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Foundations of Amateur Radio

Starting in the wonderful hobby of Amateur or HAM Radio can be daunting and challenging but can be very rewarding. Every week I look at a different aspect of the hobby, how you might fit in and get the very best from the 1000 hobbies that Amateur Radio represents. Note that this podcast started in 2011 as "What use is an F-call?".

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The Golden Age of Amateur Radio is Now

Foundations of Amateur RadioImagine a world where electronics are pervasive, a transceiver can be purchased for the price of two Big Macs, kits are designed and built using simple tools at home, software makes it possible to invent new methods of communication on an almost daily basis, where long distance contacts are made throughout the day using milliwatts while ionospheric propagation is at an all-time low, where national parks and peaks are being activated at an increasing rate, where new people join in every day, where it's easier and easier to obtain a license and where the word geek is held as a badge of honour.That world is here, it's now and when Rex, KE6MT writes that we're in the midst of a golden age of amateur radio, he hits the nail on the head, or should that be fist on the key?It's easy to notice that amateur radio is difficult, that it's big, that it's messy, that it's full of know-it-alls, but it's hard to remember that it's fun, that it's rewarding and that every day more and more people join in and enjoy this hobby. The ideals of investigation and exploration are alive and well and the urge to participate in activities, just to get out of the house and see some daylight is strong.While you're in the midst of a revolution, it's hard to see the wood for the trees, but make no mistake, the revolution is here, today, now, and you're smack bang in the middle of it.Today you can go online and find any number of different amateurs who share their skills and knowledge, you can find manufacturers and suppliers at the tap of a screen, find and draw schematics, order custom circuit boards at the click of a check-out button, print an enclosure in your bedroom using plans that you downloaded or designed minutes before.With the digitisation of amateur radio comes the promise of new adventures, with adaptive modes, with encoding and decoding in new and interesting ways, with the ability to hear what your station is producing by logging into a remote receiver anywhere on the planet, by sending messages to satellites overhead and talking to people in another country using a hand-held VHF radio.For some the loss of the valve radio is the loss of history, for others it's a sign of progress and improvement. The inventors of spark-gap transmitters were no doubt put out by the arrival of the valve when that became commonplace. Similarly, the transistor has essentially gone the way of the Dodo in the arrival of cheaply programmable integrated circuits.Our hobby keeps getting bigger, all the time.We didn't abandon valves or transistors, or the spark-gap for that matter, we improved on them. You can still build a spark-gap transmitter if you feel the urge, or ferret out a valve or two and build them into something wonderful, nobody is stopping you.Today we learn Morse Code because we want to, not because we have to.We introduce new people with new technology, new ideas, new innovations and hope that they pick up the cape to become the next superhero.You can bemoan the death of the hobby with the solar cycle at an all time low, the entry of stupid amateurs who need to learn from their betters, the passing of the valve and the abolition of Morse Code requirements, or you can celebrate the appearance of all the new and shiny toys that arrive in our hobby every day.The Golden Age of Amateur Radio is Now.I'm Onno VK6FLAB

3mins

10 Nov 2018

Rank #1

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Putting a radio in a car.

Foundations of Amateur RadioPutting a radio in a car.As you might recall, most of my radio activity is done away from my shack. I tend to operate portable, camping, sitting on a jetty or using a picnic table while a BBQ is going nearby.For me operating with my car as a mobile base made more sense than trying to cram an antenna in a home with little or no garden.Putting a radio in a car can be as simple as bringing a hand-held and hanging it from the rear-view mirror, or it can involve a mobile phone mount that allows you to clamp it in place.Pretty soon you'll want to have an antenna on the outside of the car, so then you start figuring out how to make it go through the car without needing to drill holes and sparking the ire of the other users of the car.Not long after that you'll want to charge it, then the microphone will become inconvenient, changing frequency, using it for more than talking on the local repeater.Eventually you might well get to the point that a hand-held is no longer appropriate.Without telling you which radio to buy, since there are many different ones to choose from, with different specifications, different pricing, different functions and different sizes, there are plenty of roadblocks to radio bliss in the car.The very first one is: Where to put the radio?If your radio has a detachable front, that is, the buttons and display can be separated from the main body, you'll have more options, but if that's not possible, you'll likely need to find somewhere near and preferably visible to where you'll be using it.There are transceivers that fit into a standard car radio opening which might come in handy if your car comes with all manner of bezels and curves. You might find a spot in the centre console, or overhead.If you can put the transceiver in one spot and the head in another, then you can put the radio in any little hidey hole, for example, under the passenger seat, or in the luggage compartment, in the glove box, or behind the drivers seat.When you are looking for a spot, consider how you're going to get electricity to it and how you're going to connect the antenna. You'll likely need to connect the power supply wire directly to the battery, which might determine how the power gets into the cabin of the car.If you can drill holes in your car, you'll have extra options, but consider that you'll need to protect the wire that goes through those holes and you'll also need to protect the steel, given that once you drilled that hole, it's no longer protected by paint from rusting.The same is true for the antenna. Can you use an existing path, or do you need to make a new one? If you put the radio in the luggage compartment, can the antenna lead exit that and what happens if it rains?In my set up I have an all band radio, it does HF, VHF and UHF, but I didn't want to have multiple antennas on the car. The radio has multiple sockets, so I used a coax switch that's connected to an antenna mount on the rear of the car and ran two lines back to the radio, so I can switch between HF and VHF. Of course I need to swap out the antenna, but I'm not switching whilst I'm driving, so that's no problem.Other things to consider are what noise comes from the car. I don't mean the zoom-zoom noise, I mean the noise from things like the alternator. How will you deal with that? What about grounding? How will you make the ground plane of the antenna? Can you use braid to connect the various panels of the vehicle to each other?If your mount is temporary, like for example a magnetic mount, how will you protect the paint work? Can you clamp something across an edge, or will you need to drill a hole?If you're at all unsure, then try some set-ups. Run a temporary power supply through a door, figure out where stuff goes. Look at what your friends have done, test it by going out, park somewhere and try to use it for real.It can be daunting to set-up a car, but it is very rewarding and it's a great way to get used to the many aspects that are involved once you dive into this hobby.I'm Onno VK6FLAB

4mins

16 Nov 2019

Rank #2

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Brand New Callsign

Foundations of Amateur RadioToday I have a new callsign, it's exciting, special, kind of strange, to be known as something other than VK6FLAB.It's hard to overstate how much of your identity as a radio amateur is linked to your callsign. It's a strange phenomenon to those who are not amateurs, or who have only just joined the community and are still learning to remember what callsign they have.We think of callsigns as semi-permanent fixtures, but realistically they're far from that. In your life as an amateur you'll operate many callsigns, even if you never change your own. When you're operating the local club-station, you'll use that callsign, or when you're participating in a special event, say an activation of an island, or some remote DX station, or when you get on air to make noise in another country.Some stations use special contesting callsigns, either for speed, or to commemorate another amateur. There are those who collect callsigns like badges, others only ever register one and keep it for the rest of their life.There are provisions for applying for callsigns for short duty operation, sometimes as little as 24 hours, to mark a significant event or activation. For example, in 2013 we registered VI6PROF as a special callsign for the then Chief Scientist of Western Australia, Professor Lyn Beazley, who used that callsign for two hours after dinner during the annual conference held in VK6 that year.There are callsigns registered for marking the end of Polio, VI6POLIO, 100 years of the Wireless Institute of Australia VI100WIA. VK100MARCONI commemorated the first direct wireless message from the UK to Australia. There are callsigns registered for activating an island, like VK6WDI to activate Woody Island between the 9th and the 12th of November 2012, or VK6CHI for the Cheyene Island activation in 2007.Special callsigns are a global phenomenon. The Straight Key Century Club operates K3Y. K1A gets used by amateurs throughout the USA for many different events, from Boy Scout camps through to the America Recycles Day, from the Georgia QSO party to the ARRL Field Day. The 2012 Olympic Games in the United Kingdom were celebrated with 2012L and 2012W callsigns. RG22RQ was for the Winter Olympic Games in Sochi.As with anything rare, there's an active community that collects it. For special callsigns, there are amateurs who collect by trying to make contact with an elusive call, confirm their contact and receive a QSL Card to decorate their shack with.In Australia, three times a year, on Australia Day, the 26th of January, on ANZAC Day, the 25th of April and on ITU Day, the 17th of May, a licensed amateur gets a special callsign to commemorate those special days in the calendar.Australia Day is the official national day of Australia, marking the anniversary of the 1788 arrival of the First Fleet of British ships at Port Jackson.ANZAC Day is the national day of remembrance in Australia and New Zealand that broadly commemorates all Australians and New Zealanders who served and died in all wars conflicts and peacekeeping operations. It's marked on the anniversary of the ANZAC landing at Gallipoli in 1915.ITU Day is the World Telecommunication and Information Society Day, commemorating the foundation of the International Telecommunications Union on the 17th of May, 1865.On each of these three dates, radio amateurs in Australia can replace their VK prefix with AX and use their special new callsign on-air to make contact anywhere around the world.So, for now, I'm Onno AX6FLAB

4mins

26 Jan 2019

Rank #3

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How does a Software Defined Radio or SDR work?

Foundations of Amateur RadioIf you've been around the hobby in the past decade, you may have come across the invention of a Software Defined Radio, or SDR. You might even own one and if you've looked into how it works, read the explanation that essentially describes it as a traditional radio where all the components are implemented in software. To me that's like explaining how a radio works by waiving your hands and saying: here is magic.How it actually works is something all together more interesting and thought provoking.If you think of sound, like my voice, coming from a speaker, you can imagine putting a volt meter on the speaker terminals and measuring every second what the voltage is. As my voice gets louder you might measure a large voltage, as I take a breath, it will be smaller. You could chart the different measurements and show a waveform that would represent the loud and soft parts of what I'm saying. The faster you measure, the more accurate the picture represents my voice. For comparison, a CD player does this measurement 44 thousand times per second.If you were to play back those sound measurements at the same rate into a speaker, you'd end up with my voice, and that's actually more or less, what's happening if you're listening to this podcast. Yes, for the purists, there's more to it, but not relevant at this point.Similarly, if you were to hook up a volt meter to an antenna and take measurements, you'd end up with a chart that represented the signal strength that your antenna is receiving and the faster you measured, the better the representation. What it exactly represents I'll come to in a moment.The waveform that represents my voice is actually a very complex signal. In much the same way as a piece of music is made up of different notes, played in sequence and in concert with each other, my voice is also made up of separate frequencies, played together to form the words that you hear.If you were to measure those separate frequencies and draw a waveform for each, you'd see how every one contributes a little to the overall effect, and if you were to add them all together, you'd have my voice again.In the same way, the waveform that represents an antenna signal is made up of all the separate frequencies that go into the overall signal. You might be surprised to learn that an antenna is actually hearing all frequencies at the same time. Some better than others, but typically, all of the RF spectrum at any given time.Your radio is also essentially hearing all frequencies. When you tune to a local station on 720 kHz, you're actually telling your radio to ignore all the stuff that isn't 720 kHz and to only process that small bit of what it's hearing. The selectivity of a radio is the measurement that represents how good your radio is at being deaf to all the things you don't want to hear.To help that filtering, a traditional radio and antenna works by pre-selecting part of the RF spectrum, when you press the AM button on your car-radio, you're selecting which chunk to listen to, press the FM button on the same car-radio, you'll select another chunk. On an amateur radio, you select by choosing the 80m band, the 40m band, etc. Similarly, your antenna is pre-disposed to hearing a particular chunk better than others, but that doesn't make it immune to signals across the entire range.You may have heard described that a Software Defined Radio hears all frequencies at the same time. Essentially it's a volt meter connected to your antenna, spitting out measurements as fast as it can for processing by a computer.The waveform that comes from those antenna voltage measurements represents all of the RF spectrum and it's just the beginning of what you can do next.In the same way that my voice is made up of lots of different parts, all played together, the RF spectrum is made up of the local broadcast stations, the local TV stations, mobile phones, garage remotes, Roy on the 7130 DX net, this podcast on your local repeater, all at the same time, all played together, to make the waveform that represents the measurements you make at the base of an antenna.I'm going to ignore for a moment how exactly we extract the various bits, or how we decode an FM or SSB signal using software, it involves some math, instead we can look at something that is easier to explain.Unlike with a traditional radio, which has to work hard to filter out undesirable information, a software defined radio can filter out information by just deleting those measurements you're not interested in.Yes, there is more to it, much more, but that's the beginnings of how an SDR works.If you'd like to get in touch, please do, cq@vk6flab.com.I'm Onno VK6FLAB

5mins

27 Apr 2019

Rank #4

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How far can I talk on radio?

Foundations of Amateur RadioHow 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

4mins

27 Jul 2019

Rank #5

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Learning on 2m FM

Foundations of Amateur RadioLast week during F-troop something very interesting happened. If you're not familiar with F-troop, it's a weekly net for new and returning amateurs and every Saturday we welcome callers to the one hour net to discuss anything and everything amateur radio. It's been going for about seven or so years, about as long as I have been making this weekly contribution to the hobby.Normally there's a host, often it's me, but not always, handing the microphone to the next person who then in turn hands the microphone back and the host passes it on to the next caller. This is helpful for new amateurs who then only need to remember two callsigns, their own and that of the host.It's a safe place where people can ask questions and hopefully find an answer, make a mistake, say the wrong callsign, have their roger-beep turned on, be off frequency, all the typical things you do when you're learning or when you've dusted off an old radio after having been away from the hobby for a while.Last week we had a surprise visitor, a special event station, VI4GAMES, operated by Reg VK2MNM who in the midst of the Commonwealth Games was having little success on HF and decided to join in on our net.After saying hello and calling in other stations I started handing the microphone to each caller, encouraging them to make contact with VI4GAMES so they could each claim a contact, end up in the log and get a QSO card for their trouble.Sitting on the side was hard, but at the same time it was extremely rewarding.I witnessed stations calling a special event station for the first time in their life, dealing with strange callsigns, interruptions, distortions and delays, misheard phonetics, incorrect procedures, you name it, I heard it all.There were some who just made the contact and moved on, handing the microphone back to the host and others who started a whole discussion about their life, their station and their joy in making the contact.There were stations just saying their callsign without phonetics, or saying it once, or fast, stomping on the other station, all the things that happen in real life when you're trying to make a contact using HF and SSB.Just to re-iterate, this was on 2m FM, connected via IRLP, Echolink and Allstar to repeaters across the globe, with callers in Australia, New Zealand and the United States.It was eye-opening for me.In the past I've attempted to make contest examples, to make DX contact simulations and tried to get people to change frequency and check back in. As serendipity would have it, this was by far the most learning I've ever seen in the 7 years of this net and I'd encourage anyone to try this at home.Some of the direct take-away tips from this are that using phonetics on 2m FM is not stupid and sometimes it's even required.Repeating your callsign to a new station is not a waste of airtime, since you have no insight whatsoever as to the state of their receiver. You don't know if they have a poor antenna, or if they're connected via the internet, if the link is not optimal or the volume not set correctly.Waiting until the carrier drops on the repeater is a must for many repeaters and keying and talking at the same time is a recipe for being misunderstood. Key your microphone, wait a heartbeat and then start talking.Leaving gaps between overs allows other players onto the field and you should see that as an opportunity, not a burden.I'm sure there were other things that were learned on that random Saturday and who knew that you could learn that much from 2m FM, special event stations and some patience.I'm Onno VK6FLAB

3mins

21 Apr 2018

Rank #6

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The Software Defined Radio vs. Traditional Radio choice

Foundations of Amateur RadioFor 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

3mins

6 Jul 2019

Rank #7

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What's in a Whisper?

Foundations of Amateur RadioA while ago I set up a WSPR, or Weak Signal Propagation Reporter at home. Before I go into the details, WSPR is an amateur radio protocol that allows stations to transmit their callsign, location and power level and for receivers around the globe to decode those and upload the results to a central database. It's a great way to see what you can hear and what propagation is like.A couple of months ago the regulator changed the Australian License Conditions Determination, the rules of engagement around amateur radio and now all licensed amateurs in Australia can even set-up a transmitter although I haven't yet. Receiving is plenty of fun and anyone can do that.Initially I used a piece of Windows software to track the contacts but to me it was like ordering a courier with an 18-wheeler to pick up a postage stamp. I looked around an found a piece of software that runs nicely on a single board Raspberry Pi computer. The software is called rtlsdr_wsprd, it's a mouthful, but it works nicely on a Pi with an RTL SDR dongle. The dongle I have is capable of using all HF frequencies up to 1766 MHz, so I can technically hear the 23 cm band, though I haven't actually heard any stations there.I created a list of all the published WSPR frequencies and I listen to a frequency for fifteen minutes, pick another frequency at random and do it again, all day, every day. My log for this installation goes back about eight months and I get about a hundred contacts every month or so.You might think that's a lot of contacts, but really it's not. The antenna is indoors, it's under a metal roof and while it's on the second floor, it's far from ideal, but it works surprisingly well.What have I learned from this experience?I've heard 36 different stations, across 11 countries and 23 grid squares, the furthest was G0CCL, a club station in Cambridge in the United Kingdom which was transmitting on 20m with 5 Watts. I heard it 14750 km away.There are plenty of other things that I can extract from this. The most popular band is 20m, it accounts for nearly 70% of the contacts I heard. Surprisingly, I am also hearing contacts on 80m, as well as on every other amateur band that my receiver can hear. The 6m band is pretty popular too, nearly 13% of the stations I heard.For my receiver, between 4am and 6am in the morning was the best time to hear something, together they account for just under 20% of the contacts. Locally the worst time is 8am in the morning.From the data I've collected, April and May were the most active, accounting for nearly 70% of the contacts.I must point out that the log is not continuous, there's gaps when the logging station wasn't switched on and when I was switching antennas and locations, so using the statistics I've given you here for your own station are probably not going to work quite the same.The WSPR mode isn't perfect. It will happily decode rubbish and report on that, so I've manually filtered out the bogus information, like for example a grid square XI97LK, or callsign 3KE/21XWK, where neither the location or the prefix are real.I can tell you that I was surprised that my station can hear 80m on the little telescopic rabbit-ear antenna supplied with my dongle. That same antenna is also fine at hearing 6m, so I'm pretty happy with that.One thing that this little experiment reveals for me is that a cheap dongle is a perfectly fine way to start playing with a limited budget. It offers the opportunity to explore the RF spectrum using modern tools and techniques. Much of what I describe is absolutely possible with a traditional radio. Originally I had my station set-up like that. It consisted of my Yaesu FT-857d, a 12 V power supply, a CAT cable, an audio interface and a computer.In stark contrast, my current set-up consists of two things. A Raspberry Pi with an RTL SDR dongle plugged in.While this set-up cannot transmit, neither could I at the time. Since then there have been advances in both. There are all-band WSPR transmitters for a similar cost to a Pi and a dongle. Power it up, configure it and you're good to go. I'm eyeing off that as a future project, since it's perfect to use to see what bands are open for your station at any given moment.If you've never had a go, you should. I've documented how my monitor station works and you can find it on the projects page on my website at vk6flab.com.WSPR is a really nice way to get into many different aspects of our hobby and the barrier to entry is your imagination.I'm Onno VK6FLAB

5mins

23 Nov 2019

Rank #8

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From Milk to Direct Conversion in a Software Defined Radio

Foundations of Amateur RadioIt 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

4mins

22 Jun 2019

Rank #9

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Storing your Amateur stuff ... everywhere.

Foundations of Amateur RadioThere is so much stuff associated with Amateur Radio that your family might be forgiven in thinking that your hobby is all about being in the middle of a junk-yard surrounded by the carcasses of disassembled gear, components, failed projects, obsolete equipment and scraps of wire, solder and countless screws, resistors and other bits and pieces that are just too valuable to dispose of.During the week I was given an incentive to reorganise my work-shop. I set aside an hour to do it and unsurprisingly, armed with 20/20 hind-sight, it took a day to complete. The upshot of this activity is that I can now walk into my work-shop, something which I couldn't last week, and to top it off, I could actually find things.I confess that I've reorganised my work-shop several times over the years, but each time I find that it returns to its natural state of junk everywhere. I have noticed that this state is taking longer and longer to achieve, which means that I am improving things, but not quite as well as I would like.The biggest improvement I found last time around was to install shelving. I also used cardboard boxes to put stuff into, but that turned out to be a mixed blessing, tidy, but unusable, since I had to keep stacking and un-stacking boxes to see what was inside and writing on the outside only helped if the list of what was in the box was complete, which I'm sure you know, is never ever the case.This week I made an incremental change. I have purchased a whole slew of transparent plastic boxes, about the size of a shoe box each, with lid, stackable and big enough for most of the things I need to store.I've arranged the boxes along several shelves, stacked two high, so you only ever have to lift one box if you need to get to the bottom one.When ever I go into a bottom box, I move it to the top, so over time the most used boxes will be on top and the ones I don't use often will be on the bottom.Now I have a box with Velcro straps, one with cable ties, one with electrical tape, one with self-tapping screws, one with audio connectors and so-on.Time will tell if this helps.You might recall in the past that I've also got a stack of fishing boxes. Not a whole tackle box, just a single layer box with square compartments, removable dividers, just large enough for about 4 PL259 connectors in each. They're also transparent and stackable.Each compartment has some unique component. Red Anderson Power-Pole shells in one, Black in the next, Green, Purple, Yellow etc, each in their own little space. The connector innards are in another compartment, the joiners in another, BNC male connectors in another, and so-on.I've seen similar attempts at organisation using glass jam jars, but in my experience they don't stack well, are never uniform, unless you have 100 identical jars and are not compatible with concrete floors and gravity.I'm sure that I've missed some salient storage advice, so feel free to drop me a line and share your experiences.I'm Onno VK6FLAB

2mins

16 Sep 2017

Rank #10

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Tropospheric Ducting explained

Foundations of Amateur RadioYou've always been taught that VHF communications are line of sight and that the height of your antenna determines how far your 2m communication might go. So if I tell you that last week I spoke with a station that was 300 kilometres away on the 2m band you might be forgiven in thinking that I had managed to climb up most of the side of Mount Everest to around 7 kilometres so I could make my line-of-sight communications 300 kilometres away.I'll give you a hint. I was at my home, my house isn't on the side of Mount Everest and we were both using normal gear, nothing crazy, no amplifiers, no glitzy antennas, just the basics.So what's going on?There'ss a phenomenon called "Tropospheric Ducting" that comes and goes and if conditions are right, allows you to extend your line-of-sight communications to distances far beyond your imagination.So, what is this thing and how does it work?First of all, this is something related to the lowest part of the atmosphere, called the troposphere. It has nothing to do with the ionosphere which we know and love and use regularly to make long distance communications on the HF bands. The ionosphere starts somewhere about 60km up, the troposphere stops at about 12km.Tropospheric Ducting happens much lower down. At the most around 3km up, but normally between 500m to 1500m. In essence a Tropospheric Duct is a layer of warm air trapped between two layers of colder air that acts as a tunnel for radio signals. These kinds of layers aren't caused by "weather" as such, but by climate conditions such as weather fronts. Normally as you go up into the atmosphere, the temperature drops. The rate is around 6 degrees Centigrade per kilometre.Without going into the fascinating science behind it, think about it as a phenomenon where you'll find different types of layers of air over the top of each other, each with their own density and temperature. When the conditions are just right, you get a tunnelling effect that allows you to make some very long distance communications. There's reports of signals travelling over 4000km and if conditions are right, you might be able to hear such long-distance signals on your house-hold FM radio.One aspect that you might not have considered is that the thickness of the sandwiched warm layer determines which frequencies can travel along this so-called tunnel. If the thickness is 15m, you can expect to hear 11 GHz signals, 90m thickness gives you 400 MHz propagation and 180m thickness gives your 140 MHz signals a path to travel. If you manage to find a layer that's 430m thick, you might even manage to make contact using 29 MHz using a Tropospheric Duct.Now, you might be forgiven in thinking that this is all voo-doo and unpredictable, but it turns out that there are plenty of things that you can use to observe that conditions might be right. If you have local fog, or smog trapped over your station, you might be able to take advantage of this phenomenon. It's not that the smog or fog is causing the duct, it's that they happen to occur at the same time as the ducts are created.If you see a sharp layer in the sky, then turn on your radio and have a gander. I won't guarantee success, and you can look online for William Hepburn's World Wide Tropospheric Ducting Forecast, but you really don't need that to get started.Tropospheric Ducting happens all over the planet and it might be happening right now.I'm Onno VK6FLAB

3mins

23 Sep 2017

Rank #11

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What radio should I purchase?

Foundations of Amateur RadioA regular question that I hear from amateurs, both new and experienced ones, is "What radio should I purchase?". It's a simple question that doesn't have a simple answer.The obvious variables, budget, size, frequency and modes are one side of the coin, and when you start looking, you'll learn that there is a lot of information on the subject. You'll learn that you can get amateur radios from $15 to $20,000 and everything in between. To be clear, I'm just talking about the radio, not the power supply, the amplifier, microphone, computer, antenna, interfaces, Morse key and the like.Unless you won LOTTO yesterday, and not even then, you should probably not buy a $20,000 radio first up, but if you do, make sure you give me a call and I'll help you test it.The question that often happens is, should I buy a Yaesu or Icom, which is like asking, should I buy a Mac or PC, or a Holden or a Ford. As you know, there are many different options and the same is true for your radio.The reality is that unless you have specialised measuring equipment, most modern radios are pretty similar. That's not to say that they are the same, far from it, it's just that you are unlikely to come across a situation where you'd actually notice, since the variables that make up our hobby are so vast, propagation, antennas, local environment and the like, that any slight differences in radio performance are likely to be completely masked by other factors.Again, I'm not saying that there are no differences. If you have a shack where you have 10 radios side-by-side, all connected to the same antenna, you'll be able to notice differences, sometimes they'll even be significant, but overall, in day-to-day operation, other variables beyond the simple metric of "performance" are more important.The budget you have is a big factor when you get your radio, and don't spend more than 50% of your total budget on the radio, since you'll need a whole lot of other stuff that simply isn't in the box. Antennas, power supplies, coax, headphones, microphones, etc. are just the basics.When you've narrowed it down to a couple of radios, go and visit some shacks and see them in operation. Try to work like you would work on one of those radios. If you're a contester, try a contest on a friend's radio, if you like working portable, go out with your friend and see how the radio performs.There's nothing wrong with picking the radio that your friend has, since it will help you learn more about your own gear.Since my first purchase I've learned lots about radios. I have no regrets that my first radio was a Yeasu 857d, but I picked it because it suited me. I can tell you that I don't think that my next radio will be the same. There is lots that I like, and some things I don't.Even the most experienced ham asks their friends for their opinion. My current one is to recommend an open source software defined radio, but I've not actually used one yet and I already know I dislike the software that it ships with, so there's that.I'm Onno VK6FLAB.

3mins

20 Jun 2015

Rank #12

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Hearing very weak signals

Foundations of Amateur RadioThis week I'm going to talk about a Digital Mode you can use with any Amateur License, or even without an Amateur License. You can set-up your radio, hook it to a computer and the Internet and after installing some software, you can join the Weak Signal Propagation Reporters.So how do you start, what does it do and how can it help you?First of all, WSPR, pronounced Whisper, is a way of encoding information and transmitting it across the spectrum. At the other end a radio receives that signal, sends it to a computer where a piece of software attempts to decode and then log it.This Digital Mode, invented by Joe K1JT, is one of several modes that are gaining popularity across the Amateur Radio community because the beauty of this mode is that it's so unobtrusive that you're unlikely to actually hear it if you were to tune to a dedicated WSPR frequency.If you want to find out what your station can hear, you can set yourself up as a dedicated receive-only station and report your findings to a central database where others can share your information and learn what propagation is like at that particular point in time.Of course, it also means that you can use the same information to learn what propagation looks like in your neck of the woods with your radio and your antenna set-up.There's even an option that allows you to have your radio automatically change frequency - known as band hopping - and listen for WSPR signals across the bands that you allocate.If you like, you can go to the wsprnet.org website right now and do a search for my callsign, VK6FLAB and see what stations I've heard since I turned it on. Go on, have a look, I won't mind.My station is set-up to do band hopping across all HF frequencies all day and night and during the grey-line it only listens to 80m, 40m, 15m and 10m, since those are the frequencies my license allows me to transmit on and I'm particularly interested how they work at sun-rise and sun-set.You might have heard me before talking about how the noise at my home is atrocious. Nothing has changed, it's still abysmal, but WSPR signals are coming in and being decoded.If you want to do this, you'll need a radio - any radio will work, a computer with a microphone socket and a way to pipe the audio from the radio into the computer, I'm using a 3.5mm male plug to 3.5mm male plug - you don't need a fancy audio interface, you're only listening. If you can connect an interface cable, your computer can also change frequency for you, but that's not needed to get started.Make sure that you turn the volume right down before you plug anything in. Connecting a headphone output directly into a microphone input can blow up the port if you're not careful and WSPR doesn't need much in the way of volume. The software helps you get it set right, so read the manual before you start.Once you've set-up your radio and your computer, you can watch the signals coming in on a waterfall display, a graphical representation of the audio and frequency that shows strong signals in red and no signal as blue. You'll find that turning up the volume too high will actually reduce the ability to hear signals.I'm keen to learn what I can hear and how many stations my simple 10m vertical antenna can hear across the Amateur Radio spectrum.I'd love to hear your weak signal stories and see what you can hear. As I said, it seems I'm becoming a short-wave listener after-all.I'm Onno VK6FLAB

3mins

4 Nov 2017

Rank #13

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A transistor radio curve-ball ...

Foundations of Amateur RadioToday I have a confession to make. Looking back it's clear that once your brain goes down a certain path, it's easier to follow the path than to find an alternative one. When I was growing up, above my bed, bolted to the wall were two brackets. On top of those brackets, secured with double-sided tape was a radio-cassette player. If you're unfamiliar with what an audio cassette is, don't worry, this is about the radio side of things and is from the days when Digital Music was not in wide use like it is today.I used this radio to listen to local stations, both on the AM and FM broadcast band, and I managed to even get to the beginning of the FM broadcast band where the police radio happened to be at the time in the country I was living.As years went by, that radio-cassette player was replaced with a radio tuner, then a combined amplifier tuner and I re-programmed it as I moved around the globe with new local stations filling up the quick select button memories.Over the last year or so it occurred to me that my latest device had been sitting inside a box in the garage for the better part of a decade and that the gap was filled by the radio in my car. I would drive somewhere and turn on the radio and listen to something interesting, or something boring, depending on what the airwaves brought to my antenna at the time.I started wanting to listen to the end of interviews, or rock along to some other happy tune when I got home, but I found the transition to be painful. I experimented with streaming radio, spent hours looking for software and currently the best I can do on that front is to have an App on my phone that streams a local radio station.You're likely by now doing one of two things. We'll get to the second one in a moment. The first one is probably going to be along the lines of "Yeah, so, what exactly has this got to do with Amateur Radio again?"If you're not thinking that, you might be thinking something that only occurred to me last week. "Why don't you use your Amateur Radio and tune that to a local broadcast station?"Indeed, why not?I'd never considered that even though my Yaesu FT-857d can tune from 100 KHz through to 470 MHz, covering most of the Amateur Bands, I'd never considered that it would also allow me to listen to a local broadcast station.It's not that I haven't actually tuned to those stations, or listened to the local Air Traffic Control frequencies, or the local Non Directional Beacons when they still existed, it's that those activities were in the context of Amateur Radio, along the lines of propagation, or interesting signals, not background music, or listening to an interview or a talk-back station.I've not yet gone to the trouble of pre-programming those stations, since my Amateur Radio is sensitive enough to pick up stations that my car cannot hear, but the list of frequencies that I'm tuning to during the day, using AM and FM is growing. Shame I can't get FM stereo from my Yaesu radio, perhaps that's something I should play with at some point.So, my second point is, "Duh, my Amateur Radio is also a radio, that you can listen to other broadcast stations with."Of course, it's a pretty pricey transistor radio, or short-wave radio, if you think of it like that, but if you've got it sitting next to you right now, it's simpler than making streaming radio work.I started this with paths travelled and I'll finish with that. When something like this happens, stop for a moment, celebrate the insight, share it with others and who knows what other things will bubble up.When was the last time your brain surprised you and what do you listen to that's not Amateur Radio? Who knows, I might become a short-wave listener yet!I'm Onno VK6FLAB

3mins

30 Sep 2017

Rank #14

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Planning for an outing

Foundations of Amateur RadioPlanning for an outingRecently I had the opportunity to use a new radio whilst I was far away from my shack. It wasn't unexpected, I took the radio with me, planned for the experience and packed light with intent.My original packing included a 10m length of coax, my analyser, some antenna weights, wire, rope, power leads, BNC adaptors, barrel connectors and a balun. Total weight came in at about 7kg. More than double the weight of the radio itself. The biggest weight came with the coax, so that stayed home. Got rid of all the "what-if" adaptors, dumped the antenna weights, dumped the balun and the analyser, added an un-un, and a multimeter and came in at just under 5kg.The idea was to operate from the car, chuck a long-wire into a tree and make noise.Then I got to where I was going and learnt that there were lots of SOTA peaks nearby. If you're not familiar with SOTA, it stands for Summits On The Air and it's a way of encouraging people to go out and make noise while also encouraging others to listen out for your activation of a nearby peak. As an aside, it's separate but closely related to WWFF, World Wide Flora and Fauna, since peaks are often in National Parks and who wouldn't want an excuse to activate two things in one sitting?One of the most basic rules of SOTA is that all equipment must be operated from a portable power source (batteries, solar cells, etc). Operation is expressly forbidden using permanently installed power sources or fossil-fuel generators of any kind.That of course means that using the battery in a car is not allowed, though I suppose I could unbolt the battery from the engine bay, but I'm pretty sure that the hire-car company would frown on that plan.I set about attempting to find out how much power the radio actually draws at 5 Watt, and how much battery I'd need to activate a peak.Given that my shack wasn't where I was, I couldn't just plug it into my fancy power supply and read the power draw from the display, should have done that before I left. Shoulda, Coulda, Woulda. I resorted to asking the community, but that was dependent on the kindness of strangers.Another hitch was the battery. I came up with the brilliant plan to use one of those high-capacity jump start boxes, 18Ah or so. Picked the one I liked the best, figured out if I could ship it back to my shack on return, since it likely couldn't fly, both from a weight and a dangerous goods perspective and found a supplier locally - well 108km away - and then, me being me, I downloaded the user manual, and learnt that what I wanted to do, power my radio, was expressly, strongly, not recommended, fear of explosion and the like.Planning foiled.I still wanted to operate, contest to be attempted, SOTA be damned. How could I operate and not fear that I'd be draining the car battery?A cigarette lighter mounted Volt meter!So, now I can connect the radio directly to the battery in the car and check the voltage whilst I'm operating.Now all I need is a parking spot with a nearby tree or gazebo and no noisy neighbours or overhead power lines.I'll let you know how I go.I'm Onno VK6FLAB

3mins

14 Sep 2019

Rank #15

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QRP - When you care to send the very least!

Foundations of Amateur RadioToday I'm going to talk about QRP, a term that's used in various different environments and one that I've used in the past. So, let's start at the beginning. QRP is a three letter code, part of the so-called Q-codes, that can either be a question or an answer. It's used in Morse communications to either ask "Shall I decrease transmitter power?" or to answer "Yes, decrease your transmitter power." It was perfectly valid for a kilowatt station to ask: "QRP?" and for another kilowatt station to answer: "QRP".Language changes over time, meanings get inverted, changed, adopted and transformed. The three letter combination, Q-R-P, is no different. Today in Amateur Radio, the three letters are more like a word, rather than a code and the meaning has changed to indicate that a station is running low power or as an indication to others that they're likely to be a weaker signal that requires a little more effort to pull out of the noise than any other station.As you might know, propagation is a fickle friend. There are days when you cannot talk to the station up the road and other days when you can hear a low power station clear across the globe and everything in between. The assumption that a QRP station is always hard to hear is not set in stone and often is quite incorrect. That's not to say that people think it's low, they hear QRP and think: "Hard work".It's a bit like fishing for trout. Some days are good, other days are just wet.Another aspect of the concept of QRP is the amount of power. The definitions differ. There are some that say that any station using 10 Watts or less is considered QRP. Others set the bar differently at 5 Watts. The ARRL defines it at 10 Watts or less for SSB and 5 Watts or less for CW or Digital. The WIA website uses a generic 5 Watts on their Low Power Radio page and different contests have different definitions of QRP.It's clear that there is no single definition of what constitutes QRP, just that it's low power.For me, I use 5 Watts and call myself a QRP station.Should you tell the other station that you're QRP? Should you include /QRP in your callsign and say something like, this is VK6FLAB/QRP.It depends.There are times when my statement of QRP got me through a pile-up and other times when some smart calling didn't require me to mention that I was only using 5 Watts. I've noted in exchanges that I'm using 5 Watts and had positive responses. There was a time when I signed specifically with VK6FLAB/QRP, but it causes all manner of grief with confirmation of your contact, since some stations will log the /QRP and others won't, since it's not an official callsign suffix.So, QRP is a wonderful aspect of our hobby, it teaches you to learn about propagation, to get your antennas sorted out, to pick your times and to learn better operating procedures.I find it immensely satisfying to make a contact with my 5 Watts and there are times I wished my radio would go even lower than 5 Watts.I know of amateurs who have worked across the globe, that is, the opposite side of the world, the furthest they can get with just a milliwatt SSB, so I know that while my contact from VK6 Western Australia to CO, Cuba with 5 Watts was proof that it all works, I know that there is more to explore.QRP - When you care to send the very least!I'm Onno VK6FLAB

3mins

23 Apr 2016

Rank #16

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Amateur Radio Minimalism

Foundations of Amateur RadioThe ultimate radio shack is a nirvana that most amateurs I've met strive for all their life. One of the many views I've heard on the topic keeps speaking to me, one of minimalism, less is more, what is the absolute minimum that you can use and still call yourself an amateur?As you know, I've recently moved and my shack was packed up into some boxes and is now slowly being unearthed. At the moment there are two antennas, a radio and a power supply. Keen observers will note that this is the same as it was last week.I've left well enough alone because of two reasons, one being that I'm trying to catch up on lost work during the move and the time where my internet connection was less than optimal, the other reason being that I've been attempting to work out what I actually want from my shack.Unlike my previous QTH, my current location affords me more flexibility, much more, as in four to six times more space to call my own. That's not to say that I was previously living in a shoebox and now I'm in a mansion, just that the distribution of space this time around is working out very well.So, I could go crazy, install computers, screens, multiple radios, a work bench, a soldering station, a weather monitoring station, a contest computer and the likes, or I could spend some time enjoying the breathing space around me and contemplate what I should do with this new found freedom.Initially I pictured setting up a dedicated DX cluster screen, a propagation screen, write some scripts to show the current maps using something like a raspberry pi, set up a dedicated space for doing contests and figure out how to mount several HF antennas, but the more I think about this, the more I wonder if this is what I really want.I've said many times that I adore contesting, it's a pull, a challenge, a bridge I have to cross, a mountain to climb, whatever the metaphor you see, but is that all there is about amateur radio that I enjoy? I know that I'm working on several bits of software, another DX project, some research and other activities, all related to amateur radio, but not specifically contesting.The thing I'd like to attempt to avoid, perhaps foolishly, given my less than latent hoarding tendencies, is the clutter that I see in other shacks. They're perfectly homely places, comfortable, full of interesting things, but I'm wondering what a minimalist shack might be instead, think of it as a "tiny houses" equivalent of getting rid of clutter in my life.What minimalist successes and failures can you share that helped you along the way?I'm Onno VK6FLAB

2mins

10 Mar 2018

Rank #17

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Just enough radio ...

Foundations of Amateur RadioIn the past little while you've heard me talk about WSPR, Weak Signal Propagation Reporter and I've told you about signals I've heard across the planet. The longest distance at the time was a HF report, 18656 km from Perth to Pennsylvania, very nice indeed.I switched to monitoring 6m, 2m and 70cm about a month or so ago.My reports had been pretty minimal, from my QTH to the suburb next-door and then two suburbs away. Proof that a station is working, but hardly anything to celebrate or even mention.The other day I came across a report a little further away, Perth to Adelaide, 2142 km away. Not world record beating, or even earth shattering, but proof that 6m propagation does have its moments now and then.Then a surprise contact, Perth to The Rock, not the one in the middle, or the one with the wave, the one on the Olympic Highway between Wagga Wagga and Albury, 2899 km away with 20 Watts on 6m.My reports aren't particularly far or amazing. You might recall Wally VK6YS who made a contact on 6m between Perth and Israel. He'd been at it for a little while, longer than I've been an amateur, but not quite as long as I've been the apple in the eye of my mother. 38 years it took for Wally to make that contact.So why am I making any mention of my little achievement?Simple really, my station and Wally's station are nothing alike. He had a large beam on 6m located on a property with few noise sources and his patience paid off.My station consists of a 10m antenna, that is, it's not 10m tall, it's resonant on 10m, and happens to also manage 2m. I've not actually checked to see what 6m on this antenna looks like, perhaps a project for another day, but it sits there, clamped to a metal pergola at the peak of a corrugated iron roof and connected via 20m or so of RG58 coax, cheap RG58 coax, connected to my radio that I use to host F-troop most weeks.I have to restart my WSPR node monitoring software several times a week since the Windows XP notepad computer it's running on crashes regularly. I have to remember to open the squelch when I finish F-troop and connect the WSPR node back up and I have to make sure that there's enough empty disk-space to make sure that I can actually log stuff.This isn't a sob-sob story, woe is me, my station isn't a massive station. It's more about that you can achieve these kinds of things with small and minimal resources.One of my friends is doing really well with a USB TV dongle decoding WSPR on a Raspberry Pi, others are using thousands of dollars of gear and everything in between.The point is that you too can get started without massive expense. A simple radio, something to run WSPR, which can be a Raspberry Pi, an antenna of sorts and you're on the way to check out what propagation is like around your QTH in your neck of the woods.Amateur radio doesn't have to be expensive, it doesn't have to be extensive, it doesn't even have to be elaborate, it can just be enough.I'm Onno VK6FLAB

3mins

27 Jan 2018

Rank #18

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Virtual Radio

Foundations of Amateur RadioThere is a feeling of anticipation in the air, the year has started, there are so many different ideas bubbling through my mind that I feel like an excited puppy dog wagging its tail.I've been playing with a wonderful piece of software called GNU Radio, more on that in a moment.So, I have for a while been dissatisfied with the offerings of SDR software. There is lots of development going on, lots of new toys being invented and many different hives of activity in this area.It's not unlike the progression from reel-to-reel based radio broadcasting via VHS tape, to computers with audio files. There are lots of solutions solving specific problems, but there are also a group of solutions looking for a problem and only time will sift out which one is worth the effort.In amateur radio we deal with valves, resistors, capacitors, inductors, transistors, integrated circuits, crystals, connectors, solder and many, many different physical things.I'm a computer guy, have been since I was in primary school. I grok computers, more-so than any aspect of anything else. Amateur radio was intended as an escape from this world, but initially to my dismay, but now to my delight, computers are making serious inroads into the hobby. Not just as peripherals that take care of logging, messaging, propagation forecasting and the like, but as integral parts of the radio.I looked at GNU Radio several years ago and wasn't able to understand what it did and how it worked. I didn't have enough in the way of radio skills or vocabulary to get started, but in learning about my hobby I now have a much better understanding.GNU Radio is a tool, a piece of open source software, that allows you to build circuits inside a computer that process information. Not unlike how filters, amplifiers and oscillators do this inside a physical radio.If you want to change the behaviour of a radio, you need to alter a circuit by changing components, or re-design the circuit entirely and re-build it. Hours of planning, soldering, testing and the like, just on a hunch or an idea. It's how we've been doing development for centuries.GNU Radio allows you to tweak a radio on the spot, in real-time, and see what it does. The feedback loop is immediate. You build up a sequence of blocks, an oscillator, a filter, a combiner, splitter, decoder, spectrogram, waterfall, whatever and if you need it do do something else, you either swap out one of the blocks, or change one or more parameters, better still, replace a fixed parameter with a slider so you can change it while it's running to see what happens.For example, displaying a Lissajous figure in the real world involves two signal generators, cables, an oscilloscope, power, gain settings, timing, several hundred, if not thousand dollars worth of gear. In GNU Radio it involves two signal source blocks and an oscilloscope block, joined together. All there, three blocks, two lines and it's working.Making an FM receiver in GNU Radio involves a source of radio frequency information, say a $20 RTL-TV dongle and an FM decoder block. You can display it on a waterfall with a third block, or listen to it with an audio block.To make matters even more interesting, you can build your own blocks, transmit if your radio is capable and test all of this without ever needing to go to the local electronics store or heat up a soldering iron.I have no doubt that this changes amateur radio for me and I'm fairly sure it will do the same for you.I'm Onno VK6FLAB

3mins

20 Jan 2018

Rank #19

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What did you hear last week?

Foundations of Amateur RadioLast week I spent a little time talking about the Weak Signal Propagation Reporters network, or WSPR, pronounced Whisper. You might remember that I set up my radio to receive these signals to see what I could learn. Turns out, I learnt quite a bit.I left the software running for a week. During that time my station reported 456 signals received with a total of 54 stations in 27 call areas.The longest distance 14,000 km, PC1JB in Veenendaal in the Netherlands who was using 1 watt.The best performance based on km per watt is R0AGL in Siberia, 10,000 km, with 2 milliwatt.Highest power heard, one station with 100 watts, but from a performance perspective, only just squeaks into the top 10 contacts. Typically stations used 5 watt or less.My 10m quarter-wave vertical antenna was pretty good in hearing things across all bands. I heard stations across the frequency range, from 160m through to 10m.It heard 1 station on 160m, VK7MF, using 5 watts, 3,000km away.The most prolific band was 40m, accounting for 41% of the signals, 30m was pretty close at 35% and even 10m was respectable with 5% of signals heard on that band. Which brings me to a comment about propagation. The Solar Flux Index this week was pretty abysmal. It's been the lowest it's ever been, 66 and still I was able to hear signals across all HF bands.Just think about that for a moment.All the solar numbers say the bands are dead, all the listening in the world says the bands are dead, but using WSPR reveals that this isn't true, it's not even close to being true.My station in a very high noise environment still heard signals across all bands.Based on a visual comparison with other stations, signals were generated in all directions, but for my station, I didn't hear anything coming from the North East Quadrant, that's between North and East. It could be that the signals are being suppressed by the distortion in my antenna pattern, which might be caused by a metal gutter in that direction, or it might be that signals coming from that direction, mainly Japan and the United States, are too weak to be heard above the noise level at my station. I'm investigating that further, but that's for another day.Speaking of other stations, in total during the same period as my station listening, there was a total of 6.9 million reports, representing 2490 listeners and 4463 transmitters. That means that I heard just over 1% of stations on my radio. Not bad given my meagre set-up and minimal configuration and installation.On to things that I was attempting to learn about the performance of my radio. Every WSPR transmission includes the frequency and location information, which allows you to determine what the difference is between what frequency the other station reports and what frequency your radio sees.Of course, there can be variation across both radios and to make things more interesting, this changes over time. This drift is likely to be distributed pretty evenly across all stations, but then I didn't hear all of them, so my results are not completely definitive, but overall the drift reports show a frequency drift of minus 3 to plus 2 Hertz. Slightly skewed down. That's not yet conclusive proof that my station is slightly off frequency, but it seems to indicate that my new crystal is slightly low. I'll be investigating that further.And that neatly brings me to why I have been doing this.You might not be surprised to learn that many things inside your radio are frequency controlled. Those frequencies come from a single central location, a master oscillator that in my radio vibrates at 22.625000 MHz. The crystal that does this is affected by temperature. When you transmit, the radio heats up and the frequency of the crystal changes slightly. Normally this isn't an issue, but if you're working on being on a particular frequency, especially on the 2m or 70cm band, then this starts to matter. If you leave your radio running for a few hours, things are likely to be more stable, since the temperature in your radio becomes more stable.Another way to do this is to control the crystal temperature directly. You can insulate it, or heat it in a little oven, or a combination of both. This is a so-called Temperature Controlled External Oscillator, a TCXO. It's more stable and thus over time the frequency shouldn't change much.In my case, the range is 5 Hertz and as I said, it's slightly skewed down.The next step is to measure the actual frequency that my radio is tuned to. This will require a little more effort. I'll talk about that next week.In the mean time, I'm doing some more analytics to compare how my noise-floor affects my station, how it compares to other stations across the same time-range and how little changes in volume, antenna and the like affect what results I get.There is lots of data to digest, lots of knowledge buried among the stats and I'll be spending the coming weeks seeing if there are things here of a wider interest.One thing's for sure, this is the simplest way you can measure and compare your station against a whole globe of other stations. Of course it doesn't actually get you on air to make noise, and that is the ultimate test of the success of a station.I'm Onno VK6FLAB

6mins

11 Nov 2017

Rank #20