Foundations of Amateur Radio

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Word of the day: software Mar 07, 2021

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Foundations of Amateur Radio

Every community has its own language. As a member of that community you learn the words, their meaning and their appropriate use. For example, the combination of words "Single Side Band" have a specific meaning inside amateur radio. Outside of radio, those same words are random words with no relationship.

Sometimes a term like "FM" can be heard across many communities with similar understanding, though not identical.

It gets tricky when a word is used widely but doesn't have a common understanding at all. A word like "software" for example.

A question you might hear in amateur radio is: "Can I buy a software defined radio or SDR that has digital modes built-in?"

It's a perfectly reasonable question, the radio runs software, the digital modes are software, so the answer is obvious, right?

What about: "Can the hundred or more computers in my car play Solitaire?"

Aside from the perhaps unexpected fact that your car has computers on board, you most likely know the answer to that. No, since the computers are specialised for different tasks - and if you're driving a Tesla right now, yes, you can play Solitaire, but I'd recommend that you keep your eyes on the road instead.

My point is that not all software is created equal.

The software inside an SDR is essentially doing signal processing, often by several components, each running software, transforming an antenna signal into something, that can be used somewhere else, likely sound.

The applications WSJT-X and fldigi, both software, use a computer running Linux, MacOS or Windows, software, to decode and encode digital modes while providing a way for you to interact with it. Software running on software.

You might well argue that we should be running applications like that directly on our radio and on the face of it that sounds perfectly reasonable, except that to achieve that, you'd also need to build a system to install and update different types of applications, so you could run SSTV, APRS, RTTY, PSK31, FT8 or any of the other hundreds of digital modes and new ones as they are developed.

If you did that, you'd also have to provide a way to manage the operating system, to connect to the Internet and provide security. You'd need to develop a user-interface, perhaps a keyboard and mouse solution, a screen, etc.

Before long you'll have developed a whole computing infrastructure, much like the one we already have in the form of the computer on your desk or the phone in your pocket.

Computers are getting faster and faster every day. This allows for the software on them to become more and more complex. The inter-dependencies are increasing by the second, but that doesn't mean that specialisation isn't useful.

A software defined radio likely has a Field Programmable Gate Array, an FPGA on-board that is great at processing data in streams. It too runs software. Your microwave is running software, as is your television, your smart-watch, your battery charger, the gearbox in your car and your electric tooth brush.

Making a distinction between the various types of software is helpful to understand what is possible and what is not. Being a computer nerd, I must point out that I've only barely scratched the surface of software here, in-case you're curious, microcode, firmware, hardware abstraction, the rabbit hole goes very deep.

Not all software is created equal and every now and then it's a good idea to remember that when you talk about a word in one community, it might mean a completely different thing in another and sometimes the distinction is significant.

As for having an SDR that runs WSPR, no. You can transmit from a computer though, but that's a whole other thing.

I'm Onno VK6FLAB

How many hops in a jump? Feb 28, 2021

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Foundations of Amateur Radio

Amateur radio lives and dies with the ionosphere. It's drilled into you when you get your license, it's talked about endlessly, the sun impacts on it, life is bad when the solar cycle is low and great when it's not. There's sun spots, solar K and A indices, flux, different ionosperic bands and tools online that help you predict what's possible and how likely it is depending on the time of day, the frequency, your location and the curent state of the sun. If that's not enough, the geomagnetic field splits a radio wave in the ionosphere into two separate components, ordinary and extraordinary waves.

All that complexity aside, there's at least one thing we can all agree on. A radio wave can travel from your station, bounce off the ionosphere, come back to earth and do it again. This is known as a hop or a skip. If conditions are right, you can hop all the way around the globe.

I wanted to know how big a hop might be. If you know that it's a certain distance, then you can figure out if you can talk to a particular station or not, because the hop might be on the earth, or it might be in the ionosphere. Simple enough right?

My initial research unearthed the idea that a hop was 4000 km. So, if you were attempting to talk to a station at 2000 km or at 6000 km you couldn't do that with a hop of 4000 km.

If you've been on HF, we both know that's not the case.

If you need proof, which you really should be asking for, you should check out what the propagation looks like for any FT8 station, or any WSPR beacon over time and you'll notice that it's not 4000 km.

Just like the crazy network of interacting parameters associated with propagation, the distance of a hop can vary, not a little, but a lot.

In 1962, in the Journal of Geophysical Research D.B. Muldrew and R.G. Maliphant contributed an article titled: "Long-Distance One-Hop Ionospheric Radio-Wave Propagation". They found that in temperate regions such a hop might be 7500 km and in equatorial regions even 10,000 km.

I'm mentioning this because this was based on observations and measurements.

They used frequency sweeps from 2 to 49 MHz though they called them Mega Cycles, using 100 kHz per second, that is, over the duration of a second, the frequency changed by 100 kHz, so each sweep took nearly 8 minutes using only 15 kilowatts, so substantial gear, not to mention expense and availability.

Oh, computers, yes, they used those too. A three tonne behemoth called an IBM 650, mind you, that's only the base unit, consisting of a card reader, power supply and a console holding a magnetic drum unit.

You know I'm going somewhere with this right?

Today, you can do the same measurements with a $5 computer and a $20 receiver. For a transmitter, any HF capable radio will do the trick, though you might not be transmitting long if you stray outside the amateur bands. For power, 5 Watts is plenty to get the job done.

My point is that there is a debate around the future of our hobby and why modes like FT8 are such a controversial topic in some communities.

I'm here to point out that since that publication in 1962 our hobby has made some progress and we can improve on the work done by people who came before us. We could build a glob-spanning real-time propagation visualisation tool, we already have the data and modes like FT8 keep feeding in more.

If you're inclined, you could even make such a plot in real-time for your own station.

So, how long is a hop?

You'll just have to find out.

I'm Onno VK6FLAB

You Can't Always Get What You Want Feb 21, 2021

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Foundations of Amateur Radio

One of the things about amateur radio that I find intensely fascinating and to be honest sometimes just as frustrating, is that you don't know what the outcome of an experiment might be at any one time. Not because you cannot control the experiment, or because you don't know what you're doing, but because the number of variables involved in most meaningful amateur radio experiments is pretty much infinite.

I've spoken about this before, the idea that if you were to make a simple dipole antenna and fold the ends on each other, you'd have infinite variation in antennas with just a so-called simple antenna, since you can vary the shape of it in an unending variety of ways.

The other day I was doing an experiment. An amateur radio one to be sure, but I was doing this within the realm of computing. I have been playing with digital modes for some time now and along the way shared some of what I've learnt. It occurred to me that I've been assuming that if you had the chance to follow along, you'd have access to the required hardware, simple enough, a $20 RTL-SDR dongle, but none-the-less, extra hardware.

What might happen if you rule out that dongle and instead used a web-based receiver like WebSDR, or KiwiSDR, or any number of other such sites where you can pretty much tune to any band and frequency and see what's going on at a particular antenna location.

For one it might allow you to decode something like APRS remotely, or decode an FT8 signal, perhaps even your own FT8 signal. Unfortunately most, if not all, of those sites include only the bare bones decoders for things like CW, AM, SSB and FM. After that you're pretty much on your own.

You could do some funky stuff with a web-browser, linking it via some mechanism to the tool you use to actually decode the sound and there's some examples of that around, none that I really warmed to, since it requires that I open a web browser, do the mouse-clicky thing and then set-up some audio processing stuff.

What if I wanted to figure out where the ISS was right now and wanted to listen to a receiver that was within the reception range of the ISS as it passed overhead, and automatically updated the receiver in real time as the ISS was orbiting the earth?

For that to happen you'd need something like a command-line tool that could connect to something like a KiwiSDR, tune to the right frequency and extract the raw data that you could then decode with something appropriate.

Turns out that I'm not the first person to think of this. There's even a project that outlines the idea of following a satellite, but it hasn't moved anywhere.

There's also a project that is a command-line client for web-based KiwiSDR sites, but after spending some quality time with it and its 25 clones on github, I'm not yet at the point where this will work. Mainly because the original author made a design decision to record data to a file with a specific name and any clone I've found thus far only allows you to define what name to use. None so far actually appear to send their stream to something that can be processed in real time.

Of course I could record a few minutes of data and process that, but then I'd have to deal with overlap, missing data, data that spans two files and a whole host of other issues, getting me further and further away of what I was trying to do, make a simple web-based audio stream digital mode decoder.

As the Rolling Stones put it, "You Can't Always Get What You Want"

And to me this sums up our hobby in a nutshell. When you call CQ, or go portable, or test an antenna, or attempt to build something new, there's going to be setbacks and unexpected hurdles.

I think that it is important to remember that amateur radio isn't finished, it's not turn-key, no matter how much that appeals, you cannot find a one size fits all solution for anything, not now, not yesterday and not tomorrow.

This hobby is always going to test boundaries, not only of physics, but your boundaries. It's after all one giant experiment.

So, next time you don't get what you want, you might try something you find, and get what you need.

Also, apologies to Keith Richards and Mick Jagger for butchering their words, a rockstar I am not.

I'm Onno VK6FLAB

Running out of things to do ... Feb 14, 2021

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Foundations of Amateur Radio

So, there's nothing on TV, the bands are dead, nobody is answering your CQ, you're bored and it's all too hard. You've run out of things to try, there's only so many different ways to use the radio and it's all too much.

I mean, you've only got CW, AM, SSB, FM, there's Upper and Lower Side-band, then there's RTTY, the all too popular FT8, then there's WSPR, but then you run out of things. I mean, right?

What about PSK31, SSTV, then there's AMTOR, Hellschreiber, Clover, Olivia, Thor, MFSK, Contestia, the long time favourites of Echolink and IRLP, not to forget Fusion, DMR, D-STAR, AllStar, BrandMeister or APRS.

So far I've mentioned about 20 modes, picked at random, some from the list of modes that the software Fldigi supports. Some of these don't even show up on the Signal Wiki which has a list of about 70 amateur modes.

With all the bands you have available, there's plenty of different things to play with. All. The. Time.

There's contests for many of them, so once you've got it working, you can see how well you go.

Over the past year I've been experimenting with a friend with various modes, some more successful than others. I'm mentioning this because it's not difficult to get started. Seriously, it's not.

The most important part of this whole experiment is getting your computer to talk to your radio. If you have FT8 already working you have all the hardware in place. To make the software work, you can't go past installing Fldigi. As a tool it works a lot like what you're familiar with. You'll see a band-scope, a list of frequencies and a list of decodes. It's one of many programs that can decode and generate a multitude of amateur digital modes.

If this is all completely new to you, don't be alarmed.

There are essentially two types of connections between your computer and your radio. The first one is audio, the second is control. For this to work well, both these need to be two-way, so you can both decode the audio that the radio receives and generate audio that the radio can transmit. The same is true for the control connection. You need to be able to set the transmit frequency and the mode and you need to be able to read the current state of the radio, if only to toggle the transmitter on-and-off. If you already have CAT control working, that's one half done.

I've spoken with plenty of amateurs who are reluctant to do any of this. If this is you, don't be afraid. It's like the first time you keyed up you radio. Remember the excitement? You can relive that experience, no matter how long you've been an amateur.

Depending on the age of your radio, you might find that there is only one physical connection between your computer and the radio, either using USB or even Ethernet. You'll find that your computer will still need to deal with the two types of information separately.

Notice that I've not talked about what kind of operating system you need to be running. I use and prefer Linux, but you can do this on any operating system, even using a mobile phone if that takes your fancy.

Getting on air and making noise using your microphone is one option, but doing this using computer control will open you to scores of new adventures.

I will add some words of caution here.

In general, especially using digital modes, less is more. If you drive the audio too high you'll splatter all over the place and nobody will hear you, well, actually, everyone will, but nobody will be able to talk to you because they won't be able to decode it. If the ALC on your radio is active, you're too loud. WSJT-X, the tool for modes like FT8 and WSPR, has a really easy way of ensuring that your levels are right, so if you've not done anything yet, start there.

Another issue is signal isolation. What I mean by that is you blowing up your computer because the RF travelled unexpectedly back up the serial or audio cable and caused all manner of grief. You can get all fancy with optical isolation and at some point you should, but until then, dial the power down to QRP levels, 5 Watts, and you'll be fine.

A third issue that was likely covered during your licensing is the duty cycle. It's the amount of time that your radio is transmitting continuously as compared to receiving only. For some modes, like WSPR for example, you'll be transmitting for a full 2 minutes at 100%, so you'll be working your radio hard. Even harder might unexpectedly be using FT8, which transmits in 15 second bursts every 15 seconds, so there may not be enough time for your radio to cool down. Investing in a fan is a good plan, but being aware of the issue will go a long way to keeping the magic smoke inside your radio.

I'm sure that you have plenty of questions after all that.

You can ask your friends, or drop me an email, cq@vk6flab.com and I'll be happy to point you in the right direction.

Next time there's nothing good on TV, get on air and make some digital noise!

I'm Onno VK6FLAB

What's in a prediction? Feb 07, 2021

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Foundations of Amateur Radio

Over the past little while I've been experimenting with various tools that decode radio signals. For some of those tools the signals come from space. Equipment in space is moving all the time, which means that the thing you want to hear isn't always in range.

For example.

The International Space Station or ISS has a typical orbit of 90 minutes. Several times a day there's a pass. That means that it's somewhere within receiving range of my station. It might be very close to the horizon and only visible for a few seconds, or it might be directly overhead and visible for 10 minutes. If it's transmitting APRS on a particular frequency, it can be decoded using something like multimon-ng. If it's transmitting Slow Scan TV, qsstv can do the decoding. I've done this and I must say, it's exciting to see a picture come in line-by-line, highly recommended.

The National Oceanic and Atmospheric Administration or NOAA, has a fleet of satellites in a polar orbit that lasts about 102 minutes and they're overhead at least every 12 hours. You can use something like noaa-apt to decode the images coming from the various weather satellites, or a python script and I'll talk about that at some point.

There is a growing cloud of cube satellites with interesting telemetry. They're in all kinds of orbits and you can attempt to receive data from each one as it's in sight.

Keeping track of what's where and when is a full time job for plenty of people. As a radio amateur I'm happy to defer to the experts who tell me where a piece of equipment is and when I'm likely to be able to receive a radio signal from the transmitter I'm interested in.

Previously I've mentioned in passing a tool called gpredict that does this heavy lifting for me. It presents a map of the world and shows what's visible at my location and when the next acquisition of signal for a particular satellite might occur. It talks to the internet to download the latest orbital information. It also has the ability to control a rotator to point your antenna, not that I have one, and it can update the transmit and receive frequency of your radio to compensate for the Doppler effect that changes the observed frequency as a satellite passes overhead. All this works with a graphical user-interface, that is to say, you have a screen that you're looking at and can click on.

Whilst running gpredict, you can simultaneously launch the appropriate decoding tool for the signal that you're trying to receive. If you have a powerful enough computer, you can run multiple decoding tools together. You'll have separate windows for controlling the radio and antenna, for decoding APRS, SSTV, NOAA and if you're wanting to do sunrise and sunset propagation testing using WSPR, you can also run WSJT-X or any other decoder you're interested in.

There are some implications associated with doing this, apart from needing a big enough screen, needing considerable computing power and burning electricity for no good reason, the signal that comes in from your radio will be fed to all the decoders at the same time and all of them will attempt to decode the signal, even when you know that this serves no purpose. That's fine if you don't know what you're listening to, but most of the time you know exactly what it is, even if the software doesn't.

Manually launching and quitting decoders is one option, but what if the next ISS pass is at 3am?

Aside from the computing requirements, so far this works fine with a standard analogue radio like my Yaesu FT-857d. The only limitation is that you can only receive one station at a time.

If you replace the analogue radio with an RTL-SDR dongle, you gain the ability to record and decode simultaneous stations within about 2.4 MHz of each other.

Another option is to use an ADALM Pluto and as long as the stations are within 20 MHz of each other, you can record and decode their signals. If you're not familiar with a Pluto, it's essentially a computer, receiver and transmitter, all in a little box, the size of a pack of cards.

This is where it gets interesting.

The Pluto doesn't have a screen, or a keyboard for that matter, but it's a computer. It runs Linux and you can run decoders on it. I've done this with ADS-B signals using a tool called dump1090. You'll find it on my GitHub page.

One of the sticking points in decoding signals from space was the ability to predict when a satellite pass occurs without requiring a computer screen. Thanks to a command-line tool called "predict", written by John, KD2BD and others I've now discovered a way to achieve that. My efforts are not quite at the point of show-and-tell, but I've got a Docker container that's building and running predict on its own and using a little bash script it's telling me when the ISS is overhead. You'll find that on GitHub as well.

My next challenge is to do some automated decoding of actual space signals. I'm going to start with the ISS, predict and multimon-ng. I'll let you know how I go.

What space signals are you interested in?

I'm Onno VK6FLAB

Changing of the guard ... Jan 31, 2021

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Foundations of Amateur Radio

When you begin your journey as a radio amateur you're introduced to the concept of a mode.

A mode is a catch-all phrase that describes a way of encoding information into radio signals.

Even if you're not familiar with amateur radio, you've come across modes, although you might not have known at the time.

When you tune to the AM band, you're picking a set of frequencies, but also a mode, the AM mode. When you tune to the FM band, you do a similar thing, set of frequencies, different mode, FM. The same is true when you turn on your satellite TV receiver, you're likely using a mode called DVB-S. For digital TV, the mode is likely DVB-T and for digital radio it's something like DAB or DAB+.

Even when you use your mobile phone it too is using a mode, be it CDMA, GSM, LTE and plenty of others.

Each of these modes is shared within the community so that equipment can exchange information. Initially many of these modes were built around voice communication, but increasingly, even the basic mobile phone modes, are built around data. Today, even if you're talking on your phone, the actual information being exchanged using radio is of a digital nature.

Most of these modes are pretty static. That's not to say that they don't evolve, but the speed at which that happens is pretty sedate.

In contrast, a mode like Wi-Fi has seen the explosion of different versions. During the first 20 years there were about 19 different versions of Wi-Fi. You'll recognise them as 802.11a, b, g, j, y, n, p, ad, ac and plenty more.

I mention Wi-Fi to illustrate just how frustrating changing a mode is for the end-user. You buy a gadget, but it's not compatible with the particular Wi-Fi mode that the rest of your gear is using.

It's pretty much the only end-user facing mode that changes so often as to make it hard to keep up. As bad as that might be, there is coordination happening with standards bodies involved making it possible to purchase the latest Wi-Fi equipment from a multitude of manufacturers.

In amateur radio there are amateur specific modes, like RTTY, PSK31, even CW is a mode. And just like with Wi-Fi, they evolve. There's RTTY-45, RTTY-50 and RTTY-75 Wide and Narrow, when you might have thought that there was only one RTTY. The FLDIGI software supports 18 different Olivia modes out of the box which haven't changed for a decade or so.

The speed of the evolution of Olivia is slow. The speed of the evolution of RTTY is slower still, CW is not moving at all. At the other end new amateur modes are being developed daily.

The JT modes for example are by comparison evolving at breakneck speed, to the point where they aren't even available in the latest versions of the software, for example FSK441, introduced in 2001 vanished at some point, superseded by a different mode, MSK144. It's hard to say exactly when this happened, I searched through 15 different releases and couldn't come up with anything more definitive than the first mention of MSK144 in v1.7.0, apparently released in 2015.

My point is that in amateur radio terms there are modes that are not changing at all and modes that are changing so fast that research is being published after the mode has been depreciated. Mike, WB2FKO published his research "Meteor scatter communication with very short pings" comparing the two modes FSK441 and MSK144 in September 2020, it makes for interesting reading.

There are parallels between the introduction of computing and the process of archiving. The early 1980's saw a proliferation of hardware, software, books and processes that exploded into the community. With that came a phenomenon that lasted at least a decade, if not longer, where archives of these items don't exist because nobody thought to keep them. Floppy discs thrown out, books shredded, magazines discarded, knowledge lost.

It didn't just happen in the 1980's. Much of the information that landed man on the moon is lost. We cannot today build a Saturn V rocket with all the support systems needed to land on the moon from scratch, even if we wanted to. We have lost manufacturing processes, the ability to decode magnetic tapes and lost the people who did the work through retirement and death, not to mention company collapses and mergers.

Today we're in the middle of a golden age of radio modes. Each new mode with more features and performance. In reality this means that your radio that came with CW, AM, FM and SSB will continue to work, but if it came with a specialised mode like FSK441, you're likely to run out of friends to communicate with when the mode is depreciated in favour of something new.

In my opinion, Open Source software and hardware is vitally important in this fast moving field and if we're not careful we will repeat history and lose the knowledge and skill won through perseverance and determination due to lack of documentation or depreciation by a supplier.

When did you last document what you did? What will happen to that when you too become a silent key?

I'm Onno VK6FLAB

The Vagabond HAM Jan 24, 2021

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Foundations of Amateur Radio

This podcast began life under the name "What use is an F-call?" and was renamed to "Foundations of Amateur Radio" after 206 episodes. To mark what is effectively this, the 500th episode, I considered a retrospective, highlighting some of the things that have happened over the past decade of my life as a radio amateur. I considered marking it by giving individual credit to all those amateurs who have helped me along the way by contacting me, documenting things, asking questions, sharing their experiences or participating in events I attended. Whilst all these have merit, and I should take this opportunity to thank you personally for your contribution, great or small, to amateur radio, to my experience and that of the community. Thank you for making it possible for me to make 500 episodes, for welcoming me into the community, for being a fellow amateur. Thank you.

During the week I received an email from Sunil VU3ZAN who shared with me something evocative with the encouragement to bring it the attention and appreciation it deserves.

By way of introduction, on the 13th of June 2002, Ken, W6NKE became a silent key. Ken was an amateur, an active one by all accounts. I never met Ken, but his activity list is long and varied. Ken became interested in ham radio as a teenager in the 1930s. He was a long time advocate of CW and during WWII he taught Morse code to Navy operators. In 1975 he founded The Sherlock Holmes Wireless Society and was editor of its newsletter, now called "The Log of the Canonical Hams". He received his Investiture from The Baker Street Irregulars in 1981. Ken was an early member of the International Morse Preservation Society or FISTS, he held number 0818. He was the President of Chapter 2 of the Old Old Timers Club, the OOTC for many years. In addition to drawing cover art, Ken also wrote. Lots. 73 magazine features plenty of Ken's articles with titles like: "Inexpensive Vertical", "Don't Bug me Dad" and "The DX Hunter".

Ken was also a poet, which brings us to the way that I think is appropriate to mark the 500th episode of this podcast. I'm confident that you can relate to this contribution by Ken to amateur radio, published in Volume 1, Number 3 of 73 magazine in December 1960.

The Vagabond HAM, by Ken Johnson W6NKE (SK)

A vagabond's life is the life I live Along with others, ready to give A friendly laugh and a word of cheer To each vagabond friend, both far and near.

I travel the air waves, day or night To visit places I'll never sight From the rail of a ship, or from a plane Yet I'll visit them all again and again.

I never hear from a far off land That my pulse doesn't quicken. With careful hand I tune my receiver and VFO dial To make a new friend and chat for awhile.

Africa, Asia, they're all quite near In as easy reach as my radio gear With the flip of a switch, the turn of a knob I can work a ZL, a friend named Bob.

There's an LU4, a fellow that's grand Who's described to me his native land 'Till I can hear the birds, and feel the breeze As it blows from the slopes of the mighty Andes.

I learned of the surf, and a coral strand, The smell of hybiscus where palm trees stand 'Neath a tropical moon, silver and bright From an FO8 that I worked one night.

I've thrilled to the tales of night birds' screams In the depths of the jungle where death-laden streams Flow'neath verdant growth of browns and greens From a DU6 in the Philippines.

The moors of Scotland, a little French Shrine, German castles on the River Rhine Of these things I've learned, over the air Without ever leaving my ham shack chair.

There's a KL7 on top of the world To whom the Northern Lights are a banner unfurled That sweeps across the Arctic night Makes the frozen sky a thing of delight.

Tales of silver and gold and precious stones Ancient temples and molding bones Where the natives, I'm told, are tall and tan By an XE3 down in Yucatan.

My vagabond trips over the air Will take me, well, just anywhere Where other vagabonds and I will meet From a tropical isle, to a city street.

My vagabond's life will continue, I know Through the fabulous hobby of ham radio And one day from out at the world's end We'll meet on the air, my Vagabond friend.

I'm Onno VK6FLAB

Note: The spelling of the poem is as published in 73 magazine.

The APRS of it all ... Jan 17, 2021

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Foundations of Amateur Radio

Amateur radio is a living anachronism. We have this heady mix of ancient and bleeding edge, never more evident than in a digital mode called Automatic Packet Reporting System or APRS. It's an amateur mode that's used all over the place to exchange messages like GPS coordinates, radio balloon and vehicle tracking data, battery voltages, weather station telemetry, text, bulletins and increasingly other information as part of the expanding universe of the Internet Of Things.

There are mechanisms for message priority, point-to-point messages, announcements and when internet connected computers are involved, solutions for mapping, email and other integrations. The International Space Station has an APRS repeater on-board. You'll also find disaster management like fire fighting, earthquake and propagation reporting uses for APRS. There's tools like an SMS gateway that allows you to send SMS via APRS if you're out of mobile range. There's software around that allows you to post to Twitter from APRS. You can even generate APRS packets using your mobile phone.

In my radio travels I'd come across the aprs.fi website many times. It's a place that shows you various devices on the APRS network. You can see vehicles as they move around, radio repeater information, weather, even historic charts of messages, so you can see temperatures over time, or battery voltage, or solar power generation, or whatever the specific APRS device is sending.

As part of my exploration into all things new and exciting I thought I'd start a new adventure with attempting to listen to the APRS repeater on the International Space Station. I'm interested in decoding APRS packets. Seeing what's inside them and what kinds of messages I can hear in my shack. Specifically for the experiment at hand I wanted to hear what the ISS had to say.

After testing some recommended tools and after considerable time hunting I stumbled on multimon-ng. I should mention that it started life as multimon by Tom HB9JNX, which he wrote in 1996. In 2012 Elias Oenal wanted to use multimon to decode from his new RTL-SDR dongle and in the end he patched and brought the code into this century and multimon-ng was born. It's available on Linux, MacOS and Windows and it's under active development.

It's a single command-line tool that takes an audio input and produces a text output and it's a great way to see what's happening under the hood which is precisely what I want when I'm attempting to learn something new.

In this case, my computer was already configured with a radio. I can record what the radio receives from the computer microphone and I can play audio to the radio via the computer speaker. My magical tool, multimon-ng has the ability to record audio and decode it using a whole raft of in-built decoders. For my test I wanted to use the APRS decoder, cunningly disguised as an AFSK1200 de-modulator. I'll get to that in a moment.

The actual process is as simple as tuning your radio in FM mode to the local APRS frequency and telling multimon-ng to listen. Every minute or so you'll see an APRS packet or six turn up on your screen.

The process for the ISS is only slightly different in that the APRS frequency is affected by Doppler shift, so I used gpredict to change the frequency as required; multimon-ng continued to happily decode the audio signal.

I said that I'd get back to AFSK1200. The 1200 represents the speed, 1200 Baud. The AFSK represents Audio Frequency Shift Keying and it's a way to encode digital information by changing the frequency of an audio signal. One way to think of that is having two different tones, one representing a binary zero, the other representing a binary one. Play them over a loud-speaker and you have AFSK. Do that at 1200 Baud and you have AFSK1200.

When you do listen to AFSK and you know what a dial-up modem sounds like, it will come as no surprise that they use the same technique to encode digital information. Might have to dig up an old dial-up modem and hook it up to my radio one of these days.

Speaking of ancient. The hero of our story, APRS, dates back to the early days of microcomputers. The era of the first two computers in my life, the Apple II and the Commodore VIC-20. Bob WB4APR implemented the first ancestor of APRS on an Apple II in 1982. Then in 1984 he used a VIC-20 to report the position and status of horses in a 160km radius using APRS.

As for the International Space Station, the APRS repeater is currently switched off in favour of the cross-band voice repeater, so I'll have to wait a little longer to decode something from space.

I'm Onno VK6FLAB

The other radios in the world ... Jan 10, 2021

Show notes

Foundations of Amateur Radio

When you join the community of radio amateurs you'll find a passionate group of people who to greater and lesser degree spend their time and energy playing with radios in whatever shape that takes. For some it involves building equipment, for others it means going on a hike and activating a park. Across all walks of life you'll find people who are licensed radio amateurs, each with their own take on what this hobby means.

Within that community it's easy to imagine that you're the centre of the world of radio. You know stuff, you do stuff, you invent stuff. As a community we're a place where people dream up weird and wonderful ideas and set about making them happen.

Radio amateurs have a long association with emergency services. When I joined the hobby over a decade ago one of the sales pitches made to me was that we're ready to be part of emergency communications. In some jurisdictions that's baked into the license.

There was a time when a radio amateur was expected to be ready to jump into a communications gap and render assistance with their station. There are amateur based groups groups like WICEN, the Wireless Institute Civil Emergency Network in Australia, ARES, the Amateur Radio Emergency Service in the United States, RAYNET, the Radio Amateurs' Emergency Network in the United Kingdom, AREDN, the Amateur Radio Emergency Data Network in Germany, DARES, the Dutch Amateur Radio Emergency Service, AREC or Amateur Radio Emergency Communications in New Zealand and EmComms in Trinidad and Tobago to name a few.

Each of those manages their participation in different ways. For example, ARES offers training and certification where AREDN offers software and a how-to guide, in Trinidad and Tobago the Office of Disaster Preparedness Management is actively involved in amateur radio and maintains an active amateur radio station and five repeaters.

In Australia there's a requirement to record and notify authorities if you become aware of a distress signal as a part of your license. In fact in Australia you must immediately cease all transmissions. You must continue to listen on frequency. You must record full details of the distress message, in writing and if possible recorded by tape recorder.

While that scenario can and has happened, it's not common. An amateur station being used to provide an emergency link in the case of catastrophic failure has also happened, but in Australia I'm not sure if that was in my lifetime or not.

My point is that the idea that we're going to put up a critical radio link and be the heart of communications in an emergency is, in Australia at least, not particularly likely. That's not to say that you should ignore that potential, or that it's universally true, but it's to point out that there are other things that you can do with your license that might happen more readily and help your community more.

Outside our amateur community, there's plenty of radio in use as well. The obvious ones are volunteer bush fire brigades, state emergency services and the like. Less obvious might be the local marine rescue group, surf life saving or the local council. Each of those use radios as part of their service delivery and a radio amateur can contribute to that without needing to bring their station along. In fact, if you don't have an amateur license, but want to play radio, that's an excellent place to do it as a volunteer. I should mention that radio procedures are also in use in all manner of other professions, mining, policing, the military and aviation to name a couple, not to forget occupations like tour-guides, ferry operators and pretty much any place where telephones, fixed or mobile are not readily deployed.

Within those areas there are procedures and jargon that you'll need to learn and perhaps even need to be certified for, but you as a radio amateur have several skills that you can bring to the table because you already have a license.

For example, I learnt my phonetic alphabet many years before I ever heard of amateur radio. It was a requirement for my aviation radio ticket which in turn was required before I flew solo. When it came to making my first ever transmission on amateur radio, doing the phonetic thing was second nature, much to the surprise of my fellow trainees at the time. A thank you is due to both Neil VK6BDO, now Silent Key, and Doug VK6DB for making that training happen.

You can apply the skills you bring with you when you join an organisation outside amateur radio who deals with wireless communication in whatever form that takes. For example, just the idea that you know how to pick up a microphone and push the Push To Talk button and speak and let the button go after you're done, a pretty trivial activity in amateur radio, will be something that you have that most of the untrained general public have no idea about.

Amateur radio is a massive hobby. Playing with radio, or doing something serious with it comes in all shapes and sizes. Your amateur experience can help, but be prepared to learn different procedures and methods. The amateur way isn't the only way and it's not the only place where radio is used and sometimes it's good to have a look outside your comfort zone and see what the neighbours are up to.

I'm Onno VK6FLAB

The impossible task Jan 03, 2021

Show notes

Foundations of Amateur Radio

For decades I've been playing with every new piece of technology that comes my way. In amateur radio terms that's reflected in, among other things, playing with different antennas, radios, modes and software.

One of the modes I've played with is slow scan television or SSTV. It's an amateur mode that transmits pictures rather than voice over amateur radio.

A couple of months ago a local amateur, Adrian VK6XAM, set-up an SSTV repeater. The way it works is that you tune to the repeater frequency, listen for a while and when the frequency is clear, transmit an image. The repeater will receive your image and re-transmit it. It's an excellent way to test your gear and software, so I played with it and made it all work for me.

In 2012 I was part of a public event where local schools participated in a competition to have the opportunity to ask an astronaut on board the International Space Station a question as part of the City of Light 50th anniversary of John Glenn's first orbit. The event was under the auspices of a group called Amateur Radio on the International Space Station or ARISS, an organisation that celebrated its 20th anniversary in 2020.

Assisting with the logistics behind the scenes first hand and the amount of equipment used I'd gained a healthy respect for the complexity involved.

The ISS has several radio amateurs on orbit. Among their on board activities are plenty of amateur radio friendly ones. In addition to ARISS, you'll also find repeaters, voice, packet and other interesting signals if you listen out for them.

In previous years I've made abortive attempts at using my station to listen and transmit to space, with varying degrees of success.

On a regular basis the ISS transmits SSTV using amateur radio. Often you'll find a series of images that commemorate an activity. During the final week of 2020 astronauts on the ISS celebrated 20 years of ARISS by transmitting a series of images on a rotating basis as the ISS orbits the earth.

One of my friends made a throwaway comment about listening to the international space station and decoding slow scan television. I'd heard about this event on various social media outlets but put it in the too hard basket.

Based on what I'd seen during my ARISS event, my own trials, and what local amateurs have been playing with in the way of interesting cross polarised antennas, rotators and the like, I'd decided that this was a long term project, unachievable with my current station.

My station consists of a dual-band vertical antenna for 2m and 70cm on my roof at about 2m above ground level. The radio is my trusty Yaesu FT-857d. Connected to a Debian Linux laptop running three bits of software, rigctld, gpredict and qsstv.

With a high level of apprehension I fired up my station, tuned my radio, updated the orbital information and radio frequencies and waited for the first acquisition of signal from the ISS. Imagine my surprise when a picture started appearing on my screen. It's a lot like the days of 300 baud dial up, getting a picture from some remote computer back in 1985.

With that I managed to receive several of the images by just letting it run for the next couple of days.

I'm glad my friend made their comment, because it spurred me into action to try for myself.

I'll be the first to admit that the image quality isn't broadcast ready, or that I made mistakes, or that I should have started listening at the beginning of the week rather than the last few days, but all that is just noise because I can report that it works and I have the pictures to prove it!

I now have most of the image series, number 2 is missing and I only have part of number 1, but there are some beauties among the 35 images I captured. I've published them on my project website at vk6flab.com, for you to have a look at and use as inspiration for your own seemingly impossible task.

This leaves me wondering what else I can hear from overlying spacecraft using this set-up. What have you heard and what equipment were you using to make that happen? Are there any impossible tasks that you've avoided?

I'm Onno VK6FLAB

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