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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: 2 hours 30 min ago

Path loss and very small numbers ...

Sat, 01/28/2023 - 11:00
Foundations of Amateur Radio

Sometimes you learn mind boggling things about this hobby, often when you least expect it. Recently I discussed having my 20 mW WSPR or Weak Signal Propagation Reporter beacon heard on the other side of the planet, in Denmark, 13,612 km away. That in and of itself is pretty spectacular, but it gets better if you consider just how weak the signal was by the time it got there.

In radio communications there is a concept called path loss or path attenuation. Until recently I understood this to mean the things that impede a signal getting from transmitter to receiver. That includes coax and connector losses, refraction across the ionosphere, reflection off the surface of the planet and diffraction around objects.

It turns out there is another factor called "Free Space Path Loss" to consider. It's loosely defined as the loss of signal strength between two antennas. The name sort of implies that something happens to the signal in free space, which is odd if you know that in space, radio waves, regardless of frequency, travel without loss and will travel pretty much indefinitely.

So what's going on?

To get started, think about a dome lawn sprinkler, one of those little round discs that sits on the ground with the hose connected to the side. You turn on the tap and the water sprays in all directions. If you're really close to the sprinkler when the tap is turned on you'll get sopping wet almost immediately, since most of the water will hit you directly. This is particularly fun in the heat of summer on New Years Day in Australia, not so much in the middle of winter on the other side of the globe.

If you stand a couple of meters away, you'll still get wet, eventually, but it will take much longer, because most of the water isn't hitting you. If you stand even further away and assuming the water still gets that far, it will take even longer.

A small towel and a big towel will both take the same length of time to get wet if they're held at the same distance from the sprinkler, but if you wring them both out, you'll discover that the big towel captured much more water during the same time.

In radio communications we can combine these two ideas, the distance and the size of the receiver, to describe free space path loss.

The further away from the transmitter you are, the less signal is available to you to capture since much of the signal is not heading in your direction and the bigger your antenna, the more signal you receive. The bigger the antenna, the lower the frequency, which is why you'll discover that free space path loss is dependent on both distance and frequency.

To give you an idea of scale, the free space path loss for 28 MHz over 13000 km is about 144 dB.

While the name "Free Space Path Loss" implies loss of signal across the path in free space, the loss is not due to distance as such, rather it's caused by how much the signal is spread out in space. Similarly, there isn't more loss because the frequency is increased, it's that less signal is captured by the smaller size or aperture of the antenna required for a higher frequency.

So perhaps a better name might be Spherical and Aperture Loss, but then everyone would have to learn how to spell that, so "Free Space Path Loss" it is.

I'll point out that this is the minimum theoretical loss, in reality the loss is higher than this, since it also includes all the other parts of the path loss which are things that we can control, like coax and connector loss, and things we can improve by frequency selection, like ionospheric reflection and refraction which depend on solar conditions.

The one aspect of path loss that we have no control over is the "Free Space Path Loss", so perhaps that's why we don't talk about it very much.

I'll mention that in path loss calculations often antenna gain at the transmitter and receiver are used to reduce any path loss figures. If I have an antenna with 6 dB gain, then that reduces my overall path loss by 6 dB, which is why we spend so much time and effort figuring out what antenna to use when we get on air to make noise.

I mentioned that the free space path loss for my beacon between Australia and Denmark was about 144 dB. This means that my 20 milliwatt signal arrived in Denmark as a -131 dBm signal. That might not mean much, but that's the equivalent of about 80 attowatts. If you're not sure how big that is, 1 milliwatt is 1 quadrillion attowatts, a 1 with 15 zeros. Said another way, 1 watt is 1000 milliwatts, 1 milliwatt is 1000 microwatts. 1 microwatt is 1000 nanowatts, 1 nanowatt is 1000 picowatts, 1 picowatt is 1000 femtowatts, 1 femtowatt is 1000 attowatts.

It might come as a surprise, but these numbers are not unusual. Don't believe me? When your radio shows an S0 signal on HF, it is defined as -127 dBm, so we deal with tiny numbers like this all the time, we're just not quite aware of it on a daily basis.

Remember, my numbers are theoretical only, to give you an idea of scale. In reality everything in the path between the transmitter and receiver affects what ends up at the other end and might make the difference between hearing someone, or not.

I'm Onno VK6FLAB

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

Sat, 01/21/2023 - 11:00
Foundations of Amateur Radio

If you've ever been in the market for a new radio, and truth be told, who isn't, you'll find yourself faced with a bewildering array of options varying from obvious to obscure and everything in between. At the obvious end of the scale are things like price, bands and transmit power and at the other end are things like Narrow Spaced Dynamic Range, which you'll find explained by Rob NC0B on his sherweng.com website where he's been publishing receiver test data for many decades.

One of the more subtle options you'll need to consider are handheld, mobile or base radio.

This is harder than you might think, since radios are increasing in functionality every time you wake up and if you look long enough, you'll discover that they're getting smaller at the same rate. Once upon a time you could just look at the size of a radio and define it as belonging in one or other category, but that's no longer a useful distinction. For example, my PlutoSDR is a tiny device, fits in my pocket, but there's no way I'd consider it a handheld, or even a mobile radio.

You might think that a bigger box has more stuff inside, costs more and performs better.

For example, the Drake R-4C receiver and companion T-4XC transmitter require external power and were once rated by the ARRL as very good. In reality the Drake R-4C performed terribly in a CW contest, incidentally, that was what caused Rob to start testing radios in 1976. That receiver and transmitter manage to cover 80m, 40m, 20m, 15m and 10m and together weigh in at 14.3 kg. They're considered a base radio.

The Yaesu FT-817, runs on batteries, weighs in at just over a kilogram and can be carried with a shoulder strap. It comes as a single device and covers many more bands than the Drake transmitter and receiver do, it would be considered a mobile or even portable radio. Obviously it would be hard to jam a Drake into your car or strap it to your belt, but does that mean that you cannot use an FT-817 as the base radio in your shack?

In case you're curious, the slightly beefier brother to the FT-817, the mobile FT-857d, is sitting on my desk as my current base radio. Has been for years.

So why do manufacturers continue to make this distinction between handheld, mobile and base radio? One look at the nearest radio catalogue will tell you that it's not based on either performance or price, not even close. You can buy a handheld with more functionality for the same price as a mobile radio and that same is true when you compare a mobile radio to a base radio.

Radios vary in price from $20 to $20,000. A cynical person would suggest that pricing is based around extracting the most money from your pocket, but a more charitable explanation might be that physical size dictates things like the number of buttons you can fit on a radio, how many connectors can be accessed before the radio flies off the desk from the weight of the coax hanging off the box, how big is the display and other such limitations.

I'm not being glib when I use the word charitable, since much of modern transceiver design revolves around software which can pretty much fit in any box. Using external computers, neither buttons nor a display are needed, leaving external connectors, which if we're being really honest could all fit in a box that would fit in your pocket.

At this point you might wonder if handheld, mobile or base has any meaning at all. As I said, in most cases it doesn't. There's really only one place left where this matters, and that's when you have access to strictly limited space and power if you need to put the radio in your pocket or cram it into your car.

For your home shack, the distinction is unhelpful for most, if not all, amateurs.

Don't believe me? The Yaesu FT-710 currently ranks fourth on Rob's Sherwood Engineering Receiver Test Data List. It's a quarter the size of the top radio and it's sold as a "Base/Portable Transceiver". Yaesu calls it "Compact". It might not fit in the dashboard of my car, but it will fit on the folding table we use during field days.

That isn't an exception either. The Elecraft KX3 is the smallest radio on the first page of Rob's Receiver Test Data list. It fits in your pocket.

Before you start collecting statistics for each radio, I should point out that the more you know about this hobby, the harder this process becomes, so be careful. That said, if you have a massive list of anything to choose from, a new amateur radio, pet food, car, what to have for dinner, whatever, here's a process that will guarantee a result.

It works by eliminating one item at a time until you're left with your preference.

To start, grab the first two items on your list and pick the best one between the two. Ignore everything else, just those two items. You're going to fret about the definition of "best", but don't worry, since every time you do this, you'll have a different idea. All you're doing is saying, all things being equal, between these two options, which one do I prefer. No need to describe why, just pick one. In picking one, you've removed one option from the list.

Now, compare the winner to the next item on the list, again, ignore everything else and pick one and remove the other. Keep doing this until you run out of items. You'll end up with the single option that wins, for whatever reason, from the entire list.

Now, about that radio. All I need is the next paid project.

I'm Onno VK6FLAB

What should we be learning?

Sat, 01/14/2023 - 11:00
Foundations of Amateur Radio

It's an immersive effort to create an article every week, so much so, that I've only just discovered that I passed the 600 article mark some time ago. I'd open up a bottle of something celebratory if I thought it warranted the effort, but I'd rather talk about amateur radio and what I've learnt since becoming licensed in December of 2010.

This hobby, this community, the activity of amateur radio keeps surprising me in unexpected and exciting ways. I know that there is a part of the community that thinks of this as a dying hobby, but with every fibre in my being I know this to be wrong. We explore, test, build and learn at every opportunity. Put any two amateurs in contact with each other, either physically or over the air and you'll soon witness an exchange of ideas, of things that bring joy, hints of the next thing and the next.

The inspiration for my writing comes from all manner of places. For example, here's an opinion recently shared by someone on social media:

"Basic antenna modeling using software should be included in ham radio licensing exam syllabus if it's not currently." [sic]

As opinions go it's one of the tamer ones I've come across, but it's not unique in any sense of the word. I've heard it described bemoaning the missing knowledge of new digital modes or the need to upgrade my license, or the idea that the introductory license should come with a fixed expiry date. You might have heard similar ones, phrased along the lines of a missing attribute that new licensees should be required to learn or know about before they can call themselves amateurs.

It's also completely unhelpful.

Let me explain why.

I'll start with an analogy. When was the last time your driver's license expired because you didn't upgrade it due to new road rules, new vehicle types, new car accessories or speed limits? In case you're confused, the answer is: never.

Does amateur radio cause death and mayhem in the community? No.

Do cars?

So, in the scheme of things, even if amateur radio can be used to help save lives, it's not an activity that's generally considered life threatening. You could argue that radio amateurs could cause life threatening interference, and technically they can. So can any user of any piece of radio equipment, CB radio, mobile phone, Wi-Fi, you name it. Even a half asleep electronics student in their first year of high-school could do this. The skill isn't specific to radio amateurs.

So, what is this about, the requirement for antenna modelling, or some other missing skill, and why does our community keep getting flooded with such, frankly, nonsense?

In my opinion, it's the same phenomenon that laments the loss of Morse code, the fact that we lost the 11m band, that we're playing with FT8 instead of AM, that we prefer integrated circuits to valves. The world is a flowing feast and amateur radio is along for the ride. Stand still and the world moves on.

Should amateur radio licensing change?


It should move with the times. It should lower the barrier to entry at every opportunity. It should explore the possible, not the requirements of a select group of people who decry the dumbing down of the hobby and want to pre-load every license exam with things that are absolutely irrelevant to the turning on of a radio and making noise.

Will amateurs benefit from knowing that antenna modelling software exists? Sure they will. Just like they'll benefit from knowing about valves and Morse code. That doesn't mean that they should be part of the exam process. I want new amateurs, no, all amateurs to be curious, to ask, to discover, to explore and to want to know stuff, not because it's a requirement to get a license, but because it's beneficial to their amateur journey.

Every week I come up with a different way to look at our hobby because this hobby is so divers. I've used the phrase a 1000 hobbies in one. So far I've just scratched the surface, some 600 weeks in. We'll see where we're at when I've held my license for another decade or so.

So, have at it. What is missing from the current exam and why should it be included?

I'm Onno VK6FLAB

Where does propagation data come from?

Sat, 01/07/2023 - 11:00
Foundations of Amateur Radio

One of the many questions that new amateurs ask is, "When should I get on-air, and on what band?" The often-heard reply is just to get on-air and make some noise. As time goes by, the importance of this seems to fade in favour of using HF prediction tools. Some amateurs never venture beyond that point, relying almost exclusively on technology to determine if they should turn on their radio or not.

If you search the internet for "current HF conditions", you'll end up with dozens of sites boldly claiming to provide precisely that information, some even using the label "Real-Time". You'll find instructions from countless self-proclaimed "experts" on how to read propagation conditions from their favourite site. There's even widgets that you can install on your website displaying propagation data per amateur band with helpful labels like "Band Closed" or showing conditions as "Poor", "Fair" or "Good". Some of these widgets even include an embedded time-stamp to prove just how "current" the information is.

If that's how you decide to activate your amateur station, like I once did, I have some questions.

Where is this information coming from, is it accurate, and when was it last updated?

To give you an idea of just how complex this question is, consider visiting two popular websites, solarham.net from Canada and spaceweatherlive.com from Belgium. On their home-pages, you'll find all manner of numbers, charts, photos, events, notifications, alerts, and warnings, each related in some way to HF propagation and the condition of the Sun.

Sounds great, excellent resources, job done.

Well, no.

Let's start simple. Location.

Leaving aside where the site's owner is or where the servers are, both potential sources of confusion, consider where you are and where the remote station is that you're trying to contact. Now compare that with the propagation data location. Do you know where the measurements came from and if they're relevant to you?

What about data currency?

For example, if you can see the Sun, you can count the number of sunspots since that data comes from physically looking at the Sun. Mind you, can someone count the number of sunspots at night? It's not a trick question. The Sun isn't overhead for everyone all the time, and the data from any particular observer will be out of date at night. When was the count updated? Is it still actually current, let alone real-time? Obviously, not everyone uses the same data source either.

In case you're wondering, why are we counting by eye in the space age? It turns out that, since Galileo more than 400 years ago, it's the most long-term, reliable way to keep data consistent between observers and instruments, both of which often last only one or a few solar cycles, and it's also cheap!

What about equipment changes and failures in data gathering?

Geomagnetic activity isn't global; it's measured using a device called a flux-gate magnetometer. Measurements from specific instruments scattered around the globe are combined into the planetary, or Kp index. You'll discover that locations used change over time, and when instruments are down, the numbers are estimated, but you won't see that unless you actually find and explore the source data.

It's not just solarham.net and spaceweatherlive.com; it's pretty much every single site that shows any form of HF propagation or space weather information. Even sites based in a specific country, like the Australian Space Weather Service, have many instruments scattered around Australia. If you happen to be near an actual instrument, where "near" is anything less than 500 km away, how do you know if that instrument was actually online when a measurement was made?

Even if the instrument near you is working, is the data relevant to the receiving station on the other side of the planet?

If you look closely at the sites giving out current HF conditions, you'll discover that most of these don't even tell you where the data comes from, let alone if any of it was estimated to come up with their current reported values or recommendations.

If you start searching for historical information, this problem gets bigger. You'll find many sites that claim to have data, but are invariably underfunded, are rife with broken links, out-of-date servers, and moved, deleted, and abandoned pages. If you unearth a dataset, you'll discover that everyone uses a different standard to record their measurements.

How do you even know if combined measurements are coming from the right column? Think I'm kidding? There are documents with warnings about different formats, calculations, and dates on which these changed. Aggregating this data is challenging, at best.

So, is there a better way?

Yup. You're not going to like it. "Get on-air and make noise!"

I can hear you groaning from here. It's not all bad. You can run your own beacon to see the conditions at your location. It's what started me down the path of installing a WSPR, or Weak Signal Propagation Reporter, beacon and leaving it running 24/7. Currently, I'm focused on very weak, 10 mW signals. So far, it's been reported 3,685 km away.

If you visit the VOACAP or Voice of America Coverage Analysis Program website, you'll find a visualisation of how FT8 propagation worked between ITU zones between 2017 and 2019. It's not current, but it's an excellent way to see how propagation data can be derived from actual contacts.

What we really need are more beacon transmitters and online receivers.

I'm Onno VK6FLAB.

What's the weakest signal that WSPR can decode?

Sat, 12/31/2022 - 11:00
Foundations of Amateur Radio

In 2016, Daniel EA4GPZ, documented how to discover the weakest signal that could be decoded using several weak signal modes, including WSPR, or Weak Signal Propagation Reporter. This is an interesting question because as you might recall, I've been experimenting with very weak signals coming from my shack. To date, my 20 milliwatts has been heard over 13 thousand kilometres away.

When you tune to a weak station you'll often hear both the station or desired signal as well as interference or background noise. The stronger the signal, the less noise you perceive. The weaker the signal, the more noise. You can express the relationship between the power of these two, the signal and the noise, as a ratio. If the power levels are the same, the so-called signal to noise ratio or SNR is 1:1. A higher ratio, like 2:1, indicates that the power of the signal is higher than the noise and a lower ratio, like 1:2 indicates that the signal is lower than the noise.

If you express this ratio in decibels, you'll end up with positive numbers where the signal is stronger than the noise and negative numbers where the signal is weaker than the noise and zero when they're the same. If I tell you that the signal report for my WSPR decode from Denmark was -28 dB, it means that the noise was much stronger than the signal.

For today I'm going to leave alone just how WSPR can report a negative signal to noise ratio and still successfully decode the signal, even though the signal appears to be buried in the noise.

That said, in this experiment, we're trying to learn something else. Using the technique detailed by Daniel, we test using different, known, signal to noise ratios to discover at what point the WSPR decoding process breaks down. This might help me understand if I can reduce my beacon output power even further and still anticipate a good chance of being decoded successfully.

To conduct his experiment, Daniel used the then current version of WSJT-X, version 1.7.0-rc1 and I'm using the current version today, 2.6.0-rc5 to repeat those tests. You might ask why I'm not taking Daniel's word for it and just using his findings. The process to decode a WSPR signal is all software and can be improved with better methodologies and algorithms. It's not unreasonable to think that in the years since Daniel's experiments things have changed, hopefully improved.

So, how does this work?

If you generate and attempt to decode one hundred different files, you can use the number of times that you count your callsign in the decode list as a percentage of success. If all of your files decode properly, the decode percentage is 100%. If only half of them are decoded successfully, it's 50% and so-on.

Similarly, if a different callsign, locator or signal power is decoded, you can count those as a percentage of false decodes. This is important because noise coming from the ionosphere can corrupt any signal. I should point out that because we know in advance what the decoded signal should be, since we created the message, we can actually count the ones that don't match what we sent. In the real world it's very hard, if not impossible, to do this, unless each transmitter also starts recording their efforts so data cleaning can be done after the fact.

A false decode happens when the software decodes a message and the result is not what was sent. Due to the way that WSPR works, this is not a case of a single character error and as a result the whole message is corrupt, wrong callsign, wrong grid square and wrong power level.

Just how prevalent this issue is, has to my knowledge so far not been discussed. Over the past year I've been working with the entire WSPR data set, nearly 5 billion reports, and mapping the data to explore just what's going on behind the scenes. Based on the raw data every single grid square on the planet has been activated. Of course this is not really the case, since there's plenty of parts on Earth where we haven't yet turned on a WSPR beacon.

Back to our experiment.

Two tools are used, "wsprsim" to generate an audio file and "wsprd" to decode it. Both come with WSJT-X and when you build the application from source, you get them as part of the process. The generator takes several parameters, one of which is the desired signal to noise ratio. If you ask it for a signal to noise ratio of -20 dB, wsprsim will generate the appropriate noise and the desired signal, combine them and build an audio file. You can then use wsprd to decode that file. If you repeat this many times, you end up with some data.

How many times?

Well, I probably went a little overboard. I generated a set for each SNR reading between 0 and minus 50 dB in 0.01 dB increments and then generated one hundred for each of those. At the point where the process broke down I doubled the resolution further to get a better idea of what was going on. About three quarters of a million tests. It took a while.

What did I learn from this?

First of all, false decodes happen at every signal level. I saw the first false decode at a signal to noise ratio of -0.07 dB. This is significant because it means that even at excellent signal levels there is a percentage of incorrect reports which explains why I'm seeing that result in real world data. When you start playing with really big numbers, even if the error rate is low, with enough data, it starts to matter. In my tests I saw an error rate of 0.03%. This means that there's at least 1.5 million false decodes in the current WSPR data set, likely more because wsprsim cannot emulate the real world of ionospheric and local noise.

On the flip-side, I also saw an overall success rate of nearly 94%. At -29 dB things start to change. Until then the decode is 100% successful, then it starts to decline to 0 at about -34 dB. Comparing Daniel's results directly, he saw 34% success at -30 dB, I'm seeing 95% at that same noise level. At -31 dB Daniel saw 6%, I'm seeing 75%. I don't see 34% until we get down to -31.6 dB and 6% at -32.4 dB. This indicates that the software has improved over the years.

It also means that with a signal report of -28 dB from Denmark, I've got a few dB to play with. I've now reduced my output power by another 3 dB, making it 10 mW. Point your antennas at VK6 and see what you can hear on 10m.

I'm Onno VK6FLAB

One Volt ...

Sat, 12/24/2022 - 11:00
Foundations of Amateur Radio

Have you ever asked yourself a question that turned out to be a rabbit hole so deep you could spend a lifetime exploring and likely never come out the other end?

I did. Yesterday.

What's a Volt?

This came about when I started exploring how to measure the power output of my WSPR or Weak Signal Propagation Reporter beacon. According to the specifications the output level is 23 dBm or 200 milliwatts.

If you read the fine print, you'll discover that the power output actually varies a little depending on which band you're on, for my specific transmitter it says that the output on the 10m band is 22 dBm, or 158 mW.

That comes with a disclaimer, that there can be some variation on individual transmitters of about 1 dB. So, on 10m, my output could vary between 21 and 23 dBm, or between 125 and 200 mW. With my attenuator connected, the output could be between 12 and 20 mW, and that's assuming that my attenuator is exactly 10 dB, it's not.

Measuring anything means to compare it against something else. To give you a physical example. If you look at a tape measure, the distance between the marks is determined in the factory. The machine that prints the lines is configured to make the lines just so. In the factory there will be a specific master tool that determines how far apart the lines are in that factory. That tool is called "the standard". The process of lining up the standard with the machine making the lines is called "calibration".

If you build a house on your own with just that tape measure, everything should work out fine, but if you have a mate help you and they bring their own tape measure, from a different factory, their lines might not quite match yours and the fun begins.

If you don't believe me, as I've said previously, pull out all the tape measures and rulers around your house and see just how much variation there is.

In my house, well, my CNC, there's a standard that came with my micrometer kit. It specifies physically how long 25mm is. I also have a 50mm and a 75mm standard. When I compare the 75mm with the 50mm and 25mm together, they're the same within one hundredth of a millimetre. It's likely that it's better than that, but I'm still learning how to hold a micrometer and not have it overheat and stretch while I'm measuring. Yes, temperature changes the size of things.

The point is, in my CNC world, my current standard sits in my micrometer box. At some time in the future I might want to improve on that, but for now it's fine.

The standard that I have was at some point calibrated against another standard. That standard was in turn calibrated against another standard and so-on. Eventually you end up with an SI unit of 1 meter as defined by the International System of Units. In case you're wondering, it's defined as the length of the path travelled by light in vacuum during the time interval of one second. One second is defined in terms of the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom. I know right, runs right off the tongue. I can't help myself, that frequency is 9,192,631,770 Hz.

Oh, this system is also subject to change. In 2019 four of the seven SI base units were redefined in terms of natural physical constants, rather than relying on a human artefact like the standard kilogram. This is an ongoing process. For example, in 1960, the meter was redefined as a certain number of wavelengths instead of a physical bar in a vault in Paris and there was also not just one bar, there were 30. National Prototype Metre Bar no. 27 made in 1889 was given to the United States and served as the standard for defining all units of lengths in the US between 1893 and 1960 - yes, perhaps surprisingly, the USA is metric, really. One inch used to be defined as "three grains of barley, dry and round, placed end to end lengthwise" but since 1959 is defined as exactly 2.54 centimetres or 0.0254 meters.

Back to power output on my beacon transmitter. Assuming for a moment that I had an actual tool available to measure this, I'd still be comparing my tool against another standard.

Let's imagine that I could measure the power output of my beacon with an oscilloscope. When the oscilloscope says 1 Volt per division. How do I know that it really is? If you start reading the calibration steps, you'll discover that they state that you need to connect your scope to a reference, another word for standard, and that's if you're lucky. Some documents just wave their hands in the air and say something like "push the auto calibrate button".

The Volt is defined as the electric potential between two points of a conducting wire when an electric current of one Ampere dissipates one Watt of power between those points. The Ampere definition involves counting elementary charges moving in a second. It's in the order of a 10 with 19 zeros. Not to mention that there's also a definition of how much an elementary charge is. You get the point, this is a rabbit hole.

So, now let's pretend that I have a calibrated oscilloscope. Let's say that our oscilloscope is calibrated within 1 dB. Cool. So I plug in my beacon and measure, what?

I'll end up with a reading, that's plus or minus 1 dB of "reality". In my case, perhaps I read 22.5 dBm. That means that it could be as low as 21.5 dBm or as high as 23.5 dBm, or between 141 and 224 mW. So, it's within specifications, great, but I don't actually know what the actual output power is.

Another way to look at this is to use a measurement to determine if the power is within specification or not. I'm guessing that Harry already did that test before he put my beacon in the box and shipped it to me.

Long story short, I'm no closer to knowing just how much power is coming out of my beacon, but I'm still working on finding a friend with a calibrated tool that might give me something a little more precise than fail or pass.

You know that there's a saying about turtles all the way down? I think it's rabbits myself.

I'm Onno VK6FLAB

Which way did it go?

Sat, 12/17/2022 - 11:00
Foundations of Amateur Radio

Propagation, the art of getting a radio signal from one side of the globe to the other, is a funny thing. As you might know, I've been experimenting with WSPR or Weak Signal Propagation Reporter and for about a year running a beacon on 10m. Out of the box my beacon uses 200 mW to make itself heard. I couldn't leave well enough alone and I reduced the output power. Currently a 10 dB attenuator is connected to the beacon, reducing output to a notional 20 mW. I say notional, since I haven't actually measured it, yet.

With so little power going out to my vertical antenna, a homebrew 40m helical whip, built by Walter VK6BCP (SK), and tuned to 10m with an SG-237, it's interesting to discover what's possible.

Last night my signal was heard in Denmark. Picked up by Jorgen OZ7IT, 13,612 km away. That report broke another personal best for me, achieving 680,600 kilometres per Watt. I was stoked!

I shared a screen-shot of my report with friends. One friend, Allen VK6XL, asked a very interesting question. "What makes you think it was short path?"

Before I go into exploring that question, I need to explain. If I was to fly from Perth to Sydney, the popular way to travel is across the Australian Bight, over Truro, north of Adelaide, clip the northern tip of Victoria, over the Blue Mountains to Sydney. The distance is about 3,284 km. This route is known as the great circle route, more specifically, the short great circle route.

It's not the only way to travel.

Instead of heading East out of Perth, if I head West, I'd fly out over the Indian Ocean, Africa, the Atlantic Ocean, the Americas, the Pacific Ocean and finally arrive at Sydney. That journey would also follow a great circle route, the long great circle route. It's about 37,000 km long. You might notice that I wasn't very specific with either the path or distance. There's a reason for that. None of the tools I've found actually provide that information, other than to point out that the entire circumference of the planet is about 40,000 km and that it's not uniform since Earth isn't a perfect sphere.

You might be asking yourself at this point why I'm spending so much energy worrying about taking the long way around and how that relates to my 20 mW WSPR beacon.

In amateur radio we refer to these two travel directions as the short-path and the long-path.

Radio signals travel along the curvature of Earth bouncing between the Ionosphere and the surface. How that works exactly is a whole different topic, but for the moment it's fine to imagine a radio signal skipping like a stone on water. As a stone skips a couple of things happen. If the angle at which it hits the water is just right, it will continue on its journey, get the angle wrong and you hear "plop". Every skip is slightly lower than the previous because the stone is losing a little bit of energy. Every time the stone touches the water it creates a splash that ripples out in a circle from the place where the rock hit. These ripples also get weaker as they increase in diameter. Consider what happens if you skip a rock across concrete or sand instead of water and if you really want to geek out, there's also wind resistance on the rock.

A complex equivalent dance affects a radio signal when it propagates between two stations. For success, enough radio energy needs to reach the receiver for it to be decoded. For our signal to make it to the other side of the globe it must bounce between the Ionosphere and Earth's surface. Every bounce gets it closer to the destination. Each time it loses a little bit of energy. This loss happens at the Ionosphere, at the surface and in between through the atmosphere.

To give you a sense of scale, my signal report from Jorgen in Denmark was -28 dB. It started here in Perth as 13 dB, so we lost 41 dB along the way. We're talking microwatts here. I'll note that I'm avoiding how this is exactly calculated, mainly because I'm still attempting to understand how a WSPR signal report actually works since it's based on a 2,5 kHz audio signal.

As I said, enough energy needs to make it to the receiver for any of this to work.

There's an assumption that less distance means less energy loss. It's logical. A shorter distance requires less hops and as each hop represents a specific loss, less hops means less loss.

But is that really true?

There's nothing stopping my beacon signal from taking a different route. Instead of travelling the short-path, it can just as easily head out in the opposite direction. Theoretically at least, my vertical antenna radiates equally in all directions. The long-path is mostly across water between Perth and Denmark. What if hops across the ocean were different than hops across a landmass? Turns out that they are in several ways. For example, there's less energy loss in a refraction across the ocean, how much less exactly is still being hotly debated. Much of the data is empirical at the moment.

It gets better.

What if I told you that the report was near to sunset? At that time there's a so-called grey line phenomenon related to how the sun stops exciting the Ionosphere and how different layers of the Ionosphere start merging. As a result the angles of refraction across the Ionosphere change and longer hops are possible.

What if the long-path took less energy to get to Denmark than the short-path did?

Would Jorgen's decoder care?

If that's the case, my signal didn't travel 13,612 km, it travelled twice that and I'd have well and truly cracked a million kilometres per Watt.

So, is there a way we could know for sure?

Well, yes and no.

For starters we'd need beacons that transmit at a very precise time. Then we'd need synchronised receivers to decode the signal. A signal travels 3,000 km in a millisecond, so we're going to need something more precise than the timing set by NTP or the Network Time Protocol used by your home computer. If we used GPS locked transmitters and receivers we'd be working in the order of 50 nanoseconds and be in the range of 15m accuracy.

That would allow us to calculate the physical distance a signal travelled, but that's not the whole story.

What happens if your signal travels all the way around the globe, or if some of it reflects back, so called back scatter, like the ripples from a stone coming back towards you, and that signal travelling back past you to the receiver? There's endless variation, since the planet isn't round with a flat surface nor is the Ionosphere.

So, do we know if my report was a long-path or a short-path? Not really. Based on the time of day, there's a good chance that it was a long-path report, but only if we actually measure the delay between send and receive will we have data to make a better assurance than "possibly" or "probably".

As I started, propagation is an art.

I'm Onno VK6FLAB

Morse is dead ... long live Morse!

Sat, 12/10/2022 - 11:00
Foundations of Amateur Radio

One of the oldest means of electronic messaging is Morse code. Developed by Alfred Vail and Samuel Morse and sent for the first time on the 24th of May 1844, Morse code changed the way we communicate.

For nearly a century it was required to become a licensed radio amateur until in 2003, the International Telecommunications Union or ITU left it to the discretion of individual countries to decide if a budding amateur needed to demonstrate their ability to send and receive in Morse. With that decision many thought that the end of Morse code was only a matter of time.

They were wrong.

Turns out that use and progress of Morse code continues at a surprising rate. Searching for scholarly articles on the subject, you'll discover that it's used, for communication by quadriplegics, for information exchange between IoT or Internet of Things devices, as a way to secure information combining DNA and Morse code, as a method for gesture recognition, as a research tool for psychologists interested in learning methodologies, for training neural nets, for REM sleep research and plenty more.

Learning the code is an activity that sparks joy or dread, depending on whom you ask. For me it's been a decade of anticipation with little to show for it.

How to learn is a question that prompts as many answers as there are people within earshot and most of those disagree with each other. If you do ask, you'll discover that there are dozens of websites that offer to teach you, podcasts and audio files, bits of paper, buzzers, software and video, images and cheat sheets, the list is endless. You'll also discover two terms, Koch and Farnsworth. Both are intended means of learning. You'll find proponents of both methods wherever you look. You'll also hear from people who learnt the Army way, whatever that means, there's people who were taught not to send before they could properly receive, those who were taught the opposite and everything in between.

There's discussion on the topic, heated even, but very little in the way of actual hard data. There's some research. In 1990 the Keller Method from World War 2 was explored. The method involves playing a Morse letter, followed by a gap where the student is expected to write the letter, followed by a voice prompt of the letter. Interesting, were it not for the fact that it looked at nine students and only at their ability to master the alphabet.

In 1960, 310 airmen were subjected to 14 tests to determine their ability to learn Morse. No idea what the research outcomes were, since the Journal of Applied Psychology doesn't appear to share their research unless you pay for it.

There are reports of actual science behind the Koch method of learning, but I wasn't able to find it, though it's repeated often. It's only with the introduction of computers that actually using this method of learning has become practicable and recently popular.

As you might know, I've been attempting to learn Morse code for a while now. I've tried many different things, including Farnsworth, Koch and others. I publish versions of my podcast as Morse code audio only. They're published every week and there are a few people who listen.

I also attempted to make stereo audio files with a computer generated voice in one ear and a Morse word in the other, I generated flash cards, I tried learning the code as dits and dahs, but in the end, nothing really worked for me.

About a month ago I came across a video on YouTube by Electronic Notes. It contained the Morse alphabet as audio and flashed the letter visually on the screen whilst the audio was playing. There's also a video with numbers and a combination of the two.

It gave me the idea for something entirely different to try and in preparing to talk about this, it turns out that there's even research to suggest that I might be on to something. I discovered that in 1994, sixty healthy people were tested to determine if learning Morse code in a rehabilitation setting was best achieved using visual, auditory or a combination of both. The research conclusion was that the combination works best.

My idea is a video that shows an individual word whilst Morse code for that word is heard. There's no dits and dahs on the screen, just the word, written in English, and the Morse code for the word. The speed is 25 Words Per Minute, or WPM, and it's played with a side-tone of 600 Hz. Each video is an entire podcast, lasts about 30 minutes, and plays at full speed.

I'm already beginning to notice that some words sound like a sound blob in much the same way as when I learnt a new language, so I'm hopeful that this will finally get me on my way.

It's early days and the video channel is an experiment, so please comment to share your thoughts on the experience.

Who knows, I might have introduced a new way to learn.

Now all we need is some research to compare it to other methods, Koch, Keller, Farnsworth and Onno, hi hi.

You'll be able to find this article on YouTube too, "Morse is dead ... long live Morse!"

I'm Onno VK6FLAB

Attenuators, the missing link...

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

Having been able to call myself an amateur for over a decade, it might come as a surprise to you that it wasn't until a couple of weeks ago that I thought about attenuators for the first time. They're a curious tool and once you come across them, you'll never be quite the same.

Before I dive in you should know that an amplifier is an active tool that makes things bigger and an attenuator is a passive tool that makes things smaller. To look at, attenuators are diminutive to say the least. The ones I have in my kit look like barrel connectors, a male and female connector and seemingly not much else, but looks can be deceiving and I'll mention that shape isn't universal.

The purpose of an attenuator is to reduce the power of an RF signal by a known amount, preferably without distortion or any impedance mismatches. When you go out hunting and gathering, your choice of connector is the first obvious selection, but soon after you'll be asked for a frequency range, an impedance, a power level and an attenuation level, so let's take a look.

I have some attenuators with N-type and SMA connectors. There's options for every connector under the sun, so consider what you're using with your gear and remember to think about your measuring equipment connectors as well. In my case my shack is pretty much SMA the whole way, but a friend had some broadcast N-type attenuators and I was unable to resist.

The next thing is impedance. In my case 50 Ohm, but there's options for other choices like 75 Ohm for TV based attenuators.

The purpose of an attenuator is to reduce power. It does so by converting power into heat and more power handling means more heat. Too much heat and the attenuator starts letting out the magic smoke, so consider how much power your RF source is generating. Putting out 5 Watts? Then make sure that you don't connect a 1 Watt attenuator to that radio.

Now for the attenuation level. It's described in dB or decibel. At first the numbers look bewildering, but pretty soon you'll be familiar with how it hangs together. A 3 dB attenuator will halve the signal, so a 10 Watt signal will be reduced to 5 Watts and a 200 mW signal will be reduced to 100 mW.

If you have a 6 dB attenuator, it will halve again, so 10 Watts becomes 2.5 Watts and 200 mW becomes 50 mW.

A 10 dB attenuator is a little more than 9 dB, so you could try something along the lines of a bit more than half again, but you don't need to. 10 dB attenuation is essentially moving the decimal point. A 10 Watt signal with 10 dB attenuation becomes 1 Watt. A 200 mW signal becomes 20 mW.

If you have a 20 dB attenuator, it moves the decimal point two places, 10 Watts becomes 0.1 of a Watt, or 100 mW and 200 mW with 20 dB attenuation becomes 2 mW. You can connect two attenuators together and combine their values by adding them together. For example, combining a 10 dB attenuator with a 3 dB attenuator makes for 13 dB attenuation which moves the decimal point and then halves that.

All that's fine and dandy, but what's the point?

Well, imagine that you want to measure the actual power output of your radio. If you were to pump the minimum power level of my Yaesu FT-857d into a NanoVNA you'd blow it up, but if you added say 20 dB attenuation, that 5 Watt would become 0.05 Watts or 50 mW which is half the power rating of the NanoVNA. If you're not confident that your radio is actually putting out 5 Watts, you could add 30 dB attenuation and have a safe margin at an expected output of 5 mW.

I mentioned that attenuators don't all look like an innocent barrel connector. That's because if you have to attenuate something with higher power levels, you'll need a way to dissipate heat, in much the same way as a dummy load has cooling fins, higher power attenuators can come with cooling fins too.

On the inside of this contraption is a simple circuit made from three or four resistors which combine to attenuate your signal. If you're inclined to build your own, there are plenty of online calculators to be found that show how to put an attenuator together.

One thing I've skipped over is the frequency range. Most of us are having fun with HF, VHF and UHF, generally below 1 GHz, so most attenuators will be fine, but if you are playing at higher frequencies you should take note of the frequency range specified for the attenuator.

While on the subject of frequency range. You can easily measure the actual performance of an attenuator using a NanoVNA. Connect Port 1 to Port 2 through your attenuator and using the magnitude trace you can see just how much attenuation it provides. Be sure to set the intended frequency range and calibrate without the attenuator before measuring.

Now that I know about attenuation, I cannot imagine a life without, but to be fair, I was in blissful ignorance for more than a decade, so this might not apply to you, yet, but one day perhaps you'll find yourself thinking about adding some attenuation to your tool kit.

I'm Onno VK6FLAB

How low can you go?

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

It's common knowledge that power, as in output power, makes your signal heard in more places. If you've followed my adventures you'll also know that I'm a firm believer in low power or QRP operation.

It all started when I was told that my shiny new amateur license was rubbish because I was only allowed to use 10 Watts. Seemingly the whole community around me shared that opinion and slogans like "life's too short for QRP" are still commonly heard.

As a direct result of that sentiment I decided to explore and document just how much I could actually do with my so-called introductory license, the Australian Foundation License. I've now held it for over a decade and I'm still exploring and writing.

One of my first acts of rebellion was to lower my radio output power to its minimum setting of 5 Watts and half legal power was sufficient to prove my point.

Although I'm still regularly being encouraged to upgrade, my second act of defiance is to keep my Foundation License until I decide that I need more. I'll let you know if it ever happens.

One more well known so-called "fact" about our hobby is that if you use low power you'll really only get anywhere on the higher bands, 2m, 70cm and above. There's plenty of reports of amateurs using a low power handheld radio to talk to the International Space Station and my own satellite internet used 1 Watt to get to geostationary orbit. On HF on the other hand, 5 Watts is as low as you really want to go. Making contacts is a struggle and often frustrating, but when you do, bliss!

About a year ago I took delivery of a WSPR beacon. It's capable of transmitting on all my accessible HF bands using 200 mW. Given my antenna situation I've configured it to transmit on the 10m band, 24 hours a day, thunderstorms excepted. When making the purchase decision I had no insight into how my beacon would perform. 200 mW is stretching even my love of low power, but I hooked it up and turned it on and waited.

It came as quite a surprise that my beacon was heard over 15 thousand kilometres away, not once, not a couple of times, but regularly. When I came up with my November challenge to see if I could improve on that I made an almost throw away comment about reducing power to see if I could still make the distance.

A couple of weeks ago I hooked up a 6 dB attenuator to my beacon, reducing the power from 200 down to 50 mW. It came as quite a surprise that my signal made it to the same receiver in the Canary Islands. My kilometre per Watt calculation shot up, quadrupling my previous record.

Just imagine, 50 mW making its way over a third of the way around the globe, bouncing between the ionosphere and the planet, just like any other HF signal. At that point I realised I had learnt a few things. You don't need stupid power to make a distant contact on HF either. I started wondering just how little power was needed to get out of the shack.

Yesterday I hooked up a 10 dB attenuator and within ten hours my now 20 mW beacon broke my own kilometre per Watt record again and based on the signal to noise numbers from previous contacts, I see no reason for that record to stand for very long. Once that happens I've got plenty more attenuators to play with and I'm not afraid to use them.

Now I'm on the hunt for an attenuator that will reduce my main radio output from 5 Watts. I'm told I should aim for double the power rating, but I also have to consider how to connect my antenna coupler which needs 10 Watts to tune, but that's a project for another day

When was the last time that you used really low power?

I'm Onno VK6FLAB

The nature of learning things...

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

Recently I discussed the concept of a VFO, a Variable Frequency Oscillator. It's an essential building block for our amateur radio community. In describing the idea behind it, while making an error in one of the CB radio frequencies, thanks to Ben VK6NCB for picking that up, I skirted around how a VFO actually works.

In reality the VFO is a collective term that describes a whole range of different methods to vary a frequency. Naturally I continued my exploration and discovered a whole range of documentation on the subject. I even started writing about how one common method, a Phase Locked Loop or PLL, works and how a VCO, a Voltage Controlled Oscillator, operates as part of that. I'll come back to those shortly.

In doing my reading, since, as is often the case, I use my weekly contribution to the world as a method to learn things. I'll investigate a topic and attempt to describe who came up with it, what it means, how it works and what its place is in the world, the who, where, why and what of it, if you like. I suspect that comes from my very first introduction to broadcast radio where that was one of the very first things I was taught, thirty years or so ago.

If you've followed along for the decade I've been at this you'll know that I also intersperse such learning with observations about the things that I'm interested in. This is such an observation, a meta view if you will.

I discovered somewhat to my chagrin that the ways that an essential component of our hobby, a system called a Phase Locked Loop, was described in such academic terms, complete with formulas and detailed circuits and even component lists, spread over pages and pages of verbiage, or explained in YouTube videos lasting an hour or more. Of course there were some little gems, ElectronicNotes on YouTube manages to cover the basics in little over six minutes, but that's a rare example.

It reminded me of a website that I've been using to fill in the gaps in my understanding of SDR or Software Defined Radio and Digital Signal Processing or DSP. The PySDR.org site is an online textbook written by Dr. Marc Lichtman. He says about his method: "Instead of burying ourselves in equations, an abundance of images and animations are used to help convey the concepts [...]"

My weekly efforts have always attempted to do exactly that and I found myself in a place where such a thing didn't appear to exist for the concepts behind the PLL and VCO. My obvious response to that would be to write the missing document and as I said, I have a first draft of it sitting on my computer.

There's only one problem.

I don't yet "grok" the concepts. If you're unfamiliar with what grokking is, it means to understand intuitively and emphatically. It also means that unless I can describe it in less than a single page of A4 paper I don't understand what I'm saying and you'll get bored waiting for me to make a point.

Here's my point.

How do you learn concepts? What is it that you do to discover new topics of interest and how do you progress through the various stages between discovery and grokking?

For me it's about puzzle pieces. It's always been puzzle pieces. Little nuggets of information, almost trivial on their own, but after a while you get to a point where you have enough of them that you can start joining them together to grasp a more complex concept.

Here's a puzzle piece I discovered today.

Impedance: The difference between an explosion in air and one under water is impedance.

It's little concepts like that which make me get out of bed and discover what's on the horizon next. I'm also learning about double and triple conversion superheterodyne radio which I believe has a one-on-one parallel application in Software Defined Radio and Digital Signal Processing. Once I figure out how to describe it to you, I'll let you know.

The point of all this is that learning things is as much about understanding as it is about explaining.

Feel free to point me at new and interesting basic concepts.

I'm Onno VK6FLAB

What's in a VFO?

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

One of the many acronyms that define the world of amateur radio is VFO. It stands for Variable Frequency Oscillator. That doesn't explain much if you're not familiar with the purpose of it and just how special this aspect of amateur radio is.

Much of the world of radio beyond our hobby, like broadcast television, WiFi and Citizen Band or CB, to name a few, uses radio spectrum in a particular way. On a television you change channels to switch between stations. Similarly, a WiFi network uses specific channels to make your wireless network a reality and the same goes for CB, different channels to make yourself heard.

Looking specifically at CB for a moment, if you look at channel 8 for example, depending on which type of equipment you have, your radio might be using 27.055 MHz, or 476.575 MHz, or 476.6 MHz. Each of those frequencies can be described as CB channel 8. The first is on the 27 MHz or 11m band, the second is if you're using a 40 channel radio, which is now depreciated and the third is if you're using an 80 channel radio.

If you look at digital broadcast television, channel 8 is on 191.5 MHz. On WiFi, channel 8 is on 2.447 GHz or 5.040 GHz.

You get the point, depending on where you are as a user of radio spectrum, channel 8 might mean a whole host of different things and as I've described with CB radio, that might even change over time.

Harry Potter needed magic to reach Platform Nine and Three-Quarters at Kings Cross Station to get to school. In a channelised world, getting to an in-between frequency is not possible if you're using licensed equipment, unless you're a radio amateur, then you can use magic to get into the gaps. That magic is called the VFO.

You might recall that our radios use many different frequencies internally to be able to filter out specifically what signal you want to hear. Most of those frequencies are fixed, in fact in the vast majority of cases these are actually tuned and calibrated to work in a very specific way.

The one exception is the VFO, it's by nature variable. It's likely calibrated, but it's not fixed and that allows our community to tune our equipment to any frequency we desire.

The traditional user interface for this is a big knob on the front of your radio, colloquially referred to as the dial, as-in turn the dial to change frequency.

This allows us something quite rare in radio land. We can be frequency agile. It means that if there's interference at a specific frequency, we can tweak our VFO and slightly modify where our radio is tuned. You use this almost subconsciously when you're on HF trying to tune to a particular station.

In the world of software radio there's likely no knob. You type in a number and the variable frequency oscillator in the radio is tuned to another frequency and the output signal, or transmit signal if you're making noise on-air, changes to another frequency.

Digital modes like WSPR, which generally use a very specific frequency also vary that frequency but in a different way. You set your radio to the appropriate so-called dial frequency, let's say 28.1246 MHz on the 10m band and then the software alters the signal by up to 200 Hz to change within the available audio range of your radio, altering between a low of 1400 Hz and a high of 1600 Hz, making the actual WSPR frequency on 10m between 28.1260 and 28.1262 MHz.

I'm mentioning the WSPR example because while we're frequency agile in our hobby, we do use channels as well. There's a specific set of frequencies set aside, channels if you like, for WSPR, FT8 and other modes. We do the same on the 2m and 70cm bands where we have rules for where repeaters are allowed to be.

It means that we get the best of both worlds. We have the stability and institutional knowledge where repeaters or some modes go, but we also get to play in any spot we want.

For example, there's nothing stopping me and a friend setting our radio to some random frequency within our license allocation and outside pre-allocated space and run a WSPR transmitter there. Only the two of us will know about it, well at least at first, but it allows us to experiment away from any other users who might experience interference from our tests and exploration.

The VFO is what makes our hobby so very interesting and it's what makes it possible to do weird and wonderful experiments.

I'm Onno VK6FLAB

My Virtual Workbench

Sat, 11/05/2022 - 12:00
Foundations of Amateur Radio

With the ever increasing pace of innovation, well, change, I'll leave alone if it's actual innovation instead of marketing, we see new software released at an almost alarming rate.

There is an urge to stay abreast of this process, to update, upgrade and try new solutions as soon as they are presented to you by well meaning friends and colleagues, not to mention online marketing, uh, reviews and other enticements that make you click the button to install something to avert the fear of missing out.

If you've done this for a number of years, actually, who am I kidding, a number of weeks, you'll discover that this comes at a cost. One that the corporate world has attempted to address by using terms like Standard Operating Environment, backups, administrator privileges and other such annoying things that prevent users from trying something new and breaking things.

At home and in the shack most of that is not a problem. No corporate IT division around to stop you, but soon you'll discover that something you installed caused you grief, encouraged your logging software to stop talking to your radio, prevented you radio from changing frequency, or blocked the latest digital mode from working as intended.

I live in that world too, but with the benefit of an IT background I decided nearly a decade and a half ago that enough was enough. I bit the bullet and bought myself a new computer. I vowed to install only one tool on that laptop, a virtualisation environment, also known as a hypervisor. It allows you to run a virtual computer inside a window. Given enough CPU power you can run multiple virtual computers in multiple windows inside your actual physical hardware.

This gives you flexibility. You can run a copy of your favourite operating system in a virtual environment, install the latest and greatest software on it and if it breaks, you delete it and start again. In my case I'm running my daily desktop environment where I'm currently writing this as a virtual Linux machine inside my physical computer which is also running several other virtual machines, including some network monitoring tools, a software defined radio development environment, my accounting software and plenty of other things.

Each virtual machine is nothing more than a folder on my physical computer and making a full backup is as simple as making a copy of that folder. Better still, if I want to try a new version of something on a machine that I'm already using, I can duplicate the folder, fire up the copy of the virtual machine, install the new software and test it. If it works, great, if not, throw it away and start again.

Changing physical computers is also simple. Buy a new computer. Install the hypervisor, copy the machine folders across and start working.

From a security perspective, it also means that I can install a random bit of software recommended by a friend without getting worried about it stealing any of my information, given that my private information isn't on the virtual machine on which I'm installing this unknown piece of software.

I also use this to compile new bits of code. If I come across a project on GitHub that I'd like to try, I can fire up a brand new machine and install all the prerequisites without running the risk of breaking something that I rely on. It also means that I can test with different operating systems, from macOS, any flavour of Linux, copies of Windows and play with virtual copies of Android or if I'm feeling frisky, BeOS.

There are other ways to achieve some of this. For example, you could get yourself a Raspberry Pi and half a dozen MicroSD cards. Install an operating system onto a card, boot the Pi, install your new application and if you like it, use it. If not, wipe the card, start again. You can have a dedicated WSPR beacon card, a contest logging card, whatever you need, all separate, all easy to backup and change as needed.

If that's not enough, some virtualisation environments allow you to emulate different microprocessors, so you could run ARM code on an x86 processor, or vice-versa.

If you want more, you can investigate containerisation. A tool that allows you to essentially create a mini virtual machine and run a new environment using a single command, so fast that you essentially don't need to wait for it to start-up, allowing you to mix and match environments as needed.

At this point you might ask why I'm even talking about this. What does this have to do with amateur radio?

Well, it's how I have my test bench set-up. Sure I have a soldering station, multimeters, a NanoVNA, an antenna analyser and all that kind of great stuff, but my radio world is mostly software and in that space all my tooling is pretty much virtual, put together in such a way that I can pick and choose precisely how I want to test something without killing something I rely on.

I'm telling you about it because in my experience much of the amateur community still relies on a desktop computer running Windows and I have to tell you, there is so much more out there for you to explore.

What does your virtual workbench look like?

I'm Onno VK6FLAB

A plan for distributed SDR decoding

Sat, 10/29/2022 - 12:00
Foundations of Amateur Radio

Yesterday I finally discovered the missing piece of information that will allow me to create a project that I've, if not outright spoken about, at least hinted at.

In an ideal world by now I'd have built a proof concept and would be telling you that I've published a GitHub repository under my callsign for you to explore. If wishing made it so. Unfortunately, currently sitting at a keyboard for anything longer than ten minutes or so makes it nigh on impossible to stand up, so you'll have to make do with hand waving and gesticulation rather than actual code, but for now, that's all I have. Consider this a design specification if you're so inclined.

So, big idea.

Imagine that you have a device that can listen to radio frequencies. This device is connected to a network and it shares the data to any number of different listeners which might each do something different with the information.

If you were to do this in the way we watch YouTube or listen to streaming audio, each listener would get their own unique copy of the data. If you have ten listeners, you'd have ten streams crossing your network, even if everyone was enjoying the exact same video or audio at the exact same time.

Instead I want the data coming from the device to have only one stream on the network and for as many different listeners or clients to access it as required at the same time.

Let's get specific here for a moment. I'm talking about using a software defined radio, could be a $25 RTL dongle, could be any SDR, that is tuned to a part of the spectrum, let's say the entire 40m band, and sends that radio information digitally onto the network. This network could be your local network, or it could theoretically be the internet, for now, let's just put it out on our own network.

So, you have a copy of the entire 40m band streaming across your network. Great, now what? Well imagine that you want to decode RTTY on 7.040. You fire up your decoder, point it at the network stream and decode RTTY.

Then you want to decode a WSPR signal, at 7.0386. You fire up your WSPR decoder, point it at the network stream and decode WSPR.

Then you want to decode FT8 on 7.056, same deal, fire up your decoder, point it at the network stream and decode FT8.

Now you want to compare two different RTTY decoders. Fire them both up, point them both at the same stream, decode both, simultaneously.

Of course you could do this with CW signals, with SSB signals, with any decoder you have lying around, Olivia, Hellschreiber, AM, Packet, whatever. All these decoders could be running independently but together on the same band.

You could add a tool that shows a waterfall display of the same data on a web page, or play some of the decoded data to your headphones, or record it to disk, or do spectral analysis, all at the same time.

The information that you're processing is on the network once. You don't have to flood your network with multiple copies of the 40m band, the only limit is how much CPU power you can throw at this and to be frank, most computers on the globe today spend much of their time waiting for you to do something, so processing a bit of data like this is not going to tax anything built in the past 20 years or so.

The missing ingredient for this was a Linux tool called netcat, or nc. It allows us to distribute the information across the network using a technique called broadcasting.

So, RTL dongle, data extracted by a tool called rtl_sdr, distributed across the network using netcat and used by as many clients as you can think of.

The proof of concept I'm working on uses Docker to build a bunch of different containers, or clients if you like, that each can do a different task with the same stream. When I've got something to show and tell, you'll find it, predictably, on my GitHub page.

Oh, if you want to run the same thing for say the 80m band, you can. Now you have two network streams, one for 40m, one for 80m and as many decoders on your network as you have CPU cycles to play with.

If all this sounds like magic, you've seen nothing yet.

I'm Onno VK6FLAB

The sedentary myth of radio.

Sat, 10/22/2022 - 12:00
Foundations of Amateur Radio

When people think about and discuss my chosen hobby, amateur radio, there's often a perception that it's old men sitting behind a radio tapping on a Morse key, making beeping noises surrounded by all manner of imposing equipment, stacked thick and high in a tiny room that soon becomes too stifling to spend much time in.

While such scenes might exist, often reinforced by old photos and messy radio shacks, any self respecting amateur will tell you that plenty of time is spent outside the shack dealing with antennas, coax and earthing systems, combined with pouring concrete, building, erecting and climbing towers and a myriad of other physical activity.

My experience has shown that my own inertia bending acts often involve things like camping, portable operation in ever changing environments, throwing ropes into trees and recovering those later, erecting verticals, tying down squid-poles and other muscular movements like building temporary rotators lashed to the nearest utility vehicle to take advantage of a multi-band yagi that someone brought along to play with during a field day.

The first time I really discovered just how lacking my stamina is, was in early 2014 when the FT5ZM DXpedition team to Amsterdam Island was in town. I had the pleasure of spending a day with a couple of team members showing off the sights of my QTH, Perth in Western Australia. In the middle of the city is Kings Park. To give you a sense of scale, at over 400 hectares, Perth's Kings Park is larger than New York's Central Park and London's Hyde Park. One of the attractions is the dual spiral staircase DNA tower. At 15m height, it's the highest viewing point in Kings Park offering 360 degree views of the park and the city surrounding it. Commissioned in 1966, the tower has 101 steps and has recently been refurbished. It derives its name from the DNA Double Helix molecule, which is how the staircases are arranged.

One of my companions on the climb to the top was a sprightly amateur who's been licensed a decade longer than I've been alive. I marvelled when Arnie N6HC essentially ran up the tower when all I was able to achieve was puff my way up in his wake.

Since then I've discovered that doing 24 hour contests, camping and other fun stuff now absolutely kicks the stuffing out of me, often requiring that I spend a day in a small dark room recovering with a blanket over my head. While my body shape and my callsign have things in common and my doctor continues to encourage me to lose weight, I can say that my recent visit to hospital, unexpected as it was, reminded me in no uncertain terms that I should look after myself, if only so I can actually participate in the next contest or camp-out.

I'm not going to tell you what my fitness plan is, nor am I going to tell you to embark on one of your own, other than to ask, have you considered just how much of this wonderful hobby goes beyond keying a microphone or tapping a keyboard and consider just how safe you really are when you next climb up a ladder, tower or other height to fix an antenna?

Speaking of health, I've been absolutely blown away by the incoming messages, offers of help, shared gallbladder emergency and post-operative experiences and more, from people whom I've known for years through to amateurs who took a chance to introduce themselves and wish me well. It wasn't until this week that I really understood that this community is rich in personal lived history, going well beyond the experiences I've had outside the hobby. I'm ever so grateful for your encouragement and intend to keep fighting to get well. It's going to take some time, but I'm looking forward to when I can next camp-out and not regret my life choices.

So, get off your sedentary and go do something will ya?

I'm Onno VK6FLAB

Setting a little personal challenge ...

Sat, 10/15/2022 - 12:00
Foundations of Amateur Radio

A week ago I unexpectedly had my gallbladder removed. As emergencies go, I was lucky to be in a major metropolitan area with a remarkable hospital, supported by a group of humanity whom I've never much interacted with in my life. The staff at Sir Charles Gairdner Hospital were without exception amazing, from the orderlies to the nurses and everyone behind those, I interacted with about fifty people directly during my stay and every single person had a smile to share and an encouraging word to give. As life experiences go it was as uplifting as I've ever had the opportunity to celebrate. Sure it hurt like hell and there were things I'd rather not have to try again, but on the whole it was, if not pleasant, at least memorable. Recovery is going to take a little while and I understand my voice is expected to return to normal in a few weeks having been intubated for most of a day.

Half an hour after being discharged from my five days in hospital I was faced with a choice. Produce nothing for my weekly contribution to our hobby and face the risk of an astronomical bill from my hosting provider because the script that I wrote didn't foresee that there might be a time when I was unable to provide content, or produce something that, to be sure, was lacking in every way, but at least know that there wouldn't be a surprise waiting on my bank statement next month. So, my inadequate production saw the light of day. For that I apologise, it should have been silence.

During the week I returned to my shack and had a look at my beacon. As you might recall, I've been using Weak Signal Propagation Reports, or WSPR in my shack for a while. According to the logs the very first time was in November of 2017. At the end of last year I took delivery of a ZachTek desktop WSPR transmitter which has been reported on air over 16 thousand times since. I've only been using the 10m band and it's been heard as far away from me in Western Australia as the Canary Islands, the home of Johann EA8/DF4UE and Peter EA8BFK who between them reported my signal nearly 90 times. It's remarkable to note that this is a distance of over 15 thousand kilometres, on the 10m band, using only 200 mW.

During the week I made another milestone, a report in the opposite direction, across the Pacific Ocean to mainland USA. While that didn't break any distance records, it was a thrill to see a report from the Maritime Radio Historical Society, logging WSPR signals using KPH.

Other things to note about these reports are that its been heard across 81 different grid squares, by 144 different stations from all directions of the compass.

During my hospital stay and since, I've come to appreciate setting little goals. Little personal achievements that in and of themselves are not meaningful to anyone but me, and in some cases, my medical support team. It reminded me of a time when I attempted to achieve this in amateur radio, making a contact every day. Looking back over my logs I can tell you that I've not managed to maintain that, though, technically, on average, given that I host a weekly net and there's generally more than seven people who join in, I could claim an average of one QSO per day, but both you and I would know that I was stretching the truth somewhat.

It occurred to me that my signal report by KPH could be considered the beginning of my new 10m adventures. Much of my start in this hobby was during the previous solar cycle and the 10m band featured heavily in much of my activities, especially since you can get on that band with the very minimum of antenna, a quarter wave on 10m is a 2.5m whip and that can fit even on my car and it did, for years.

When the solar cycle eventually wound its way down, the 10m band was quiet for much of the year with the odd spot to whet your appetite, but rare enough to have little in the way of ongoing contacts.

As far as I'm concerned, 10m is back in play and it's my personal special band, so I'm setting myself a little challenge for the month of November and you can join in, open to anyone who wants to play. There's no prize, no scoreboard, no accolades, no nothing, other than the personal satisfaction of achievement.

Here's the challenge. How many kilometres per Watt can you achieve during November? To explain, my beacon uses 200 milliwatts, so any distance is multiplied by five to get the km/W number. If you use more than a Watt, you'll need to divide your distance by the number of Watts you use. As I said, this is a personal challenge. I'm not going to adjudicate, there's no rules to break, no one to tell you that you're cheating, it's just between you and your WSPR beacon.

For now, my record is 75630 km per Watt. I'm going to take the opportunity to consider what I might do to improve on that. Perhaps if I reduce power I'll still be heard in the Canary Islands, but I'll have more bang for my buck. Time will tell. Feel free to share your own achievement, or keep it to yourself, entirely up to you.

In case you're wondering about the capacitor thing, a gallbladder is like a bile capacitor, the analogy came from a story I wrote whilst in hospital, it might even see the light of day...

I'm Onno VK6FLAB