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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?".
  1. Foundations of Amateur Radio

    If you've ever used a spray can of WD-40, you might have wondered what the name means. It stands for "Water Displacement, 40th formula". In my time as a radio amateur I'd never stopped to think what the RG in RG-58 stood for. Turns out that it too has a meaning, "Radio Guide", though I have found some interesting alternative descriptions where the G stood for Government.

    This radio guide, really a transmission line, gets a signal from point A to point B. Depending on how you construct that transmission line determines what you'll get at the other end.

    Coaxial cable or coax is a length of cable made from several components. There's the outer layer or jacket, that protects the cable from electrical shorting, U/V deterioration and water ingress which causes all manner of problems. Inside that is an electrically conductive shield that forms one half of the transmission line, inside that is a dielectric, essentially a separator or insulator between the shield and the inner most, or central conductor, the core.

    Each of these components can change. On the outside the first thing you might notice is the thickness of the cable. The next thing you might observe is how flexible it is. Below the outer surface other things can also be altered. For example, the core could be a solid copper wire, or it could be strands of copper. It could be aluminium, silver or even steel. It might not even be wire. Some coax like Heliax, used in broadcasting, uses a central conductive tube as the core with air as the insulator between the core and the shield.

    The dielectric that separates the core from the shield can be made from different materials such as plastics, air and even inert gas such as nitrogen and it comes in varying thickness. Similarly the shield can vary in thickness, material and construction. There are also variations that have multiple levels of shielding, such as for example Quad Shield RG-6, common in satellite television and internet connections that has four layers of shielding.

    Other aspects might not be nearly as obvious. If you're running coax down a power line it will need physical strength. If you're burying it in the ground it will need to be protected from water ingress. Temperature and heat dissipation are also considerations and if you're using the coax in a nuclear reactor, its ability to deal with radiation. More commonly if you need to run the coax around a corner, how tight it can be bent is another consideration.

    As the materials and dimensions are changed, the characteristics of the coax changes. Each of these are documented and standardised.

    The standardisation is both a blessing and a curse. So many options and so much to choose from.

    For example, if you compare RG-58 to RG-59 they look pretty similar. If you cut into them you'll notice that they're made from similar materials. If you put them side-by-side, you'll notice that RG-59 is thicker, by about 20%, conversely the core for RG-59 is thinner by about 20%, this also means that the dielectric is about 30% different in thickness. As a consequence, connectors for one might fit on the other, but rarely work well.

    These variations mean that while both types of coax are common and priced similarly, they're not interchangeable. RG-59 used to be common in satellite TV installations and is still used in CCTV, whilst RG-58 is common in radio communications.

    If you made the decision to actually go out and buy RG-58, you'll come across many variations indicated by extra letters. For example, BC means Bare Copper and TC means Tinned Copper.

    The final piece of the puzzle in this tangled offering of transmission line is that each manufacturer has their own way of doing and naming things in pursuit of market share. For example, the coax I installed recently is known as LMR-400, CNT-400, WBC-400 and several others.

    If the performance of your coax actually matters that much, I'd recommend that you spend some time looking at your options before handing over any money.

    All that behind the name of a piece of coax that runs between your radio and antenna.

    I'm Onno VK6FLAB

  2. Foundations of Amateur Radio

    During the week I climbed on my roof and installed a base antenna for the 2m and 70cm band. The antenna is a Diamond X-300N. It's 3 meters tall, has a gain of 6.5 dB on 2m and 9 dB on 70cm. I've owned it for just under eight years and this week I finally took it out of the box and installed it. I know, I know, in my defence, you shouldn't rush these things.

    Truth is, until this week I really didn't have a realistic way of installing it. Several factors needed to come together. Some of them trivial, others less so. In the end, the antenna is now installed on my roof, connected via coax through my roof to my radio.

    Now before we get all excited about what that means, let's compare my previous outdoor setting to the current one.

    Today I'm using LMR-400 coax, 30 meters of it. Previously I used RG-58, but only 20 meters of it.

    From a coax perspective, even though I increased the length by 30%, my loss actually went down, on 70cm it went down by over 4 dB. If you recall, 3 dB loss is the same as losing half your signal, so before my 5 Watts even got to the antenna, I'd already lost more than half of it using RG-58.

    I will mention right now that the numbers I'm giving here are purposefully not exact. There's no point. Your situation and mine are not the same, and my two installations are barely equivalent, so actual numbers don't help you.

    The point I'm making is that the type of coax you use to feed your antenna can make a massive difference. In my case that difference means that half of my 5 Watts never even made it to the antenna.

    In addition to this the two antennas are different. Not by much, but enough to make a difference. As icing on the cake the new antenna is longer by a third, so my new antenna has a better horizon, it's higher off the ground, even if it's installed at a similar height.

    You might recall that loss and gain are dependent on frequency, so any calculation needs to be done for each band you're going to use. In my case I had to do this twice, once for the 2m band and once for the 70cm band.

    I should also mention that depending on the SWR of your antenna, the losses also change, but let's not go there today.

    If you want to actually figure out what this means for your station, the calculation goes a little like this.

    Take the power output from your radio, subtract the coax loss and add the antenna gain. The end result is a number that represents the gain - or loss - from the entire system. If coax loss and antenna gain are the same, you're not losing anything, but you're also not gaining anything.

    The reward for the aches and pains from climbing on and in my roof are represented by the fact that now my 5 Watt signal on 2m effectively became 10 Watts. On 70cm it became 13 Watts.

    With the added height and gain in addition to being able to hit all the local repeaters, I can now hear the local beacon and I've successfully decoded the JT4 and JT65 messages that the beacon spits out.

    It's only been a week, but it's already made a massive difference.

    No doubt my on-air experience will also benefit from this adventure.

    Unfortunately, to do this for yourself is not quite as simple as giving you a link and punching in the numbers. I won't make any promises I cannot keep, but I am looking into it.

    I'm Onno VK6FLAB

  3. Foundations of Amateur Radio

    The other day I received an email from Colin VK2JCC who mentioned that he was a keen home brewer and he was interested in a discussion about using ex-military gear in amateur radio. If you want to see his beautiful rig, check out Colin's Clansman PRC 320 Radio, does 2 to 30 MHz at 3 or 30 Watts. Look for his callsign and you'll also find a video of him calling CQ.

    Colin also shared his efforts for the construction of a Ground Tuning Unit which started a whole different exploration, but I'll leave that for another day.

    Back to the topic at hand, ex-military gear in our hobby. My initial thoughts on the subject were predictable: "What on earth do I know about this and do I have anything useful to contribute on the matter?"

    It turns out that this isn't something new to me. You might recall that I'm an IT professional in my non-amateur life. In that role you'll likely never see me buying second hand or refurbished gear, unless I installed it myself and was the person responsible for its maintenance.

    This same mindset prevails within my hobby. Although I am the owner of several pieces of pre-loved equipment, it arrived either because I knew the previous owner and where they live, or because it arrived unencumbered at my door.

    I go to hamfests and look askance at the gear on offer. I'll buy connectors, a tower, but not so much anything in the way of electronics. I asked around and I'm not alone in this. Many of my peers have the same view. Why pay good money for something that has been abused?

    It occurred to me, that this mindset is based on the idea that something can go wrong because the equipment has been invisibly damaged. Of course that is possible. However, on reflection, the reality is likely different.

    In my professional life I've seen plenty of badly maltreated equipment. I remember being called out to a faulty computer that sat on the ground in the office in a car mechanics workshop. The computer, used for accounting, would on warm days just stop. On opening it up, in 2006, I found a motherboard with a Pentium processor on board. It was untouched from when it had been built in around 1994. The CPU fan was no longer moving and the amount of caked on dust - complete with microscopic motor oil - had formed a solid cake around the cooling fins. After removing the dirt, the fan spun back into life and the computer was once again rock-solid.

    That is the definition of abused electronics.

    Yes, in case you're wondering, I did recommend replacing the computer, but out in the back roads of Australia, that's easier said than done.

    Story aside, I came to the conclusion that while abuse might reduce the circuit life from a millennium down to a century, that was unlikely to happen in my lifetime.

    Back to the ex-military gear.

    Based on Colin's comments, his historic radio, and my insights into the scale of abuse and their impact, I'm more inclined today than I was yesterday to investigate.

    I will note that I'm spoilt for choice. I can pretty much buy off the shelf any gadget required, limited by my imagination and my budget, but that wasn't true for several of my amateur friends. I know of several modifications of aviation and military rigs, born from necessity, that eventually made it into amateur radio and come to think of it, there's not much difference from me adding a serial interface to my Commodore VIC 20 back in the 1980's.

    Before I start shopping for radios that glow in the dark, there is another consideration. I did the same with computers over 20 years ago. I ended up with about a dozen of them in my office. Today that's replaced by a single one that runs as many virtual computers as I need.

    In radio terms, do I fill my shack with boxes, or should I spend my efforts on getting an RF signal into a black box with SDR written on the side? It's hard to know what the differences are without seeing both sides of the equation, but I'm sure that at my next hamfest I'll be looking around with different coloured glasses.

    Thank you to Colin VK2JCC for asking the question and showing his toys.

    I'm Onno VK6FLAB

  4. Foundations of Amateur Radio

    During the week I finally made the decision to purchase my first software defined transmit capable radio. It wasn't an easy choice for me, given that the range of options vary in price from "not much" to "more than my car is worth" and an infinite number of choices between those.

    One of the considerations, other than price, was a thing called bit-depth. In the past I've spoken about how an analogue to digital converter or ADC uses bits to represent a radio signal. In short, a voltage coming from an antenna is represented as a digital value inside the radio. No signal represents a value of zero and maximum signal represents the maximum value that fits into the decoder. A concrete example might be an 8-bit ADC which can represent 256 different values.

    If you look at the choices available to you, you'll see that there are 8-bit radios, 12-bit ones, 16-bit, 18-bit and 24-bit radios. On the face of it you could just say, more bits is better, but how much better?

    For example, an ANAN-10 and a FLEX-3000 radio, both costing about the same, have a different ADC. The ANAN is a 16-bit device and the FLEX is a 24-bit device. At the other end, a HackRF One is an 8-bit device and costs twice as much as an ADALM Pluto that's a 12-bit device.

    How do you choose and what are you choosing?

    Essentially you're choosing something called dynamic range. Think of it as the range of signal strengths that you can represent using a number of bits.

    As it happens there's a formula for that. It's 20 times the log 10 of 2 to the power of the number of bits times the square root of 3 divided by 2 and it represents decibels relative to full scale or dBFS.

    In more recognisable terms, it comes down to a bit being worth 6 dB of range. A good approximation is the number of bits times six plus two.

    For example, a 6-bit SDR will have a dynamic range of 6 times 6 bits is 36, plus 2 makes 38 dB of range. An 8-bit SDR has 6 times 8 bits is 48 plus 2 makes 50 dB of dynamic range.

    I'm using rounded off numbers here but it gives you a pretty accurate sense of scale. Six times the bits plus 2 works until about 36-bits and then it's off by one dB, until we hit 85-bits - which we won't likely be able to buy at the local ham store for a little while yet - and then it'll be off by 2 dB.

    Another way to think of dynamic range is to think of it as the difference between the weakest signal you can measure and the strongest signal. Given your SDR is going to be using a whole chunk of radio spectrum, you likely will have to deal with your local broadcast stations as well as that QRP signal you want to decipher, so more dynamic range is better.

    Let's give this some context. The Australian Broadcasting Corporation, the ABC, has a local AM station on 720 kHz that has a transmitter with an EIRP of just under 155 kilowatts. My QRP station uses 5 watts. My signal is 45 dB weaker than that local transmitter.

    This means that in order for an SDR to be able detect my signal in comparison to the broadcast station, it would need to have a range of 45 dB or 45 less 2 is 43 divided by 6 is 8 bits range at a minimum.

    Now this isn't precise or complete, but it should give you some sense of scale.

    In this example, the amplitude range of my 5 watt signal is represented by a digital range of 1 and the broadcast transmitter is represented by a range of 255 values.

    That means that the best you could hope for in decoding my signal would be if I was transmitting Morse, the absence or presence of my signal would make the value representing my signal go from 0 to 1.

    As you might imagine, this is not suitable to decode something more complex like SSB. My Morse signal is also right at the noise floor, so it might not even be detectable at all.

    Similarly, in the absence of a 150 kilowatt station, but say a 1500 watt station, you'd need just under 25 dB range, or 4-bits.

    Now before you start pointing out that there are other issues, yes, there are, sample rate, clock stability to name two. We'll get to those. I should also point out that normally you'd represent the voltage range using both positive and negative values and I didn't mention that the maximum is calculated using RMS.

    In the meantime, I'm getting excited to see my new toy arrive. I'll let you know how it goes.

    I'm Onno VK6FLAB

  5. Foundations of Amateur Radio

    The other day I stumbled on a social media post titled "So, you want to be an astronomer..." by /u/Andromeda321 on reddit. Look it up if you're interested how she puts together the prerequisites from her perspective as an astronomer.

    Apart from the fact that a few of my friends are astronomers, one even a radio amateur - and I have to confess, that's a combination that is exciting and intriguing - it got me considering how you become a radio amateur.

    In my mind I started putting together lists and links and other prerequisites that help you become an amateur when it occurred to me that being an amateur is in my view a state of mind.

    While it's true that there is a licensing process that gives you transmission privileges, that to me is not what makes an amateur.

    When I started my amateur radio involvement in 2010 I'd seen amateur radio exactly twice. Once as a sea-scout during a Jamboree on the Air at the end of the 1970's and once when my manager parked his tiny car, I think it was a champagne coloured Daihatsu Charade, with a massive 40m or 80m vertical in the car park at work.

    As I started learning about amateur radio and passed my test I'd commenced the journey into what I now consider to be membership of the amateur community. That same journey is undertaken by people across the planet. For some it starts like mine, with a course. For others it starts with a neighbour or a parent, a friend or an aunt. They might start with listening to short-wave radio, or playing with electronics.

    People start their journey at all different places and times in their life.

    There is a perspective within the amateur radio community that says that you're not a real amateur until you've passed a test.

    I don't think that's right. Passing a test is part of the experience and you may or may not start there, or even pursue the test. That doesn't describe your radio amateur status, that's just giving you responsibilities and regulations that permit you to expand your thirst for knowledge.

    In my experience, the real test of being an amateur lies in something much simpler than that.

    Being a radio amateur isn't a profession, it's a hobby. An amazing one, but a hobby. I know that there are plenty of amateurs that will argue that it's a service. I don't deny that there is a service aspect, but that doesn't take away the rest of the community, it adds to it.

    You might wonder why I'm even bringing this up. The reason is that all too often our community erects fences. "You don't have a license", "You don't know Morse", "You only have an introductory license", "You only own a cheap Chinese hand held", followed by: "You're not a real amateur."

    I think that you're an amateur when you decide to be one.

    So, if you're not yet here, what's stopping you?

    I'm Onno VK6FLAB

  6. Foundations of Amateur Radio

    The activities that our community places under the banner of amateur radio are many and varied. I've referred to this as a thousand hobbies in one. If you look at the surface, you'll find all manner of activities that readily attach to our hobby.

    Activations for example are invented at any opportunity, from parks to peaks, light houses, bridges, trains, boats, lakes, roads, locators and countries. We pursue contesting, making contacts using different modes, different power levels, we pick the frequencies on which we operate.

    If you dig a little deeper you might consider investigating propagation, or antenna builds, electronics, physics and more.

    It occurs to me that there is an underlying activity, one that any amateur can participate in and most do at what ever level they choose.

    It's the act of being curious.

    You can choose to turn your radio on and be curious to what's going on around you on the bands, or you can be curious as to what the underlying principles are of the mode you're using to make a contact. You can be curious as to the electrical principles and you can be curious as to the maths behind that.

    Superficially you might think that being curious isn't really something that is remarkable. I'm here to disagree with that.

    If you drive a car, you can choose to be curious, but many just put fuel in the right hole and keep air in the tyres. Most will wash their car from time to time. Some will dig into the innards of their car, but the vast majority lacking even a superficial understanding will have their car serviced by an expert. The same is true for computers. You might not wash your computer, but doing maintenance is often a case of waiting for it to die and calling your local IT expert.

    There is absolutely opportunity for curiosity in relation to cars and computers and there are plenty of stories from those who follow that path.

    In our community I think that this balance is completely different. In amateur radio there are a few people who use their radio like the majority of the general public uses their car, but in the whole, I think that the bulk of radio amateurs travel down a rabbit hole on a regular basis, armed with multi-meters, screw drivers and soldering irons. I see their reports, I hear their questions, I read their emails and respond to their requests.

    You might say that I'm biased, since those are the amateurs I come across, but I think that's underselling quite how special this hobby of ours really is.

    I love that you can be curious about an antenna and keep digging and become curious about the underlying laws, right down to the fundamental principles behind the phenomenon we experience as radio.

    I've said many times that getting your license is like receiving the keys to the hobby. You have the ability to open the door and come inside to see and explore for yourself.

    What have you been curious about lately and what did you do about it?

    I'm Onno VK6FLAB

  7. Foundations of Amateur Radio

    When you start life you learn early on the difference between being told about an experience and the actual experience. There's a saying that comes to mind, I use it regularly in my day job: In theory there is no difference between theory and practice, while in practice there is.

    I thought I'd do the quote justice to see where it came from, not from Einstein, who was three years old at the time it was coined and neither Yogi Berra or Richard Feynman had been born. Quote Investigator puts it in the Yale Literary Magazine of February 1882 and attributes it to Benjamin Brewster, but I digress.

    A little while ago the regulator in Australia altered the rules of engagement in relation to amateur radio for people holding the license that I do. All Australian amateurs are now permitted to transmit digital modes. Not that this should have been any impediment to the exploration of the receive side, but I had a few other things on my plate to try. Still do.

    Over the weekend I sat in my driveway with my radio and had the urge to see if I could actually do some PSK31, a digital mode that had a low entry barrier, since there were defined frequencies, and I could use a decoder on my phone.

    So, I set about doing just that. I had already programmed in the various frequencies into my radio the week before. I hadn't actually heard any signals, but that didn't deter me. I set about getting myself set-up for what I'm calling a driveway hack.

    Picture this. A folding table with my radio. A stool next to it with me on it. The radio connected to an antenna, a vertical that was attached to a neighbour's roof with a magnetic mount and my phone running DroidPSK. I was tuned to the 10m PSK frequency, had the volume turned up, holding my phone next to the speaker, watching the waterfall.

    Nothing.

    I called up a mate who had this all working and we set about trouble shooting my set up.

    He made some transmissions; nothing.

    I listened to the 10m beacon, loud and clear.

    He made some more transmissions, still nothing.

    Then we realised while I was switching back and forth between the beacon and the PSK frequency that his radio was set up for a different standard PSK frequency. Gotta love standards, there's one for every occasion. Changed my frequency and for the first time I could actually see stuff in the waterfall display on my phone.

    If you've never seen a waterfall display, it's a tool that helps visualise the signal strength of a chunk of spectrum over time. It's pretty nifty and a waterfall displays a lot of information.

    Starting with colour, the idea is that a colour represents a particular signal strength. Red for full signal, yellow for half, blue for the lowest detected signal and black for no signal. Fill in the gaps with the colours of the rainbow.

    If you represent a line made of dots with the start of the line at say 0 Hz and the end of the line at say 3 kHz, you could split the line into 300 dots, and each dot could be coloured to represent the average signal strength for a little 10 Hz slice of spectrum.

    If you wait a second, move the line you drew down and then measure again, you'd end up with two lines. The line from now at the top, the line from a second ago below it. If you do this every second, you'll end up with lines flowing off the bottom of the screen, the oldest lines at the bottom and the newest ones at the top.

    That is a waterfall display. Over time you'll start to recognise what a particular signal looks like on the waterfall and there are even modes where you can draw on the waterfall, but I'll leave that for another day.

    As I said, I could now finally see signals on my waterfall display.

    I'm not going to dig too deep here, because there's much confusion in the language surrounding all this and I intend to get the names straight in my mind before I express them here, but after figuring out that you have to tell DroidPSK which signal you want to decode, I finally managed to decode the transmission from my friend.

    After putting on some headphones and realising that the clicks I was hearing from my phone were actually artefacts from the speaker, I also managed to transmit a CQ signal which my friend decoded. He then acknowledged my callsign in his next transmission.

    So, I now have two screen shots, his and mine, showing that we both saw each other using 10m PSK31. There wasn't a signal strength exchange, mainly because I have yet to figure out how to determine that and where it's visible, but for all the things that matter, I managed a contact with PSK31 thanks to Randall VK6WR, very exciting!

    Since then I've started experimenting with decoding WebSDR, that's HF signals coming in via the internet and being decoded on my computer from the web audio. I'm still working on that, but there is so much to learn and play with and a transmitter isn't yet needed to have fun. I should mention that you can also decode satellite signals like this.

    Digital modes, just when you thought that the rabbit hole couldn't get any deeper.

    I'm Onno VK6FLAB

  8. Foundations of Amateur Radio

    The other day it occurred to me that my callsign had been away from HF for months, probably longer. I didn't really want to think about how long it had been. I moved QTH over two years ago and ever since I've been working on a new antenna set-up. You know the kind, you shouldn't rush this. Anyway, having just had a camp-out with some friends for a portable contest, where I gleefully had fun with the station callsign, I thought it was time to actually do what I keep advocating to anyone who stands still long enough, to get on air and make some noise.

    So I did.

    You know that feeling when the longer you wait, the harder it gets and the more you put it off? That had invaded my thinking and my avoidance. The typical excuses of not enough space, too much noise, no antenna, radio not ready, too hard, all fought their way into prominence. I'd had enough.

    So, on Saturday I collected all the bits that make up my portable station. It had clearly been a while since I'd used it, since I couldn't for the life of me remember where the head of my Yaesu FT-857d was, that was until I remembered that it had previously been installed in my car, so that's precisely where I found it. The tiny jumper cable between the head and the body was located in my headset bag where I'd stashed it after forgetting it for a contest one year. The microphone was where I'd stored it in the car. The battery was easier, since I'd used that the weekend before. Pulled out a table, a chair and set about putting my station together right there in the driveway.

    I'd been meaning to test an antenna that to all intents and purposes was doomed to fail, a long-wire on the ground. I didn't have an un-un or a balun, but I did have my trusty antenna coupler, so I used that. One end of the antenna, twelve and a half meters going one way, the other half going at a right angle. That pretty much solved that.

    Then for the final touch, I turned the radio on. All worked and I set about figuring out what I could hear. Across all the NCDXF beacons and bands I could hear the local beacon about 30km away.

    I have mentioned the NCDXF before, but in short, the Northern California DX Foundation has since 1979 coordinated the installation and maintenance of a collection of transmitters that 24 hours a day, every three minutes transmits on a staggered schedule across 5 different bands. It's called the International Beacon Project. For funding, the NCDXF relies on donations from people like you and in Western Australia the WA Repeater Group maintain the beacon, VK6RBP.

    Each transmission consists of a callsign, a beep at a 100 watts, a beep at 10 watts, 1 watt and 100 milliwatts. You can hear the beacons on 20m, 17m, 15m, 12m and 10m. Their purpose is to determine what propagation is like across the world on each of the bands, in pretty much real time. It was the impetus for me to start learning Morse Code - in case you're wondering, no, I know, I'm still at it.

    On my wire on the ground antenna the local beacon on the 10m band was by far the strongest. I also had a listen on 80m and 40m and even found two stations in deep discussion about something or other. Didn't manage to catch their callsigns, but good readability, not so much in the way of signal strength.

    I called up a friend on 900 MHz, in case you're sceptical, yes I hold a licence for that, so do you, it's cunningly encapsulated in a sophisticated portable battery powered multifunctional gadget made of electronics and glass. He was in the middle of repairing some damage sustained to his G5RV Jr. antenna during our latest adventures - Hi Glynn - and afterwards we had a go to see if we could in fact hear each other. I was using 5 Watts, he something like 70 Watts. Neither of us could hear the other, even though we're a similar distance from each other as the beacon. Not yet sure if it was his radio acting up, or mine for that matter.

    I then started down the digital modes path. Installed a PSK31 decoder and set about programming my radio for the traditional PSK31 frequencies. Didn't hear anything, didn't decode anything, but had a ball none the less.

    You might think to yourself right about now what the point of all this was if I didn't make any contacts? The answer is simple, I got outside, in the sun, soaked up some Vitamin D and played radio, just like the weekend was intended for. My next adventures are likely going to involve the same antenna and a vertical for transmit to see how that goes.

    You don't need an excuse to get out and play and when you do you might not make any contacts, but that's not really the point of playing, is it?

    I'm Onno VK6FLAB

  9. Foundations of Amateur Radio

    In our hobby we regularly talk about its purpose, its need, its usefulness and other potentially abstract notions. Often there's a nod towards science, learning, self-discovery, challenge, emergency service or some other higher order concept. I know I've discussed many of those over the years and encouraged you to find what the hobby means to you.

    There is one aspect of our hobby that's pretty much left unsaid. It's left unsaid because it's obvious, since radio is about communication at its heart, the idea that we use our radios for communication is ingrained and unheralded. You might find a few new amateurs talking about how they made their first contact on the local repeater, or how they want to use the hobby to stay in touch when they're out and about.

    It occurred to me the other day that much of the world is subject to travel restrictions and social or physical distancing requirements. There's places that are in total lock-down and whilst there are strong recommendations for people over 70 to stay completely isolated, that's not yet a requirement where I live. It might come to that, but at the moment the COVID-19 pandemic is changing habits and communities on an hourly basis.

    Technology is often sought as a solution. There's plenty of video-conferences being held. Local amateur clubs are going online to stay in touch with members while face-to-face meetings are off the menu. Then there's the ongoing access to social media, blogs, discussion groups, mailing lists and the like.

    There are a few brave radio clubs using something a little less technical. The radio. Shock, horror, imagine that, an amateur radio club using an actual, you know radio, to talk to each other. I must admit that communication via radio, as obvious as that sounds isn't always the first thing that comes to mind. I've lost count of the number of times when at the local club one member stood outside yelling back into the shack which way the rotator on the Yagi was pointing whilst adjustments were being made - turns out that the rotator was spinning on the mast in the wind. Took a concerted effort, seriously, to actually turn on a hand-held radio and talk to each other, like civilised people.

    On the weekend during F-troop, a weekly net for new and returning amateurs, I also asked how people were doing given the social isolation that is pervasive.

    I also started toying with the idea of running an F-troop every day, then I scaled it back to every Wednesday and Saturday and then it occurred to me that the power to host a net is in the thumb of any amateur clicking their push to talk button and I finally settled on continuing the normal activity of hosting F-troop on Saturday morning at 00:00 UTC for an hour.

    I understand that in a technically connected world with cheap internet and fully functional gadgets like smart phones, the idea of going back to radio might seem like a step backwards, but I'd like to point out that we're radio amateurs. That's like being a chef and ordering take-out when you have a fully stocked kitchen.

    If you're experienced in this hobby you'll know that nobody needs to grant you permission to host a net, but if you're new here you might not. So, to you I say: "You don't need permission to host a net, so get to it."

    There are some things I've learnt since starting F-troop nearly a decade ago. Start small. Depending on the skill-level of the participants, choose an option for hosting it. F-troop is run with a single net-controller, often that's me, and the role of net-control directs who's next to talk. If you're just playing around, the tried and true version is a round-robin net. You'll need to pay attention a little better because you'll need to know who comes after you so you can hand the call to them. There are also variations on this, but again, start small.

    I track contacts in a spreadsheet, but a piece of paper is just fine. Writing down all the stations you hear is a great idea, since it helps you keep track of who's said what. You can add information as it comes to hand. If the net is on HF you might record the signal strength you see when you're listening to each station, as well as the name and location or QTH.

    Pro-Tip, use a new piece of paper for each net and put a date on it. Future you will love you for it.

    My point is that there should be absolutely no impediment to getting on air, making noise and breaking isolation from the comfort of your own shack.

    I'm Onno VK6FLAB

  10. Foundations of Amateur Radio

    When I started learning about antennas I was told height is might. The higher the better. For many years I've followed that advice and like a good little parrot I've dispensed that advice. Turns out that as is usual in our hobby, that's not the whole story.

    I first came across a ground based antenna with a BOG, that's a Beverage On Ground antenna. It's essentially a long length of coax that's pointed at what you want to hear. You can either terminate the end, or not, different effects result with plenty of discussion about directivity, angles, lobes and the like.

    One of the things you'll notice with you use a Beverage antenna is that it's quiet. All signals are reduced in strength, but that also means that noise is reduced. Turns out that this pays off and you hear stuff that you've not heard before. Excellent for a field day or if you want to hear some serious DX stations.

    There's plenty of stuff that's not nice about a Beverage antenna. For one, it's highly directional, it takes up lots of space and if you want to listen in another direction, you'll either build a second or third and switch between them. That, or you'll be rolling up and laying out the coax to point at a new DX entity.

    You also cannot transmit with a Beverage antenna. While we're on the subject, often a beverage can be combined with a vertical, one for receive, the other for transmit. It's one of the projects that lying in my to-do pile. I've even got a remote controlled coax switch, but I'm still figuring out how to make my FT-857d do the switching.

    I could stop there, but I came across another idea a couple of weeks ago. At the time I was being introduced to the local emergency communications team. They showed me their HF stand-by gear. Long piece of wire that you could chuck out on the ground and make contact. As a good little amateur I remember thinking to myself, these poor people they have a lot to learn. I'm glad I'm an eager apprentice in learning the art of keeping my big mouth shut.

    During F-troop, a weekly net for new and returning amateurs, you'll find details on vk6flab.com, another amateur was talking about putting a wire near the ground, like about a foot off the turf with great results.

    I tried it on the weekend with a friend. We were out camping for a local amateur contest, miles from anywhere and anyone and I recalled the emergency communications people and the story during F-troop. We had some time to play, so we started with a long-wire, actually, pretty-much a wire dipole on the ground. Plugged it in, turned on the radio, magic. Same kind of sound effect as a Beverage antenna. Nice and quiet, good signals to be heard. We turned the whole contraption 90 degrees, no difference. Since then I've learned that it's pretty much omni directional and unlike a Beverage antenna, you can use it to transmit.

    Of course it's not going to act in quite the same way as a dipole high in the air, and that's pretty obvious, since it's not in the air. It'll give you communications that are called NVIS, or Near Vertical Incident Skywave, essentially stuff that goes straight up and comes down, stations up to about 400 km or so away. For scale, that's enough to cover all of Holland. In Australia it's enough to cover the state of Victoria, or the width of the UK, and most of the width of the State of New York.

    Before you get all huffy and point out that this is not a great DX antenna I'll beat you to it and tell you that this is not a great DX antenna. It's not meant to be. Nor is it intended to be an instruction on what antenna to build next. This is purely intended to illustrate that antennas come in all manner of shapes and sizes and there is lots to be learnt from trial and error.

    I know that this is a "compromise" antenna. Guess what, so is every other antenna. Today the compromise is that we don't need any poles, trees or unsuspecting human support structures to keep an antenna in the air. You can essentially try this one for free at any time, on your own, on the beach, in a park or on the side of a mountain.

    Another great use is to talk to your friends who live in the same city on HF. I have no doubt you could even manage some FT8 contacts using this antenna.

    Next time someone tells you to put your antenna in the air, ask them who they want to talk to. If it's locals, then there is absolutely no need at all. As for mastering the art of keeping my big mouth shut, we'll see.

    I'll leave you with this. It's not the answer that's important, it's the question, for everything else there's experimentation.

    I'm Onno VK6FLAB

  11. Foundations of Amateur Radio

    An often repeated statement about the purpose of our hobby is related to emergency preparedness. The various peak bodies around the world devote plenty of resources to the concept, with helpful examples, umbrella organisations, training, coordinators, grants and funding, photo-opportunities and all the other trimmings that come from the idea that you and I are going to be of assistance in the case of some or other emergency.

    Looking up the various emergency coordination groups is a disappointing experience. From broken web-sites with non-existent pages to latest news that's over two years old, through to the latest sausage sizzle and fun-run. Entreaties to make sure that you have your current Membership ID card, otherwise you won't be covered for insurance purposes. As I said, all the trimmings with lots of evidence of paper pushing and little or no evidence of actual preparedness, let alone public information that might help any new or old radio amateur become prepared.

    Back to the topic at hand and leaving aside the nature of the emergency for a moment, given that the response for a bush-fire, a cyclone, flood or pestilence is likely to be different.

    Let's look at the things we have direct control over.

    If you have at any time taken your radio out of the shack and carried it into a paddock, connected it to an antenna, fired it up and made a contact, you're well ahead of the curve.

    There are plenty of amateurs who have never ever considered what going field-portable might look like, let alone tried it. That's fine if you live in a bunker, have independent power and are able to withstand all manner of disaster scenarios, but realistically it likely means that your emergency assistance will be of the kind that's outside the emergency zone. Helpful to be sure, but there's plenty of those stations to be found - unless the issue is global, in which case we have a completely different set of problems, pandemic, anyone, anyone?

    Let's focus on the other side of the fence.

    You're in an emergency zone. Doesn't matter what kind of emergency. Communications are limited or overwhelmed, information is restricted, messaging is hampered and you're a radio amateur with a working radio. If all goes well you should be able to help.

    So what does a working radio look like and what does helping mean?

    First thing to think of is power. Have you got a battery? Is it charged? When was the last time you tested it? How long has it been sitting on the shelf? Did it discharge in the meantime? What about a charger? Have you got a generator? What about fuel and oil? What about spare parts? Have you got something else, like a solar panel, a wind generator or a water turbine? What about a push-bike with a dynamo attached? How long does your radio run on a battery and at which transmitter power level is that?

    After thoroughly investigating power, what does your actual emergency station look like? Will it be used for voice communication, or will it be used as a digital gateway? Can you use it to send rudimentary messages, or can it be used as an internet gateway for a local community?

    What bands are you planning to operate on? Do you have an antenna? What happens if your current antenna is taken out by a fire, lighting strike or something else? When was it last tested? Do you have a back-up antenna? Have you actually used this antenna? Does it have all the right connectors and are they with the antenna?

    So, pretend that you got all that right. What about you? Have you got spare clothes? Food? Shelter? Medication? What about Personal Protective Equipment, masks, gloves, what-ever? What about ancillary items like pen and paper? Do you have power for the laptop that's being used to create the digital mode messages?

    Note that I've not said a word about the usefulness of any of this. This is the base level of preparedness just so you can actually look yourself in the mirror and say that you have at least got a level of ability to be of assistance in the case of an emergency.

    You can of course argue that you should hook up with the local emergency services and offer your skills as a radio amateur. That's helpful, but what if you cannot actually go to the muster point? How does that help?

    Now lets pretend that you actually have done all this. When was the last time you tested it?

    What does the actual helping look like?

    Have you ever attempted to pass emergency messages? What about messages that must be transferred absolutely 100% correctly, think medication dosages? Who did you pass them to? When was the last time you did a regional emergency simulation between your amateur friends? How often do you do this? Once a decade, or more often than that? What if the local repeater isn't working? What about in your club or your local neighbourhood? Do your neighbours even know you exist?

    The point of all of this is to reveal that the level of emergency preparedness for radio amateurs is in my opinion spotty at best. If you disagree with me because you are prepared I'd like to ask if you helped prepare your local amateur community and the wider community around it? I don't doubt that there are individuals, even groups who are prepared, but I suspect that they are far and few between.

    When was the last time you actually went into the field for a week and played radio, for real, battery only, limited resources, no outside help?

    I'd love to believe that this is universal, but you and I both know that there is plenty more to be done. How realistic is your emergency preparedness and what are you going to do about it?

    I'm Onno VK6FLAB

  12. Foundations of Amateur Radio

    One of the things I love most about this hobby is the ability to randomly dart off into any related direction and learn new stuff. For example, the names Nikola, Guglielmo, Heinrich and Edwin emblazoned on a t-shirt sent to me by a very appreciative listener Jack KI4KEP, started an exploration into the deeds and misdeeds of the people behind those names.

    The first three might be somewhat familiar, Nikola Tesla whom we have to thank for inventions like Alternating Current, the Tesla coil, wireless power, radio remote control and many others. The Tesla company is named as a tribute to him. The magnetic flux density uses the letter T as its symbol and its called the Tesla.

    As a side note, if you've ever struggled to decide if a symbol needs to be a capital letter or not, like say the V for volt, the A for ampere, the O for ohm, the m for meter, the s in second or the K in kelvin, you just need to remember that if the unit is named after a person, the symbol needs to be a capital letter. That does assume that you know that the unit is named after an actual person, like say the Earl of Sandwich.

    Name two in our list, Guglielmo Marconi is the person whom we can thank for the practical development of radio communication, using improved spark-gap transmitters, the development and commercialisation of long-distance radio transmissions and his association with many other services such as a transatlantic radio-telegraph service, providing communications to shipping such as Jack Phillips and Harold Bride who were employed by the Marconi International Marine Communication Company to act as radio operators on the RMS Titanic on its fateful voyage.

    Our third name, Heinrich comes into sharp focus when I add his surname, Hertz. His name continues on in our day-to-day language and Heinrich Hertz is responsible for validating many of the underlying principles of our hobby. Using a spark-gap transmitter he was the first to conclusively prove the existence of electromagnetic waves which were predicted by James Clerk Maxwell. He also came up with the parabolic antenna, the dipole antenna, measurement of electric field intensity, electromagnetic waves and many other experiments. If you've ever seen a bullet hole in glass, you've seen a Hertzian cone.

    The last name had me stumped. It took a question to learn that Edwin shares a name with a famous cyclist and a famous astronaut, namely Armstrong. Edwin Howard Armstrong has been called "the most prolific and influential inventor in radio history".

    If you're like me you may not have heard of Edwin Armstrong. You might be surprised to learn that he's responsible for the regenerative circuit, the super-heterodyne circuit and while he was working on defending his invention against a claim made by a patent attorney he stumbled on the super-regeneration circuit. If you're a radio amateur, you'll likely have heard those terms, if not, they're electronic circuits that make radio receivers more sensitive which forms the basis of many radios in use today. My Yaesu FT-857d is a super-heterodyne radio for example.

    It doesn't stop there. The biggest claim to fame that Edwin Armstrong brings to the table is the invention of FM radio. It took many years and a protracted lawsuit that lasted until almost a year after he died to finally have Armstrong formally established as the inventor of FM.

    Not for a minute will I suggest that my exploration was comprehensive or in-depth, but it made my day when I put on a t-shirt with the names of those inventors who made it possible for me to be here and share this with you today.

    On the shoulders of giants wearing a t-shirt with their names I stand.

    I'm Onno VK6FLAB

  13. Foundations of Amateur Radio

    A regular lament is the lack of things to do in our hobby. I know, it's foreign to me, but there are plenty of amateurs who express frustration at the lack of activity, no contacts, nothing new, no challenges.

    For my poison, I started the process of contacting 100 different countries using 5 Watts. I've been at it for a number of years and truth be told, since my latest domestic move, over two years ago now, my efforts have been put on hold. Not because I didn't want to, but because I was getting annoyed with having to leave my home and wanting desperately to have a functional shack at home. As you might know, that's a project that's still in hand and thanks to some magnificent assistance from various places, I'm still making progress.

    That said, your perspective might be dulled by the notion that this pretty much concludes the on-air activity possibilities that exist. Within my own license class, until recently, I was permitted to use voice modes like SSB, AM and FM and I was permitted to use hand-keyed Morse. I have access to 10 Watts and am currently allowed to use six different amateur bands, namely 80m, 40m, 15m, 10m, 2m and 70cm. So together with the four modes, I'd be able to make 24 different contacts to 100 different countries, that's 2400 different combinations.

    Of course there are more than 100 countries, that is, DXCC entities. The 2018 list has 340 of them, so that's over 8-thousand different options for getting on air and making noise.

    Last year all that changed. The local regulator in Australia, the ACMA decreed that all amateurs in Australia were permitted to use all modes.

    It's taken a little while for that to sink in. Specifically what it means for me.

    A quick search reveals that there are at least 60 different digital modes, think RTTY, Olivia, PSK31, etc. In addition to those, there's a plethora of other modes like IRLP, AllStar Link, EchoLink, CODEC2 and Brandmeister.

    So conservatively I'm going to estimate that I now have got access to over a hundred different modes, across six bands with 340 countries, that's over 200-thousand different options for making a contact.

    Of course it's unlikely that I'll make a contact between say Belize V3A and Perth VK6 on 2m using Olivia, but even if we limit our calculation to HF, we still have at least 136-thousand opportunities for adding something interesting to your logbook.

    I've been hunting for a canonical list of all the various amateur modes and the tools needed to make and receive them. No doubt that will take me some time. I'll be documenting it on the projects page on vk6flab.com if you want to follow along. Speaking of which, you'll also find past episodes of this podcast there.

    I suppose I should start by converting my current efforts into some pretty pictures that show what I've been up to so far, but that's a mapping exercise that I'll have to add to my to-do list, since I'm guessing it involves learning how to use some fun mapping tools.

    If 136-thousand opportunities isn't enough, you can also add grid-squares, large and small, different prefectures in Japan, provinces in the Netherlands, CQ zones across the world or ITU areas, prefixes and operating modes.

    Clearly there's plenty to do and see.

    I wonder if there's an award for all modes all bands all countries and I wonder what happens if someone invents a new mode?

    I'm Onno VK6FLAB

  14. Foundations of Amateur Radio

    The other day I bumped into a concept that I've heard repeated before. The so-called "impersonal nature" of digital modes.

    There's this idea that any communication that isn't using voice, is devoid of the human touch. Often this assertion is specifically made in relation to modern digital modes like JT65 and FT8. As an aside, I've never heard it in relation to other digital amateur modes like slow-scan television, RTTY or PSK31.

    In the early 1900's when amateur radio was beginning to be a thing, the means of communication was Morse Code. With beeps across the globe contacts were made between amateur stations. With every incoming dit and dah, letters were received, words constructed and meaning derived. This is long distance communication in its early stages.

    Each amateur was said to have a fist, their particular rhythm of touching the key. Across multiple stations it was possible for an experienced operator to distinguish between two amateurs based on how they were sending Morse Code. I can confirm that if you've ever had the privilege of hearing lots of amateurs clamour in a so-called pile-up, you can hear for yourself that different stations sound different, even if they're all sending Morse Code.

    So on the one hand we have this deeply inhuman means of communications like Morse Code which is by the language we use considered to be made by humans, personalised with a fist. On the other hand we have a deeply technical mode like FT8 which isn't.

    During the week I was discussing this change of perception during a haircut. I pointed out that this happens everywhere. For example, in the hairdressing profession an electric clipper might have been seen as impersonal when it was invented in 1921. Today it makes quick work of a Number 1 cut. In mobile phone communication an SMS was seen as impersonal with voice preferred, but today the world would look quite different without the 5 billion messaging mobile phone subscribers. In 2013 it was estimated that there were 8 trillion SMS messages, and 10 trillion other smart phone messages. As you might realise, behind each of those messages is a human, well, apart from the SPAM and the computer notifications, but even those are programmed by a human.

    So what makes the difference between Morse Code and FT8? Why is an SMS impersonal in 1992, but preferred by most today?

    I'd hazard a guess and state that the experience of the person making the statement has a lot to say about their perception of the nature of the medium.

    My typing away at a keyboard and seeing words appear on my screen might not appeal to someone who chased a turkey around the yard in search of a quill, but then electricity might also be surprising.

    It's interesting to me that PSK31, something that's not particularly thought of as being impersonal, was introduced to the amateur radio community in December 1998 by Peter G3PLX. The first Weak Signal modes, commonly known as WSJT modes, were introduced in 2001 by Joe K1JT, only three years later. JT65 came around in 2003. We have this situation where PSK31 is not impersonal, but JT65, which is five years younger, is considered impersonal and the popular mode FT8, which is an extension of JT65 is said to be the end of the hobby.

    If hyperbole would relate to truth, the end of our hobby in sight, we should all get rid of our radios and hand back our licenses.

    Perhaps we should take a step back and notice that behind every FT8 station, behind every voice-call, behind every amateur transmitter is at some point a human with a license. If we're splitting hairs, then a local automatic voice repeater must be the height of impersonal.

    The other thing I'd like to point out is that how you perceive the use of a particular mode is also important. If you think of FT8 as having a personal beacon in your shack that uses your radio and your antenna to measure how well your signal is heard across the globe, you might just start enjoying this so-called impersonal mode.

    One of my friends, Wally VK6YS, now silent key, told a story where he was driving down the highway to meet his friend. They were chatting away using Morse Code, Wally in his car, the friend in his shack. Once Wally arrived the friend wanted to see how Wally was able to send Morse Code whilst driving and could he please see his Morse key? Wally confessed to having whistled into his microphone to make the contact, since he didn't have a Morse key in his car. According to Wally, his friend was off the air for months in disgust.

    I should mention that my Number 1 haircut looks great, if only for the fact that it allowed me to spend some quality time discussing and contemplating the nature of the hobby that I love.

    I'm Onno VK6FLAB

  15. Foundations of Amateur Radio

    In my day to day activities as a radio amateur I come in contact with people across all parts of their amateur journey. Some who don't yet know that they're amateurs, through to those who've just passed their test and are waiting for their callsign. Then there are those who have been amateurs for a while, experimented a bit and have settled down into the comfort of being a member of an active community. Stretch that further and I also spend regular quality time with amateurs who have been licensed longer than I've been alive.

    Recently I received an email from a freshly minted amateur. Just like me, still pretty much wet behind the ears, keen as mustard, trying very hard to figure out what to do next and where to go.

    The basic gist of the email from this amateur was that they didn't know what kind of antenna they could erect at their home and failing that, couldn't decide on what radio to acquire to match the antenna that they hadn't decided on, not to mention that the antenna needed to match the radio that didn't yet exist.

    If you've been around this community for a while you might recognise the chicken and the egg, which comes first, the antenna or the radio?

    The answer is obvious, hidden in plain sight, easy to deduce, simple to understand, and completely useless.

    Let me help you with the answer: It depends.

    If that didn't test your patience, even if you've been an amateur for longer than my parents have been alive, you'll know that this is an unanswerable question.

    So how do you break the egg and get started?

    Easy.

    Start somewhere.

    As it happens I have a recommendation. It's cheap, simple and it will get your feet wet sooner rather than later. My recommendation is neither, or both, depending on your perspective. I promise, I'll get to the point shortly. The reason I'm making it last and savouring the point, some might say, belabouring it, is because it's one that happens over and over again, day in, day out, year in, year out.

    My recommendation is that you spend $25 on an RTL-SDR dongle and hunt around your home for a piece of wire. That's it.

    If you're not familiar with an RTL-SDR dongle, it's essentially a USB thumb-drive sized device that plugs into the nearest computer and paired with the correct software it has access to many if not all of the frequencies that you as an amateur are allowed to play with.

    Given that it's a receiver, the antenna doesn't really matter all that much, at least not initially, so any piece of conductive wire will suit. Most dongles even come with an antenna of sorts, so you can get started straight away.

    Resources associated with this podcast are on the vk6flab.com website where I've also collected a few links under F-troop to get you on your way with an RTL-SDR dongle.

    The purist radio amateurs will likely arc up at this point and mention that this isn't real amateur radio, to which I can only say: Bah Humbug. Radio is about receiving as much as it is about transmitting. Any fool with two bits of wire can transmit, but it takes finesse to receive, so start there.

    There are other benefits from going this way. Other than ease of entry, that's another way of saying - cheap - you can easily spot where and when there is activity. You can use all the traditional modes like CW, SSB, AM and FM, but you can also play with all of the new modes like WSPR, FT8, JT65 and investigate some of the other modes like RTTY, PSK31, Olivia, SSTV and others.

    All this will help you have a better idea of the landscape you're stepping into without a major purchase.

    To really set a cat among the pigeons, I'm also looking into a Raspberry Pi based transmitter, rpitx by Evariste F5OEO. When that bears fruit I'll let you know. In the mean time, play, learn, listen, experiment. No need to spend hundreds or thousands of dollars while you're still unsure.

    Even if you already have a lovely amateur station, an RTL-SDR dongle is worth every cent and then some.

    I'm Onno VK6FLAB

  16. Foundations of Amateur Radio

    Every person is the product of their environment. Unsurprisingly this is even true for radio amateurs. That's not too say that we can't break our mould, but it takes effort. I grew up around technology in the 1980's. As a result I'm familiar with 8-bit microprocessors like the Motorola 6502 which featured heavily at the time. I tend to think in terms of the presence or absence of a signal, rather than the intricacies of circuits and components.

    As a child of my time, I'm not particularly familiar with the punch card or paper tape, or core memory, or valves, 386 machine code or what's in an FPGA. As a direct result of my age, my knowledge and understanding of circuits is sparse at best. I understand basic components like resisters and capacitors in a DC setting, Ohms Law and the fun you can have with a battery, a few resistors, diodes and an LED light.

    As a radio amateur I've been introduced to how some things work differently in an AC circuit, like an antenna and a feed-line.

    Until very recently my knowledge about filters was based on what I'd read. I know that there is fun to be had with coax and stubs and other cute things, but how and why they work eluded me. Today I'm a step closer.

    Before I dig in and share some of what I've learnt, let's have a quick look at what a filter is and does. You'll have likely heard of high-pass and low-pass filters. You might have heard of band-pass and band-stop filters.

    If you think of a high-pass filter as a device that lets through high frequencies and a low-pass filter as a device that lets through low frequencies, we're already well on our way. If you put a high-pass filter together with a low-pass filter, you end up with a range of frequencies that doesn't pass, known as a band-stop filter.

    Similarly, if you tweak the frequencies that pass just so, you can combine a high-pass and a low-pass filter to make a band-pass filter.

    Let me illustrate.

    Imagine a 15m band-pass filter. It allows all frequencies in the 15m amateur band through, but blocks everything else. You could construct such a thing from a high-pass filter that allows 15m and above through combined with a low-pass filter that allows 15m and below through. Everything below 15m is stopped by the high-pass filter and everything above 15m is stopped by the low-pass filter. The gap between the overlap of the high-pass and low-pass filters is what creates a space where the 15m band gets through.

    If you move things around a little, the same can be constructed to make a 15m band-stop filter. Something that lets anything through, except a 15m amateur signal. To make such a gadget would require a low-pass filter that allows everything below 15m combined with a high-pass filter that lets everything above 15m through.

    So, if you can construct a high-pass filter and a low-pass filter, you can pretty much create any combination and allow or stop specific frequency ranges.

    If you're wondering why this might be useful, think about a contest. Two radios in the same shack. One transmitting on 15m and one on 40m. These two bands, one at 21 MHz and one at 7 MHz are third harmonics to each other. This means essentially that a radio on 40m affects one on 15m and vice-versa. If you had a set of filters that stopped 15m and passed 40m on one transceiver and a set of filters that stopped 40m and passed 15m on the other, both of you would be much happier.

    You don't need to do contesting to benefit from a filter. If you use an RTL-SDR dongle, it's affected by nearby strong signals, like say a local radio or television station. That's fine if that's what you're trying to hear, but not so much if you're trying to hear something else. Filters can help to make your life better.

    Now, to round this off at a suitable point, you can think of an inductor as device that lets low frequencies through but blocks high frequencies. Similarly, a capacitor is a device that blocks low frequencies but lets high frequencies through. So, it's fair to think of an inductor as a low-pass filter and a capacitor as a high-pass filter. The symbol for a capacitor is the letter C (Charlie) and for an inductor it's the letter L (Lima).

    You could make a circuit that either directly blocks from a certain frequency, or one that lets it through, but sends it to ground. This gives you two designs for a low pass filter one using an inductor or an RL circuit and one using a capacitor or an RC circuit. Similarly you can create a high-pass filter using either an inductor or a capacitor. That gives you four designs for two filters.

    Each of these can be combined to create band-pass and band-stop filters.

    The maths behind it isn't particularly daunting with basic high-school maths and if you want to see it happen before your eyes, check out the "Organic Chemistry Tutor" on YouTube. The play list you're looking for is cleverly disguised as "Electronic Circuits".

    As a direct result, I started hunting for breadboards, but it turns out that you can simulate these circuits online using any number of simulators. Of course there's going to be a gap between simulation and reality, but that's when you get out your soldering iron.

    Remember, if you smell chicken, you're holding it wrong.

    I'm Onno VK6FLAB

  17. Foundations of Amateur Radio

    If you've ever found yourself in the position of attempting to screw a PL259 into an SO239, or an N-type plug into an N-type socket you'll have likely come across the situation where the thread doesn't quite fit. If it does, you might have issues attempting to undo the connection, even if you didn't particularly do anything strenuous in relation to mating the two in the first place.

    This kind of situation happens to me more than I think is reasonable. It happens on cheap connectors, on expensive ones, on the back of radio gear, on adaptors, patch leads and the like.

    Initially I put this down to cheap vs. expensive, but that really doesn't add up if you're attempting to connect an expensive plug into an expensive radio.

    If you're into machining you'll know about swarf. If not, think metallic dust. Of course it doesn't have to be metallic, it could be a single grain of sand, or it could be a slightly damaged thread.

    A couple of months ago I went on the hunt for a tap and die set that would solve this issue once and for all. If you're not familiar with the terms, a tap is like a long bolt with a square head and a die is like a thick washer with holes cut out.

    In addition to being hardened, they each have cutting edges, which allows these two tools to do their job, the job of cutting threads.

    Normally you'd use a tap to make a thread into a hole that you've drilled. You'd use a die to make a thread onto a rod that you have. There's lots of technique associated with this, cutting fluids, alignment, pressure and the like. Plenty of relaxing YouTube videos around - which is how I came upon this idea in the first place.

    You can also use a tap or a die to cut across an existing thread and you can do this with connectors.

    A die, threaded over a socket, will clean up the socket threads. Similarly a tap screwed into a plug will clean up the plug thread. There's a disclaimer coming for that last point, but stick around.

    Trying to find a tap and die to match can be a challenge. The PL259, SO239 and N-type connectors are all 5/8th size threads. They're 24 turns per inch, and also known as UNEF (Uniform November Echo Foxtrot) threads, or Unified Extra Fine.

    So if you start on your hunt, you'll be looking for 5/8th, 24 TPI, UNEF taps and dies.

    I found mine online at $15 or so from a US supplier. Got to me in about a week.

    When they arrived I immediately set about cleaning up all my sockets. This was amazing, all of a sudden stuff started fitting well. Unfortunately I couldn't use the tap. The centre hole in a standard tap isn't big enough for the pin of a PL259, let alone an N-type connector, but a friend of a friend has access to machine tools and made the centre hole bigger. Word of warning, this is hardened steel. A hand-drill won't cut it.

    I must mention that this won't allow you to use the tap inside an N-type plug, but you can use a die on the socket.

    I'll also point out that if you need to use a tap wrench or a die holder, you're doing it wrong. We're cleaning up the thread, not making a new one. If you need extra force the most likely scenario is that you've cross threaded the tool onto the connector.

    Of course if you've got a completely stuffed connector thread, then these tools can help, but you might want to consider replacing the connector.

    My tap and die live in my go-kit right next to the coax adaptors. On my next field-day I won't be having to deal with poor connections, nor will I have to worry about unscrewing them after the event.

    A tap and die, great simple tools to fix a recurring issue.

    I'm Onno VK6FLAB

  18. Foundations of Amateur Radio

    If you've ever had the pleasure or misfortune to hear an on-air net, you might have considered, however briefly, how that net came to be, how it's run and what's involved behind the scenes to make it happen.

    I host a weekly net called "F-troop". It's been running every week since the 12th of June in 2011. Since then I've made over 5000 contacts with stations scattered all over the globe. A typical net has about ten people, but depending on the weather, what's on TV or if people had a hard Friday night that number fluctuates. The biggest was about 40, the smallest just two.

    At this point I could tell you that the infrastructure to make this happen, the preparation, management processes, network and marketing are what take up the bulk of my week. I mean, there might be a weekly stand-up between stakeholders on a Wednesday, a plan for the content, what to discuss, you know, the typical.

    If I told you that, I'd be lying.

    The reality is that F-troop is an organic animal. I generally get to my radio a couple of minutes before we start, midnight UTC, switch on, kerplunk the local repeater and wait for the clock to tick over.

    I then launch into my opening spiel, something along the lines of: "Hi folks, it's me, it's F-troop, who's awake?"

    After taking a few calls and logging them, I'll circulate through, call for more people, rinse and repeat.

    There are two invisible things happening, one required, the other I do because I'm a computer geek. The required activity is logging. I chose to log in an online spreadsheet. It's helpful because it makes for a single place where all contacts are stored and it allows for others to host the net if I happen to fall off the air, either by being somewhere else, like a holiday every decade or so, or because my radio isn't being cooperative.

    The other thing that logging gives you is a memory. I generally recall a person's name from their callsign, but if you listen closely you'll notice that every now and again I'll extend my babble so I can search for a callsign and appear not to be suffering from memory loss.

    The other thing that happens is that I update the website. I'll be merrily adding articles from emails or discussion as it's happening. If someone mentions a product or a website, a callsign or a project, I'll often be searching for it in real time and adding it as a post to the F-troop website. That way people who want to refer back at a later time, that includes me, can search and find the thing that someone showed us.

    As simple or as complex as that sounds, depending on your level of experience, it's really not rocket science. You can do this with pen and paper. I know, I've done it, standing in a car-park with a notepad, whilst dodging rain showers and preparing for a field-day. It's fun to test your skill and to get out of your comfort zone every now and again.

    I should interrupt this story for a word from our sponsors. Don't have a kitten, we're not talking about advertising, we're talking about repeater and network operators who graciously give of their time and resources to link the main F-troop repeater to others around the world. The network of AllStar, Echolink, IRLP and IRN radios that carry F-troop is astonishing to me. We have regular participants all over Australia, the United States and the United Kingdom. There have been contacts with stations in Asia and Europe.

    For that to happen I don't do a single thing. Well, technically I let repeater operators know I exist and when it breaks, but that's pretty much the sum total of my efforts.

    Why am I telling you this?

    Last week it broke. My radio was acting up and someone commented on that. I handed over the reigns and let them at it. They were very unsure. I let them know that F-troop is for beginners. It's expected that people are going to make a mistake, I know I do, plenty of times.

    It occurred to me afterwards that hosting a net can be scary. If you have no idea what's involved, how to make it happen, what to do, then hosting must be immensely daunting.

    I hope that sharing how I do this will give you the confidence to host your own net in your own community. Perhaps you can tell me more about it, or come and visit F-troop. Saturday morning at midnight UTC. If you want I'll even help you host it.

    I'm Onno VK6FLAB

  19. Foundations of Amateur Radio

    When you switch your radio on to start a radio fishing expedition you join all the other spectrum users across the planet. To be fair, you'll likely only become aware of some of those for the time that your radio is switched on, even if there are thousands around.

    One of the ways you can find other users is by ditting out "QRL?" in Morse or saying "Is this frequency in use?" into your microphone.

    This simple courtesy of checking to see if the frequency you're on is actually being used by someone, is part of your license. You're taught to do this and it's expected.

    What's not clear is what happens next.

    It's simple if you hear a callsign, or a "yes", but what if you hear nothing?

    Sometimes nothing means exactly that, there's nobody on the frequency, but that's not always the case. There's plenty of opportunity for the frequency to be in use and you still not getting a response back.

    Let's imagine for a moment that the frequency you're on is in use by two stations talking to each other. You come on frequency, hear nothing and ask if the frequency is in use. You hear nothing. You try again, still nothing. You start calling CQ. Moments later, you get an earful from some random station.

    Sound familiar? If it doesn't, you'll need to spend more time on-air. I can guarantee that you'll experience this in your amateur adventures, much more than once.

    How does this happen? You did everything right.

    Imagine two stations, let's call them Amanda VK4FRST and Marc VK3OHM, having a conversation, a QSO. They're discussing the ins- and outs of the WIA awards system and having a grand old time.

    You turn your radio on, happen to tune to the same frequency as their QSO and after listening to nothing for a bit, you call "Is this frequency in use?". You still hear nothing so you try again: "Is this frequency in use? VK6FLAB". Still nothing. You call "Nothing heard." and start calling CQ.

    You're on one side of the country, Amanda and Marc are on the other side. They cannot hear you and you cannot hear them. Then the sun moves a bit and all of a sudden your CQ is all over their discussion. Unhappy people on both sides of the country.

    There are six paths to consider here. The one between you and Amanda, and the reverse. Similarly the path between you and Marc and that reverse. If you ask for frequency in-use, neither Amanda, nor Marc can hear you. Similarly, you cannot hear either Amanda or Marc. You should also take a moment to consider the path between Amanda and Marc and vice-versa. They might have a really great 5 and 9 conversation, or they might be struggling along with a 3 and 2.

    I've simplified this, because of course, you calling over the top of a conversation can also disturb the contact under way. Saying that the frequency is in use makes it worse.

    While all this is happening, the sun is moving, the ionosphere is moving, propagation is moving, the whole thing is like the Cat in the Hat balancing on a beach ball, complete with cake, rake and a fish still in its bowl.

    The first thing you need to do when this happens is stop and take a breath. Nobody owns any frequency, so claiming that this is your frequency is not going to help anyone. If the other station is having a QSO and you're calling CQ, it's time for you to move, change frequency and QSY.

    If you're Amanda or Marc, you can tell your contact that there is some interference and then call the other station that the frequency is in use. If they change frequency, all good, if they don't, tell your contact to change frequency.

    There's no need for aggravation. There is no ownership. There's no point in getting upset and no mileage in making life hard for the other station. The fact of the matter is that there was what we call in networking, a collision. It's time to back off and renegotiate.

    All this is exactly the same if you're using voice, Morse, FT8, or any other mode.

    Take a breath, renegotiate, move on.

    Now, if you're a QRP station like me, it's much more likely that you'll not be heard most of the time. In that case it's often much quicker to just to move without going through the negotiation process. Of course you can attempt to make a QRP contact with one of the other stations, but it's considered pretty rude to stick your head between two people who are having a cup of coffee together and ask them for their autograph, so don't do it on air either.

    If you assume malice from the get-go, you'll find yourself unhappy most of the time. If you celebrate that all of a sudden there's propagation between VK6, VK4 and VK2 you'll end up much happier with your on-air experiences.

    While I'm giving out advice, here's something I learnt during the week.

    If you break a toe, tread carefully. Stubbing a broken toe hurts. Really. Badly. In case you're wondering, my new boot is not a fashion accessory.

    I'm Onno VK6FLAB

  20. Foundations of Amateur Radio

    When you become a member of the amateur radio community you become part of a small group of humans who know and understand certain aspects of life. That's not to say that others don't share this or that the knowledge is unique or special, but radio amateurs are required to know this before they receive their license.

    In the past I've spoken about how getting a license is like receiving a key that opens the door to the world of radio communications. It's one of the more accessible ways to grab hold of this key and it's the recipe for life long learning.

    During the week a friend of mine, a newly minted amateur, pointed out that this represents something that the general population isn't aware of or attaches little in the way of value to. The interconnectedness of radio spectrum is something that radio amateurs take for granted. To us it's obvious. A transmitter on 3585 kHz is fundamentally the same as one on 92.1 MHz. A key fob on 434 MHz is similar to a computer on 2.45 GHz as is a laser on 500 THz or an X-ray machine on 30 PHz.

    As a radio amateur we're taught that the radio spectrum is a continuous phenomenon and that spectrum is shared among users with specific rules around interference and interaction.

    Another thing we know as radio amateurs is the difference between the front and the back of a Yagi-antenna. We know about radiation patterns, about the ionosphere and how the sun and sun-spots interact with some of our activities.

    The point is that our knowledge, it's fair to say, specialised knowledge, even at the lowest level of licensing, exceeds that of the general public.

    This is all by way of background because this leads to something that I learnt during the week.

    As amateurs we have a responsibility to be custodians of that knowledge, that is, to care for it and to ensure its accuracy and to preserve that knowledge.

    For some amateurs that means that they want this information to be exclusive, but for me it means that this information should be shared and nurtured and encouraged in those people who make choices based on incorrect information.

    For example, as a radio amateur it's my duty to inform a person who is contemplating breaking the radio spectrum licensing rules that they are doing so. Not because I'm a regulator, but because I have specialised information that they lack. Importing a radio module that's using a frequency that's not available in your country is an example of something that I am compelled to point out.

    I know that some amateurs take this compulsion to the next level and become a de-facto police officer attempting to enforce those restrictions. I understand where that comes from, but I also know that this is not my role and it's not your role. If you feel strongly enough about a transgression, perceived or real, there are plenty of ways to deal with that. Reporting the offence to the regulator is one option for example.

    Knowing which end is the front of a TV antenna means that you can point out a mistake to a home-owner about the direction their antenna is pointing at, but it doesn't mean that you need to climb on their roof to turn it around.

    I've said many times before that having an amateur license is a privilege. It's a gift, even if you worked hard for it, it was given to you, bestowed on you by the regulator in your country.

    It seems to me that having such a gift means that it should be treated as such. As radio amateurs we're not entitled to a license, nor are we entitled to transmit. We're granted permission to do so.

    I think that it's important to keep that in the back of our minds when we set out to educate those around us.

    As for the education itself. It pays to consider what you take for granted when you're giving advice. Telling a person about Wi-Fi propagation through a home is a complex topic. You can make the explanation as hard or as simple as you want, but don't expect that the person receiving the advice has the same background information or interest that you have.

    I was once told by a statistician about how various statistics worked and what their background was. I was translating a program from Modula-2 into WingZ hyper-script. I didn't care about how it worked, just that the provided code did what it was supposed to and that what I wrote did the same thing. I had no interest in becoming a professor in statistics, despite the earnest instruction enforced on me by my employer 30 years ago.

    It's been said that you must learn from the mistakes of others. You can't possibly live long enough to make them all yourself.

    What and how we teach those around us can be the seed of something bigger. I may well have become a statistician if the information had been tailored to my requirements, but that chance was lost 30 years ago.

    I think it's a great way to consider what we teach and how.

    I'm Onno VK6FLAB