Foundations of Amateur Radio

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When failure doesn't matter ... Nov 18, 2018

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Foundations of Amateur Radio

The other day I read a message from Theodore KS5I who has been around the block a couple of times. He recalls the excitement he experienced when he was first licensed in 1967, the year I was born.

He described that at the time transistors were just coming into their own and it was so wonderful to be learning about them.

The closing sentence sealed it for me:

Theodore wrote: Perhaps, its time for some of us more mature operators to release the past so our hands are free to grab hold of the future and share the enthusiasm of those who look ahead with the same hope and excitement that we had so many years ago..

It's that level of enthusiasm that our hobby needs to foster and develop. The landscape we live in is changing all the time, but new adventures are always just around the corner. They might not look like what was available 50 years ago, or last year, or even yesterday, but they too have their place in the pursuit of amateur radio.

Learning is a lifelong activity. If you stop learning, you - as Theodore eloquently puts it - just die.

Learning can be scary. Educator Eduardo Briceño talks about the learning zone and the performance zone. The learning zone is when the goal is to improve, concentrating on what we've not yet mastered and the expectation is that mistakes will happen.

The performance zone on the other hand is when we do something as best as we can. We concentrate on what we already know and try to minimise mistakes.

Amateur radio can operate in either of those zones, doing a contest and going hard can be a performance zone activity, do what we do, do it fast and avoid mistakes.

We could also see our activities as a learning zone. We try new things, some will work and some will fail. If we're doing a contest as a learning activity, what skill do you want to master? Is it handing off the QSO, taking the log, recognising a callsign, knowing the CQ zones, matching prefixes to countries and antenna directions, picking the right band, managing battery life or recognising the band conditions?

Pick one of those skills and try different things, expect mistakes and learn from them. Over time the thing you practised will be a new skill you've mastered, ready for use when you're going hell for leather in the CQ WW making contacts left right and centre to the envy of your peers.

Of course, this doesn't just apply to contesting. For me it's currently about electronics, about figuring out how stuff works and how to apply that to my shack. For you it might be something else in the myriad of options that the 1000 hobbies that amateur radio represents.

Life is about growing. Amateur radio is a journey, not a destination. Closing off your options because valves are no longer in vogue and Allstar isn't real radio is just a recipe for stagnation.

If you have a dozen minutes to spare, check out Eduardo Briceño's TED talk: How to get better at the things you care about

One final point.

If you're new to this adventure, your license still wet, then you don't know what you don't know, so you'll spend lots of time in the learning zone. Don't be afraid, it's a great place to be and a wonderful way to explore the hobby in all its variety.

I'm Onno VK6FLAB

The Golden Age of Amateur Radio is Now Nov 11, 2018

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Foundations of Amateur Radio

Imagine 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

Everything you wanted to know about amateur radio but were afraid to ask! Nov 04, 2018

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Foundations of Amateur Radio

There are people who ask questions and there are people who answer them. Sometimes the people who answer even know what they're talking about, but sometimes they just repeat what they've been told without any form of critical thought.

The reason I raise this is because when you're a new amateur with a shiny new license, you're like a little puppydog, going from tree to tree to have a sniff. Does this smell good, what about this, ooh, that's a nice smell, I wonder what it tastes like.

Puppydog analogies aside, as a new amateur you're filled with questions and uncertainty. You don't know what you don't know, you don't know how much you don't know, your license is still wet, so even if you know something, it might not be true.

Interestingly the more I look at this, the more I find that new amateurs, filled with questions are more likely to dig around in the fundamental understanding of things and learn something along the way.

I've been around this community for a little while now. I obtained my license in 2010. I've learnt a lot of different things about this hobby, how it works, what the mechanisms, phenomenon, etiquette, physics and so-on make amateur radio work. Most of the time I'm learning about some or other new thing. Right now I'm learning about what a Vector Network Analyser is and how it works, so I can explain it to someone else.

Foundations of Amateur Radio is about how stuff works, much like Joe Kaufman's book - What makes it go? Though I read it in Dutch when I was growing up - Hoe zit dat in elkaar? There's another series of books by David Macaulay that are my inspiration, The Way Things Work, Unbuilding, Underground and Motel of The Mysteries to name a few.

It seems that my drive to ask questions is fundamental to my existence, my uncertainty doesn't scare me off, in fact the opposite is true, it gets me asking more questions, learning more things, gaining a deeper understanding and finding out more than I ever dreamt was possible.

If you're a new amateur, I'd recommend that you attempt to keep your curiosity alive. When you're faced with a fact, question it, attempt to discover what is underlying the response.

There are amateurs who think that to ask the question, Why is the length of a dipole calculated using some random constant? - is the equivalent of heresy, lack of skill, incompetence and the source of much derision, when it's clear that even a cursory search reveals that not only is the notion incomplete, it's wrong for most, if not all, examples.

My perspective is a little different and I'll admit that for some it might be confronting.

Why is it so?, What makes it go?, How come? and Why? are all questions to live by. You might conclude that a world where there are no certain answers is a scary place, but for my money the opposite is true.

Just because you think it's simple and answerable, doesn't make it so. If you walk in with your eyes open asking questions, then you'll be much more prepared for an unexpected response.

If you've just obtained your license and you're not sure about something, ask. You might not like or understand the answers, but that is just a recipe for more questions. Don't be deterred by those who provide certainty, the more certain they are of their answer, the more you should ask.

Amateur Radio is about experimentation, it's a license to play, a license to explore, it's a license to investigate.

For me Amateur Radio is encapsulated in a quote attributed to Albert Einstein: The more I learn, the more I realise how much I don't know.

I'm Onno VK6FLAB

Get on air and make some noise ... Oct 28, 2018

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Foundations of Amateur Radio

Get on air and make some noise is a phrase I use often to encourage amateurs to be active on-air and use the bands that are available to us.

One thing that's often glossed over is how to actually make that noise. It can be scary to make that first contact.

If you've got your radio installed, your antenna erected, your operating position set-up just right and you're ready to actually key your microphone, how do you do that and how do you get the attention of those around you?

First things first.

You need to establish if your radio is actually working as expected. If you're using a UHF or VHF radio, often the simplest way is to find a local repeater, key-up your radio and give your callsign. The result should be at least a carrier, a beep or a callsign in Morse-code. Some repeaters even have a voice ident, so you can hear that your action of keying the push-to-talk had an effect. If that isn't working, then there are lots of things you can troubleshoot, but that's for another day.

If you want to do the same on HF, unless you happen to be in a position that there is a repeater within propagation distance, generally only on the 6m and 10m bands, then you're essentially out of luck. There isn't a beep, or a carrier, or a voice-ident to be found. This means we have to solve the problem in a different way.

First of all, if you cannot hear any stations, the chances of someone hearing you are slim. So, the first thing to do is to check that the squelch on your radio is set to allow all signals to arrive at your speaker. Then find a band where it's noisy. When I say noisy, find one where there is lots of hiss. Generally speaking an open band, one where propagation is getting a signal to you, makes noise, lots of noise. There are exceptions to this, but for now, find the noise.

Depending on how you have your antenna set-up, you need to make sure that you're using the right antenna for the band you're using. Some antennas work on multiple bands, others only on one, it depends entirely on what you have got hanging off the end of your radio.

Once you've found the noisiest band, go hunting for beeps, as-in Morse-code beeps, or voices, or digital sounds. Find a signal, find evidence of activity. If you have multiple noisy bands, check them all.

You might recall that this is all dependent on the ionosphere, so depending on what's going on with the sun, things will change, sometimes within a minute, an hour, or weeks. Generally there is a difference between day and night and sunrise and sunset, so experiment.

Once you've found some activity, you need to find someone to talk to. If the voice you hear is weak, look for a strong one. The stronger the better. While this isn't universally true, it's a good starting experience. Every radio and antenna combination has a sweet spot on where you know that they can hear you, but you don't know yet what that sweet spot is, so trial and error is the way to go.

HF is not like the local repeater. The people on HF can be anywhere on the planet. They might be there for the first time, or for the third time that day having been on air for sixty years, it's hard to tell.

A good analogy is to think of a sport stadium with a hundred thousand people in it. There are people all around you and you're trying to make contact with one of them. You can pick their frequency, but they're likely to be talking to someone else. You might be interrupting a daily chat, a regular net, or happen upon a contest or a special event station. You don't know which one it is and sometimes you can't hear both sides of the conversation. So, before you key your microphone and make some noise, listen to what is going on.

Once you've figured out that the station you're hearing might be amenable to talking, wait for a break in the conversation, key your microphone and just say your callsign phonetically, once. If there's no break, that's a good indication that the other station doesn't want to talk to you, unless there is an endless stream of stations, in which case the going might be tough and you might be there for a while.

If the other station acknowledges your call, great, you just made contact. Confirm that you have their callsign and that they have yours, write it down with the time and frequency, then start with exchanging information, start with a signal report. In the beginning, less is more. Your first name and city is often more than enough.

All we're doing is establishing that we can talk to someone and that they can talk to us. Don't overdo it, get a feeling for what's going on.

Then do it again.

And again.

Before long you'll have some experience on how to get on air and make some noise and you can start learning about improving your skills, becoming familiar with your radio and being an active amateur.

Hopefully that wasn't so scary, and remember, every amateur had to make their first contact one day, even those who have been on-air for longer than you've been alive.

I'm Onno VK6FLAB

Celebrate accomplishments Oct 21, 2018

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Foundations of Amateur Radio

Mistakes are common in all aspects of life. Sometimes they are only known to you, other times they are public knowledge and open to ridicule and lambasting. Getting on air for the first time is an accomplishment and often the initial source of mistakes, mishaps and great frustration. Once you've made it on air, the reception to this feat is often underwhelming, people around you don't appear to appreciate the amount of effort you went to in order to key your microphone and for others to be able to hear that.

If you've been in this community for a while it's easy to forget what is involved to make that first contact and to dismiss those around you who've managed to obtain their license, acquire their equipment, install and configure it just so and to actually achieve the first visible milestone in their amateur radio journey, though technically it's audible.

If you've never done this, or if you have but have delegated it to the historical backwaters of your mind, here's an outline of some steps and mistakes along the path of making your first contact.

The first question you're likely to ask is, which radio followed quickly by, from where? Then, if you're like me and many other starting amateurs, you'll have set up your radio for operation on the local 2m or 70cm repeater, you're likely to have some kind of vertical antenna with the microphone gain and squelch set just so and have your radio set for FM. I'm skipping over power, the electrical type, but that in itself can be a feat of endurance.

After hunting around for a list of relevant frequencies, you might also have set up something like CTCSS to ensure that your signal actually gets acknowledged by the repeater.

If that's not enough, you'll also have made your radio use an offset which makes it receive using one frequency and transmit using another.

There's possibly more things you've had to do to make this work and not be subjected to the ire of the local repeater troll who appears to delight in telling you off when they feel you've done something wrong, like leave the roger beep activated or some other infraction.

If you did manage to achieve all these things and actually made your first contact on the repeater, congratulations and welcome to the hobby! Take a breath, you did well.

After a while you're likely to become more familiar with your radio and start exploring the local bands. You might program another repeater into your radio and even experiment with local simplex frequencies.

Each of these activities brings a new experience and new mistakes. For example, not all repeaters use the same offset, or even an offset in the same direction. Not all repeaters have the same CTCSS requirements.

If you're using a simplex frequency, remember to turn off the squelch - don't ask me how I know - so you have a chance to actually hear the other stations, even if you are using FM as the mode.

The process of getting on air as a first time user can be daunting, with many different points of failure along the way.

Ignore the trolls, try your best and ask for help if you get stuck and celebrate your accomplishment when you manage to make a contact.

My point is that achieving all this isn't trivial and it would be helpful if that's remembered from time to time. It's easy to dismiss an achievement made by another, but much more rewarding to celebrate it.

I'm Onno VK6FLAB

Everything you know about dipole (calculators) is wrong ... Oct 14, 2018

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Foundations of Amateur Radio

The other day I did an experiment. I searched for "dipole calculator" and using the first 20 results I calculated the length of a dipole suitable for 7.130 MHz. I chose the frequency for no other reason that there is a 7130 DX net every Monday, Wednesday and Friday and for the longest time I've been unable to participate due to the lack of a HF antenna in my new shack.

So here's some things I learnt from doing this experiment.

Depending on which calculator I use, the length of my dipole can vary by over a meter from longest to shortest result.

Depending on my desire to use metric or imperial measurements, my dipole will be a different length, because of course electrons move at a different speed if you're not using the metric system.

In case you're wondering, 1 inch is defined as being exactly 2.54 cm, so there's plenty of opportunity to vary that.

Speaking of standards, we all agree that the speed of light is a constant, right? Turns out that for some calculators, you can change the speed of light.

I'll skip over the notion that none of the calculators actually show what they're using as the speed of light and move on to other interesting discoveries.

Apparently you can determine the length of a dipole down to the sub-atomic length, with one calculator going down to the size of an electron to indicate how much wire you should cut from a spool.

There are forms that make doing the calculation really easy, single box to type in the frequency, so the answer must be right.

There are some that use random standard numbers, even a text book example that uses some number, but no indication where it comes from. For example, the number 486 features regularly, but so does 150 and 5905.

There are forms that provide you with several boxes, but no indication which box needs what value, so your answer may or may not indicate the number of eggs per chicken per parsec.

One dipole calculator result is actually for a vertical, so your search engine helping you might not actually give you the calculator you expect.

There are percentage correction factors. 5% seems to be a favourite number, but no indication as to what the origin of that number is.

There's a calculator that allows you to specify the feed point impedance, not sure how that works, but it's a nice feature to have when you're calculating the length of your dipole. Not.

One regular instruction is to cut long, that is, measure your wire and cut it longer than the calculator states. How much longer is left as an exercise to the reader. Should it be 1 mm longer, 1 cm longer, or should it be 1 m longer and how much should that change if the frequency changes?

Let's move on. The word ground features heavily in these calculators. The phrase "average ground" does too. No indication as to what makes an average ground, or how to go about determining what changes if your ground isn't average.

We all agree that the dipole should be half a wave-length above the ground, right?

How much is that?

The same wave length as the length of the dipole we've just calculated, or a different one?

How does the length of the dipole vary if the height varies? While we're looking at variation, how much variation is there depending on how thick the wire you're using is and what about insulation? None of those things are even mentioned in any of these calculators.

Dipole calculators, wonderful invention, shame about the implementation.

I'm Onno VK6FLAB

Random bits of wire ... Oct 07, 2018

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Foundations of Amateur Radio

One topic that is longer than all other topics combined is that of antennas. Designing, planning, sourcing, building, tuning, using, you name it, all of this is regular fare in the day of a radio amateur. I've discussed the topic here regularly and no doubt I'll revisit that when the mood or necessity takes me.

One topic that is rarely discussed is that of failure.

About six months ago I moved house. I've been rebuilding my shack, doing all manner of fancy shuffling of gear and yesterday I finally got to the point of getting some HF activity happening. During that process I went through boxes and boxes of stuff, with coax, connectors, wire, nuts, bolts, heat shrink and all the other necessities of being a member of an experimental hobby like ours.

One box contained wire. You know the adage, only two types of wire required in our hobby, cheap wire or free wire with a preference for free. This box was stuffed with wire. Bits with connectors, bits wound around spools, bits in zip-loc bags with labels, bits of random length - lots of bits of random length.

There was even an abortive attempt at labelling dipoles for various bands on the outside of a couple of zip-loc bags, but no idea if the bit of wire in the bag was actually ever tested and resonant on whatever band was on the label, so who knows, they might have just been cut long waiting for another day and another set of experiments and measurements.

I needed around 50 meters of hook-up wire for my HF antenna experiment and it occurred to me when I was hunting through my box that I couldn't look at a spool and tell you how much wire there was. I did a dodgy measurement of one bit, put it on the kitchen scales and determined that another spool was heavier, so it was likely longer, but without bringing in my calculator, doing extra measurements and doing some head scratching there was no way that I was going to get to the point of knowing how much actual wire was on that spool.

In the end I made do with the dodgy piece, soldered some joins, that's a whole other adventure, involving a gas-powered soldering iron and a flame, the flame won, as well as several other breaks and fixes.

While I was in the process of putting up my new antenna experiment it occurred to me that part of the process of experimentation, even of shack maintenance should be the documentation stage.

I have bits of terminated coax, some of it 20 meters long, some longer, some shorter. How much longer, and how much shorter you ask? No idea. But wouldn't it be great if I could put my hands on a piece of kit that I needed that was the length that I expected and not 10 meters over length, or 1 meter short.

In my audio kit, I have started labelling patch leads with their functions, using key-ring tags. I don't expect that to work for plain wire, but it should be a good solution for coax. I could use cable tie labels, but past experience with those leaves the text fading on the label. I've experimented with a printed label with clear heat shrink, but for reasons best known to chemists, the clear heat shrink becomes yellow in short order leaving the label unreadable.

I've heard of people using electrical tape with colour coding, perhaps one ring for every 5 meters of length, but they seem to come undone in the dust when you go camping.

One thing I do know is that this is a recurring problem for me. This is the first time I've actually stopped to talk about it and perhaps it means that I'll get a little closer to a solution.

I'd love to hear what you do to deal with this and how you keep track of the countless different lengths of wire, coax and rope that's lying around your shack.

I'm Onno VK6FLAB

Is man-made noise really vertical? Sep 30, 2018

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Foundations of Amateur Radio

One of the often repeated attributes of noise and antennas is that man-made noise is vertically polarised and that is why a vertical antenna sounds noisier than a horizontal dipole. It's an interesting thing to say, but it it true?

Let's start with what constitutes man-made noise. Cars driving past, solar panel inverters, pool pumps, high-tension power lines, garage door openers, broadband internet modems, LED lights, lawn mowers, leaf blowers, plasma televisions and so on. The more you think about this, the more noise makers you discover.

So, are these noise sources all aligned in the same way, making the same noise?

Clearly not. There is no alignment standard for installing a lamp, how to align your lawn mower, which direction to drive, what angle to point your garage door opener, so the statement that man-made noise is vertical is clearly bogus.

That doesn't mean that the rest of the statement is also wrong. A vertical antenna in an urban environment often sounds much noisier than a horizontal one, sometimes by several dB.

So what's going on?

One suggestion is that the difference lies in the antenna itself. What if both noise sources, horizontal and vertically polarised were the same, but the antenna heard them differently, how would that look?

For starters, a horizontal dipole has a higher sensitivity at a higher angle than a vertical antenna does. So anything arriving at a low angle is picked up by the vertical, but not by the horizontal dipole.

The noise that we're talking about is local, we'll get to why in just a moment. Being local, it gets to the antenna via ground wave propagation rather than via the ionosphere. I claimed that the man-made noise we're discussing is local. It's not all local, but if it's remote, it's coming via the ionosphere and we know that it arrives at whatever angle it pleases, so there is little or no difference between a vertical and a horizontal dipole from a noise perspective for signals arriving via the ionosphere.

There is another effect. Attenuation or signal loss. In this case loss of strength. Specifically noise strength. More attenuation is the same as more signal loss.

Combining ground wave propagation and attenuation brings us to another difference between a horizontal and a vertically polarised noise source. A horizontally polarised ground wave experiences more attenuation than a vertical one. This means that noise that is local travels further and is louder when it's vertical, compared to when it's horizontal, sometimes the difference is over 20 dB.

I've been talking about horizontal and vertically polarised noise, but what if the noise is coming at an angle, like the random noise makers around you? A simple way to think of it is that every angle has a horizontal and a vertical part, in much the same way as a right-angle triangle has three sides, one horizontal, one vertical and one on an angle.

Putting this all together, we have a number of different effects, all conspiring to make the vertically polarised part of noise travel further, be louder and received better by a vertical antenna, compared to the horizontally polarised part which doesn't travel as far, is softer and heard less by a horizontal dipole.

One more thing. The isolation between vertical and horizontal polarisation can be as much as 40 dB, so a horizontal dipole won't hear vertically polarised signals well if at all and vice versa.

That doesn't make the vertical antenna useless, far from it. It's great for transmitting a long distance signal, it's small, simple to set-up and if you're in a quiet area, away from noise makers, around 500m to a kilometre or so, it's just fine as an antenna. It also doesn't need to be erected half a wavelength above the ground, doesn't need any sky-hooks, is omni-directional and in common use for most local mobile communications, so don't write off the vertical, just because it sounds noisier.

All antennas are a compromise between various elements. I've said it before and I'll say it again, likely plenty more times beyond that. The perfect antenna does not exist. We can prove that, so what ever you pick, what ever you think is the most important, that's what you'll start with and select various aspects as you go.

A vertical antenna is no worse than a horizontal dipole, it's different. Just like a Yagi is different, or a discone, or any one of the infinite supplies of antenna options. Knowing what the parameters are is the first step.

Oh, and if your neighbours complain about your lawn, tell them it's because of your noise-floor.

I'm Onno VK6FLAB

Antenna Polarisation and you Sep 23, 2018

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Foundations of Amateur Radio

The first time I came across the concept of antenna polarisation was a decade before I became a radio amateur. To connect to the internet while driving around Australia I became the proud owner of a portable satellite dish. Portable in the broadest sense of the word, 150 kilos with a dish that's 2.4m high, 1.8m wide, steel base, electronics, power and patience to erect and point.

The dish has a receiver and transmitter component that needs to be aligned, just so, in order to be able to have two-way communications using 5 Watts into geosynchronous orbit. The transmit and the receive are exactly 90 degrees offset from each other. One is called horizontal polarisation, the other vertical.

The first thing to observe is that if you're using the wrong polarisation, it doesn't really work well. We'll get into what is right in a moment. Depending on where you you ask, the definition of not working well can be as bad as 40 dB loss.

Just let that sink in for a moment.

If you want to punch through with more power, you'll need to bring 10 kilowatt with you for the receiving station with the opposite polarisation to hear 1 Watt.

If you're using a VHF or UHF FM radio in your car, you're likely to have a vertical antenna. The combination of a repeater on a hill and a radio in a car adds up to much more than the the two alone. The line is blurred today because repeaters are very popular and home-base stations are becoming smaller and smaller by the week, so vertical antennas for VHF and UHF at home are today just as common as they are on cars.

It wasn't always that way. In fact, in HF, it's almost never that way and if you're a fan of Tropospheric Ducting or long distance VHF, then you'll also shy away from vertical antennas.

Let me explain.

If you want to erect a HF antenna and you want it to rotate and you want it to be high enough off the ground, you'll build the simplest mast you can get away with. Imagine a HF Yagi. It's got several elements, long to short along a boom, rotator somewhere in the middle. If you mount this Yagi horizontally, your mast will be around half a wave length in height.

If you mount the same Yagi vertically, aside from the height discussion - should it be mounted higher or not - now your mast becomes another interfering element within your Yagi. The steel wires that keep your mast standing will also interfere with the Yagi elements and your elements will be closer to the ground where they can potentially cause harmful radiation.

So from a mechanical perspective, putting a Yagi on a mast vertically is not trivial.

From a radiation perspective you may theoretically get some gain, but adding an element or two will make up for any potential gain that a vertical arrangement interacting with Earth might assist with.

There's another reason. The ionosphere. It sounds like a smooth billiard ball, it's drawn as a uniform layer around the earth, but in reality, clouds and their appearance are much more likely to represent the actual surface shapes that the ionosphere presents to your radio waves.

A signal coming in one way is unlikely to come out at the other end in the same way and vice versa.

That's HF. On VHF and UHF a horizontal signal and a vertical signal when they're used with line of sight are pretty similar, but once you get beyond that, a horizontal signal will travel further, how exactly is a story for another day. If you're doing point to point VHF or UHF contesting, horizontal is the way to go.

What about a single HF vertical?

It's excellent for a portable station, it is simple to set up, works in all directions, but it means you'll be able to hear all the local man-made noise as well, so find a quiet spot near the beach if you can.

So what's the right way? Almost always horizontal, except on cars or when you're on a DXpedition on a beach sipping pina collada and getting caught in the rain.

I'm Onno VK6FLAB

Cloud Warming in style or what is NVIS? Sep 16, 2018

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Foundations of Amateur Radio

The term NVIS, or Near Vertical Incidence Skywave is in my short experience as an amateur heaped with scorn and ridicule. Terms like cloud-warmer come to mind when people discuss the principles associated with NVIS, but that does happen in the context of where I live, that is, one of the most isolated cities on the planet, Perth in Western Australia.

NVIS has several advantages over other forms of HF communication, it can be done with low power, there is little or no signal fading, simple antennas work well, it has low path loss, better signal to noise ratios and if you're in a valley, you can still use it.

So what exactly is NVIS?

In the past I've talked about long distance HF communication. Your radio signal bounces off the ionosphere, bounces back to earth and so-on. Like skipping a stone on a pond, the angle at which your signal hits the ionosphere determines what happens next. In general, shallow is good, steep is bad, much like the plop you hear when you don't hit the pond just right, a radio signal can go through the ionosphere, never to be heard again.

NVIS is about hitting the ionosphere at a steep angle, in such a way that it reflects back to earth. Without going into detail, generally you can use 40m during the day and 80m at night with some variation depending on the solar cycle and whom you want to talk to.

NVIS gives you communications less than 1000 km away, plenty to talk to everyone in your city and surrounding area. In the case of an emergency that's also likely enough to get out of any emergency affected area, so plenty of excuses to set up and try for yourself.

I can start talking about angles, maximum usable frequencies and so-on, but I won't. These all relate to specific circumstances, depend on what antenna you're using, what the ground conductivity below you is and as is typical in our hobby, many other variables.

What I can say is that NVIS to NVIS station works best, so if you're going to test this with a friend, it will help if you both set up a similar station while you learn the variation associated with this kind of communications.

Now I did mention up to 1000 km, that isn't enough to leave Western Australia, Perth to the border is about 1500 km, but if you live in the Netherlands, you can get to 15 or so countries. Depending on where you are, NVIS will give you different outcomes and what I'm talking about affects each station differently.

For me, the attraction of NVIS is solid communications on 40m and 80m, something that has eluded me so far. It also allows for a low simple wire antenna, an inverted vee dipole, two bits of wire strung up on a pole, 6m in the middle 2.5m at the end will get me up and running. Perfect for a field-day, excellent for a local contest and brilliant if you're only using low power as a beginner.

Because the antenna is close to the ground, it's pretty much omni-directional. If you set-up an antenna for 40m and then cross that with an 80m antenna and feed them both from the same point, you'll have a configuration that will operate well for 24 hours without needing to move antennas in the dark.

I have no illusions that an NVIS antenna will help me make contact between Perth and Japan, but then it's not intended for that. I've spoken in the past about finding the right tool for the job. NVIS is a tool, it has a job and it's very good at doing that. It's not for everyone, all the time, but it's a tool that you as an ambitious amateur should know about.

I'm Onno VK6FLAB

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