Foundations of Amateur Radio

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New Entrants are Everywhere Aug 25, 2019

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Foundations of Amateur Radio

New Entrants are Everywhere

The hobby of amateur radio has been around for a long time. It was here before I was born and it will be here after I become a silent key. The same is true for you. While there is a recurring discussion about the death of the hobby, the reality is that our community changes continually. People come and go all the time. Reasons for change are as varied as the number of people you care to look at, from interest through to family, from money through to time, from boredom through to excitement, from life through to death.

As our community fluctuates, our skill level varies. We see new people come into the hobby, bright-eyed and bushy-tailed, ready for a new adventure, at the same time we have people who are experienced, or jaded, or both, participating in the community and finding themselves answering the same questions over and over again.

What radio should I get? Is this radio better? How do I do HF? How do I get my license? Where is everyone? How do you participate in a net? Which antenna should I buy? What is a QSO or a QTH? How come this and why that? At some point I was that person and I have no doubt that at some point you were, or are that person.

The challenge in maintaining a semblance of community coherence is to balance the needs for new and aspiring amateurs with the expectations of those already in the community. How do you answer the same questions while staying fresh and encouraging, when all you really want to do is ignore the noise and get on with the hobby?

The answer is simple.

You need to recognise that the change in the hobby is fundamental. New people coming in, new technologies, new hardware, new modes, new rules, new customs, all of it is in flux all the time. It shouldn't be seen as a threat, but as par for the course, something that is part of our community and part of why and how we exist.

To draw an analogy with something else, cooking. We've been doing that for a while, some suggest as far back as 2 million years ago. Every day new people learn to cook, new people invent or reinvent recipes, cooking classes abound, television shows with competitive cooking, new ingredients, new tools, new techniques and relearned old methods, there's celebrity chefs, awards and the more you look at cooking, the more you understand how it changes and continues to change. In many ways cooking and amateur radio are the same.

The idea of teaching your child, or a friend, or a person on social media how to cook something is accepted as how it is and how cooking evolves.

In amateur radio we can do the same.

It's easy to dismiss silly questions, or to give snide answers, or to ignore new arrivals, but that's not something that grows our community, strengthens it, or broadens it.

Of course, how much you participate in this is the real yardstick of how much of an amateur you really are. Said in another way, if an amateur calls CQ into a dummy load, does anyone care?

One of the challenges as a new entrant into the community is to figure out where to go and how to learn more. It's never been easier than it is today, even if you think that it's hard. In a bygone era you had to go to a library, or to find another amateur, or go to a club to even know that our hobby existed, these days the access to our community is within reach for any person on the planet.

We have endless resources, in the form of web-sites, books, both electronic and paper, clubs, virtual and physical, social media, podcasts and articles such as this, video channels, and an endlessly growing and evolving community that cannot help but document its adventures and exploits.

Amateur radio today is as close as the nearest search engine and as far as you want to take it.

Never be afraid of asking a question and consider it a right of passage if a grumpy bugger tells you off for asking a stupid one.

The worst question is the one you never asked.

I'm Onno VK6FLAB

What's in a Watt? Aug 18, 2019

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Foundations of Amateur Radio

What's in a Watt?

We need more power. I'm giving her all she's got, Captain! She cannae take anymore.

I'm sure your Scottish ancestors are rolling in their graves right now, but in our community of radio amateurs we have a tendency to advocate the use of more power. More power fixes all problems and hides all sins.

Another way to look at that is to think of the station with more power as an aligator, all mouth, no ears.

Before you dismiss this as another avocacy for QRP or low power, let me point out that more power creates more interference, more potential for harm, more electricity consumption, more wear and tear and more cost.

Previously I've spoken extensively about QRP communications, making contact with 5 Watt or less, but let's have a look at how much less.

I've shared with you that I managed to contact a station on the other side of the planet with only 5 Watts, Perth to Cuba and for me that was proof positive that all this was possible, even feasable.

We're doing much better than that.

One measurement is to calculate how many kilometers per Watt you achieved. My example of 5 Watt between Perth and Cuba is the equivalent of 3592 km per Watt. The maximum distance to the opposite side of our globe is about 20,000 km and my contact did nearly 18,000 km.

If you think that's amazing, I should warn you, my contact was special, for me, but as low power contacts go, it's not that amazing.

The first solid state radio contact made across the Atlantic ocean managed over 76,000 km per Watt. That was on 18 September 1956. You'll find the radio on display at the ARRL Laboratory, together with the bug and station log showing the contact between Chelmsford, Massachusetts and Copenhagen, Denmark between Gus W1OGU and Bo OZ7BO, on a radio made of two germanium transistors and built by Gus W1OGU, Al W1OSF and Dick W1UBC, who built the diminutive gadget on a lark to see if they could Work All Continents with it.

If you can copy the 40 microwatt CW beacon run by the North American QRP CW Club, you too can join in the fun. The current record stands at just under 22 million km per Watt when Bill W4ZV managed to copy the code word OMAHA from the N2XE beacon from New London, North Carolina.

Just to be clear, we're talking about a signal that travelled the equivalent of 22 million km using 1 Watt of power.

If you think that was amazing, Pioneer 10 managed to achieve 1.3 billion, that's 1.3 thousand million km per Watt in 2003. Mind you, that record was achieved with a slightly bulky antenna, the Deep Space Network.

Are you ready for more?

The current record stands at just under double the Pioneer 10 record, just under 2.6 billion km per Watt. That was achieved by Dick KL7YU and Bill W7BVV who made contacts between Alaska and Oregon in December 1969 and January 1970. A distance of 2655 km using one micro Watt.

Yes, you can throw a Kilowatt at the problem, or you can take your time, do some work and have some fun with low power.

You can call it QRP, or you can call it just enough to get the job done.

I'm Onno VK6FLAB

It broke and now what? Aug 11, 2019

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Foundations of Amateur Radio

It broke and now what?

Imagine you're a new amateur. You've woken up in the middle of the night because insomnia seems like a good way to use amateur radio as an excuse to get on air and make some noise. You turn on the radio, key up the transmitter and the next thing you know it's dark. The breaker that powers your radio popped and there's no more glow coming from the hardware that's warming up your shack.

You get up, reset the breaker, tighten up your dressing gown and switch on your gear. You sit down and key up. Pop, darkness.

What do you do next?

The first thing to realise is that there is something wrong. That might sound obvious, the radio just tripped the breaker and it went off, but sometimes it's not that obvious, sometimes there's something wrong, but it's not nearly as clear as light and dark. For example, you might key up and the SWR goes high. You might not even notice if your radio is set to monitor the power output, or the automatic gain control that indicates how well your audio is going out.

The point is that noticing that something is wrong is a matter of paying attention. Just sitting there all dumb and happy, mashing the microphone is going to cost money or cost something else one day when you stop paying attention.

So, finding out what's wrong starts with noticing that something is amiss.

If you've been clued in that something is broken, and you're not standing next to your radio with a fire extinguisher, or tears running down your cheeks because you just blew up your new radio, you can move onto the next part of this little adventure.

One thing to note is that it's really easy to make it worse at this point. Making it worse arrives in all manner of different ways, pain, either physical, RF burns, smoke, sparks, or mental like the emptying of your wallet when it goes pear-shape.

The art of troubleshooting is the process of attempting to learn what's going on. Some people know instinctively how to do this, others just wiggle stuff, unplug stuff and hope for the best. Hoping for the best is not the best plan.

One of the most basic aspects of troubleshooting, of trying to figure out what's happened, is to document what you find. Write it down. I know you're going to skip this, but it's going to bite you and then you'll be sorry and I'll be here telling you that I told you so. So write it down. Be meticulous. In case you're wondering, you're doing this for your own benefit, not my sense of curiosity. If you measure a value now and it's 7 Ohm and you change something and then you measure again and it's 23 Ohm, if you didn't write it down, you'll never know. Especially if the two measurements are a week apart.

Next basic concept is to change as little as possible, preferably one thing at a time. That's easy for me to say while your reptilian hind-brain is currently attempting to decide between whom to murder first and how fast to run. There is a tendency during panic to wildly wave your hands about and fiddle with lots of stuff. The urge to do that is strong. Resist that urge with all that you have. Again, you're going to ignore that and I'm going to stifle my I told you so chant, but less is more. This is important. If you change two things, you've just doubled the possible causes. If you change three, there are now six different causes and if you change four things, we're up to 24 different versions of the problem. Keep it simple.

Third concept is to test things. The smaller the test, the better. For example, you're connected to the right antenna, right? The power supply is giving out the right voltage, right? The squelch is open, right? The microphone is plugged in, right? Test each of those, one at a time. The more you troubleshoot, the more this list will come naturally. Right now you're probably cursing me for not supplying you with a ready-made list. That's because my shack is nothing like yours, not even a little bit. Also, your shack keeps changing. Besides we're learning the skill of troubleshooting and I already know how to do that. Mind you, truth be told, I've been known to make mistakes too, so there's that.

Forth concept is about testing gear. There is a tendency within our community to buy gadgets. The more the better, a volt meter, an ohm meter, an ammeter, an SWR meter, an oscilloscope, a VNA, a what-ever. The more toys the better. While toys, uh tools, help, they're not the answer to every question. You have a more fundamental issue to deal with. Garbage in equals garbage out. If you measure ohms, but needed volts, there's no helping you. So, instead of focussing on what new tool to acquire, focus on what measurement you need to make to prove that something works, or doesn't.

The process of troubleshooting doesn't come naturally to everyone. I know, I've seen some very panicked people break some very expensive hardware, seen full-bright scholars make bonehead mistakes and heard stories of physicists narrowly avoiding electrocution, so don't be shy when you say that you're not sure how to really do troubleshooting.

You can learn. We all did, me included.

I'm Onno VK6FLAB

What's in a word? Aug 04, 2019

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Foundations of Amateur Radio

What's in a word?

When you join a new community you learn very quickly that each community has its own language. A word in one community has a different or extra meaning in another. For example, the word "Snowflake" in one community might refer to a phenomenon related to water and freezing, in another community it refers to a person who is sensitive, easily hurt and offended. If you mix the two meanings all manner of misunderstanding ensues.

In amateur radio, one of those words is the word gain.

This word is used in many different aspects of our hobby, but today I'm going to focus on one specific use of it, in relation to antennas, antenna gain.

This mythical property of an antenna is often used as a way to distinguish two different antennas and in advertising terms, bigger is better, more gain, more better. I'll skip over the marketing shenanigans related to artificially making the number larger by comparing apples and pears, or dBi and dBd and move on to how gain comes about.

Let's look at something completely different. A light bulb. One of those tiny ones you find in a torch, or on the front of your bike or even one in your car. In essence we have a gadget that emits energy in the form of light and heat when electricity is applied. The specifics aren't important, but let's just say we're going to ignore more voltage and more amps for the moment.

If you have a bare light bulb, light and heat radiates in almost all directions. You can't see any light where the fitting is, but everywhere else is a pretty uniform pattern. For the moment, let's ignore the fitting.

If you were to get a piece of black cardboard and drill a hole and put the light through it, you've essentially removed half of the light. Below the cardboard there is no light. Above the cardboard is the same amount of light as before. Half the light is being stopped by the cardboard and it's essentially lost - technically it's getting absorbed and the cardboard is getting a little warmer, but let's not confuse the issue for the moment.

If you were to make the cardboard reflective, say some foil, white, a mirror, whatever, the light that was hitting the cardboard would be reflected away from the cardboard and you'd experience that as the light getting brighter. Notice though, it's still dark below the cardboard.

In essence you've just increased the gain of your light bulb and it didn't cost you any more electricity to make that happen.

Antennas work in much the same way. There are a few more wrinkles. A light bulb is working with light and heat frequencies, wavelengths are between 100 micrometers and 100 nanometres, where the antennas we use in amateur radio typically look at 100 meter to 23 centimetre, so the material aspects of our mirror equivalent are different, but have a similar idea.

One thing that's fundamentally different between a light bulb and an antenna in our hobby is that a light bulb is generally only transmitting, where we tend to both transmit and receive with an antenna.

Remember when I skipped over the bit of the light bulb below the cardboard being dark? That's the antenna equivalent to not hearing something, which means that you're better able to hear the signal in the direction you're pointing. The same is true for the bit about the light bulb fitting and no light below it.

In antenna terms, this phenomenon relates to the front-to-back ratio. Imagine turning your antenna 180 degrees. Pointing one way the signal is of this strength, pointing the other way it's that strength. Divide the two. If they're the same, the front-to-back ratio is 1, otherwise they express the directivity of the antenna. Another number you can use to market your antenna to an unsuspecting amateur.

So far we've only looked at using a single reflector for our light bulb, but if you were to use a torch, you'd get even more directivity and more gain. The same amount of energy, pointing at a smaller area. The ultimate expression of this is a laser beam, which is essentially a single focussed beam of light with no light anywhere other than where it's pointing.

Antennas do the same thing, using different methods, but the most common one is to add more bits of metal to focus the radio energy.

A light bulb emits energy in all directions and an antenna does too. Even if you were to make an antenna made of elements, all aligned in the same direction, the pattern is still mostly round, that is, it's like a cone of radio, regardless of the shape of the antenna.

Yes, there are ways of making antennas that don't make round cones, but that's a conversation for another day, but think about this, what would happen if you were to squash an antenna pattern and then focus it?

I'm Onno VK6FLAB

How far can I talk on radio? Jul 28, 2019

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Foundations of Amateur Radio

How far can I talk on radio?

A question that regularly hits the enquiring minds of people who are not (yet) radio amateurs is one about distance. For both amateurs and those who are not ye) inducted into our community the concept of distance speaks in ways that other parts of our hobby don't. It's a simple concept, between these two points, how far can you talk?

The interesting thing to me about this phenomenon is that distance isn't a metric that we as amateurs use for anything other than calculating repeater coverage and then only for frequencies that are line-of-sight. If you're not an amateur then this might be unexpected or even illogical.

Let me give you two questions:

How far can you talk in amateur radio? - and - How far does light shine?

If you're an amateur you'll know that those two questions are pretty similar, if not identical for certain frequencies, but if you're not, then these two questions appear completely unrelated to each other.

Let me start with something that you might not realise. If you tune to a local AM radio station, let's say ABC 720 in Perth. It's located in the AM broadcast band and the number of the station, 720, is the frequency at which it's transmitting. 720 kHz, or 720 thousand Hz. If you had a radio capable, you could turn the dial to the right, and after passing 810 Radio National, eventually, if you kept turning to the right, you'd find ABC Classic FM at 97.7fm in the FM broadcast band. The station indicator, 97.7 is again the frequency, 97.7 MHz, or 97.7 million Hz. So, 720 and 97.7 are both on the same dial, just at different ends.

Now if your radio was capable, you'd be able to keep winding it to the right, and after passing by Wi-Fi, at 2.4 GHz, or 2.4 billion Hz, you'd eventually come across light. Green light for example is about 560 THz, or 560 trillion Hz. You could keep going and end up with even more exotic stuff, like X-rays and Gamma-rays, in the exahertz range, a 1 with 18 zeros, but you get the point. Radio and light are the same thing. If fact, there are experiments around that are using light for Wi-Fi communications.

So, How far does light shine is the same thing as How far can you talk in amateur radio?

Before you start complaining about when it's different, let me point out that the only difference between these two is the frequencies at which we're comparing, with the characteristics that come with that. I'll get to that in a moment.

Look at light.

If you have a light bulb that's bright enough, you can see it in full daylight. If it's dark outside then you'll need less of a light bulb to see it. If it's raining, or if there is smoke in the air, you'll need more. If there's a wall between you and the bulb, you'd need a pretty bright light to shine through the wall, but you already know this. Covering up a torch with your palm shows the bones in your hand. Light gets through different parts of your hand in different ways.

Another thing you've seen is when you put a straw into a glass and it looks like it's broken. That too is related to how light travels through different materials. You may even have been underwater in a pool and looked up to see a reflection. That too is a phenomenon familiar in amateur radio.

Something that you might not realise is that something like an X-ray is identical to shining a light of a torch through your palm. Only X-ray's are used for diagnostic purposes, we shine an X-ray light at your body and some gets through and some doesn't. We take a photo of that and use it to figure out what's under your skin.

Back to radio.

The same phenomena happen in radio. Buildings are good at stopping certain radio frequencies, in much the same way as they block light, but other frequencies barely get noticed, they shine right through. Similarly, the ionosphere around the earth can act as a reflection like the surface of a swimming pool for some frequencies, but not for other frequencies. Interestingly this changes throughout the day, depending on the sun and a whole range of other factors which I'm not getting into today.

Finally, just like with light, you can turn up the brightness for different effects, you'll get further, but only if the conditions allow for it.

To answer the original question about how far you can talk on amateur radio becomes much harder and now you know why.

I'm Onno VK6FLAB

What's allowed on our bands? Jul 21, 2019

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Foundations of Amateur Radio

Recently there was a discussion on social media about the legality of various types of transmissions. Before I get into the specifics, it's worth looking at some of the rules around this. I will point out that this isn't exhaustive, but it gives you an idea of what I'm talking about.

In Australia, the rules about this are encapsulated in the Radiocommunications Licence Conditions Determination, referred to as the LCD. It essentially says that you must not operate an amateur station to transmit signals that are encoded for the purpose of obscuring the meaning of the signals, except for amateur satellite and repeater command and control purposes or emergency service operation and training.

In the United States, the rules are covered under the FCC rules, Part 97 Amateur Radio Service. It says that you may transmit using a digital code who's technical characteristics have been documented publicly. It goes on to prevent such transmissions for anyone communicating with a country that doesn't have an agreement with the United States. It also states that using unspecified digital codes must not be transmitted for the purpose of obscuring the meaning of any communication and if it's deemed necessary, you must maintain a record, convertible to the original information, of all digital communications transmitted.

In the United Kingdom, the amateur terms say that the licensee may use codes and abbreviations for communications as long as they do not obscure or confuse the meaning of the message and messages shall not be encrypted for the purpose of rendering the message unintelligible to other radio spectrum users, except for during emergencies or if used by various emergency or government departments.

Just by looking at three different sets of rules we can already tell that law makers across the globe have different ideas of what's allowed and what isn't. I will point out that the rules in the United States are much more prescriptive than those in Australia or the United Kingdom. I'll leave it to lawyers to determine which of the rules is more effective and what their actual effect is on our global amateur community.

Let's get back to the original question. What's allowed?

The purpose of obscuring the meaning of the message is essentially not allowed. What happens if that's a beneficial side-effect? Is that allowed?

For example, let's imagine that I have a new mode that is more efficient than any other mode in getting information between point A and point B. It does this by transmitting a single number, which is simply sent and received, it could even be done with Morse code.

Station A knows what the message means and Station B also knows what it means. How they come to a common understanding of the message is something I'll leave to your imagination, but is this kind of transmission in violation of the idea of obscuring the meaning of the message, if all we're doing is making communications faster?

Let's say that we have a public web-site that links those numbers we've exchanged to a more meaningful message. Let's say that Station A uploads an image to this website, and then sends an ID number of that image to Station B, which then goes to the same website and looks up that ID and sees the image. Bingo, transmission complete. Message exchanged. It's all public, there's no intent to obscure the meaning, everyone happy. In case you're wondering, I've just described how Hybrid EasyPal works.

What happens if I require a password to access the website to see which file was intended for me? Have I just obscured the meaning of the message? Note that I'm talking about two stations exchanging a unique identifier of some sort, that both stations have agreed on, so they can communicate via a password protected website using amateur radio.

That appears to be in violation of the amateur radio rules for all three countries.

It gets better.

What if I build a gadget that makes squeaky noises and knows how to receive them? Station A plugs their microphone into the gadget and talks into it. The gadget makes squeaky noises and those are transmitted. Station B has the same gadget, which understands squeaky noises and makes it into perfect audio. The purpose is to get information between the two stations, no intent to obscure the message, right?

What if I only make two of these gadgets?

The purpose isn't to obscure, but the outcome is that the messages are actually obscured. At this point we get lawyers involved who argue both sides. Your honour, I wasn't trying to hide my communications, I was just making them more efficient.

Clearly this isn't what our hobby is about. It's about exchanging information, un-obscured information, between stations that want to talk to each other.

If the intent is to make apples, but the outcome is that you're making pears, you're making pears.

I'm Onno VK6FLAB

Your Software Defined Radio around the home Jul 14, 2019

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Foundations of Amateur Radio

What would you do if you found that at random times your garage door opener didn't work, or the Wi-Fi network dropped out, or you couldn't switch off a light with an RF controller?

That's the position I found myself in and the times at which this was happening were madly unpredictable. One moment everything would work fine and the next all things radio would just stop.

As a radio amateur you're likely nodding your head and thinking, radio interference, there's some direction finding in your future. Sure enough, that's the case, but before that, I needed to know if the interference was random, if it had a particular pattern and how widespread it was, since it seemed to impact multiple different devices using different parts of the radio spectrum.

Initially I focussed on getting a recording of it. I turned on my radio, tuned it to a 2m frequency and recorded the noise. Only one problem. There was no noise. All I could see was an extreme signal strength, but it wasn't showing up as noise.

I enrolled the help of my RTL dongle and recorded some raw data, essentially capturing a 3 MHz slice of noise centred around 147 MHz. All that revealed was that there was noise. I already knew that.

At that point I decided that a bigger hammer was needed. Something you can do if you have a $5 RTL-SDR dongle and some free software, in my case I used a tool called rtl_power and a visualisation tool called gnuplot.

rtl_power is a nifty piece of software. It takes measurements and averages out the power level across the measurement range. To make it work, you specify a starting frequency, a stopping frequency, how big a step to use to average, how often you want to measure and for how long.

For my little investigation I started with measuring between 0 and 1.7 GHz, at 1 MHz intervals, every 2 minutes for 10 days. That creates a big CSV file that you can process with gnuplot into a picture that tells a thousand lies.

Seriously, it showed me that the interference was very wide, 0 to 300 MHz, it occurred every 20 or so hours, lasted up to six hour at a time. There were other things happening as well, similar patterns, but across an even larger frequency range, from 0 to 600 MHz, but in shorter duration and of lesser strength.

Based on the times alone, I can immediately, almost certainly, eliminate any source under my control.

Based on the timings I can also determine that the noise is likely not created by an automatic process, given that they vary in duration and the way they're clustered around specific times.

The variation of the interference allows me to determine that there are at least three separate types of noise, each with specific characteristics and times, sometimes overlapping.

It's too early to tell if this pattern will continue. One possible next step is to set up the same measurement tool and powering it from a battery. Once I've got that working, I expect to turn off the house power during an interference session and determine if the noise is coming from my house, or if it's an external source, which seems likely.

Once I've determined if it's in house or not, I can start either eliminating gadgets by switching off specific power circuits, or I can start direction finding and locating a nearby source of pain.

At that point I can decide what to do next. That said, at the moment it looks like several televisions around me are creating an RF noise storm of epic proportions.

I've documented all of how I did this and you can find it and the scripts I created on the web at vk6flab.com.

One thing that has happened since I started documenting my efforts is the idea that we could collectively as a community make measurements like this and document the state of our RF space and how it changes over time. I plan to update my code to incorporate this idea, perhaps log in 24 hour blocks and generate a chart over that time, perhaps make it into a video.

One challenge ahead of us would be to come up with a universal way to calibrate our various dongles, so we all report the same signal level in the same way. One thought is to use the sun as a global calibration, but I'm not yet sure how that might be implemented.

One thing's for sure. If you've ever wondered what use can a $5 RTL dongle possibly be, this is one thing that you just cannot do with a traditional radio. That's not to say there's a place for both in the world, just different tools for different problems.

I'm Onno VK6FLAB

The Software Defined Radio vs. Traditional Radio choice Jul 07, 2019

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Foundations of Amateur Radio

For some time I've been explaining how some of the internal workings of a Software Defined Radio operate with a view to getting into the nitty gritty of the why and the how. This exploration is happening within the context of a world where there are countless choices for selecting a radio to match your budget. Increasingly that selection process starts with a simple question: Should I purchase a Software Defined Radio or a traditional radio?

This is not a new question, previously it may have been: Should I select a radio with transistors or one with valves? Presumably the same happened when your ancestors faced a choice to buy a new car or update their horse and carriage. Of course I'm being flippant, but the point stands, as things evolve, choices change. Today we don't know what comes after the Software Defined Radio that we currently know, but it's likely to force the same selection on future generations of radio amateurs.

So, if you're in the market for a new radio, what things should you consider in your selection?

SDR is becoming pervasive, that is, the more you look, the more you'll find. Much like transistors overtook valves, not because they're better, but because there's a smaller component count and related price advantage.

SDR come in all forms, from nondescript black boxes to a traditional radio form factor and everything in-between.

If you choose a black box model SDR, there are tools around that allow you to use external controllers to provide knobs and buttons. These external controllers might be a fully-fledged radio head, or it might be using an external USB connected knob to change the frequency, or you might integrate your solution with a DJ Console, a big panel with lots of knobs, sliders and dials, repurposed as a user interface for your radio.

The software behind most SDR platforms appears to continuously be in a state of rapid development. This means that every update potentially gives you more functionality. Of course the opposite is also true, things break, get taken away, get redeveloped, in ways that may be unexpected or unwanted.

In my opinion, there's an awful lot of crap software around, attempting to use a computer screen to emulate a physical environment, forcing you to use a mouse to turn a knob, or slide a slider. It's getting better, but so far I've not seen a single solution that does this all well. That's not to say that there aren't any innovative things happening either. For example, something I've mentionned in the past, is the user interface for the diversity receive function inside PowerSDR. You set the phase angle and the strength by pulling on a line inside a circle.

There's plenty of open source software around, and functionally it's pretty good. Fortunately Windows is not your only option, Mac OS and Linux provide many opportunities.

Traditional radios have not finished, nor are they likely to go the way of the Dodo anytime soon, but while people are getting excited, you can pick up bargains from those migrating away from traditional radio to SDR.

If your selection is based on using a computer or not, there's things to use your computer for with a traditional radio, numerous and growing digital modes and other cool stuff to get your teeth into.

I should mention that there are radios about that are both traditional and SDR, so you can have the best (or worst) of both.

My recommendation is to set a budget and see what that buys you. Regardless of what you end up with, your requirements will evolve.

I'm Onno VK6FLAB

The Regulator Jun 30, 2019

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Foundations of Amateur Radio

From time to time our hobby changes. While the idea that we're all a bunch of old men playing with spark gap transmitters, or using strange noises to the annoyance of others, the reality of amateur radio is markedly different from that stereotype.

The changes we experience come from many different sources. As amateurs we're always trying something new, inventing things and building stuff. That type of change is integral to the hobby and in many ways it's why our community exists in the first place.

Other changes are external. A new product arrives into the marketplace and we gleefully take possession of a new gadget. That in turn creates other changes which are incorporated into our day to day life as amateurs.

A more structured change happens when the regulator makes a proposal, instigates a new rule, enforces an old rule or does something else that affects us.

In the time I've been an amateur, I've seen changes happen that originate from the regulator that both benefit and impede our activities. Things like the introduction of new bands, the trial of high power, but also the removal of frequencies, the restriction on modes and across the globe this happens in every single jurisdiction.

For example, in Sweden the regulator proposed and then implemented a reduction in transmitter power, from 1 kW down to 200 Watt. I'm sure it made lots of noise in Sweden, but here in Australia there was hardly a squeak.

In France proposals have been drafted to reallocate the 2m band to the Aeronautical Mobile Service, to be discussed as an agenda item at WRT 2023. The 2m band is a band that is widely used, often as the first band for most amateurs, a band that offers local communication, hosts local discussion nets, has many options of affordable equipment, uses small antennas commonly installed on vehicles.

In Australia the regulator is looking at removing access to the 3.6 GHz band for specific areas and defining more precise access restrictions, removing emission mode and bandwidth restrictions and removing specific Foundation restrictions, such as the ability to build radios, connect radios to the Internet and use digital modes.

The Australian regulator is also of the opinion that any station should be able to use 400 Watts, regardless of the license level, since it's unlikely to increase interference. Interestingly, the local representative bodies are at odds with this, since they appear to believe that we need multiple levels of licence, even though I've never actually heard a coherent argument to support that.

There's more, but let's move on. What strikes me is that the benefits are celebrated and the impediments are bemoaned with hardly any thought expressed on how these changes happened and what brought them about. There are representations made by representative bodies, but most of that is at arms-length.

We're a tiny community in the scheme of things, we always have been, but we have access to one of the richest resources available and we have a regulator who is required to consider our existence when new rules are made and old rules retired.

In discussion with other amateurs I hear time and time again that making a submission is hard, it's a waste of time and takes too long. For me that makes no sense. The notion that our tiny community has no impact is not credible in the face of the evidence, so why is it that the idea of making submissions to the regulator is such a waste of time and so difficult?

Why is it that we give up before we even start? What is it in our DNA that leaves these submissions to others and what is it that makes us think we're unworthy or unable or unheard of if we never even try.

A submission doesn't have to be a book, it doesn't need to have more than one page. You can write a letter to your regulator that says: Hey, I'm an amateur, I'm affected by your proposal and I think the following.

My point is this. If amateur radio is important to you, if it gives you joy, if it teaches you stuff, if it gives you a community, if it justifies buying gadgets, then why don't you express that to the regulator when they announce a request for consultation?

What are you waiting for? Share your opinion, make your voice count, you can be part of the change.

I'm Onno VK6FLAB

From Milk to Direct Conversion in a Software Defined Radio Jun 23, 2019

Show notes

Foundations of Amateur Radio

It seems my analogy with milk glasses hit a nerve when I explained some of the inner workings of a simple Analogue to Digital Converter, also known as an A/D Converter or ADC as part of my exploration into Software Defined Radio. Thank you for your comments, suggestions and corrections.

I did make an error when I said, grab eight of them and you'll have a byte, I'll get into that. Thank you for pointing it out.

With my milk glass analogy, if you missed it, without naming it, I drew a picture explaining how a flash or direct-conversion ADC works. Briefly, I said that if you were to pour milk into a glass and continued to do that until you ran out of glasses or milk, you'd have converted a signal into bits. I also covered how a partially filled glass was neither full nor empty and if you ended up with milk all over the desk you wouldn't know how much there was.

In terms of electronics, how does this actually work?

In essence you're comparing a reference voltage against your incoming antenna signal. The way that happens is you have a series of resistors between ground and your reference voltage. For simplicity, lets say five identical resistors against a reference of 5 Volts. The result is a series of steps of voltage. At the first resistor the reference voltage is 1 Volt, at the second, it's 2 Volt and so on.

If you were to compare your antenna signal at the first resistor, you'd compare it against 1 Volt and your antenna signal might be higher or lower. If it's higher than 1 Volt, we'd record a full glass or one and if it's lower we'd record an empty glass or zero.

This is done with a nifty circuit called a comparator that compares two voltages. If the signal is higher than the reference, it returns a one and if it's lower, it returns a zero. If that sounds familiar, an op-amp does a similar thing and if you're wondering, a comparator is an op-amp without a feedback resistor.

In a circuit diagram you might see a triangle with two voltages coming in, the one you're measuring and the reference voltage with a single output that's either zero or one. Inside that triangle, which you can purchase as a component for cents, you'll find the whole circuit that makes all this happen.

I'll acknowledge there is an opportunity here to go into how an op-amp actually works, how it slightly differs from a comparator and more, but we're talking about an Analogue to Digital Converter, which in turn is part of a discussion about how a Software Defined Radio works, so I'll leave the circuit diagram and building an op-amp from basic components for another time.

One thing to note though is that this type of ADC is essentially independent of frequency, it's a direct-conversion ADC and the speed of sampling is determined later on in the process.

Back to comparators. We have several of these, each comparing the incoming signal against a stepped reference voltage. In actual fact, if you're doing 8-bit sampling, you'd need 255 of these comparators, if you're sampling at 16-bits, you'd need 65535 of them.

As I explained with glasses of milk previously, you'll have interesting results if the voltage you're measuring is between steps. You could increase the number of steps and measure more accurately, but as I said before, you're only kidding yourself if you think that solves the actual problem.

In the same way, if the voltage you're measuring is higher than the total reference voltage, you're up the creek without a paddle and you won't know what happened, unless you saw magic smoke appear, in which case you know that lightning probably struck somewhere nearby.

You could increase the reference voltage, like making the glasses bigger, but that's actually making it worse, since we now have bigger steps between each measuring point.

So, a flash ADC is a series of comparators which compare an incoming signal against a reference voltage and returns a series of bits that digitally represent your signal.

The final piece of the puzzle is how we get from the bits coming out of the pile of comparators to the byte going into your computer. Basically we're tallying each bit, that is, we're counting how many there are and returning the number as a value to the computer. The speed of this counting process is what determines how fast we can measure our signal.

Did I mention how deep the rabbit hole goes? Amateur Radio for me is the gift that just keeps giving, more to find every time you look.

I'm Onno VK6FLAB

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