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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?".
Updated: 1 hour 31 min ago

When should I go on air?

Sat, 05/14/2022 - 12:00
Foundations of Amateur Radio

When you obtain your license there's a whole lot of learning to be had before you even get started with your first transmission, but when you get there you'll discover that learning has just begun and the rest of your life will be beset with challenges, quests, discovery and dawning understanding.

One of the early and recurring questions is around the best time to be on air. Before I get into the why, the answer is, right now.

This interminable question will continue to haunt you throughout your life, and the most pressing answer will be shaped around the missed opportunity. You'll discover tools that assist with predicting propagation, web-sites that explain what the various layers of the ionosphere do and how they affect your ability to use radio to make contact with other amateurs.

There's learned discussion around testing and tracking propagation, special modes that help create your own maps for your own station and you'll discover an endless supply of experts who will advise you when you should power up your transceiver and call CQ.

Whilst I've only been an amateur for a short time. In the decade to date I've learnt one thing about propagation. Despite all the tools, the discussion, the maps and forecasts, there is no substitute for actually getting on air and making noise. Over the past while I've been watching the propagation from my own shack using a 200 milliwatt beacon and I've discovered that running 24 hours a day, every day, well, almost every day, my signal gets to places far beyond my wildest dreams.

I have also discovered trends. That is, the average distance of the signal reports is increasing over time. This isn't a linear thing, not even a recurring thing, much like the ebb and flow of the tides, varying from day to day, a little bit at a time, inexorably making your shoes wet when you least expect it.

While to some extent we've tamed the prediction of the tides with complex and interrelated cycles, discovered by using Fourier transforms, we're no-where near achieving this level of sophistication for the ionosphere and its associated propagation.

Just like predicting a specific wave is still beyond the capabilities of a tide table, predicting the ability of a radio wave to make it from your antenna to that of another amateur is beyond any tool we have today.

Another way to look at predicting the complexity associated with the ionosphere is comparing it to weather forecasting. We have national forecasting bodies, with millions of sensors, super computing cycles that dwarf most other research, a global network of satellite sensors, roughly a quarter of which have some form of earth sensing capability, transmitting terrabytes of data every day and still we cannot determine where on Earth it's going to rain tomorrow.

The ionosphere, whilst it's being monitored, is not nearly as well resourced. It's not nearly as visible to the average person as the packing of an umbrella and the political perception of need is nowehere near as urgent as getting the weather right.

So, absent accurate forecasting, finding a better way to determine when to get on air is required. That said, I've discovered that regret is the biggest motivator to get on air. The day after a contest when a friend made a contact with an amazing station, or the lunch break where I didn't power the radio on to discover a random opening to a clamouring horde of calls looking to make contact.

So, my best advice to you is to get on air whenever you can. You might not make a contact every time, but you'll discover what the bands look like right now and you'll have the chance of hitting the jackpot with a rare contact and truth be told, I think your chances of making a contact are higher than winning the lottery.

When you do take that step, you'll start discovering the ebb and flow of the bands, discover the characteristic sound that each band makes and what a band sounds like when it's open and when it's not. You'll hear stations far and wide, discover that while there are trends in propagation, there are no rules. From one moment to the next, you'll discover the thrill of hearing something unexpected.

One thing to consider, if you get on air for the sole purpose to make contacts, you're likely going to be disappointed. It's like fishing. Most people don't get up at some crazy hour, sit on a damp jetty, freezing parts of their anatomy off for the sole purpose of catching fish.

So, get on air and make some noise, today.

I'm Onno VK6FLAB

Augustin-Jean Fresnel, Zeppelins and a picket fence ...

Sat, 05/07/2022 - 12:00
Foundations of Amateur Radio

In our hobby we regularly invoke line of sight when we discuss the VHF and higher bands. It's a simple concept to help describe when two transceivers can hear each other. The process evokes an image of a beam of light travelling unobstructed between the antennas at either end. Some might picture a laser, others a flashlight, both are useful to become familiar with some of the concepts.

If there's a pole between the two, a laser beam, unless it's particularly powerful, won't go through to the other side. A flashlight beam on the other hand might fit around the pole and still be visible at the destination. That illustrates that objects can get in the way of a signal, reducing strength and sometimes blocking it entirely, but it's not the only effect at play.

Imagine a building with a mirror glued to its side. If you shine a laser at an angle at the mirror, you can reflect the light off the mirror and essentially still land on target. This is useful if you want to avoid an obstacle directly between you and your destination.

The reflected light travels a different and slightly longer distance than direct light would, but if there's no obstacles, both will arrive at the destination.

This is an example of a multipath, where the same signal arrives at its destination using multiple different paths.

If you've ever used HF radio, making a contact on the other side of the planet, it should come as no surprise that radio waves travel in more than just straight lines. Depending on frequency, radio waves can be affected by phenomena like ionospheric reflection and refraction, atmospheric ducting and even bounce off water, the ground, mountains, hills and objects like buildings, aircraft and even water droplets, along their path.

Each of these cause a radio signal to take multiple paths to arrive at the destination.

It gets better.

A radio signal that travels along a different path takes a measurable difference in time to get to its destination when compared with another path for the same signal. From a radio signal perspective, this difference in time is also known as a phase shift.

Now consider a single radio signal that travels along two paths, just like our laser beam and mirror. If you imagine a radio signal as a sine wave, you can draw the two signals on the same chart. They will be in lock-step with each other, since they're the same radio signal, but they won't be on the same place on the chart. In relation to each other they'll be shifted along the time axis, since one took longer than the other to get to the destination.

At the destination, the receiver hears a combination of both those signals. They're added together. That means that what's sent and what's received are not the same thing and why it's a great idea to use phonetics in radio communications. In some cases the two signals help and strengthen each other, they're said to interfere constructively, and sometimes the signals hinder and cancel each other out, or interfere destructively.

Said in another way, a radio signal can arrive at a receiver along multiple paths at the same time. What's heard at the receiver is essentially a cacophony, caused by each slightly different path. Since the signals are essentially all the same, some of these signals reinforce each other, where some cancel each other out.

This effect isn't absolute, since the different path lengths aren't all exact multiples of the wavelength of the signal, they're all over the place, but there will be groups of paths that help and groups that hinder. This phenomenon was first described by Augustin-Jean Fresnel on the 14th of July, 1816 in relation to light and we now call these groups, Fresnel zones.

Fresnel zones are numbered, one, two, three and up. The first or primary Fresnel zone is the first group of radio signals that helps strengthen the signal, the second zone is the first group of signals that hinders. The third zone is the second group of radio signals that helps and so-on. Odd helps, even hinders.

I should point out that a Fresnel zone is three dimensional. The primary Fresnel zone essentially has the shape of a Zeppelin stretched between the source and the target. The secondary zone is wrapped around the outside of the primary zone like a second skin, but it's thicker in the middle.

In practical terms, what this means in point-to-point radio communications is that your antenna needs to be located in a place where most of the signal arrives. The rule of thumb is that the primary Fresnel zone needs to be at least 60% clear, but ideally 80%.

If you're in a situation where a receiver is moving, say in a car, you can imagine that your antenna is moving in and out of direct line of sight to a transmitter, but it's also moving between the various Fresnel zones. If you were to move your antenna from the first Fresnel zone to the second and then the third, the signal would be strong, then weak, then strong again.

If your receiver is an FM receiver and it's moving from the first zone to the second, it could fall below a threshold and the signal would effectively vanish. Continue to move from the second into the third zone and the signal would sound like it suddenly reappeared as it climbed above the threshold. Do it fast enough and the signal sounds like it's stuttering.

That stuttering has a name. In amateur radio we call it picket fencing or flutter and it's commonly heard in mobile situations on FM transmissions on the VHF and higher bands, but it can be caused by other changes in propagation distance, for example an antenna moving in the wind. The higher the frequency, the less movement is needed to experience this.

To add to the fun of radio, the same threshold effects, actually called the FM capture effect, can be caused by other phenomena, like two stations of similar strength on the same frequency, or interference from the electronics in your vehicle.

And finally, I should point out that the higher the frequency, the smaller the Fresnel zones, and the more susceptible to an object in the path a signal is, but you already knew that, a pole will block a laser beam, but not a 2m conversation on the local repeater.

So, line-of-sight isn't just a straight line, it's a whole lot more fun.

I'm Onno VK6FLAB

The Science of Amateur Radio

Sat, 04/30/2022 - 12:00
Foundations of Amateur Radio

The amateur radio community is as varied as humanity across the globe. It represents an endless supply of ideas and experiments that continue to attract people looking for something new and exiting.

On the face of it, our hobby is about radio and electronics, about propagation and antennas, about modes and contacts, but if you limit your outlook to those topics you'll miss out on a vast expanse of opportunity that is only just beginning to emerge.

Until quite recently, computing in amateur radio was essentially limited to logging and contest scoring. It has evolved to include digital modes like PSK31 and the advent of smaller, faster and cheaper computers in the home has brought the possibility of processing unimaginable amounts of data leading to modes like WSPR and FT8.

In the past I've spoken about how amateur radio means different things to different people. Making contact using a digital internet enabled repeater is sacrileges to one and manna from heaven to another. Between those two extremes there is room to move and explore. Similarly where one uses valves, another expects an integrated circuit. One wants low power, the other wants every Watt they can lay their hands on. Contesting versus rag chewing, nets vs contacts, SSB vs. CW, FT8 vs. RTTY. Each of these attracts a different part of the community with different outcomes and expectations. For some it's about antenna building, others going portable, climbing a mountain, or setting up in a park.

Those are all traditional amateur activities, but the choice and opportunity don't end there.

The longer I play with computers the more I see a convergence in the world, a coming together of technologies and techniques. I've talked about some of this before when in 1994 I produced a competition broadcast promotion for the radio station I was working at, using just a computer in the era of reel-to-reel tape and razor blades. My station manager couldn't quite put his finger on what was different, but with hindsight it represented a landslide change in how radio stations have operated since. Mind you, I'm not saying that I was the first, just the first in that particular radio station.

In many ways computing is an abstract effort. When asked, I like to express it as designing something intangible in an imaginary world using an made up language and getting paid real money to make it happen, well, numbers in my bank account at least.

Within that context, amateur radio is slowly beginning to reap the rewards that come from the exponential growth in home computing power. While the majority of humanity might use the vast amount of CPU cycles to scroll through cat videos online, that access to processing power allows us to do other things as well.

For example, right now I'm playing with the dataset that represents all the WSPR spots since March of 2008. As of now there are around four billion rows of contacts, containing data points like a time-stamp, the transmitter, the receiver, the signal strength, location, direction, and more.

As part of that investigation I went looking for documents containing the words "RStudio" and "maidenhead", so I could consider creating a map in my statistical tool that allowed me to represent my dataset. In making that search I discovered a thesis by a mathematician who was using the reverse beacon network in an attempt to predict which station could hear which transmitter at what time.

In reading the thesis, which I opened because I was looking for an example on how to convert a maidenhead locator into geo-spacial data types in R, a popular statistics platform, I discovered that the author didn't appear to have much, if any, amateur knowledge or experience, but they approached their task, attempting to predict as a mathematician what we in our community call propagation, based on a public dataset, downloaded straight from the reverse beacon network, created by amateurs like you and I.

This interaction between science and the amateur community isn't new. Sometimes it's driven by science, other times it's driven by amateur radio. There's a team exploring the ionospheric prediction models that we've used for decades, popularly referred to as VOACAP or Voice of America Coverage Analysis Program, based on multiple evolutions of empirical models of the ionosphere that were first developed in the 1960's, headed by both a scientist and an amateur, Chris KL3WX.

With the advent of WSPR and the associated data collection some experiments have started to compare the reality of propagation as logged by WSPR to the predicted propagation as modelled by VOACAP. One such experiment happened in 2018 where Chris and his team at HAARP, the High-Frequency Active Auroral Research Program, set out to make transmissions at specific times and frequencies, using the amateur community logging of WSPR spots to compare their transmissions to the predictions.

Interestingly they did not match. Just think about that for a moment. The tool we love and use all across our community, VOACAP, doesn't match the reality of propagation.

My own playing with WSPR data is driven by the very same thing that I use to be a better contester, a burning curiosity in all things. My VOACAP prediction experience has been poor to date. Setting up my own WSPR beacon is the first step in attempting to discover what my actual propagation looks like, but in doing so, it's also a possible contribution to the wider challenges of predicting propagation based on a dataset with four billion spots. One such approach might be to create an ionospheric prediction map based on actual data and compare that to the models as well as the published space weather maps and combining these efforts into a machine learning project which might give us the next generation of ionospheric prediction tools, but only time will tell.

No doubt I will have to learn more about statistics and machine learning than I expect, but then, that's half the fun.

So, next time you think of amateur radio as being limited to valves, transistors, soldering, antennas and rag chewing on HF, consider that there might be other aspects to this hobby that you have not yet considered.

What other research are you aware of that relates to amateur radio?

I'm Onno VK6FLAB

The art of troubleshooting the digital world.

Sat, 04/23/2022 - 12:00
Foundations of Amateur Radio

The lure of digital modes and the opportunities they bring are enough to tempt some amateurs to begin a journey into integrating their radio and computer to make a new world come to life. This isn't without pain or challenge, but the outcomes are so enticing that many embark on this adventure every day.

As a person who has made this trip it's heart warming to see the joy writ large on the face of an amateur who makes their first FT8 contact on a home brew wire dipole rigged together on a Sunday afternoon to take advantage of the latest opening on the 10m band.

On the flip side, it's heart breaking to see an amateur falter at the first hurdle, attempting to make their computer talk to their radio and giving up because it just won't work. At first this attitude bewildered me in a community of experimenters, but over time I've come to understand that sometimes an analogue approach isn't suited to the digital world. There isn't really a place where you can attach your multimeter and see why the serial connection isn't working, nor is there any universal document that can walk you through how to set things up.

So, for you, if you're in a place where you've all but given up, let me see if I can find words to encourage you to keep trying. I'll skip the propaganda about going digital and move straight to making it work.

This might come as a surprise, but in the digital world, things are built in complex layers of interdependence. Said in another way, using an analogy, to turn on a light you need flick a switch, which depends on power to the switch, which depends on power from the fuse box, which depends on power from the street, which depends on power from the substation and so-on.

If you flick the switch and the light stays off, you need to figure out which part of the chain failed. Did it fail at the bulb or at the substation? If the street is dark, do you need to check the fuse box or the bulb? That's not to say that either, or even both, can also be faulty, but there's no point in checking until the street has power.

From a fault finding perspective, the number of variables that you have control over, in the case of a light bulb not switching on, is strictly limited. You can control the bulb and the fuse and in most cases that's about it, the rest of the chain is outside your direct control.

In attempting to make a computer talk to a radio you can be forgiven in thinking that the level of complexity associated with such a trivial task is just as direct and straightforward. Unfortunately, you'd be wrong. It's not your fault. A popular slogan "Plug and Play" made people think that computers were easy to use and control.

The truth is a far darker reality. One of the hidden sources of frustration in the digital world is the extreme level of complexity. In our quest to standardise and simplify we have built a fragile Jenga tower of software that can collapse at any point. Most of the time this is completely invisible but that doesn't cause it to be any less real. Computers are simple, but only if you control the environment. And when I say control, I mean take ownership of each change.

Updating the operating system? Installing a new application? Adding a new peripheral? Changing location? All these things, innocuous as they might seem, can fundamentally alter the behaviour of your environment.

As an example, consider the location of your device. Let's say that you changed the location of your computer, either physically or via a preference. All of a sudden your Wi-Fi network stops working. The one that you used for years. Turns out that changing location changed the Wi-Fi driver to stop using a particular channel, not permitted in your new location. If you're curious, this happened to me last week.

The point being that troubleshooting is about controlling change in that fragile environment.

So, when you're trying to figure out how to make your serial connection work, you need to stop fiddling with everything all at once and change one thing at a time. Discovering the layers of dependency makes this difficult at times, but not impossible.

For example, a working serial connection requires that both ends are physically connected, speaking the same language at the same speed. That depends on the radio being correctly configured, but it also depends on the computer having the right drivers installed. It also depends on the software you're using being configured correctly to talk to the right serial device and the operating system giving your software permission to do so. It depends on the software using the right radio mode and it depends on the radio being switched on.

Now, imagine the serial connection "not working".

Do you check the radio mode before you check if the radio is turned on?

What about the physical connection?

When you're troubleshooting, you cannot just look at the error message on the screen and follow that path. You need to ensure that all the underlying things are working first. You don't check the bulb until there's light in the street. Same thing. No need to worry about the error until you've discovered that the radio is on, the cable connected correctly, the driver installed correctly, the speeds set right and the mode configured properly. If and only if that's all correct, then look at the error.

This becomes harder if it worked yesterday. What changed between then and now? Did your operating system do an update? Did your radio forget its settings? Did the cat jump on your desk and dislodge a cable overnight? Is there an earth fault that caused the serial connection to cease working?

Sometimes, despite your best efforts, you cannot find the problem.

At that point you need to take a step back and think about how to prove that something is working in the way that you think it is. Multimeter to a light bulb to check continuity - style. In the case of a serial connection, what can you use to test the link if your favourite tool doesn't work or stopped working suddenly?

I've said this before, but it bears repeating, since it's not obvious.

Troubleshooting is all about discovering and controlling change.

Pick one thing to test, prove that it's correct, then pick the next. Eventually you'll come across a "Duh" moment. Don't sweat it, we've all been there. Now do it again!

What's your best troubleshooting moment?

I'm Onno VK6FLAB

How far can you go?

Sat, 04/16/2022 - 12:00
Foundations of Amateur Radio

Antennas and propagation are the two single most discussed topics in our hobby, that and how an FT8 contact isn't real. Not a day goes by without some conversation about what antenna is the best one and by how much? In my opinion it's a futile effort made all the worse by so called experts explaining in undeniable gobbledegook, or sometimes even using science, just how any particular antenna is a compromise.

The truth is that most conductive materials radiate to more or lesser degree. Sometimes there is enough of that to make it outside your backyard into the antenna of a fellow hobbyist. To make a point, as is my wont, over the past months I've been conducting an experiment. It's the first in a series all related to antennas and propagation. As has been said, the difference between fiddling and science, is writing it down, so this is me writing it down.

I'm using the tools available to me to explore the various attributes of my station and how it affects what's possible. I will observe that this is within the dynamic nature of the environment, so the solar cycle, solar events, thunderstorms and noise are making an impact. No doubt I'll create a visualisation that links some of those extra variables, but for now I'm just noting that these external events affect what I'm doing.

You might recall that I took delivery of a WSPR beacon a few months ago. If you're unfamiliar, WSPR or Weak Signal Propagation Reporter, is a tool that allows a station to transmit a time synchronised signal on a specific frequency, so other stations can look for, and attempt to decode it. Think of it as a timed Morse code signal and you'll have a pretty close understanding of what it does.

The beacon I purchased was a 200 milliwatt, ZachTek 80To10 desktop transmitter, built by Harry, SM7PNV. It can operate on all the HF bands I'm licensed for and can run all day, every day. It's time-synchronised using a supplied GPS antenna and powered by a Micro USB cable. It's currently connected to my vertical antenna.

That vertical antenna is a homebrew helically wound whip, tuned for the 40m band, clamped to the side of my metal patio roof. It's fed by an SGC-237 antenna coupler which is held by magnets to the roof. A 75 Ohm, RG6 quad shield coax cable, about 20m long, left over from my satellite dish installation days, is connected via several adaptors and coax switches to the beacon.

This is not a fancy set-up by any stretch of the imagination, but it's my station and what I use to get on air to make noise and that's the whole point of this exercise. You might recall that one of the reasons I want to learn Morse is so I can hear an NCDXF beacon and know which one I'm hearing on my own station. In many ways, this is a different way to approach the same problem.

Said plainly, "How do I determine what propagation is like for me, right now, on my own gear?"

There are countless tools available, from the Voice of America VOACAP propagation prediction, through the graphs and charts on clublog.org to the Space Weather Services run by the Bureau of Meteorology in Australia.

All of these tools have one thing in common, they don't use your own gear.

Unsurprisingly, you're likely to wonder what it is that I can achieve with a mere 200 milliwatt transmitter and a vertical. Turns out, quite a lot. As of right now, my WSPR beacon has been heard multiple times over the past three months in the Canary Islands, over 15 thousand kilometres away. The Watts per Kilometre calculation puts that at over 76 thousand kilometres per Watt, not bad for a little amateur station located in the middle of a residential suburb. Did I mention that this was on the 10m band?

I was asked if I would put a pin in my DXCC map, tracking the countries for each of these WSPR reports and my answer to that is "No". This is not a contact, this is a propagation ping. I suppose that I could, if I really wanted to argue the point, which I don't, use a pin if I had a reciprocal report from the other station within a set period of time, but that's not why I'm doing this. The purpose of this exercise is to discover what my station is capable of, what propagation is like, how it changes over time, how uniform my radiation pattern is and how much of the globe can hear my signal.

One observation to make is that much of the West Coast of the United States is a similar distance away from me, but so far there are no reports from that continent. As a quick and dirty test, I'm using my Yaesu radio and 5 Watts for the next day to see if this is an edge case, or if there is something else going on. For example, my house has a peak metal roof, to the West of my antenna. Is it possible that it's affecting the radiation pattern, or is there something else going on, like the neighbour's house that sits to the East?

For all I know the noise floor in the Canary Islands is significantly better than anywhere in the USA, but only time will tell.

I've recently taken delivery of a multi-band vertical antenna which I'm planning to use to replace my current vertical. The main reason being that my antenna coupler cannot tune with 200 milliwatts and to do band-hopping I'd have to re-tune manually each time, not something that is sustainable 24 hours a day.

No doubt that change will bring other discoveries, but then, I'm keeping track.

The intent of all of this is that you can experiment with your own station, test ideas, trial a set-up, keep a log and discover new things that your station presents to you. Amateur Radio is never just about one thing, it's always a dozen different things, all at the same time.

What are you going to discover next?

I'm Onno VK6FLAB

After the chaos ... building the ideal shack

Sat, 04/09/2022 - 12:00
Foundations of Amateur Radio

One of the first questions a new amateur asks is "Which radio should I buy?" It's a topic I've discussed at length and the answer "It depends." is unhelpful without doing more research, but after you've done the work, you'll be able to answer it for yourself.

A question that is just as important, but not asked nearly enough, frankly, I've not heard it in the decade I've been part of this community, is: "How should I build my shack?" The answer is just as useful, "It depends."

So, let's explore what precisely your shack design depends on. Let me start with pointing out that I'm not here to give you answers, you can watch hundreds of YouTube videos, read a gazillion web-pages and get no closer than discover how others have answered this question. It wasn't until recently that I understood that it was a question at all, but airing my frustration at the level of dysfunction of my shack unearthed it and in attempting to answer my own question, I started to explore the landscape.

As with choosing a first radio, one of the very first answers you need for yourself about the ideal shack is: "What do you want to use it for?"

That in and of itself is not enough. I had an answer for that, I want to operate my weekly net, I want to do casual HF contesting, have a beacon running and have space for experimentation. It wasn't until Ben VK6NCB suggested that I dedicate a single radio to the weekly net and the contesting and use the other for experimentation, that I discovered that this wasn't going to work for me.

I want to be able to use both my radios at the same time, in a so-called Single Operator Two Radio setup, or SO2R. This will allow me to extend the boundaries of my comfort zone and in doing so, will give me plenty of new things to learn.

So, the question: "What do you want to use your shack for?" is probably the single most important thing you need to discover. If you're like me, the obvious answer is: "Everything!", but reality soon sets in and you might start to create an actual list of things that you want to do. Prompted by Ben's suggestion, I was able to articulate for the very first time something that I didn't want to do. I didn't want to set a radio aside for experimentation. So when you're considering what you want to achieve, also think about what you don't want.

For example, I have no interest in using the 6 meter band at this time. Not because it's a bad band, far from it, it's because I'm not permitted to use it with my current license. Same for the 23 cm band. This means that I don't have to find ways of making my shack accommodate those two bands. My current license permits me access to precisely six bands and the station I'm building only needs to access those bands at the moment. That brings me to the next question for the ideal shack design.

"How long do you expect the layout to last?"

For example, are you going to build a new building for your shack, for the next 50 years, or is it something that's going to last for the weekend? Is your shack going to be moved, or is it something a little more permanent? Are you going to change your needs and should you incorporate some of that into your design, or are you perfectly happy with what you're doing today? You have to remember, this is your shack, not mine, not your friends, yours. It means that it needs to accommodate what you want.

The next question, boring as it might be, "How much money are you going to spend?"

Building a whole new shack out of a catalogue is perfectly fine, but you might discover that the gear you have today is ample to get your shack started. You might leave space for a different piece of kit, or you might decide that the shack needs changing when a new shiny piece of equipment arrives in a nondescript brown box.

Some other things to consider are, "What operating actually looks like?"

I've seen shack videos that look like a tour through a radio museum with more radios than I have keys on my keyboard, sometimes all connected, other times, just stored on shelves to look at.

Are you going to have more than one radio operating at the same time and if so, how are you planning to control them? How many antennas are connected to this shack and how do you track which antenna is connected to which radio?

What are you going to do about power? Does everything run on mains power, or are you going to build a 13.8 Volt supply for all your gear?

Where are you planning to put computer screens, what about keyboard, mouse, Morse key and antenna switching controls? In other words, "What do the ergonomics of your shack look like?"

Remember, there is no right answer. The answer you come up with is yours and yours alone. Look at things that work for you and take note of things that make you wince when you see it in another shack somewhere. That's not to say that you should be dismissive, rather, use the opportunity to ask the shack owner why they made that choice. Who knows, it might cover something you hadn't considered yet.

So, what does your ideal shack look like?

I'm Onno VK6FLAB

In the beginning there was chaos...

Sat, 04/02/2022 - 12:00
Foundations of Amateur Radio

Over the weekend I learnt to my chagrin that my shack was not ready for the contest I decided to participate in for an hour. Truth be told, it was probably me who wasn't ready, but I'm going to blame my shack, since it can't argue and besides this is my story.

It started off with turning on the HF radio. That involved turning off my 10m WSPR beacon which is transmitting its little heart out 24 hours a day into the one vertical antenna it shares with my HF radio.

Turning off the beacon was simple enough, reach into the mass of cable and dig out the USB power lead that plugs into the beacon. Then follow the antenna coax to the correct switch. Whoops, that's the GPS coax, the other one, there's the switch, now switching it to the HF radio.

Why didn't the sound change, actually, come to think of it, what sound? Hmm, the audio is going into, nothing, actually, it's going into the audio mixer that's turned off. Turn that on. Then audio at last, nope. Hmm, oh wait, the audio needs to go from the HF radio, not the VHF radio that's configured to do some audio spectrum recording. Turn off the Raspberry Pi at the same time, since there's no more audio going into that and who needs more potential noise? Locate the two audio plugs that go into the radio audio adaptor, disconnect the Pi audio, connect the radio audio, now, which one is the microphone?

Now I've got it all plugged in, still no audio. Hmm, two of the mixer channels are muted. Turn on one, radio goes into TX, that's not good. Turn it off, radio stops transmitting, sigh of relief. Turn on the other channel, finally hear some squeaky sounds. Ahha, it's coming from the headset.

Don the headset, now I've got glorious mono in my brain. Test the microphone, nothing. Hmm, ah the switch on the microphone lead. Now I've got RX and TX going. Yay, victory!

Now turn on the computer so I can do some logging. Fire up my trusty, wait, which tool? The one I normally use for casual contesting hasn't seen a new version since the author became a silent key, no idea if the rules for this contest are still current, fire up the next one, that needs a brand new configuration file, but that means reading the manual and I've got more important things to do.

Try another one, Yes, that's got the rules ready to go. No idea if the rules are current, but at least there's no configuration file to contend with.

At this point I'm two hours into my one hour contesting window and I have to stop. Haven't even tuned the antenna and I'm already out of time.

Hmm, this shack is rigged.

Wonder who I should blame for that?

Some days all good intentions come together. Other days they don't. There's always the next contest.

Lessons learnt, my shack needs a serious rethink on how best to set it up so I can operate daily, experiment and accommodate a casual contest. Looks like I'm off to the hardware store for some brackets and my documentation clearly needs updating, actually, truthfully, needs writing.

I'm Onno VK6FLAB

Planning for an emergency...

Sat, 03/26/2022 - 12:00
Foundations of Amateur Radio

Identifying the problem is the first step in fixing it and with that I want to talk about emergencies. One of the very first things I was told about our amateur radio community was that we're here for when emergencies happen. Our purpose is to communicate, so in a crisis, we can assist by supplying communication to the situation.

I've talked about some of this before. Preparedness in the way of on-air training by contesting, in getting gear ready and even exercises for when this occurs. There are amateur clubs dedicated to putting up repeaters for just such an eventuality.

Recently there was a local news item about radio amateurs banding together, sending gear to fellow amateurs who were hit by severe flooding that wiped out their shack and with it their ability to communicate.

Another event was a friend who lost a big chunk of his shack when his basement flooded.

Across Australia and in other parts of the world in recent times we've been witness to the most devastating fires that destroyed entire towns and communities, taking with it infrastructure, communications, not to mention stock, local flora and fauna and entire wildlife ecosystems, bringing some to extinction levels.

The destruction doesn't end there. War and famine, drought, cyclones, hurricanes or typhoons, snow storms, heatwaves and the like.

All those situations can to greater or lesser degree benefit from amateur radio communications, either for amateurs affected, or for the community at large.

I started considering what would actually be required to be useful in such a situation. Could you be prepared for anything, or are you required to pick and choose? What does "being prepared" actually look like and what steps can you take once it's happening?

I asked myself if sending radio gear to amateurs who are affected by floods is the most effective way to actually help, or would it be better to pass the hat around and send the proceeds to their bank account?

Should you as an amateur drive into an emergency area and start communicating, or are there better ways to help?

There are local amateur radio emergency service groups under various names in different countries, some of which are highly effective, others much less so.

One attempt I made was to join the local volunteer state emergency services. For several reasons that didn't work out for me, but it remains a viable option for some.

Joining those types of groups gives you a framework, but does it actually answer the underlying question, that of effectiveness?

I have a drawer full of emergency service training manuals, each more dense than the next, but very little of it relates to the amateur radio. Many pages are dedicated to search and rescue, staying alert, first aid, keeping alive, hand signals, log books, mapping and the like.

I am left wondering why we as a community, with a proud century of activity, having one of the main principles as emergency communication appear to have such a poor track record of actually considering what dealing with an emergency looks like and what your own individual place could be in that situation.

We document our radios, antennas, power supplies, contacts, circuit board designs, contesting procedures and all the rest of it, but we don't seem to do the same for emergencies.

Why is that?

In my opinion, it's time to document emergency amateur radio and if you have already started, get in touch.

I'm Onno VK6FLAB

Why do we communicate?

Sat, 03/19/2022 - 12:00
Foundations of Amateur Radio

The art of amateur radio is many things to many people. For me it's a technological challenge, a learning, a way to broaden my experience, a way to be technically active away from my consultancy. The place that amateur radio takes in your life might be the same, or it might be completely different, as varied as the people I've encountered since I became an amateur.

People from all walks of life with different experiences and vastly different stories. Truth be told, in the decade that I've been an amateur, I've spoken to and met people from more diverse backgrounds than in the forty years before that. I make that statement as a person who migrated across the globe twice, travelled through a dozen or so countries, stood on stage in front of thousands of people, taught countless classes and as a radio broadcaster interviewed people from all over the planet.

From paraplegic to quadriplegics, from people with terminal diseases to people struggling with their identity, from astronomers to astrologers, from train drivers to truck drivers, from mariners to motorcyclists, from working to retired, from healthy to hospitalised, from local to remote, from energetic to sedentary, from happy to sad, from connected to isolated and everything in between.

As a host of a weekly net for new and returning amateurs I've begun to notice that some people are falling away, either sitting on the side because they feel that they have nothing to contribute, or stopping communication altogether.

It occurred to me that for some people amateur radio is the only way that they connect to the world around them. It's the only way for them to meet people who are different, who walk a different path, who tell a different story. It's also sometimes the only thing that makes them get out of bed.

In a world where we're all busy, dealing with the realities of daily life, trying hard to figure out what our place is in that experience and trying hard not to lose your identity while you're attempting this, it's easy to overlook the amateur you didn't hear from for a week or a month.

I know that for several of my new friends, amateur radio kept them alive for longer and made them smile more often and made their life a little easier, even if several of them have become a Silent Key since I counted them as my friend.

When one of the main activities of our hobby is communication, it seems appropriate to take a moment to consider what that looks like from the other person's perspective. What might it be like to be acknowledged, to be validated as a human, to see them and their life, to speak with them, even if only briefly, and to take a moment out of our own busy existence and answer that CQ, or respond to a question, or smile with a fellow amateur.

There is another aspect to this, one which I've not actually seen in the amateur community. Perhaps I've been too busy to notice, but it appears that the venerable telephone circle, the idea that one person calls the next person on the list, who then calls the next and so-on. If the last person doesn't get a call within a set time, they call the list backwards and discover who is not answering their phone. It's an effective way for people to regularly talk to each other and it's an excellent way to make sure that everyone is OK.

In our own community of amateurs we can do the very same thing. Hosting a net is one way, having a daily commuter chat is another, but when you do this, take a moment to consider who didn't check in and see what they're up to.

It's fascinating to me that we're a hobby that's primarily made of old men, yet we haven't actually embraced our own ageing process as part of the experience. Sure there is a need to encourage new people into the hobby, but that's not the entire story. We should be so lucky as to speak with our friends on a regular basis, to check-in with each other and to make sure that we're all getting our daily dose of RF.

So, ask yourself how the community around you is doing and how you might take a moment to check-in with those not so near, but just as dear to you.

I'm Onno VK6FLAB

Introduction to the terms of contesting

Sat, 03/12/2022 - 11:00
Foundations of Amateur Radio

One of my favourite activities is contesting. Essentially it's a time-limited activation of your station for the purposes of testing your skill and station against other participants. Contests are controlled by rules as varied as the amateur community itself.

That said, there are common terms and concepts and if you're not familiar with them, they can lead to confusion and disappointment when you inadvertently break a rule and see your hard work vanish into thin air.

I will note that what I'm discussing here is not universally true, so read the rules for each contest you participate in, something you should already be doing since rules are refined over time and it's rare to keep the same rules between years.

A contest starts and stops at a specific time, often expressed in UTC, or Universal Coordinated Time. You should know what your local timezone is in relation to UTC and take into account any variations like Summer and Winter time. Any contacts made outside these times don't count and you cannot log these against the contest.

Each contact or QSO is awarded a set number of points. It might be scored based on mode, band, power, time and sometimes distance. To encourage specific types of contacts, some might attract a score of zero. This does not mean that the contact is useless, which I'll get to shortly.

Your score is the sum of all the points you make for each contact. I will mention that contest logging software can track this to make your life easier, although it comes at the price of requiring a computer.

Sometimes a prohibited contact attracts penalties. Prohibited, as-in, by the rules of that contest. For example, some allow you to contact the same station more than once, others allow this only if you do it on a different band.

Speaking of bands. It's not permitted to make contest contacts on the WARC bands. In 1979, the World Administrative Radio Conference allocated the 30m, 17m and 12m bands for amateur use. These are not used for contesting. To avoid a contest, you can use those bands, but truth be told, you should try to use all the bands, even during contests, since it will help you operate your station in adverse conditions, something worth practising.

Many contests allocate additional scoring based on state, country, DXCC entity, CQ or ITU zone, prefix, or all of these together.

Both the CQ and ITU zones represent regions of the world. The CQ zones are managed by CQ Magazine and the ITU zones are managed by the International Telecommunications Union. A zone is represented by a number.

The DXCC is a system that tracks individual countries across the globe. If you make contact with 100 of these places, you've achieved your DX Century and you join the DX Century Club, or DXCC.

Consider a contact with me. You'd have a contact with VK6FLAB. It would also be a contact with the VK6 prefix, the VK DXCC entity, CQ zone 29 and ITU zone 58. If that's not enough, it would also be a contact with OC-001, the IOTA or Islands On The Air designation for Australia.

This is useful because for some contests these extra features represent points, often significant ones, generally referred to as a "multiplier".

To calculate your score, tally up all your contact points, then count all the features, CQ Zones, the ITU Zones, DXCC entities, states, countries, etc. and multiply your score with that count. If you contact 10 callsigns and get one point for each, you have 10 points. If in doing so you contact five contest features, you end up with an overall score of 50 points.

Often contests have different categories and rules for transmitter power level, the number of transmitters and the number of operators.

Definitions for these vary. High Power might be 400 Watts in Australia, but 1500 Watts in the United States. QRP or very low power might be 10 Watts in one contest, but 5 in another, so check.

Some contests have an assisted category where you're permitted to use tools like the DX Cluster where other stations alert you online to their presence on a particular frequency.

There is a concept of an overlay, where how long you've held your license, your age, working portable, battery operated, using a wire antenna or mobile, groups you with others doing the same thing. This means that you could be a rookie, youth, portable, battery, wire antenna, single assisted operator, all at the same time. It often pays to consider who else is in a particular group and make your claims accordingly.

If you're contesting with more than one person, a Multi station, there are rules for that too. Sometimes this includes the amount of land a contest station is permitted to use.

If you're a Multi-Single station, you might be permitted to use one transmitted signal on one band during any 10 minute period.

A Multi-Two might be permitted to use two simultaneous transmitted signals, but they must be on two different bands.

A Multi-Multi may activate all six contest bands at the same time, but only use one transmitter per band.

Some contests have a Short Wave Listener or SWL category, where you log all stations heard. There is also the concept of a check-log, where you log all your contacts, submit them, but don't enter the contest itself. You might have worked stations during the contest, but not according to the rules, because you might be aiming to get your DXCC. Submitting your log will help the contest organisers check other entries and validate the scores of the stations you contacted.

This might all be daunting, but if you read the rules of a contest and you're not sure, every contest manager I've ever spoken to is more than happy to help you understand what's allowed and what isn't.

One tip. Contesting is as much about the rules that are written as it is about the rules that are not. If you find a gap in the rules, and it doesn't go against the spirit of the contest, you're absolutely encouraged to use that to your advantage. If you do, you'll quickly discover why the rules change so often.

Preparation is everything!


It beeps!

Sat, 03/05/2022 - 11:00
Foundations of Amateur Radio

After weeks of attempting to get some noise, any noise out of my PlutoSDR I have finally cracked it. Not sure if cracked it refers to my sanity or the outcome, but beeping was heard from the Pluto on my radio, so I'm doing victory laps around the house, all conquering hero type affair, complete with whooping and hand waving.

In the end it all came down to serendipity and truth be told, I know it beeps, I've heard it beep, it does so on a predictable frequency, but why it exactly works is still a mystery that has yet to be discovered since the documentation I have isn't sharing and the example code I have contradicts what I'm seeing.

For context, a PlutoSDR, or Pluto, is a very capable software defined radio, perfect for experimentation. I've talked about it before in the context of using it as a receiver.

My most recent efforts involved coaxing my Pluto out of a corner after it sat there sulking for weeks. Turns out that not only was my USB power lead broken, which caused the blinken lights to stay off. When I finally figured that out, I discovered that one of the two wireless dongles I'd purchased together was Dead On Arrival. After a frustrating morning with the manufacturer who wouldn't take my word for it that swapping out the two identical units would not require installing the driver, something about Windows Device Manager on my Linux computer, I went back to the store who happily swapped out the faulty device on the spot. Mind you, the Pluto still isn't talking to my wireless network, but at least it's not the dongle anymore.

I plugged the Pluto into the back of my main workstation and discovered to my surprise that in addition to showing up as a thumb-drive, which I knew about, it also turned up as a network device, which I didn't know about.

It's been a while since I powered this up to play, so I updated the firmware which fixed some annoying issues and started to explore.

The aim of my quest was to create a proof of concept beep from the command-line on the Pluto.

If you're not familiar with this. The Pluto is running a flavour of Linux. You can connect to its command-line and run commands from inside the hardware.

This is important because for most radios, of both the analogue and software kind, you generate the information somewhere, like Morse Code, a WSPR signal, your voice, what-ever and then you send that to the radio. On an analogue radio it's likely to go across an audio cable of some sort and if you have a software defined radio, it's likely to travel from your computer across a USB or network cable to the radio to get processed.

This is different in that there is no such signal coming across the USB link. The link is used as a network cable to ssh into the radio where you can generate whatever you want. In my case Morse. If you're not familiar with ssh, think of it as a keyboard connection to a remote computer.

My script, hacked together as it is, more on that shortly, takes a string, like say "CQ DE VK6FLAB" and processes that character by character. It converts each into the equivalent Morse code dits and dahs and then uses those to turn on a test tone for an appropriate amount of time.

So, to send "CQ", the script changes that into -.-. --.- and then turns on the transmitter for three units, off for one, on for one, off for one, on for three, off for one, etc.

This is Morse code at its very simplest, the software equivalent of holding down a Morse key for the correct amount of time and then releasing it.

I disparagingly called it hacked together, because it's using the in-built busybox command shell that comes with the Pluto. If you're familiar, the actual shell is called ash, or Almquist shell. It's strictly limited in functionality, no arrays, minimal redirection, all very basic. Perfect for what I want to do, but not so much if you want to write software.

After working around the lack of arrays, one of the things that caused me the most problems was to discover just how to setup the Pluto to actually do this. I found a couple of examples online that pretended to work, claimed to be doing what they said they were, but nothing was heard on my local analogue radio. At one point I heard clicks, but no beeping.

After spending literally hours testing, scanning up and down the radio dial with my Yaesu FT-857d, I stumbled on a tone that stopped when my test script stopped. I started the script again and the tone came back. When it ended, the tone stopped again. I finally had a relationship between a tone on the PlutoSDR and the frequency on my radio.

So, with all manner of funky offsets in my code, subject to me understanding the how and what of them, I can now beep to my hearts content. Of course I've shared my efforts on github, cunningly called Pluto Beacon.

Have a look and tell me what I did wrong.

I'm Onno VK6FLAB

What happens when you plug it in?

Sat, 02/26/2022 - 11:00
Foundations of Amateur Radio

The other day I took delivery of a shiny new circuit board populated with components and connectors. Knowing me, you'd assume that I'd been the recipient of some kind of software defined radio gadget and you'd be right.

One of the connectors was a micro USB socket, intended to be used to plug the hardware into a computer and to drive the circuit board.

The board came to me by way of a friend who saw it online, waxed lyrical about it and for less than $35, who could begrudge this exploration into a new toy?

Once it arrived, it sat on my shelf for a few weeks, enticingly packed in an anti-static bag, transparent enough to see the device inside, taunting me to open it up, plug it in and have some fun.

Today I opened it up and started researching my new gadget. It didn't come with any user manual, no URL, no model number, but it did have a callsign on it, so I started there. I'll note that I'm not going to repeat that callsign here for a number of reasons, which I'll get to.

My exploration discovered a site where this device was being sold. It also unearthed several international amateur radio forums describing what appeared to be this device, including circuit diagrams and specifications.

What I found harder to discover was software.

It appears that I have a clone of a device that may still be manufactured, or not, I cannot tell. I found some example code on github for the original hardware, but it seemed to require other libraries, but didn't actually specify those anywhere.

I opened up an online translation tool and started translating some of the wording on the circuit board in an attempt to discover just what information was written on the board.

The wording was clearly from a different culture, a different perspective and while it claims to come from a maker space that appears to promote women, it also contained a militaristic phrase which caused me to pause.

In that moment I came to a sudden and abrupt realisation.

How do I know what this piece of hardware actually does?

How do I know if when I plug it into the first available USB socket on my computer, it won't install anything nefarious, start connecting to the internet and start doing something unexpected? There's enough hardware on the circuit board to do that and even if the labels on the components tell me that they are a specific integrated circuit, how do I know that it actually is that chip?

The chips on this circuit appear to have a lot more connectivity than a simple receiver might warrant. One has 40 pins, the other 32. If the label is accurate, the data sheet for one of the chips indicates that it includes an 8-bit micro controller among its various functions.

I'll admit that I'm coming from an IT security background at this and you are free to argue that I'm being paranoid, but does that make me wrong?

I know that I don't know enough about this particular board or its origins that for now it's going to remain inside its anti-static bag, taunting me with the possibilities of the connectors it offers, but until I know more about the provenance of this gadget, it's going nowhere near any of my computers.

If you have suggestions on how to proceed, don't be shy. I did briefly consider plugging it into a Pi, but how would I know if it updated the firmware, forever compromising that Pi?

Don't get me wrong, I'm not saying that this board does any of this. My point is around discovering if it does, or not, one way or another.

No doubt some might think I'm overly suspicious and there is truth in that, but in my profession it pays to be vigilant. The underlying issue is that of validation. There's anti-virus software available to deal with malicious code, but how do you do such a thing for malicious hardware?

Again, I'm not saying that this circuit board is doing anything other than being a USB connected receiver, but how would you know? How would you verify that? And how do we in the amateur community weed out the nefarious tools from the legitimate ones?

I'll leave you with one thought. When was the last time you plugged your phone into a free charger on the bus or at the airport? How do you know that your phone wasn't hacked?

I'm Onno VK6FLAB

How to compare radios

Sat, 02/19/2022 - 11:00
Foundations of Amateur Radio

One of the topics I've been talking about lately is the idea that we might be able to measure the performance of your radio in some meaningful way using equipment that can be either obtained by any amateur, or by introducing a process that allows results to be compared, even if they have been generated differently.

Recently I came up with a tool that automatically generates a spectrogram of an audio recording. That on its own isn't particularly interesting, but it's step one in the processing of an audio signal. In addition to the spectrogram, I also created a tool that generates a tone frequency sweep, think of it as a tone that changes frequency over time, let's call it a sweep.

If you combine the two, you can generate a spectrogram of the sweep to give you a starting point or baseline for comparison. You can build on that by using your radio to transmit that sweep and record the result using a receiver. In my initial experiments, I used an RTLSDR dongle to receive the audio with some success and a boatload of spectacular harmonics, but I wanted to find a better, more accessible way to do this and during the week I realised that my Yaesu FT-857d that's sitting in my shack, is connected to a perfectly functional antenna and with a few settings it could do the job perfectly.

One of the biggest issues with my RTLSDR setup was squelch. That is the difference between what is a legitimate transmission and what is noise. Set it too high and you hear nothing, set it too low and you hear everything, including background noise.

Since the VHF or 2m noise levels are quite high at my location, or QTH, I normally have the squelch completely closed. This is fine if you're normally using a strong repeater, but if you're attempting to receive a weak hand-held, that's never going to work.

As any self-respecting amateur I was dragged down the path of last resort to read my user manual where I discovered that in addition to CTCSS, a way to transmit a tone to open a repeater, there's also a setting called Tone Squelch or on my radio TSQ, which will keep my radio squelch closed, unless it hears the CTCSS tone from another radio.

Truth be told, I had to read a different user manual to discover how to actually set the CTCSS tone on my handheld to test, but that's just adding insult to injury. It has been a while since I read any manual, even though I try to get to it once a year or so. I blame it on the lack of field-day camping. That's my story and I'm sticking to it.

So, combining all this, the spectrogram generator, the sweep, CTCSS, and adding a Raspberry Pi with some website magic, if you're interested, an AWS S3 bucket, I now have a service that listens on a local frequency, opens the squelch if it hears the correct CTCSS tone, records the incoming signal until it stops, then generates a spectrogram from that audio and uploads it to a web site.

None of this is particularly complicated, though I did have some bugs to work through. I've published the code as a branch to my existing frequency-response project on github and I've asked my local community to experiment with what I have on-air before I start doing more far reaching experiments.

For example.

If I were to tune my radio to a local repeater output frequency, rather than the simplex one I'm currently on, I'd be able to record and generate spectrograms for each transmission coming from that repeater. If that repeater was connected to the internet, using AllStar, IRLP, Echolink, DMR or Brandmeister, or even all of them, the global community could send their audio to my recorder and it could generate a spectrogram on the spot.

If using that repeater, you played a sweep into your microphone, or used your digital audio interface to play the sound, you could then compare your signal path against others and against the baseline response.

One of the issues with doing this is that much of the audio that travels across the internet is pretty munched, that is, it's compressed, frequencies are cut-off, there's all manner of interesting harmonics and the value of the comparison appears limited at best.

Once I have my multi-band HF antenna, which I'm told is still being built, I intend to set this contraption up on HF where we can do point-to-point recordings and we end up having a direct comparison between two stations who transmit into my frequency-response software.

I should add some disclaimers here too. At the moment I'm only using FM. The intent is to get this to a point where I can compare any mode, but when I move to HF, I'll likely start with Single Side Band and go on from there.

One other annoyance is that any user needs to configure CTCSS to make this work, which is yet another hurdle to overcome, not insurmountable, but I like to keep things simple when you're starting to learn.

Also, the harmonics still show, even on an analogue radio, so there's plenty more to discover.

In the meantime, what kinds of things can you think of to use this for?

I'm Onno VK6FLAB

Pictures can say more than words

Sat, 02/12/2022 - 11:00
Foundations of Amateur Radio

Recently I've spoken about measuring the frequency response of your radio and what the benefits of doing so might be. Today I've got some progress to report and some initial discoveries. Again, this is preliminary, but then all of this hobby is experimentation, so that should come as no surprise.

Let's start with the mechanics of what I'm doing and a "duh" moment I need to confess.

The aim of this process is to transmit a known audio signal, receive it, record it and create a spectrogram from it. This allows us to compare the original spectrogram against the received one and show just how the audio path has been affected by getting the audio into the transmitter, the processing by the transmitter, the propagation between the transmitter and receiver, the artefacts introduced in the receiver and any recording device.

To begin this process I started off with an audio file of my voice. That wasn't very helpful, since it's a complex signal and comparing my voice before and after is a non-trivial process. At some point I intend to come back to voice before and after comparison, but that's on the shelf for now.

The audio that I'm using is a frequency sweep, lasting 5 seconds. That is, there's a tone that changes frequency from DC to 5 kHz. When I looked at the spectrogram of that, it shows as a curve with time against frequency. It occurred to me that I could make two of those sweeps at the same time to measure distortion, so I added a reverse frequency sweep from 5 kHz down to DC. Now I've got two crossing lines showing in my spectrogram.

To transmit this audio, I'm using the same tool I use to automatically call CQ during a contest. Every so many seconds I transmit this audio into a dummy load and at this point I should mention that my "duh" moment was that I was attempting to transmit into an antenna and record from a dummy load, rather than transmit into a dummy load and record from an antenna. I still cannot believe that I did that.

Moving on.

The recording is done using an RTLSDR dongle. In the current initial version I'm using a tool called rtl_fm to tune the dongle to the same frequency as my transmitter. I send the audio from there to the same tool I used to generate the original audio, SoX, that's Sierra, Oscar, X-Ray, and have it detect the silence between each transmission and record each into a new file. If I leave it running, every time I transmit something, SoX will create a new audio file.

I'm saying that quite quickly, but getting the squelch and silence detection working in my noisy environment took most of a day and it's specific to my station, today. I'll have to figure out how to make this smarter, but for now I have some data.

A spectrogram is generated for each audio file and then we can compare pictures. What was sent, audio wise, and what was received, audio wise. To be clear, I'm not sending images, I'm sending audio and comparing the spectrograms of this audio.

I will also note that I'm currently using FM as the mode. I intended to do this with SSB, but the amount of effort to get the squelch right has left me with a future project to achieve that.

The code itself is pretty rudimentary, but I've uploaded it to my github page. I've also added the pictures to my project website, which you can find at vk6flab.com.

One initial observation, one that I don't yet understand, is that what I sent and what I received don't look the same. My pretty curves in the original audio come back with spectacular harmonics all over the place, very pretty to be sure, but not quite what I was expecting, let's call it an educational challenge.

Before I forget, just because I'm using a Yaesu FT-857d, a Raspberry Pi, an RTLSDR dongle, an antenna and a dummy load, doesn't mean that you need to. Essentially, what this does is generate a special audio file, transmit it, receive it, record it and generate a spectrogram. You can play the audio from your own computer if you have digital modes set-up, or from your mobile phone if not.

Recording can be something sophisticated with off-air monitoring, or it can be a recorder held in front of your receiver.

One final note. You can change settings on both the transmitter and the receiver to see what they do in relation to the audio, so experiment.

I'm Onno VK6FLAB

Testing your radio's audio frequency response

Sat, 02/05/2022 - 11:00
Foundations of Amateur Radio

During the week I was reading a comment from another amateur about digital modes. Tucked inside that comment was a phrase that could easily have been overlooked, but it reminded me that there is plenty to learn and test in the field of amateur radio.

The phrase, "requires actual understanding of audio level paths" was uttered by Chris, VK2CJB and it prompted a brief conversation at the time, but I've been working on it ever since.

Where I arrived at is an attempt, incomplete as yet, to design a mechanism to show the impact of various transmitter settings on the received audio in such a way that you can test your own gear and see the result.

Before I explain how I'm doing this, let me describe why it's important.

Using a radio in concept is pretty simple, if you yell into the microphone, the audio comes out distorted and if you whisper, it might also be distorted, but in a different way, neither is conducive to communication.

One way to improve this is a tool called the ALC. Using Automatic Level Control as a guide to what level your audio should be is outlined in every amateur radio manual I've seen, but how much it matters and to what extent is left unsaid. If you apply a filter or any number of other fancy options, what happens to your audio?

To get some sense of what I'm describing, listening back to your own voice after it comes across HF SSB is surprisingly distorted in comparison to a local recording.

You might argue, what's the harm, as long as the other station can hear my voice, we're good to go.

Sure, if voice is all you're using, but what if it's data? In that case, the audio you're transmitting is actually encoded digital information. To decode it, the software needs to deal with frequencies, distortion and levels to name a few.

In computer science, "garbage in, garbage out" is the concept that flawed, or nonsense input data produces nonsense output. In our case, if you transmit garbage, the receiver is going to start with garbage and what gets decoded is likely not what you expect.

Without going into error correction, essentially, the cleaner the path between the transmitter and the receiver, the higher the chances of success and to be fair, you already know this when you attempt to work a pile-up on a noisy band. "Again, again, just the prefix, again!", sound familiar?

To achieve this I started with the idea that you could transmit a tone and if you knew what it was, you could determine the difference between what was sent and what was received.

My first step was to generate a single 1 kHz tone, but then I wondered what would happen if you did multiple tones, one after the other. My current version is an audio frequency sweep, running from 0 to 5 kHz in five seconds. It's essentially a computer generated sequence of tones with known characteristics. You transmit this audio file using your radio and then record it off air, either from a local receiver, WebSDR, or the radio belonging to a friend.

Using the recording, you can create a spectrogram, a picture, showing the frequencies over time present in the audio. Compare the two and you just learnt what each setting on your radio does precisely to the audio.

Of course it's simple for me to say this, but I'm working on using a tool I've spoken about before, csdr, to do the heavy lifting, so you can actually do a meaningful comparison between the various audio files.

In the mean time, I've managed to use SoX, the so-called Swiss Army knife of sound processing programs to both generate the audio sweep and draw a preliminary spectrogram.

Next up is showing some side-by-side images of various radio settings and their effect on the spectrogram. I'll publish this on my website when I have something to show-and-tell.

I also don't yet know if my source audio file is going to be sufficient, but I'll subject that to some testing as well. For example, I'm investigating multiple simultaneous audio sweeps with different frequency ranges. The more complex the spectrogram, the more we might be able to learn from the distortion on receive, but time will tell.

If you have some ideas on how to improve this, let me know.

I'm Onno VK6FLAB

What's in a Dream?

Sat, 01/29/2022 - 11:00
Foundations of Amateur Radio

On the 6th of June, 2004, two Brazilian amateurs Roland, PY4ZBZ and Arnaldo, PY4BL made a historic contact on 40m. The distance was not particularly significant, only 70 km, but the mode was.

Using 2.1 kHz bandwidth, so it could fit within an amateur radio SSB transmission, they used software created by Swiss amateur Francesco, HB9TLK to make the very first HamDream exchange.

This technological advancement represents the birth of what we now call HamDRM and Digital SSTV and how it came about is an adventure that needs documenting, since what we have is written in a combination of Portuguese, German and English, cobbled together from broken websites, archives, source code, commit comments and lost links.

To provide some context, there is a broadcast radio mode called DRM, or Digital Radio Mondiale. At this point I should mention that this has absolutely nothing to do with Digital Rights Management with the catchy acronym of, you guessed it, DRM. As you might expect, this acronym clash is unhelpful, to say the least, when you're trying to find information about this radio mode.

Digital Radio Mondiale, or DRM, essentially defines a digital standard for radio broadcast transmissions. It can handle multiple audio streams as well as file exchange and is used by broadcasters across the globe. Mondiale, in case you're curious means worldwide in French, seems my high school language lessons have finally been put to good use, my French teacher in the Netherlands will be thrilled.

DRM is more efficient than AM and FM and as an open standard, it's gaining popularity. The first broadcast using this mode took place on the 16th of June 2003, during the World Radiocommunication Conference in Geneva.

An open source implementation of this mode is called Dream. The source code is available online and is capable of being compiled for Windows, MacOS and Linux. Dream was originally written by Volker Fischer and Alexander Kurpiers. The Dream project started in June of 2001 and today it has many contributors.

The DRM standard uses different bandwidths depending on which mode is used. The narrowest DRM mode uses 4.5 kHz, but modes using 100 kHz exist. By comparison, a typical analogue amateur radio uses 2.7 kHz for SSB. Using the source of Dream, Francesco built a modified version, called it HamDream and let it loose on the world. It was used for that very first 70 km contact between Roland and Arnaldo.

Several versions of HamDream existed. The first QSO used 2.1 kHz and the last version of HamDream used 2.5 kHz bandwidth. To fit digital audio inside that narrow bandwidth it used different audio compression techniques, called a CODEC, namely LPC10 and SPEEX.

According to Francesco, HamDream is the basis for all current amateur radio 2.5 kHz HamDRM programs. He goes on to say that it's outdated and the source and executables were removed from the net. Personally I think that's a shame, since it represents part of the history of our community and I think that putting the source online in a place like GitHub would be beneficial to the hobby.

The 2.5 kHz HamDRM mode is implemented in several places. QSSTV, EasyPal and WinDRM to name a few. No doubt it's elsewhere. Of those three, only QSSTV survives. The source code for EasyPal, written by Erik VK4AES, now SK, was lost, apparently when the computer on which it lived was sold by his estate. Ironic really, since EasyPal was written because Erik lost a previous application due to a lightning strike nearby and was forced to write a new application from scratch.

WinDRM appears even more elusive. There's a repository on the now archived Google Code site. There are derivatives that appear to use a version of WinDRM, but details are hard to find. An archive I have shows a commit by Francesco, HB9TLK from 2008. I've yet to learn how this relates to the overall picture.

In parallel, in 2005, a few enterprising students made a MATLAB implementation of DRM. Called Diorama and written by Andreas Dittrich and Torsten Schorr it forms the basis of a Linux open source HamDRM receiver written by Ties, PA0MBO, chosen because it had a better performance in marginal conditions than Dream did. It's called RXAMADRM. Ties also wrote an open source transmitter, cunningly called TXAMADRM. It was based on the source code of Dream, specifically v1.12b.

If at this point your head is exploding, I wouldn't blame you.

Let's recap.

There's an open broadcast standard called DRM. An open source, cross platform tool called Dream, in active development, implements that standard.

A special, now discontinued, version of Dream was created called HamDream. It used less bandwidth than DRM and forms the basis of a standard that we now call HamDRM, which underpins Digital SSTV.

HamDream forms the basis of the discontinued products, EasyPal and WinDRM, and lives on in TRXAMADRM and QSSTV, both Linux open source.

In amateur radio terms HamDRM is one of the ways we can efficiently exchange digital information across long distances.

At this point you might wonder why it matters?

For starters, this is part of our history of amateur radio. The HamDRM mode is poorly documented, if at all. It forms the basis of several modes in use today and writing your own software is made all the more challenging because much of the design and development of this mode has been lost.

What's more, HamDRM is an example of "modern radio". It uses the same fundamental techniques used by the 4G and 5G mobile phone network, as well as modern Wi-Fi. Losing this is a massive step backwards for amateur radio.

This article alone represents a week of research by two people, thank you Randall VK6WR, and I won't be surprised to learn that it contains errors and omissions. It shouldn't have to be this hard to discover how a mode works, what is used to make it tick and how to write new software to implement a new application.

Gotta love open source. Speaking of which. If you have source code copies of HamDream or WinDRM, I'd love to hear from you. cq@vk6flab.com is my address. If you have documentation on the design of the HamDRM mode, I'll owe you a beer, or a glass of milk, your choice.

I'm Onno VK6FLAB