I experienced a partial eclipse and people lucky enough to be directly in line, places like Ningaloo Reef, Exmouth and Barrow Island, experienced a total eclipse. Timor-Leste had the experience of the peak total eclipse. At the time I went into my shack and refreshed the WSPR or Weak Signal Propagation Reporter beacon map I have open and noticed that my beacon wasn't reported. I sagely nodded my head, that makes sense, no Sun, no propagation and I got on with my life. Last week a fellow amateur, Will VK6UU, asked if anyone had any VK6 specific HF propagation reports to make. Being the data geek that I am, I thought to myself, "Aha! I can do some data analytics on the WSPR dataset that I have." So, the die was cast for a few enjoyable hours of importing 2.4 gigabytes of compressed data into a database and constructing a set of SQL queries to see what I could learn. Before getting stuck in, I spent a few hours thinking about the problem. How could I go about doing this? Propagation information is notoriously fickle. You have to consider the obvious things like the Solar Index and the Geomagnetic Index which vary considerably. Then there's the nature of the various reports themselves. Not everyone has their beacon on all the time, not everyone has their receiver on all the time. Weekends are more popular than weekdays and popularity overall is growing exponentially. The solar cycle is on the way to its peak, so there's that variation to consider and if that's not enough, how should you compare the Signal To Noise ratio between weak and strong beacons? With all that in hand I set about constructing a plan. I created a folder to hold my charts and SQL queries, intent on uploading that to GitHub when the work was done. For my very first test I thought I'd count the number of reports per band in a 24 hour window around the eclipse. I imported all the WSPR records that had a VK6 callsign, either as the transmitter or the receiver, given that I was interested in learning if stations transmitting from VK6 could be heard elsewhere and inversely, could VK6 stations hear any other stations? As my first effort, I created a scatter-plot to get a sense of what kind of numbers I was looking at. The initial result was interesting. Around the eclipse itself there was no propagation. This wasn't unexpected, since that's what I'd seen on the day at the time on my own map. I changed my data to use a cumulative count per band to see if any band was particularly different and then discovered that there was no propagation at all, on any band. That seemed ... odd. So, I had a look at the source data and discovered a gap, which accounted for what my chart was showing. I added a fake record for the eclipse time itself, just so I could see where on the chart this gap was. Turns out that for VK6 stations, the gap is just over five hours, but it's not centred around the eclipse. There's a four hour window before the eclipse and a one hour window after it. Then I started looking at all the reports from across the world. To give you a sense of scale, across April 2023 the dataset has nearly 139 million rows. It's 12 gigabytes in size. By contrast, in March of 2008 when the first reports started, there were just over 93 thousand reports in a 7 megabyte file. Charting this shows exponential growth, hitting a million reports in July of 2009, 10 million reports in January 2016 and 100 million reports in October of 2021. So, the eclipse and global propagation. The results came in and the reports are that there was no propagation, on any band at any point during the just under two hours and 12 minutes before the eclipse and the 38 minutes following it. That ... or the database was down during the eclipse. So, unfortunately I cannot tell you what propagation was like during the eclipse,...


Doing the same thing over and over again ...

Foundations of Amateur Radio Over the years I've used the phrase, which I shamelessly stole, that amateur radio is a thousand hobbies in one. I've discussed countless different activities and adventures that all fall under the banner of amateur radio, in one way or another. Since becoming a licensed radio amateur I've had the opportunity to speak with many different amateurs and hear their views on what amateur radio means to them. Based on their responses I've often found myself exploring new aspects of the hobby and discovering new and interesting ways to participate in this community. Recently I put together a list of projects that are currently underway in my shack. I discovered that over time this list has evolved from physical radio activities, like portable activations, building antennas, camping, and going to HAMfests, the amateur radio version of a swap meet, into more computer related things like data analytics, writing software, fixing bugs and learning how the insides of a Software Defined Radio works. That's not to say that I've given up on camping, or any of the other things, just that my priorities have shifted over time as I discover over and over again, just how big this hobby really is. I mention this because one of the recurring observations I encounter is that others are doing the same thing day in and day out. That in and of itself isn't an issue, it's that they begin to describe that they're bored, that they've lost interest, that the hobby is in stagnation, that there's nothing new, that they're frustrated with their progress towards whatever goal they've set themselves. For me, the key motivator in this hobby is learning. Everything else follows from there. That might not be your thing. You might be here for the emergency service aspect, or the hill climbing, the soldering and electronics. It really doesn't matter why you're here at all. What keeps it fresh is trying new things. For example, if you're here for emergencies, have you set up a disaster event simulation in your community, or attempted to set-up your station 100 km from home and make contacts, using just the very basics? If you're into soldering and electronics, have you ever designed your own circuit board, had it manufactured, or even manufactured it yourself, built the project and tested it? What about documenting it and making it available as a project for someone else? If you've climbed all the hills in your state, have you tried doing this across the border, or overseas? What about testing with different antennas, or modes, power levels or logging tools? The point being that it's easy to keep doing the same thing. What's harder, but potentially more rewarding, is to try something new and experience what happens. One thing to keep in mind is that things will go wrong. That's where all the learning happens, so keep at it. So, are you doing the same thing over and over again and expecting a different outcome, or are you excited like a newborn puppy, wagging your tail ready for the next adventure? I'm Onno VK6FLAB


Why is radio regulated?

Foundations of Amateur Radio One of the more perplexing things is the nature of radio regulation. If you're a licensed radio amateur, you'll be familiar with this idea, but if you're not it's bewildering and apparently absurd. To explain, let me start with a light bulb that your neighbour put on their back porch. It's bright. It's pointing at your house. Like the apparent radiation from a gazillion suns it lights up the bedroom and sleep is hard to come by. Pretty annoying right? As it happens, radio is a lot like that. If you know physics, it's exactly like that, but I'll ignore that for today. In our modern world we have many different radios that each rely on a specific, let's call it colour, of light. In radio terms this is known as frequencies or radio bands and the entire collection is known as the radio spectrum. You've likely seen this without knowing. Your 2.4 GHz WiFi has an in-built frequency, 2.4 GHz, as does your 5 GHz WiFi. Your FM radio in the car has frequencies as well, 97.7 on the dial indicates 97.7 MHz. If you have an AM radio, 720 AM refers to 720 kHz. Hidden in plain sight is why radio is regulated. Those numbers, 5 GHz, 2.4 GHz, 97.7 MHz and 720 kHz are all radio frequencies, or as I suggested, colours. Now imagine turning on a really bright light in the middle of that. All of a sudden your WiFi, FM and AM are wiped out. It doesn't stop there. As I said, there are many different radios, and sources of radio frequencies. Radio transmissions come from your mobile phone, Bluetooth headset, microwave oven, computer, television, remote control, key-less fob, power supply, car, power meter, solar panel, battery charger, LED light bulb, and the list goes on. Essentially anything electronic has a radio component. Some of these are transmitting unintentionally, like an electric motor or a switch mode power supply. Other things are transmitting on purpose, your microwave oven, your Bluetooth headset and your mobile phone. As I mentioned, they're all sharing the same resource, the radio spectrum. At this point you might ask about the impact of a single transmitter among all that. Well, there are a few phenomena that you should know about. Radio waves don't stop. They keep going. There's no boundary. To illustrate that, I have a tiny beacon, a transmitter, that every two minutes sends out a signal that shows my amateur callsign and location. It uses 10 milliwatts. To give you a sense of scale. A typical incandescent light bulb is about 60 Watts. My transmitter uses sixty thousand times less power. It has been heard 13,455 km away, about a third of the way around the planet. I will point out that different frequencies can be absorbed differently depending on how they're used, but you cannot rely on the idea that any radio frequency stops anywhere. Another phenomenon is a thing called harmonics. Radio waves not only share the same space or spectrum, they're related to each other. Unless you take very specific precautions, a transmission made at 100 MHz, will be heard at 200 MHz, 300 MHz, 400 MHz, 500 MHz and so-on. While each of those transmissions gets progressively weaker, they still exist. Now imagine that someone else is using one of those other frequencies to communicate emergency information. It's like their backyard just got hit with a bright light. To give you a specific example of why this can matter. Consider a radio amateur who uses 7 MHz. This is a licensed amateur radio frequency. Unless that amateur takes specific precautions, the 16th harmonic for 7 MHz is 112 MHz. If that doesn't mean anything to you, it's in the middle of the so-called air-band, frequencies used by aircraft around the planet to talk to each other and the ground. Very bad things could happen if safeguards weren't made. As a result, radio is highly controlled and regulated. I'm not going into the laws or legalese here, given that this is a global phenomenon and the rules in their specifics are different in each country....


The antenna system

Foundations of Amateur Radio Several years ago I participated in a local contest. Over a 24 hour period I activated my mobile station in about 30 different locations. On my car, my vertical antenna screwed into a boot-lip mount connected to an antenna tuner or ATU, and my radio. I used rope to guy the antenna, threaded through the rear windows and held tight by closing the car boot. Setting up consisted of parking the car, triggering the ATU to tune the antenna system and calling CQ. Moving to the next location consisted of driving there and setting up again. Although this worked really well, I'm skipping over what I'm interested in exploring today. The phrase "triggering the ATU to tune the antenna system" hides a lot of complexity. It was a surprise to me that there were several locations where the ATU just wouldn't tune. Despite my best efforts I was unable to get the system to a point where the radio was happy. In some cases I tuned off frequency and put up with a poor SWR. In others I physically had to move the car and park somewhere else. In every case it was completely unknown if a particular location was going to be a problem. I recall for example parking in an empty nondescript car-park and having to drive around to find a location where my set-up would work. Afterwards I considered that the car-park was potentially built on top of an iron ore deposit, an old industrial area, or a pipe-line, all of which were a good possibility. The point of this is that an antenna doesn't exist in isolation, it's called a system for a reason. We talk about the theoretical isotropic antenna and add disclaimers about that it cannot physically exist because it's infinitely small. One often overlooked aspect of an isotropic antenna is that it's in free space. Free space is defined as space that contains no electromagnetic or gravitational fields and used as a reference. It's a theoretical place. On Earth there is no such thing, there's a planet under your feet, but even in outer space there are both gravitational and electromagnetic fields that impact on an antenna and its performance. Staying nearer to home, recently we had a discussion about how close two antennas can be together. A suggested rule of thumb was that they need to be at least one banana or 30 cm away from each other. Similarly when we erect a dipole, there's recommendations around needing to have it mounted more than half a wavelength over the ground. Some sources say higher. I'll ask the first obvious question. Is that dipole completely straight? In other words, should the centre be half a wavelength above the ground, or should the ends, and how far should the ends be from their mounts? My point is that every antenna exists within the context of its environment and together it's a system. Some environments help the performance of your antenna system and some don't. Depending on frequency, this might not be the same for any location, or antenna design. To be clear, an antenna system consists of the antenna, the feed line and the clips that hold it, the tuner, the radio and its power supply, the mount and the space around it, the radials, the tower, the pigeon poop on the wire, all of it. Until recently my process to get any antenna to perform in a reasonable manner was to set it up, connect an antenna analyser, scan the appropriate range, tweak the antenna, scan again, rinse and repeat until it arrived at something approaching useful, or until it was good enough. If you recall, I recently added some loading coils to a telescopic antenna to attempt to make it resonant on 10m, so I could connect my Weak Signal Propagation Reporter or WSPR beacon to it directly and leave it running independently from my main station. I used the antenna analyser method, got it to the point where I had an antenna with a nice dip right at the required frequency and then watched it go completely sideways when I mounted the antenna in the window. Having spent several hours getting...


How much antenna is enough?

Foundations of Amateur Radio When you start in this hobby one of the most frustrating aspects is that of selecting the right antenna. If you've been around for a while, you'll discover that this continues to be the case, even when you've been licensed longer than I've been alive. In the past I've discussed at length why that is the case, but to recap, consider a dipole antenna. In essence it's two pieces of wire that are connected to the radio via some form of feed-line. Now consider the idea of changing the length of each wire. You could trim each end in the same way, or you could make one end longer than the other. You could fold the ends at an angle, or you could mount the dipole near the ground, or high up in the trees, you could position it vertically, or arrange the wires at an angle towards each other. You could make the wire thicker, or thinner, from different material or arrange the ends so they meet up in a circle, or a square, a triangle or some other shape. You get the point, there is endless variation arranging this single antenna and I've not even discussed things like feed-lines, traps, chokes, counterpoise and other RF shenanigans. With that in mind, amateurs around the world are attempting to improve their antenna system every time they get on air to make noise. Recently I reported that my 10 mW WSPR, or Weak Signal Propagation Reporter beacon was heard 13,455 km away in Sweden by Mats SM3LNM on the 10m band. The signal report was -25 dB, which means that with an experimental cut-off for a successful decode at -34 dB, I have 9 dB to play with, so at least theoretically, I could reduce my power even further, to 1 dBm, or just over 1 mW and still make the distance. The antenna I'm using is one built by Walter VK6BCP (SK). It's a 40m vertical antenna, helically wound on a fibreglass blank and clamped to the side of a metal pergola. The antenna is tuned to the 10m band using an SGC SG-237 antenna coupler, essentially a device that can add or remove inductance or capacitance to make my antenna appear resonant on the appropriate frequency. The antenna coupler in turn is attached to about 20 or 30 meters of 75 Ohm, quad shield RG6 which I have left over from my remote internet satellite dish installation days. That's all to say that the antenna system for my beacon is sub-optimal and it's likely that my actual power output is lower than the 10 mW that my beacon is reporting. So, with all that in mind, what else could I try? I have an indoor telescopic antenna stuck to the window and I've been wondering if I can attach my beacon to it directly and leave it running without the need to worry about disconnecting the beacon when I'm wanting to fire up my actual station to make other noises on air. A quick scan with the analyser reveals that the lowest frequency out of the box is about 60 MHz. I decided that adding some loading coils might help, so I set about fabricobbling an antenna, yes, you heard me, fabricobbling, fabricating and cobbling together. Anyway, using 7mm thick drip irrigation riser poly pipe as a form I wound two coils with 1.25mm copper wire that I had lying around. Depending on which calculator you used, that was either too much or not enough for my needs. I managed 53 windings, shy of the planned 60, but still a good start. Using the same irrigation riser, which as luck would have it managed to match the thread for the telescopic antenna elements and feed point, I separated each element by about 100 mm from the feed point, then used the two loading coils to connect the feed point back to each element. An hour later I now have a telescopic antenna, with two loading coils and as luck would have it, I'm much closer. The resonant point is now 30 MHz, down from 60 MHz, so I have a little more tinkering ahead of me. I might change the wire and use some eyelets at the ends to make assembly simpler, but the general idea seems to work as intended. If it doesn't work, I've come across a design for...


Lost in space ...

Foundations of Amateur Radio There is a fascination with space that arguably started long before the first time that human spaceflight was proposed by Scottish astronomer William Leitch in 1861. Names like Sputnik, Mercury, Gemini, Apollo and Columbia speak to millions of people and organisations like NASA, SpaceX and Blue Origin, to name a few, continue to feed that obsession. In amateur radio we have our own names, things like ARISS, or Amateur Radio on the International Space Station, or its predecessor SAREX, the Shuttle Amateur Radio Experiment. Today, stories about people making contact with the International Space Station continue to make news. We have school programs where amateur radio ground stations schedule a call to speak with an astronaut in space and we've been launching our own amateur satellites for a long time. Launched on the 12th of December 1961, OSCAR1, or Orbiting Satellites Carrying Amateur Radio was built by a group of California based amateur radio operators for 63 dollars. It operated for nearly 20 days, transmitting "Hi" in Morse on 144.983 MHz. The first amateur radio space voice contact was made on the 1st of December 1983, almost forty years ago. It's surprising that in the age of technology such a significant event has been so poorly recorded for posterity. If you go searching for the actual audio, you'll discover several versions of this contact including varying transcripts. I've attempted to reconstruct the wording, but I've yet to hear a complete and unedited version. For example, there's an ARRL movie called "Amateur Radio's Newest Frontier" with out of sync audio. There's also an audio file with a transcript from an archived copy of a website by W7APD. The most recent one is on a video called "HAM - Official Documentary 2022", produced by students from the School of Visual and Media Arts program at the University of Montana and broadcast on Montana PBS on November 24th, 2022. So, what follows is not necessarily complete, but calling from Space Shuttle Columbia it went a little like this: "..U.S. west coast and calling CQ. Calling CQ North America. This is W5LFL in Columbia. In another 30 seconds I'll be standing by. Our spacecraft is in a rotation at the moment and we're just now getting the antenna pointed down somewhat more toward the Earth. So I should be able to pick up your signals a little bit better in the next few minutes. So W5LFL in Columbia is calling CQ and standing by. Go ahead." "This is W5LFL in Colombia, W5LFL in Columbia, orbiting the Earth at an altitude of 135 Nautical Miles. Passing over the US West Coast and calling CQ. So W5LFL in Columbia is calling CQ and, ah, standing by. Go ahead." "W5LFL on STS-9, WA1JXN, WA1 Japan X-Ray Norway, WA1JXN, Frenchtown Montana, WA1JXN standing by." "Hello W1JXN, WA1 Juliet X-Ray November, this is W5LFL, I picked up your signals fairly weakly. I think our attitude is not really the best as yet, but you're our first contact from orbit. WA1 Juliet X-Ray November. How do you read? Over." On board STS-9, Space Shuttle Columbia, was Dr Owen Garriott, W5LFL, now silent key. On the ground was Lance Collister, then WA1JXN, now W7GJ. NASA published an Educational Brief for the Classroom that described Owen's set-up as a battery powered 5 Watt FM transceiver feeding a split-ring on a printed circuit board antenna that will be placed in the upper crew compartment window on the aft flight deck. Others reported that the radio was a Motorola handheld. Logging was done with a tape recorder velcroed to the transceiver. Owen describes the antenna as a "well-designed, hand-held antenna, known as a 'cavity antenna', which could be velcroed to the window. It was about 24 inches in diameter and looked somewhat like a large aluminum (sic) cake pan" There's an edited version of a similarly titled ARRL video called "Amateur Radio's Newest Frontier - ARRL documentary featuring Owen Garriot, W5LFL, on STS-9" showing the antenna as a copper tube,...


The Contester In Me...

Foundations of Amateur Radio So, I have a confession to make. I'm a contester. I'm not ashamed of this. While I'm in a confessing mood, I'll also mention that I've not participated in many contests in the past few years. This is not for the want of desire, but for the lack of motivation to fix things in my shack that are fundamentally broken. On the weekend I participated in a local contest. I took part for six hours, got on-air and made noise, made about 30 contacts, had a ball. I wasn't playing to win, though I did use the opportunity to refresh and hone some of my rusty skills. The next day I spent much too long converting my log into something that the contest organiser asked for. I also discovered that there was a duplicate entry in my log, not something which I'd expect with only so few contacts, but a reflection on the tool I was using to create my log. I started writing down what I learnt from the experience, operating from my own shack, documenting what worked and what didn't. I commented on several things relevant to me, but to give you a flavour, my operator position is terrible because I'm logging on my main computer and the radio is side-on when I'm facing the computer. The sun was shining directly into my eyes when facing the computer. Holding a microphone I didn't have hands-free, I still don't have an auto-keyer to save my voice, my foot pedal didn't work and my data interface was on loan to another amateur. As I said, these things are specific to me. Logging was worse. It didn't quite bring me to tears, but as the contest went on, it became a problem. I started to write down what was wrong with the tool I was using with a view to submitting patches to fix it when I realised that it wasn't actually built as a contesting logging tool, so I stopped and instead started writing a new list, one that describes what a good contesting tool looks like. It builds on a decade of using different tools and participating in contests in all manner of different situations, from special portable event activations, through to the annual top-tier contests run from a purpose built contest station and everything in between. So, what does the ideal contesting tool look like, for me? It needs to be cross platform, as-in, I should be able to use it on whatever computer I have access to, my Linux workstation, a Macintosh Laptop, an Android phone or tablet and while I'm at it, Windows and iOS and I think it should be able to run on a Raspberry Pi. In other words, there shouldn't be a situation where you cannot run the tool because you have some random combination of operating system or CPU that the developer doesn't support. It must be open source. By that I mean, the code should be available to the entire community. There are too many stories of great tools dying or being held hostage by individuals or small groups. The tool should continue to exist and be usable regardless of the participation of the original developer. Users should be able to fix things, add functionality, change themes, whatever. You should be able to customise it because not every contest needs the same information. For example, the John Moyle Memorial Field Day, a contest run every year during March in Australia requires that VHF and UHF contacts record the maidenhead locator, a four or six character message that designates the location of the station. This is used to calculate distance between two stations and award points accordingly. Such a requirement isn't needed in most other contests. Some contests are considered friendly contests, like the Remembrance Day contest in August. It's common to exchange your name, details about your station and have a chat. You'd be unpopular if you used that approach for the Oceania DX, the CQ World Wide or the CQ WPX contests. In other words, some fields are expected for some contests, but not for others. The tool needs to be able to show if a contact is valid by whatever means the rules for a particular contest...


What's with a negative SNR?

Foundations of Amateur Radio We describe the relationship between the power of a wanted signal and unwanted noise as the signal to noise ratio or SNR. It's often expressed in decibels or dB which makes it possible to represent really big and really small numbers side-by-side, rather than using lots of leading and trailing zeros. For example one million is the same as 60 on a dB scale and one millionth, or 0.000001 is -60. One of the potentially more perplexing ideas in communication is the notion of a negative signal to noise ratio. Before I dig in how that works and how we can still communicate, I should point out that in general for communication to happen, there needs to be a way to distinguish unwanted noise from a desired signal and how that is achieved is where the magic happens. Let's look at a negative SNR, let's say -20 dB. What that means is that the ratio between the wanted signal and the unwanted noise is equivalent to 0.01, said differently, the signal is 100 times weaker than the noise. In other words, all that a negative SNR means is that the ratio between signal and noise is a fraction, as-in, more than zero, but less than one. It's simpler to say the SNR is -30 dB than saying the noise is 1000 times stronger than the signal. Numbers like this are not unusual. The Weak Signal Propagation Reporter or WSPR is often described as being able to work with an SNR of -29 dB, which indicates that the signal is about 800 times weaker than the noise. To see how this works behind the scenes, let's start with the idea of bandwidth. On a typical SSB amateur radio, voice takes up about 3000 Hz. For better readability, most radios filter out the lower and upper audio frequencies. For example, my Yaesu FT857d has a frequency response of 400 Hz to 2600 Hz for SSB, effectively keeping 2200 Hz of usable signal. Another way to say this is that the bandwidth of my voice is about 2200 Hz, when I'm using single side band. That bandwidth is how much of the radio spectrum is used to transmit a signal. For comparison, a typical RTTY or radio teletype signal has a bandwidth of about 270 Hz. A typical Morse Code signal is about 100 Hz and a WSPR signal is about 6 Hz. Before I continue, I should point out that the standard for measuring in amateur radio is 2500 Hz. This is significant because when you're comparing wide and narrow signals to each other you'll end up with some interesting results like negative signal to noise ratios. This happens because you can filter out the unwanted noise before you even start to decode the signal. That means that the signal stays the same, but the average noise reduces in comparison to the 2500 Hz standard. This adds up quickly. For a Morse Code signal, it means that turning on your 100 Hz filter, will feel like improving the signal to noise ratio by 14 dB, that's a 25 fold increase in your desired signal. Similarly, filtering the WSPR signal before you start decoding will give you roughly a 26 dB improvement before you even start. But there's more, since I started off with claiming that WSPR can operate with an SNR of -29 dB. I'll note that -29 dB is only one of the many figures quoted. I have described testing the WSPR decoder on my system and it finally failed at about -34 dB. Even with a 26 dB gain from filtering we're still deep into negative territory, so our signal is still much weaker than the noise. There are several phenomena that affect the decoding of a signal. To give you a sense, consider using a limited vocabulary, like say the phonetic alphabet, or a Morse character, the higher the chance of figuring out which letter you meant. This is why it's important that everyone uses the same alphabet and why there's a standard for it. To send a message, WSPR uses an alphabet of four characters, that is, four different tones or symbols. Another is how long you send a symbol. A Morse dit sent at 6 words per minute or WPM lasts two tenths of a second, but sent at 25 WPM lasts less than...


Acronym not found ...

Foundations of Amateur Radio Our community is full of TLAs, or three letter acronyms. Some of them more useful than others. For example, I can tell you thank you for the QSO, I'm going QRT, QSY to my QTH. Or, thanks for the chat, I'll just shut up and take my bat and ball and go home. Acronyms arise every day and it came as no surprise to spot a new one in the wild the other day, SHF. It was in a serious forum, discussing antennas if I recall, so I didn't blink and looked it up. Super High Frequency. Okay, so, where's that? I'm familiar with VHF and UHF and as radio amateurs we're often found somewhere on HF, that's Very High Frequency, Ultra High Frequency and High Frequency if you're curious. Turns out that the ITU, the International Telecommunications Union has an official list, of course it does. The current ITU "Radio Regulations" is the 2020 edition. It's great bedtime reading. Volume one of four, Chapter one of ten, Article two of three, Section one of three, Provision 2.1 starts off with these words: "The radio spectrum shall be subdivided into nine frequency bands, which shall be designated by progressive whole numbers in accordance with the following table." When you look at this table you'll discover it starts with band number four and ends with band number twelve, between them covering 3 kHz to 3000 GHz. In position ten you'll see the designation "SHF", covering 3 to 30 GHz, centrimetric waves. A couple of things to note. The list starts at band four. There are of course frequencies below 3 kHz. The list ends at twelve, but there are frequencies above 3000 GHz. You'll also note that I'm not saying 3 Terahertz, since the ITU regulations specify that you shall express frequencies up to 3000 GHz using "gigahertz". Interestingly the same document has a provision for reporting interference where you can report using Terahertz frequencies, so I'm not sure how the ITU deals with such reports. Another thing to note is that this table doesn't actually define what SHF means. It's nowhere in the radio regulations either, I looked. I'm not sure where the words Super High Frequency came from. There is an ITU online database for looking up acronyms and terms. That leads to a document called "Nomenclature of the frequency and wavelength bands used in telecommunications", which also doesn't use "Super High Frequency" anywhere. That said, using the ITU band four, where its definition starts, the VLF band, or Very Low Frequency, followed by LF, Low Frequency, MF, Medium Frequency, the familiar HF or High Frequency, VHF, UHF, then SHF and beyond that, EHF, Extremely High Frequency and THF or Tremendously High Frequency, yes, Tremendously High. There's a report called the "Technical and operational characteristics and applications of the point-to-point fixed service applications operating in the frequency band 275-450 GHz". It introduces the term "THF which stands for tremendously high frequency" but adds the disclaimer that "this terminology is used only within this Report." Seems that there are plenty of documents on the ITU website using that same definition, so I'm guessing that the cat is out of the bag. THF by the way is defined as being for 300 to 3000 GHz frequencies. By the way, the ITU TLA finder exposes that THF stands for Topology Hiding Function. Where's a good acronym when you need it? Speaking of definitions, I came across the definition of a "taboo channel" which according to the ITU is "A channel which coincides with the frequency of the local oscillator in the single super heterodyne receiver which is tuned to an analogue channel." Anyway, we still have a way to go. Below band four, less than 3 kHz, we have ULF or Ultra Low Frequency, SLF, Super Low Frequency and ELF, Extremely Low Frequency, which is defined as band one, between 3 and 30 Hz. Below that, some have suggested TLF, or Tremendously Low Frequency which apparently goes between 1 and 3 Hz with a wavelength between 300,000 down to 100,000...


Antenna Testing Day ...

Foundations of Amateur Radio Last week I went outside. I know, it was a shock to me too. The purpose of this adventure was to test an antenna that has been sitting in my garage for nearly a year. Together with a friend we researched our options and at the end of the process the Hustler 6BTV was the answer to our question. Before the commercial interest police come out of the woodwork, I'll point out that I'm not providing a review, good or bad, of this antenna, it was the antenna I purchased and went to test. Between the two of us we have three of these antennas. I have the idea to use one as a portable station antenna and another as my base station antenna. Glynn VK6PAW intends to use his as a base station antenna. To set the scene. The antennas came in quite large boxes, just over six bananas long, or more than 180 cm. When they arrived I opened my boxes and checked their content, then sealed it all up and put the boxes on a shelf. Last week Glynn proposed that we set one up and see what we could learn from the experience. You know that I love a good spreadsheet, so planning went into overdrive, well, I put together a list of the things we'd need, starting with the antenna and ending with sunscreen to protect my pasty skin from the fusion experiment in the sky. In between were things like an antenna analyser, spare batteries, tools, imperial, since apparently there are still parts of the world that haven't gone beyond barley measurements. I jest, they authorised the use of the metric system in 1866. My list also included a magnetic bowl to capture loose nuts and washers, you get the idea, anything you might need to test an antenna in the field. Our setup was on a rural property where we had lovely shady trees and oodles of space to extend out a 25m radial mat. We tested many different set-ups. I won't go through them all, but to give you an idea of scale, in the time we were there, we recorded forty different antenna frequency scans. The 6BTV antenna is suitable for 80m, 40m, 30m, 20m, 15m and 10m. We tested with and without radials, raised and on the ground and several other installations. We learnt several useful things. For starters, sitting on the ground with radials the antenna measurements line up pretty well with the specifications and with a suitable base mount to protect the plastic base the portable station antenna is usable out of the box. Any variation on this will result in change, sometimes subtle, sometimes less so. For example, we came up with one installation where the SWR never dropped below 3:1. That's with the antenna on the ground without any radials in case you're wondering. Other things we learnt were that manually scanning each band is painful. When we do this again we'll have to come up with a better way of measuring. The aim for my base antenna is to install it on my roof, bolted to a clamp on the side of my metal pergola. This means that we're going to have to do some serious tuning to make this work for us. It might turn out that we'll start with installing the antenna at Glynn's QTH first, but we haven't yet made that decision. Other things I learnt are that I had actually put together the base clamp when I checked the boxes a year ago, so that was a bonus. The magnetic bowl saved our hides once when a spring washer fell into the lawn. The hose-clamps that come with the antenna require a spanner, but there are thumb screw variations of those that I'll likely use for my portable setup. Other things we need to do is learn exactly how the traps work and how adjusting them affects things. In case you're unfamiliar with the concept of a trap, think of it as a radio signal switch that lets signals below a certain resonant frequency pass and blocks signals above that frequency. In other words, a 10m trap resonates just below 28 MHz. It lets frequencies below 28 MHz pass, but blocks those above it, essentially reducing the length of the antenna to the point where the trap is installed. One...


Are all spiky antennas the same?

Foundations of Amateur Radio The world is filled with antennas. You'll find them on towers, buildings, cars and on your next door neighbour's roof. They come in an astonishing variety, to the point where you might start thinking that antennas are a fashion accessory that vary with the season and if you start digging through the history books you'll come across designs that dial that variety up to eleven. Possibly the most visible antenna today is the television antenna and when you start noticing them, the more variation you'll discover. Their basic shape consists of a vertical pole, the mast, with a horizontal pole, the boom. Attached to the boom are various different shapes, or elements, that often vary in length according to some pattern. The shape is designed to collect as much electromagnetic radiation from a particular direction, or in the case of a transmitter, focus as much energy as possible into one direction. This focus is called gain. The more focus, the more gain. One of the oldest designs for this kind of antenna, still in use today, is the Yagi-Uda or Yagi antenna. It was invented in 1923 by Shintaro Uda at the Tohoku Imperial University in Japan and popularised to the English speaking world by his boss Hidetsugu Yagi who claimed to be the sole inventor in his Japanese patent application. He went on to file similar patents in Germany and the United States. Gain for a Yagi varies depending on design. Generally more elements means more gain. Sometimes you'll see a Yagi with weird shorter elements along the boom. This is a design to make the antenna work across multiple frequencies. Another way that this can be achieved is by adding traps along an element. They look like a thick stubby tube at some distance along an element. You can have more than one of these to allow for more frequencies. These improvements allow for several Yagi antennas to share elements and boom space, essentially combining several independent antennas into one. It can be tricky to discover in which direction a Yagi is pointing, but essentially the boom indicates the direction and the end with the shortest element is the front. There's another type of antenna that to the casual observer looks similar. It's called a log periodic dipole array, LPDA or log periodic antenna. It was invented in 1952 by John Dunlavy whilst he was contracted to the United States Air Force. He wasn't credited because it was classified as "Secret", later changed to "Restricted". In 1958 Dwight Isbell built a log periodic antenna as an undergraduate student at the University of Illinois at Urbana-Champaign. He was part of a larger team that included Raymond DuHamel, John Dyson and Robert Carrell. Later Paul Mayes developed a variant that improved performance. Before I dig in, I'll also note that this antenna caused all manner of legal issues that are still in force today. The so-called Blonder-Tongue Doctrine states that a patent holder isn't permitted to re-litigate the validity of a patent that has been held invalid previously. It was a result of the University attempting and ultimately failing to protect its patent for the widely copied antenna design. Reading about this is a fascinating discovery in how a single Judge can make a massive impact on law and society. The log periodic antenna is designed in a way that to the uninitiated looks very similar to a Yagi antenna. It's based on the idea that you can design an antenna made up from independent dipoles that are spaced in such a way that they form an antenna where each dipole radiates to take advantage of its neighbours. Generally a log periodic antenna looks like a triangle. Often the elements are on two separate booms, alternating side-to-side, or you'll see a zig-zag structure that causes the antenna signal to alternate side-to-side. One characteristic of an antenna is called bandwidth. It's a measure of how many frequencies it can operate on within the constraints of the antenna. The wider the...


Some Amateur Radio ABCs ...

Foundations of Amateur Radio A is for Antenna, the eyes and ears of any amateur station. You'll spend eighty percent of your life attempting to get twenty percent improvement for any antenna you'll ever use. B is for Balun, bringing together the balanced and unbalanced parts of your antenna system. C is for Coax, the versatile conductor that snakes into your station, one roll at a time. D is for Dipole, the standard against which all antennas are measured, simple to make, simple to use and often first in the many antenna experiments you'll embark on in your amateur journey. E is for Electron, source of all things RF, the beginning, middle and end of electromagnetism, the reason you are an amateur. F is for Frequency, the higher you go, the faster it happens. G is for Gain, measured against a baseline, you'll throw increasing amounts of effort at getting more, one decibel at a time. H is for Hertz, Heinrich to his mother, the first person to transmit and receive controlled radio waves in November of 1886 proving that James Clerk Maxwell's theory of electromagnetism was correct. I is for Ionosphere, the complex and ever changing layers that surround Earth which led radio amateurs to discover HF propagation in 1923. J is for JOTA, the Jamboree On The Air where radio amateurs, guides and scouts come together on the third full weekend of October to share global communications. K is for Kerchunk, the sound caused by the local repeater that brings a smile to the operator and a grimace to the listener, created by pushing the talk button and not saying anything. L is for Logging, the only way you'll ever remember who you spoke to and when and the perfect excuse for bragging to your friends after you managed to collect contacts all over the globe. M is for Modulation, adding information to a radio signal by varying the amplitude, frequency, or phase. N is for Net, a social excuse for getting on air and making noise with your friends. O is for Oscillator, making repeating currents or voltages by non-mechanical means. P is for Prefix, the beginning part of an amateur callsign that identifies your country or region of origin. Q is for QRP, the best way to make just enough noise to make yourself heard, low power is the way to go! R is for Resonance, the point where a circuit responds strongly to a particular frequency and less to others, used every time you tune a radio or an antenna or both. S is for Shack, the space you call home, where you live your radio dream. The size of the corner of the kitchen table, the back-seat of your car or a purpose built structure with never enough space, no matter how much you try. T is for Transceiver, a single box that contains both a transmitter and receiver that share a common circuit. U is for UTC, Coordinated Universal Time, the only time zone that radio amateurs should use for any activity that goes beyond their suburb. V is for VFO, the Variable Frequency Oscillator that provides radio amateurs with frequency agility, the means to listen anywhere, any-time. W is for Waterfall, which displays radio signals across multiple frequencies at the same time. X is for XIT, Transmit Incremental Tuning, changing your transmitter frequency whilst listening on the same frequency, helpful when you're trying to break through a DX pile-up. Y is for Yagi, or Yagi-Uda antenna, the most popular directional antenna invented in 1926 by Shintaro Uda at the Tohoku Imperial University in Japan and popularised to the English speaking world by his boss Hidetsugu Yagi. Z is for Zulu, the last word in the phonetic alphabet that every amateur should know and use. 73 is for best regards. Saying goodbye is hard to do, this says so without fanfare and clears your station from the air. I'm Onno VK6FLAB


Do you really know when the best time is to go on air?

Foundations of Amateur Radio Getting on air and making noise is a phrase that you've likely heard me repeat often, actually, this will be the 24th time or so. It's an attempt at encouraging you to actually transmit and use the radio spectrum that is available to you. It's a nicer way of saying: Use it or lose it! One of the more frustrating aspects of our hobby is finding other people to interact with. At the beginning of your hobby you have access to all these magic radio frequencies with no idea on how to use them. Often a new amateur will turn on their radio, call CQ a couple of times to see if there's anyone out there, hear nothing and give up. As you get more experience you'll discover that radio frequencies change over time and that some work better at certain times of the day. This is reinforced by others who will talk to you about propagation, the solar cycle and how the ionosphere and its various so-called layers will change and what you can achieve throughout the day, the year and the long term cycle. Armed with all this knowledge you are likely to get to a point where you make noise on a certain band depending on the time of day. For example, experienced amateurs will avoid the 10m band at night because it's a so-called day-time band, in other words, their perception is that you cannot make contact on the 10m band after sunset and for the same reason, it's not suitable for early morning contacts. What if we could test that perception and see if it's true or not? Turns out that we have a perfect dataset to discover what actually happens. If I look at the 10m band WSPR or Weak Signal Propagation Reporter data for the past year, a year that had me using a beacon pretty much 24 hours a day, you'd expect that you could see just which times worked and which ones didn't. Turns out that regardless of time of day, my beacon was heard across every hour of the day. Of course the numbers aren't uniform across the day. The peak is at noon local time, the trough is at 5 am local time, 10% of reports are at noon, about 1.5% at 5 am. In other words, the worst time of day for my beacon to be reported is 5 am in the morning and it's not zero. Interestingly the same isn't true for the signal to noise ratio, a measure of just how weak or strong a signal is in comparison to the local noise at the receiver. If you account for differences in transmitter power, meaning that a stronger transmitter is measured in the same way as a weaker one, the 10m band has the best signal to noise ratio at my location at 9 pm local time and the worst at 4 pm local time. Given that I'm only using the 10m band with my beacon I also looked at the local OF78 grid square across all bands. It shows that reports are not directly related to when the average signal to noise is best. It seems to me that people are transmitting when they think it works best, not when it actually works best and I'll mention that the definition of "best" depends on each user. Note that I haven't yet sat down to discover if there are automatic transmitter and receiver pairs that have been reporting 24/7 across a year on the same band to determine if there is more to learn about the relationship between how often something is reported and what the signal report was at the time. I can say that it's likely that your favourite band is more popular when others think it's popular, not when the conditions are better. Consider for example that there are no local reports on the 12m band at 10am, but there are at 9am and 11am, so, was the band magically unusable the whole year at that time, or did people just not use it? The same is true for 160m. No reports at all before 5pm or after 3am, despite the bands around it having contacts throughout the day. I will point out some things I've ignored. For example, what is a useful contact? Is it measured by distance, by quantity, by uniqueness? Is this choice the same for each band? Is it reasonable to compare a whole year, or should it be...


The evolution of software in radio ...

Foundations of Amateur Radio The amateur community is nothing if not entertaining. Look at any discussion about a mode like FT8 and you'll discover people who describe it as the dehumanising end of the hobby. In the same thread you'll find an amateur who's been licensed longer than I have been alive who welcomes it using words like revitalising, more active, and the like. If you're not familiar, FT8 is one of many weak signal digital modes that gained popularity over the past years during the most recent solar minimum when long distance HF propagation was challenging. That example discussion was about the visible end of a mode like FT8, but there's an often overlooked all but invisible aspect of these modes that is much more significant, namely the popularisation of signal processing in software. In many ways amateur radio is more about receiving than transmitting. This might not be obvious, but what's the point of transmitting if you cannot receive? Using software to do the listening makes for an interesting evolution that might be hard to grasp if I start digging into the fundamental algorithms that make this happen, instead let me describe a process that is easier to explain. Imagine that there's a piece of software that knows how to decode digital signals. As the user of that decoding software, or decoder, you send audio into one end and callsigns and grid-squares come out the other end. How it does this isn't important right now. We measure the quality of this decoder by how many times it correctly does this, in other words, how many times a correct callsign and grid-square comes out. The decoder can be improved by changing the way that the decoding process works. If the number of correct callsign and grid-squares that come out increases, the quality of the decoder is improved. Now imagine that the decoder spits out the callsign 7N5EC with the grid-square OF78. This particular combination emerged as a WSPR decode on the 10th of December 2022. It was reported by AA7NM as a 100 Watt signal, 14,882 km away on the 40m band. The signal report was -30 dB. If you know where OF78 is, you'll immediately spot a potential problem, if not, I'll help you out, OF78 is located near Perth in Western Australia. It's unlikely that a transmitted callsign in that part of the world starts with anything other than VK6. Mind you, a weather balloon with an odd callsign could theoretically be overhead in that location, but I've not yet heard of a 100 Watt transmitter on 7 MHz that someone hung from a weather balloon. Another problem is that 7N5EC is a callsign that appears to be Japanese. It starts with 7N which is part of the Japanese callsign block, but the next symbol is the number 5 and at least according to the research I was able to do is not actually a currently valid callsign. The prefix 7N4 is allocated to the Kanto region on Honshu island, the largest island in Japan. 7N5 doesn't seem to be valid as a prefix. Ironically, that callsign will now exist on the Internet as soon as this article is published, but that's a whole other problem. Either way, the chances of the combination of the callsign 7N5EC with the grid-square OF78 is unlikely to be correct. It gets even less likely if you consider that the callsign was reported only once in fifteen years and over 500 million WSPR decodes, I checked. That means that if you updated the software to ignore that particular decode, you'd have improved the decoder by removing an incorrect combination. You could keep doing this by checking callsigns against grid-squares and against allocated callsigns and you'd have made a higher quality decoder. Before you start arguing that this isn't fair, it's exactly the same process as the super check partial list does for people operating in a contest. The idea being that if you only recognise known contesting callsigns, you've got a better chance of making contact. Think of it as a way of filtering out potentially incorrect callsigns. It still...


Path loss and very small numbers ...

Foundations of Amateur Radio Sometimes you learn mind boggling things about this hobby, often when you least expect it. Recently I discussed having my 20 mW WSPR or Weak Signal Propagation Reporter beacon heard on the other side of the planet, in Denmark, 13,612 km away. That in and of itself is pretty spectacular, but it gets better if you consider just how weak the signal was by the time it got there. In radio communications there is a concept called path loss or path attenuation. Until recently I understood this to mean the things that impede a signal getting from transmitter to receiver. That includes coax and connector losses, refraction across the ionosphere, reflection off the surface of the planet and diffraction around objects. It turns out there is another factor called "Free Space Path Loss" to consider. It's loosely defined as the loss of signal strength between two antennas. The name sort of implies that something happens to the signal in free space, which is odd if you know that in space, radio waves, regardless of frequency, travel without loss and will travel pretty much indefinitely. So what's going on? To get started, think about a dome lawn sprinkler, one of those little round discs that sits on the ground with the hose connected to the side. You turn on the tap and the water sprays in all directions. If you're really close to the sprinkler when the tap is turned on you'll get sopping wet almost immediately, since most of the water will hit you directly. This is particularly fun in the heat of summer on New Years Day in Australia, not so much in the middle of winter on the other side of the globe. If you stand a couple of meters away, you'll still get wet, eventually, but it will take much longer, because most of the water isn't hitting you. If you stand even further away and assuming the water still gets that far, it will take even longer. A small towel and a big towel will both take the same length of time to get wet if they're held at the same distance from the sprinkler, but if you wring them both out, you'll discover that the big towel captured much more water during the same time. In radio communications we can combine these two ideas, the distance and the size of the receiver, to describe free space path loss. The further away from the transmitter you are, the less signal is available to you to capture since much of the signal is not heading in your direction and the bigger your antenna, the more signal you receive. The bigger the antenna, the lower the frequency, which is why you'll discover that free space path loss is dependent on both distance and frequency. To give you an idea of scale, the free space path loss for 28 MHz over 13000 km is about 144 dB. While the name "Free Space Path Loss" implies loss of signal across the path in free space, the loss is not due to distance as such, rather it's caused by how much the signal is spread out in space. Similarly, there isn't more loss because the frequency is increased, it's that less signal is captured by the smaller size or aperture of the antenna required for a higher frequency. So perhaps a better name might be Spherical and Aperture Loss, but then everyone would have to learn how to spell that, so "Free Space Path Loss" it is. I'll point out that this is the minimum theoretical loss, in reality the loss is higher than this, since it also includes all the other parts of the path loss which are things that we can control, like coax and connector loss, and things we can improve by frequency selection, like ionospheric reflection and refraction which depend on solar conditions. The one aspect of path loss that we have no control over is the "Free Space Path Loss", so perhaps that's why we don't talk about it very much. I'll mention that in path loss calculations often antenna gain at the transmitter and receiver are used to reduce any path loss figures. If I have an antenna with 6 dB gain, then that reduces my overall path loss by 6...


What is the difference between handheld, mobile and a base radio?

Foundations of Amateur Radio If you've ever been in the market for a new radio, and truth be told, who isn't, you'll find yourself faced with a bewildering array of options varying from obvious to obscure and everything in between. At the obvious end of the scale are things like price, bands and transmit power and at the other end are things like Narrow Spaced Dynamic Range, which you'll find explained by Rob NC0B on his website where he's been publishing receiver test data for many decades. One of the more subtle options you'll need to consider are handheld, mobile or base radio. This is harder than you might think, since radios are increasing in functionality every time you wake up and if you look long enough, you'll discover that they're getting smaller at the same rate. Once upon a time you could just look at the size of a radio and define it as belonging in one or other category, but that's no longer a useful distinction. For example, my PlutoSDR is a tiny device, fits in my pocket, but there's no way I'd consider it a handheld, or even a mobile radio. You might think that a bigger box has more stuff inside, costs more and performs better. For example, the Drake R-4C receiver and companion T-4XC transmitter require external power and were once rated by the ARRL as very good. In reality the Drake R-4C performed terribly in a CW contest, incidentally, that was what caused Rob to start testing radios in 1976. That receiver and transmitter manage to cover 80m, 40m, 20m, 15m and 10m and together weigh in at 14.3 kg. They're considered a base radio. The Yaesu FT-817, runs on batteries, weighs in at just over a kilogram and can be carried with a shoulder strap. It comes as a single device and covers many more bands than the Drake transmitter and receiver do, it would be considered a mobile or even portable radio. Obviously it would be hard to jam a Drake into your car or strap it to your belt, but does that mean that you cannot use an FT-817 as the base radio in your shack? In case you're curious, the slightly beefier brother to the FT-817, the mobile FT-857d, is sitting on my desk as my current base radio. Has been for years. So why do manufacturers continue to make this distinction between handheld, mobile and base radio? One look at the nearest radio catalogue will tell you that it's not based on either performance or price, not even close. You can buy a handheld with more functionality for the same price as a mobile radio and that same is true when you compare a mobile radio to a base radio. Radios vary in price from $20 to $20,000. A cynical person would suggest that pricing is based around extracting the most money from your pocket, but a more charitable explanation might be that physical size dictates things like the number of buttons you can fit on a radio, how many connectors can be accessed before the radio flies off the desk from the weight of the coax hanging off the box, how big is the display and other such limitations. I'm not being glib when I use the word charitable, since much of modern transceiver design revolves around software which can pretty much fit in any box. Using external computers, neither buttons nor a display are needed, leaving external connectors, which if we're being really honest could all fit in a box that would fit in your pocket. At this point you might wonder if handheld, mobile or base has any meaning at all. As I said, in most cases it doesn't. There's really only one place left where this matters, and that's when you have access to strictly limited space and power if you need to put the radio in your pocket or cram it into your car. For your home shack, the distinction is unhelpful for most, if not all, amateurs. Don't believe me? The Yaesu FT-710 currently ranks fourth on Rob's Sherwood Engineering Receiver Test Data List. It's a quarter the size of the top radio and it's sold as a "Base/Portable Transceiver". Yaesu calls it "Compact". It might not fit in the...