Podcasts by VK6FLAB

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Starting in the wonderful hobby of Amateur or HAM Radio can be daunting and challenging but can be very rewarding. Every week I look at a different aspect of the hobby, how you might fit in and get the very best from the 1000 hobbies that Amateur Radio represents. Note that this podcast started in 2011 as "What use is an F-call?".
Updated: 1 hour 38 min ago

Simplicity among the complexity ...

Sat, 09/19/2020 - 12:00
Foundations of Amateur Radio

My radio shack consists of two radios, identical, well, in as much as that they're the same model, a Yaesu FT-857d. Their memories are different, their microphones are different, but both of them are connected via a coaxial switch to the same VHF and UHF antenna. One of them is also connected to a HF antenna.

Let's call these two radios alpha and bravo.

Alpha is used to host F-troop and play on the local repeater. Bravo is used to do HF stuff. It's also connected to a computer via a serial cable, called a CAT cable, Computer Assisted Tuning, but really, a way to control the radio remotely.

The audio output on the rear of the radio is also connected to the computer.

These two connections are combined to provide me with access to digital modes like PSK31, WSPR and SSTV, though I haven't actually yet made that work. The computer itself is running Linux and depending on what I'm doing on the radio some or other software, often it's fldigi, a cross-platform tool that knows about many different digital modes.

The computer is also connected to the Internet via Wi-Fi, and is used to see what various reporting websites have to say about my station, things like propagation, the DX cluster, an electronic way of seeing what other stations can hear, then there's solar radiation information and other neat tools.

This shack is pretty typical in my circle of friends. I'm lucky enough to have a dedicated table with my shack on it, for others they're lucky to have a shelf in a cupboard, or at the other end of the spectrum, a whole room or building dedicated to the task.

The level of complexity associated with this set-up is not extreme, let's call it in the middle of the range of things you can add to the system to add complexity.

In case you're wondering, you might consider automatic antenna switching, band switches, band filters, amplifiers, more radios, audio switching, automatic voice keyers. If you look at the world of Software Defined Radio, the hardware might include many of those things and then add a computer that's actually doing all the signal processing, making life even more complex.

At the other end of the complexity scale there's a crystal radio.

As I've been growing into this field of amateur radio it's becoming increasingly clear that we as a community, by enlarge, are heading towards maximum complexity.

There's nothing wrong with that as such, but as a QRP, or low-power operator, I often set-up my radio in a temporary setting like a car or a camp site. Complexity in the field is not to be sneezed at and I've lost count of the number of times where complexity has caused me to go off-air.

It occurred to me that it would be helpful to investigate a little bit more just what's possible at the other end of the scale, at the simple end of complexity if you like.

So, I'm intending, before the year is out, supplies permitting, to build a crystal radio from scratch. I realise that I have absolutely no idea what I'm getting myself into, no doubt there will be more complexity that I'm anticipating, but I'm getting myself ready to build something to be able to look at it and say to myself, look, this is how simple you can get with radio.

I'm currently too chicken to commit to making the simplest - legal - transmitter, but if you have suggestions, I'll look into it.

Just so you know, simplicity is an option.

I'm Onno VK6FLAB

Yak Shaving ...

Sat, 09/12/2020 - 12:00
Foundations of Amateur Radio

Yak Shaving ...

Not every adventure gives you an outcome. Today started with reading a thank-you email from a listener who shared their activities and wanted to express their gratitude for encouraging them to get on air and make noise.

That in turn prompted the question on the country of origin of that listener and did I know where all my listeners were? For the past few hours I've been attempting to answer that seemingly simple question.

Aside from using the opportunity to make an attempt at mapping the distribution of amateurs in Australia, which on the face of it is a trivial exercise, consisting of extracting the postcode from each registered amateur and then putting those on a map.

Only the postcodes are not actually single points. They're boundaries defined by Australia Post and they're copyrighted. Not only that, they change. To access them, you have to pay the Post Office. If you want to combine a postcode with a population density, so you can see where amateurs are represented and at what level, you go to the Australian Bureau of Statistics for a population density data-set. At that point you realise that the Bureau uses standardised regions. Mesh-blocks at the smallest end of the scale are essentially the size of 30 to 60 households. The Bureau uses these as the fundamental size for all its statistics.

When you attempt to map this onto postcodes you learn that there isn't a one-to-one mapping and even if there was, it would change every time Australia Post changed a postcode boundary.

I will note that this is all by way of a side-street in my investigation. I wondered how amateur radio is distributed across the country and I didn't want to end up with essentially a population density map, more people means more amateurs, I wanted to see where amateur radio had the potential to affect more people because there are more of them in a group.

Anyway, then I attempted to look at the podcast downloads and map those to countries. I use AWS CloudFront to make the podcast available, so it gets to the user, you, quicker. The logs show which data-centre a request is handled by. Then I needed to map a data-centre to an airport code, look that up in a database so I could extract the country, then count how many requests were made per country.

Then I started doing that across time, so you can see how that changes over time.

At this point I still don't actually have a map to show.

While all this was happening, my computer started running low on disk-space, not because I'd just downloaded some data from the Australian Bureau of Statistics, but because some rogue process was writing a log somewhere, so I spent an hour looking for what process that was, killing it and removing the superfluous log file.

If this sounds familiar, there's a name for it. Yak shaving. It's originally named after a Ren and Stimpy episode called "Yak Shaving Day". Essentially you do a whole lot of unrelated activities in the pursuit of the actual activity, essentially a string of dependencies that distract you from the end-goal. In my case, trying to answer which countries are represented within my audience.

Why am I not using an amateur radio example?

Two reasons.

This is amateur radio. For me. Doing charts, wrangling data, massaging stats, finding answers and presenting those are an integral part of the hobby, to me. Just like making this podcast, contributing to discussion, reading and learning. All part of the mix.

Second reason is that I wanted to illustrate this with something that wasn't immediately obviously linked to the hobby for most people. A more amateur example might be wanting to go and operate portable, attempting to locate you battery, when you find that it's not charged, so you go looking for the charger which you find has a broken connector, so you drive to the electronics store to get the connector when you run out of petrol, so you pull over, get out of the car and trip over the curb and end up in hospital emergency waiting for a doctor to see you. If you think that's far-fetched, I know an amateur who ended up in hospital from yak-shaving.

We've all had days like that.

The idea is that any day that you are on the right side of the earth, doing something you love is a good day.

Regardless of the end result, this is a hobby after all.

I'm Onno VK6FLAB

What is so different about using software for signal processing?

Sat, 09/05/2020 - 12:00
Foundations of Amateur Radio

In my ongoing software explorations I've discussed that Software Defined Radio or SDR is a fundamentally different way of dealing with radio. It's been in use across non-amateur circles for decades. Your mobile phone has an SDR on board for example.

The original term of "digital receiver" was coined in 1970, "software radio" was coined in 1984 and in 1991 Joe Mitola reinvented the term "software radio" for a planned mobile phone base station.

So, this idea has been around for half a century and in amateur radio this idea is also catching on. You can buy a few pure SDR devices today, some hybrid ones, or you can begin to experiment in a more indirect manner using your traditional radio and a computer.

One of the things that sets this idea of a software defined radio apart from anything we've done so far is that the bulk of the signal processing is done in software. That sounds obvious, but it's really not.

One of the impacts of this idea is that you can improve your radio communications by either writing better software, or by using a faster computer. Unless you write software for a living, these things aren't immediately obvious, so let me explain.

Imagine that you've written software that detects beeps in a particular slice of audio spectrum that's being fed to your application. As you write better software to detect those beeps, you get a better digital mode, one with a better chance of being decoded, or using radio terms, it has a better signal to noise ratio.

If that's not a familiar term, signal to noise ratio is the a measure that describes the difference between a wanted signal and the background noise. Higher signal to noise means that you can better distinguish between the two.

If you stand in a room full of people talking and you use your hands to cup your ears towards the person you want to hear, you've increased the signal to noise ratio and your chance of understanding them has improved.

As you write this software, it gains complexity. As you deal with more maths, more samples, more tests, you end up running out of time to make your decoder return a relevant answer. There's no point in having a real-time signal being decoded late. If it were to take say 10 seconds to decode 1 second of audio, then the next second would be 20 seconds late and the one after that would be 30 seconds late.

That's where a faster computer comes in.

If you have the ability to do more maths, or do the same maths at a higher resolution, you will essentially improve the reception of your radio without ever needing to change your antenna or anything on the circuit board.

Think of it in another way.

Imagine that your tool has access to 2.3 kHz of audio. It's the equivalent of a Single Side Band audio stream. If you break that down into 23 chunks of 100 Hz each, you can deal with the average of 100 Hz of audio for each calculation. If you have a faster computer, you might be able to break that down into 230 chunks of 10 Hz each, or 2300 chunks of 1 Hz. So instead of doing calculations across 23 chunks of audio, you're doing it across 2300 chunks.

Why is this significant you might ask?

Well, in a traditional radio you get one bite at the cookie. You get to design and build your circuit and then package it and sell it. The end result is something like my FT-857d. It does what it does well, but it will never get any better.

However, if I plug that same radio into my computer, I can extract the audio and do stuff with it. If I get a faster computer, I can do more stuff. I don't have to change my radio, or my antenna, or even my shack. Most of the time I run a different application and I get a different result.

I will point out that I'm deliberately ignoring where and how the RF gets to the computer, or where that computer actually is, or what operating system it's running, since none of those things matter to get an understanding of how changing software can change the performance of your radio.

I've said this before and I'll say it again: "The SDR earthquake will change our hobby forever"

Before I go. I'm not for a minute suggesting that your current radio is obsolete. If it were legal, a spark-gap transmitter could still exchange information today, but if you want to explore what might be just over the horizon, going down the SDR path by connecting your radio to your computer is a really nice place to start.

I'm Onno VK6FLAB

When you run into a pounce ...

Sat, 08/29/2020 - 12:00
Foundations of Amateur Radio

Contesting is a fun way to learn about amateur radio. It tests your skill, your station, your patience and your ability to change approach at a moments notice. For those reasons alone it's an activity that I recommend you have a go at.

For me it's also about self-improvement. With each contest, can you make better use of your station, can you learn more about your radio, about bands, about conditions and ultimately become a better operator. I know that there are individuals who keep telling me that giving out signal reports of 5 and 9 isn't helpful, to them I say, try it in a contest setting and see what else you learn.

When you start out contesting you'll quickly come across two terms, technically three, that need some explanation. The terms are Run, Search and Pounce, though the last two come as a matched pair.

The essential bit of information is that when you're on a Run, or Running, you're calling CQ and responding to other stations. You essentially sit on a frequency for a bit, start calling CQ and hope that others hear you and start to gather around to make contact with you.

The other side of that is Search and Pounce, or searching on a band for a station you want to talk to and pouncing into a gap when you can.

The two methods are mirror images of each other, so one station is generally running whilst the stations calling in are searching and pouncing.

Doing this in a contest setting requires slightly, some might say subtle, differences.

Let's investigate a contest RTTY contact. I'll simulate it between myself, VK6FLAB and Matt, VK6QS. I'll add that this is done in text in a RTTY contest, rather than voice, and, this exact exchange didn't actually happen, but for different reasons which I'll get into shortly.

It goes a little like this.

My station transmits: CQ TEST VK6FLAB VK6FLAB CQ Matt responds: VK6QS VK6QS VK6QS I reply: VK6QS 599 010 010 Matt replies: 599 032 032 And I finish off with: TU CQ VK6FLAB

Now this is the ideal contact, nothing extraneous, no duplication, nothing about having to repeat yourself. Mind you, if you're getting picky, you might notice that we're both sending our exchange twice, in my case 010, Matt is sending 032.

If you look closer you'll notice that all pertinent information is sent at least twice because it turns out that unlike a keyboard on a computer connected to a screen, what you type in RTTY might not actually get to the other end if you're using HF radio.

My three transmissions are the one where I call CQ, the one where I say Matt's callsign plus the exchange and the one where I say TU or Thank You, and move on. Those are the run calls.

Matt's calls consist of his callsign, and his exchange.

Note that Matt doesn't say my callsign, since I already know it and I'm running and he's searching and pouncing. He should already know who I am before he transmits. If he were to add my callsign, that would just slow things down. This is a way to keep things moving along.

In fldigi, I can program a function key that does each of those five calls. You click on a callsign, push the appropriate button and magically you're either running or pouncing. There's also a button for asking for a repeat, or "AGN?, AGN?" and one for making a log entry, which you can combine into the final thank you for running, but it's needed separately if you're pouncing.

I did say that this exchange didn't actually happen and you might well wonder why I shared it with you.

Simple. This is the bare-bones of what's required. Everything else is extra in case things break down. If there are multiple stations on the same frequency, or if your levels aren't quite right and the decoder is having a hissy fit, the human in the chain, you, need to do something manually. Very much like when you're dealing with a voice pile-up and there's this one station calling over the top of everyone else and drowning out whomever you actually want to talk to.

In a contest setting there's plenty of opportunity to do both running and pouncing and you should. If you're running on a dead band you won't know because you're getting old calling CQ, but if you're searching on that same band you'll figure out pretty quick that there's nothing happening.

Similarly, you might have a desirable callsign or location and find that running is more effective in making contacts than searching and pouncing.

Whatever mode of contesting you choose, make sure that you're flexible, since band conditions change from second to second and you will need to adapt to the winds of change. A lot like when you learn to sail and find out that you cannot just hold the helm in one spot for the entire time.

I will note that the ideal RTTY contact that I've outlined isn't universal. There's plenty of debate about the most effective way to go about things. I started with what I knew about making voice contacts, shamelessly copied the RTTY macros from another amateur and used them as a basis to learn what I needed and what I didn't, and because this was my first actual RTTY contest I watched several YouTube videos, rather than hear actual contesting stations on the air, which is something I recommend you do to get a feel for what's going on.

Contesting can be a way of life, or it can be just plain fun with learning thrown in.

I'm Onno VK6FLAB

After channelling your RTTY ...

Sat, 08/22/2020 - 12:00
Foundations of Amateur Radio

It's the morning after the day before. I've been calling CQ for 24 hours and for the first time in my life after a contest I still have my voice. That in and of itself is novel. I also don't have ringing ears, that's a blessing. I have learnt heaps and had fun doing it. I made contacts and I heard stations across the globe and I did it all from the comfort of my shack chair.

Before I dig in and expand, the contest I just completed ran for 24 hours. I didn't sit at my radio for all of it, nor was my radio on for all of it. I managed to have lunch, dinner, desert, breakfast and morning tea. I snuck in a few naps and I managed to help with bringing in the shopping. My station did not transmit unattended at any time in case you're wondering.

My setup consisted of a little 11 year old netbook computer running the current version of Debian Linux and the heart of this adventure, the software called fldigi. The computer is connected to my Yaesu FT-857d via three cables, well, two and a half. A microphone and a headphone lead that combine into the data port in the back of the radio. The other cable is a USB CAT cable, a Computer Assisted Tuning cable, that plugs into the CAT port on the back of the radio. I also used an external monitor to have my main contest screen on and used it to display the main fldigi window.

My license class allows me access to a selected number of amateur bands, 80m, 40m, 15m, 10m, 2m and 70cm. I managed at least one RTTY contact on each band.

As I described previously, my radio is set to use Single Side Band and the audio from the radio is fed via the microphone socket on the computer into fldigi that processes the information. Similarly, when I transmit, the audio is generated via fldigi and leaves the computer via the headphone socket and goes into the radio as a Single Side Band audio signal.

The information in the audio is all RTTY, a digital mode that I've described previously. The software is using Audio Frequency Shift Keying, AFSK, simulating the switching between the two RTTY frequencies.

On my screen I have a waterfall display that shows all the signals that are happening within the 2.3 kHz audio stream that's coming from the radio. Fldigi is also decoding this in real-time and showing each decode as a virtual channel in a list. Click on a channel entry and your next transmission will happen at that frequency.

If you've ever used WSJT-X this will sound very familiar.

That's the mechanics of what I've been doing.

So, what did I learn in this adventure?

Well, most of Australia goes to sleep at night, at least the ones that do RTTY. I have evidence of exactly one station on-air, and that was only because they were named in the DX Cluster, which by the way this contest allows as assistance. Since then I've found logs from at least two more stations.

Local contacts did happen during the more civil hours and in total I managed ten of them. You may think that's not much for say 12 hours of work, but that's 5 Watts QRP, or low power, RTTY contacts, in an actual contest, on a new antenna, from my shack, dodging thunderstorms and learning to use filters and levels.

You might not be impressed, but I'm absolutely stoked!

During the midnight-to-dawn run, on 40m, when there were double points to be had, which I missed out on, I did manage to hear several stations across Europe, 14,000 km away, which means that I can pretty much count on global coverage with my current setup. Sadly they didn't hear me, too many competing stations, but I'm sure that with practice I'll manage to contact them too.

The software crashed once. That's not nice. It seems to have a habit of corrupting one of the preference files, which prevents it from starting up. That's also not nice. I hasten to add that I don't yet know the source of this. It may well be a dud-hard-disk sector on my ancient laptop, rather than the software, so I'm not assigning blame here.

Getting started with fldigi is an adventure. It's not point-and-click, nor plug-and-play, more like running a mainframe whilst cranking the handle, but when you get it to fly there's lots to love about this tool.

Other things that worked well were that I'd spent some preparation time getting the keyboard macros right. These are pre-defined bits of text that you send as you're calling CQ and making a contact. They're a whole topic in and of themselves, so I'll skip past the detail and just mention that I was very happy with the choices I made, gathered from years of voice-only contacts, reading RTTY contest information and looking for exchange details.

From a technical perspective, I used both contest modes, "Running" and "Search and Pounce". Running is when you call CQ, Pouncing is when they call CQ. The running was by far the most successful for me. I'm not yet sure if that was a reflection on how much I still have to learn about levels.

One thing that I can say with confidence is that there's absolutely nothing like having a wall of RTTY signals to learn how to make sure you're actually decoding something useful. I spent a good couple of the wee hours tuning my levels.

I would like to thank the stations who came back to my call and for those who tried without me noticing them.

I had a blast.

I'm Onno VK6FLAB

Channelling RTTY

Sat, 08/15/2020 - 12:00
Foundations of Amateur Radio

When you start playing with radio your first interaction is likely to be voice. It could be SSB, AM, FM or something more recent like FreeDV or DMR. Your next challenge is likely going to be a digital mode like Morse Code, Radio Teletype or my recommendation for your first adventure, WSPR or Weak Signal Propagation Reporter.

I've previously discussed WSPR, today I would like to look at Radio Teletype or RTTY. It's a digital mode that allows you to send and receive free-form text. It's a mode with a long and illustrious history and it's a good next step after WSPR.

The way it works is that using an alphabet made up from two tones, information is transmitted, one character at a time at a specific speed. The code that describes the alphabet is called the Baudot code, invented by Jean-Maurice-Emile Baudot in 1849. In computing terms it's a 5-bit alphabet and in amateur radio it's traditionally sent at 45.45 baud or bits per second, in case you're wondering, named after the very same man.

The two tones have names, a Mark and a Space and they're a set distance apart. In amateur radio, they're separated by 170 Hz but there are plenty of other frequencies and speeds in use. In amateur radio the standard Mark and Space frequencies are 2125 Hz and 2295 Hz.

In a traditional RTTY capable radio the two tones are generated by transmitting a carrier whilst switching the transmitter frequency back and forth, called Frequency Shift Keying or FSK. Think of it as having a Morse key that sends dits on one frequency and dahs on another, having the radio change frequency whilst you're keying.

If you use this method to create and decode RTTY by switching between two frequencies, your radio can generally only deal with one RTTY signal at a time, just the one you're sending and just the one that's being received. Receiving is generally achieved by showing some indication on your radio how close you are to the Mark and Space frequencies that you're trying to receive and decode.

Another way to make a RTTY signal is to use sound. If you alternately whistle at 2125 Hz and 2295 Hz and you do it at 45.45 bits per second, you're also generating RTTY. This technique is called Audio Frequency Shift Keying or AFSK. Think of it as using audio to simulate the shifting of frequency by transmitting two alternating tones.

There is a fundamental difference between the two. Before I explain, permit a diversion. It's relevant, I promise.

If you've ever spoken on the radio using SSB you might have noticed that if two stations are transmitting at the same time you get both signals. With a little practice you can even understand both. This isn't true for every radio mode. If you use FM, the strongest signal wins and if you use AM, you get a garbled beep from two stations being on slightly different frequencies. As an aside, this is why aviation uses AM, so any station not transmitting can hear that two stations doubled up.

Back to RTTY.

If you use audio to generate the two RTTY carriers, rather than shift frequency, you can deal with as many as you can fit into an SSB audio signal, as long as the Mark and Space for each station are 170 Hz apart you can have as many stations as you want, overlapping even. As long as your software knows what to do with that, you'll be able to decode each one at the same time, since they're essentially multiple SSB signals being transmitted simultaneously.

An added bonus is that you don't have to invest in an SDR to play with this. You can use an analogue radio, like my FT-857d, and use software to generate an audio RTTY signal with all the benefits I've just mentioned. The magic is in the software you use to do the decoding.

As it happens, I'm about to do a contest using RTTY and I'll let you know how that goes using my radio, a computer and a piece of software called fldigi. I'll be following in the footsteps of the first ever RTTY contest, held in the last weekend of October in 1953 and organised by the RTTY Society of Southern California. In as much as I'm following in the footsteps of Morse code by spark-gap.

Wish me luck.

I'm Onno VK6FLAB

How much do you really know about your radio?

Sat, 08/08/2020 - 12:00
Foundations of Amateur Radio

When I came across amateur radio nearly a decade ago I did a course, passed my test and got licensed. At that point I didn't have any equipment, didn't know about any, hadn't touched anything, other than the radio in the classroom, and had no idea about what to buy and how to choose.

So, instead I asked the friend who introduced me to the hobby, Meg, at the time VK6LUX, what radio to get. I asked her what was the second radio she ever got because I figured that I'd get very disappointed with the first one in short order. She explained that there were plenty of brands to choose from and that each had their own champions. Just like the perennial choice between Ford and Chevrolet, Apple vs Microsoft, Tea vs Coffee, you'd end up with one radio and be told by someone in a different camp that you chose the wrong one.

Her advice, which is just as solid today as it was a decade ago, was to buy something that people you knew had, so whilst you're learning there'd be someone nearby who could help. As a result I bought a Yaesu FT-857d for precisely that reason. I still have it and it has a sister, another FT-857d, bought when I needed to broadcast the local news when one of the local volunteers went on holiday.

For most beginners their journey is similar. They buy their first radio and generally that sets the tone for what comes next.

In the decade that I've been around amateur radio I've had the opportunity to play with about 30 or so different radios. For some that playing consisted of picking up the microphone and making a QSO, a contact, and not much else. For others it consisted of sitting with the radio for a full contest, 48 hours, with sporadic sleep, dealing with pile-ups where there wasn't time to breathe, but plenty of stuff to learn about filtering.

Then there were the radios that came to my shack for a visit, those at various clubs and plenty of outings where I was able to sit down and figure out how stuff works.

On the surface that's all fine and dandy. A radio is a radio, you pick up the microphone and hit go, off to the races. Then you need to figure out how to set the volume, change frequency, change bands, read what the mode is and how to change it, tune the thing, set up a filter, change the pre-amp, operate split.

For some radios this was easy, consisting of a channel button and a microphone push to talk, for others there were no buttons, just a big Ethernet socket, then there were the radios with a hundred buttons, some so small that you missed them on first glance. I've used solid-state radios, valve radios, software defined radios and virtual radios, each with their quirks and idiosyncrasies.

Every time I operate a new radio I learn something about that radio, but I also learn something about my own radio. I can begin to hear differences, observe how easy or hard it is to do something, a missing feature on my own radio, or the one I happen to be operating at the time.

In my travels I've seen plenty of radio amateurs who only have a passing understanding of their own radio, let alone any other radio.

I completely respect that this might be enough for you, but I'd like to point out that this might be a missed opportunity.

I remember vividly sitting in the middle of a bush-camp with my own radio powered by a battery connected to a hap-hazard dipole antenna strung between two trees attempting to hear a station discussing her global circumnavigation by sailing boat and being frustrated with my ability to make it work.

A friend who was sitting nearby asked if they could have a go and within seconds he was able to use the filters and offsets to make the station pop out of the noise. It's with the image of Kim VK6TQ in mind, the person who knew my radio better than I did, that I'd like to urge you to play with any radio you come across, no matter how trivial or different.

One day it will mean the difference between making a contact or not.

I'm Onno VK6FLAB

First Digital DX contact!

Sat, 08/01/2020 - 12:00
Foundations of Amateur Radio

The other day day I managed my first DX contact using a new mode, FT8. It wasn't very far away, all of 2600 km or so, but it evoked memories of my first ever on-air DX contact nearly a decade ago. I should say thank you to YD3YOG for my 15m contact, fitting because my first ever was also on 15m as I recall. Unfortunately I never did log my first.

Recently a friend asked me how the two compared.

15m and logging aside, there's a lot of similarities, even though I'm a more experienced operator today when compared to when I made my first ever contact.

The preparation and the building anticipation is what made the contact all the sweeter.

A while ago I managed to connect the audio of my radio to a computer. This is pretty much the first step in starting to use digital modes. Essentially many common digital modes use an SSB transmission to generate and receive audio that in turn contains digitally encoded information.

There are hundreds of modes like this, from PSK31 to RTTY, WSPR, FT8, SSTV and many more. If you've not yet dabbled in this area, I'd recommend starting with WSJT-X. The software is so far the best tool I've found to make sure that your digital levels are correct and offers several popular modes to see how your station is operating. If you're asking for a first mode recommendation, I'd start with WSPR. Just do the receive part first, then work on from there.

There are many tutorials available, some better than others, so if the one you find doesn't float your boat, keep looking. A fly-over view is that there are several things that you need to get working and if they don't all work together, you'll get no result.

Obviously you'll need to install the software, but that's not the whole story. For the software to be able to control your radio, change bands, frequency and set-up things like split operation, you'll need to set-up the hardware to do this, in my case a CAT cable between the radio and the computer. You'll also need to set-up control software that knows how to talk to the hardware. In my case that's Hamlib on Linux, but it could be Hamlib or flrig on MacOS or something like OmniRig on your Windows machine.

The purpose is to control the radio. When you're troubleshooting, keep that in mind, hardware plus software need to work together to control the radio and this is before you actually do anything useful with the radio.

Then you need to have both hardware and software to have audio go between the computer and the radio. In my case the headphone and microphone connectors on my computer are connected to the data port on the back of the radio. If your computer doesn't have access to sockets you might need to use a USB sound-card. If your radio doesn't have an easily accessible port, you might need to have an interface.

The computer software in this case is likely setting the volume levels using the audio mixer in your operating system.

I will add that some radios have a USB socket on the back that combines both CAT control and audio. The principle though is the same. You need to make the CAT interface work, which is essentially a serial connection, and you need to make the audio work, which is essentially a sound-card.

Nothing else will make sense until you've managed to make those two work.

Then, and only then, can you try to launch something like WSJT-X, point it at the various things you've configured, then you can actually start decoding signals.

For WSJT-X to work properly, there's one more thing. An accurate clock is required. Likely you'll need to use a piece of software that knows how to synchronise with something called NTP or Network Time Protocol. The simplest is to point your clock tool at a time-server called pool.ntp.org which will get you global time coverage. Each operating system does this differently, but getting it right is essential before WSJT-X will actually make sense. You can visit time.is in a web browser to see how accurate your clock currently is.

So, get computer control of your radio working, get audio working, set the clock, then you can run WSPR, FT8, JT65 or any other mode.

I will note that I'm not attempting to give you specific computer support here, just an overview of what's needed before anything will work.

If you've been contesting then CAT control might already be operational. If you've been using a computer voice-keyer, then audio might also be ready. Depending on where you are on your digital journey, these steps might be complicated or trivial.

Once you've done all that you can start doing things like figuring out where satellites are or how to talk to the International Space Station, or use Fldigi to make a PSK31 contact or send a picture using SSTV or decode a weather fax.

When you've made that first digital DX contact, I'm sure that you too will have a sense of accomplishment!

I'm Onno VK6FLAB

What do you talk about?

Sat, 07/25/2020 - 12:00
Foundations of Amateur Radio

When was the last time you told anyone anything about your hobby? What about someone who isn't also an amateur?

Have you ever considered why there is a perception that our hobby is dying, why it's running out of people, why we struggle to get air-time in mainstream media, why attracting new members is hard and why there is a very narrow range of understanding about what our hobby is, what it does and how it's relevant in the world today?

I'm a radio amateur. So are you. You might not be licensed yet, but the fact that you're here right now indicates a willingness to understand and learn, to participate and question.

Those qualities are the fundamental building blocks that make up a radio amateur.

I'm also a self-employed computer consultant, a radio broadcaster, an interviewer, a software developer, a public speaker, a blogger, author, publisher and a partner. My friends include people who are process managers, astronomers, gynaecologists, mariners, tow truck drivers, communications technicians, volunteer fire-fighters, business owners, employees, retirees, fathers, mothers, old, young and everything in between. Radio Amateurs one and all.

When you sign up to be an amateur, you don't give up all the other things you are. You don't stop being a member of society, you just add in another box marked radio amateur and you get on with your life.

If you get into this hobby you begin to realise that it sneaks into everyday life all the time. You use it to figure out how something works, or explain why it doesn't, you use it to trace a circuit or to plug in your new surround sound system. You use it to encourage curiosity in your children and to talk to your grand-children. It's not an add-on, it's part of who you are.

That's always been the case, but the perception in the general public has not been like that, it's been based around the idea that being a radio amateur is being special, being separate, being knowledgeable, studied, licensed. The reality is that the world we live in is more connected than ever and the things we once did in isolation are now part of mainstream life.

There is a perception that amateur radio is dying. Articles describe how we need to attract more people, how we need to appeal to children, how we need to recruit, become sexy or relevant. There's discussion about what's broken in the hobby, how we need to fix it.

I think that none of those things are what's in need of investigation. I think it's us. You and I. I think we need to stop being shy about being a radio amateur, about what we do and why we enjoy it; what it means and how it works.

When you talk about your activities of the day, if you made a rare contact with Tuvalu, or managed to connect your computer to your radio, or made an antenna work, or climbed on a hill or learnt Morse Code, you need to share your victories and the excitement that they bring you.

As a society we're not shy about tweeting what we had for breakfast, sharing an interesting picture or discussing an article we saw on reddit. Fundamentally what you do and who you are is worth talking about and sharing.

So, next time you talk about going camping, or discuss a barbecue you had with friends, or relate to your friends something that happened, don't be shy about your amateur radio affiliation.

It's not a secret society, it's not weird or embarrassing, it's just part of what makes you who you are.

I'm Onno VK6FLAB

What's the point of this hobby?

Sat, 07/18/2020 - 12:00
Foundations of Amateur Radio

One of the recurring questions in this hobby, technically outside this hobby, asked by people who've not yet, or have only just been bitten by the bug, is: "What's the point of this hobby?"

In some ways I too have asked this question, though for me the answer came within a few months of learning that amateur radio exists. In response to others asking this I've also made meagre attempts to answer this question with varying degrees of success and satisfaction.

The typical responses are things like: there's a thousand hobbies inside amateur radio, it's about the communication, about the camaraderie, about climbing and hiking, about technology, science, physics, electronics. The truth is that this is just a fly-over view of what it means to have this as your hobby.

It occurs to me, having now been licensed for a little while, I can actually express a little more clearly what this hobby has given me.

At a basic level, I now know what the front of a TV aerial is and how Wi-Fi is attenuated by walls, how line of sight works and why you can talk to the International Space Station with a hand-held radio. I've learnt about sunrise and sunset and how they affect propagation, the grey line and how the ionosphere is broken into layers that are affected by solar radiation. I've learnt about sunspots and how they change over time, that there are cycles, that there is a thing called the Maunder Minimum and that propagation is a fickle beast. I've learnt about the Ionospheric Prediction Service and about band planning in contests, about dealing with pile-ups and making contacts, about voice-keyers and computer controlled radios, about contesting software and logging, about contest scoring and contest rules.

I've learnt about gain and about loss, about how 75 Ohm coax differs from 50 Ohm coax, how connectors work, about soldering and crimping, how to use a crimper and what connectors to use with which coax. I've learnt about path-loss and about bouncing signals off the moon, about Sagittarius A*, a bright and very compact astronomical radio source at the centre of the Milky Way and about inclination and ascension, about galactic coordinates and observation windows, about programming in Python and the astropy library.

I've learnt about how radio signals are used to encode information, the seemingly infinite supply of digital modes and how a radio signal can be described in three dimensions. I've learnt how maths can describe amplitude modulation and how side-bands can be described, about signal to noise ratios and decibels.

I've experienced the joys of making a rare contact, to places like Amsterdam Island, Prince Edward & Marion Island, Heard Island, Micronesia, Cuba, Kiribati, and many more. I've learnt more about geography, about maidenhead locators, learnt new phrases and started learning new languages.

I've gone out camping more times than I can count, spent nights under the stars making contacts across the globe. I've set-up my station in parks and on peaks across the country, made life-long friends locally and abroad, tested my patience and my endurance.

I've learnt about the pioneers and inventors who came before me, about their successes and failures, their enduring legacies and their inventiveness. I've gained insight into Apollo radio communications and distance measuring, global positioning before there was GPS, about satellite dishes and radio during disasters, about emergency communications and temporary set-ups with just enough to get the job done.

I've written software, made charts, learnt how to use GNUPlot, written articles, recorded podcasts, interviewed amateurs, published books, produced, presented and transmitted amateur news broadcasts, built amateur radio websites, chaired meetings, raised funds, contributed to club committees and helped as I was able.

I've helped organise a national amateur radio conference, learnt how to teach others and created a weekly radio net for new and returning amateurs. I've acted as a point of contact, offered life advice and acted as a shoulder to cry on when the going got tough for some of my fellow amateurs.

I've built more, tested more, explored more, learnt more and done more in the past decade than I have in the 40 years before that.

When I look back over the 472 podcast episodes I've written so-far, that massive list is only just scratching the surface and it only just begins to describe how deeply affected I've been by this hobby. It only barely describes the width and depth of this hobby and I've only been here for a little while.

I must point out that I did all these things because I could, because I had radio amateur friends who prodded and poked, who helped and asked, who gave and received. My exposure over this decade was only possible because there are others who share my interests and stopped to take a moment to express that.

Next time you're asked about how amateur radio is relevant, how it relates to the world, how it affects you and your life, what it's given you, or what you can gain from it, consider, even just for a moment, just how much is possible within this massive hobby.

I'm Onno VK6FLAB

Homebrew radio for the 21st Century

Sat, 07/11/2020 - 12:00
Foundations of Amateur Radio

The hobby of Amateur Radio is essentially one of experimentation. Within our community we endlessly build things, from amplifiers to Yagis and every letter of the alphabet in between. With every experiment we grow the amateur radio sphere of influence just a little bit.

As our hobby is evolving into Software Defined Radio, or SDR, the homebrew aspect of our community is also changing bit by bit and as a result, homebrew today is just as likely to be based on software as it is in hardware.

Unlike the physical world where you need to source and buy components, design a circuit, build it, test it and then put it in a box, in the software realm you can get started with the computer that is more than likely within reach right now.

Recently I took delivery of a new SDR, an ADALM Pluto. It's essentially a Linux computer, FPGA and transmit capable SDR in a small box. I bought it specifically for the purpose of experimentation.

One of the first things I did with this device was install an existing piece of software called dump1090. The tool listens to 1090 MHz and decodes Mode S transponders, used by aviation to report aircraft information in real-time.

Originally written by Salvatore Sanfilippo in 2012 for the RTL-SDR dongle, it was patched by several people and in 2017 it was updated by Jiang Wei to support the Pluto SDR. My contribution to the project is minor. I've updated the on-board web-server to use Open Street Map and a few other cosmetic changes.

For me it was a "Hello World" project, something that's the software equivalent of warming up your soldering iron and pre-tinning the wire you're about to use.

The tools to do this is what I want to discuss.

When you look at the software that underlies much of the SDR world, the digital modes, logging, contesting, even the software inside tools like the Nano-VNA, much of it is open source. That means that as a curious amateur you can have access to the underlying equivalent of the circuit diagram. As you can with a soldering iron, a scribe and wire, you can patch or update a circuit. In the software realm you can do the same once you have access to the source code.

The tools you're going to get in touch with are text editors, compilers, libraries and configuration files. If that's not your thing, I appreciate that, but if it sparks your interest, you'll open the door into a brand new world of software development where you can determine how a mode works or what it supports or how it interacts with your radio or testing gear.

When you jump in, likely feet first, you're going to make mistakes and lose hair and sleep and you'll be shaking your virtual or physical fist at the person who came before you, but then that's the world of experimentation, so likely you'll already have that down pat.

You'll likely play with different tools that require different versions, often installed side-by-side, much to your chagrin when you learn that it just won't work. Not to mention that removal of the offending tool often leaves interfering cruft behind, not unlike unsightly and short-circuiting blobs of solder.

I'm here to introduce you, albeit briefly, to a tool that will take much of that pain away. The free tool is called Docker. It has got little in the way of visibility in the amateur radio world, but in the software development world it's pretty much old hat.

Essentially the idea is that you can install stuff into a so called disposable container so you can have your copy of dump1090 installed in one container and your copy of codec2 in another, a copy of rtl-sdr in a third container, all working independently from each other, without needing to complicate things with multiple computers or virtual machines. If a developer uses Debian, another uses Ubuntu and a third uses Red Hat, you can run these side-by-side without any issue. If they need an ancient version of something, that too is handled without a problem. Make a mistake, destroy the container and start again, fresh.

Docker is a tool that allows you to build an environment on Linux, MacOS and Windows, as well as the Raspberry Pi, that acts and behaves in many ways like a virtual machine. In all the ways that you're likely to use it, at least initially, it's indistinguishable. What that means is that the operating system, the compiler and the libraries that you need for one tool won't affect those needed for another tool.

The best part of this is that you can build on a massive library of pre-existing Docker containers and use files that describe how to build and compile tools like dump1090.

If you look for my callsign vk6flab on github.com, you'll find my version of dump1090 and you'll find a Dockerfile that describes how I built it. The project contains all the bits you'll need to get started with your own version of dump1090, or some other project that tickles your fancy.

Every time you build something, the amateur radio sphere of influence grows just that little bit.

I'm Onno VK6FLAB

What is a repeater offset and how does it work?

Sat, 07/04/2020 - 12:00
Foundations of Amateur Radio

Every week I run a net for new and returning amateurs. A variety of people join in with varying degrees of skill, knowledge and number of birthdays.

One of the regular things I say during that net is that if I'm not acknowledging you, it's because I cannot hear you. I then start a spiel about repeater offsets and give some examples, but what is it really and how does it work?

As you might recall, a repeater is a radio, generally located somewhere useful, like on a hill or tall building, that offers the ability to talk to other amateurs who are not within range of your radio.

For bands like 2m, 70cm and 23cm, generally speaking, contacts are line-of-sight. If you're standing on a hill, you can talk to more people because your line of sight is further away.

This is also why you can talk to the International Space Station with a hand-held, since it's in your line-of-sight, at least some of the time.

A repeater acts as a line-of-sight extender. If it can see both you and another station, it can act as a bridge between you.

How it does this is pretty simple. A repeater listens to your signal and transmits that to the other station. It uses two separate frequencies to make this happen. A receive and a transmit frequency, or more precisely an input and an output frequency. To remember which is which, you can think of a repeater as a giant megaphone, you talk into it and sound comes out. Said differently, think of a repeater as a device that takes an input from one station and makes an output for everyone to listen to.

To actually use a repeater, your radio needs to be setup to transmit on the repeater input and it needs to receive on the repeater output. This means that when you transmit, the repeater can hear you and when you're listening, you can hear the repeater.

To achieve this, you can set your radio up using repeater mode. It uses a thing called an offset to set the difference between the input and output frequencies.

To find out what the offset is, you take the repeater input frequency and subtract the repeater output. If you've set-up your radio correctly you're tuned and listening to the repeater output. When you hit the Push to Talk or PTT, you'll transmit on the input frequency and when you let go, you're back to receiving on the output frequency.

One final roadblock might be that your local repeater has a tone lock. If it does, the repeater will ignore you even if you have all the frequencies correct. This tone is generally published by the repeater owner or your local regulator. You can also check a website called repeaterbook.com to see many of the world's repeaters and their specific settings.

Now, I should point out that while repeater offsets are standardised, they're not the same across bands, across the world, or even within a country or city. Depending on where you are, what the density of repeaters is and what band you're on, the offset number and direction will change.

It's even possible that you have a variety of offsets on the same band in the same city. This means that you cannot just pick a standard offset for your radio but most modern radios will have a method to deal with this.

It's easy to get this wrong.

Setting up your radio for using a repeater is deciptively simple. Three things to look out for when it's not working. You have the input and output reversed, the offset is wrong, or there's a tone blocking your transmission.

I'm Onno VK6FLAB

Your antenna is a filter (of sorts).

Sat, 06/27/2020 - 12:00
Foundations of Amateur Radio

The single most discussed topic in amateur radio is that of antenna design, that and medical procedures on 80m, but I kid. Previously I've discussed the notion that all frequencies are on-air all the time and that your traditional radio uses much of its electronic circuitry to filter out all the things you don't want to hear.

Parallel to that is the concept that you tune your antenna to be resonant on a particular band or frequency. As amateurs we might look for a wide-band antenna that makes it possible to use our radio across several bands. We often construct our antennas to be multiple harmonics of a band so we can have access to more spectrum without needing more physical antennas.

None of this is new and as an amateur you'll likely spend the rest of your days improving your antenna situation, or at least talking about it, if not outright bemoaning the lack of antenna space, family approval, budget or some other excuse.

As I started my journey into Software Defined Radio a new idea occurred to me. If an antenna is a resonant circuit, could you think of your antenna as a filter, as-in, something that leaves out the things you don't care about?

In and of itself I'm sure I'm not the first to consider this notion, but the idea means that you essentially turn your idea of an antenna on its head, from something that receives to something that rejects.

Consider for example the small transmitting loop antenna, often also called a magnetic loop antenna. It's got one characteristic that isn't often considered a benefit, it has something called a High-Q, or a high Quality Factor. The higher the Q, the narrower the bandwidth.

I should digress here for a moment. Q is a number. Big number means narrow bandwidth, little number means wide bandwidth. It's easy to calculate. If you look at an SWR plot of an antenna you'll see a curve where the bottom of the curve is the lowest SWR of your antenna, that's the centre frequency. You'll also see two points on the same curve where the SWR hits 2:1. If you take the centre frequency and divide that by the difference between the two edge frequencies, you'll have the Q of that antenna.

Using numbers, consider an antenna that's got an SWR below 2 between say 7 MHz and 7.2 MHz, a bandwidth of 200 kHz, you'd have a centre frequency of 7.1 MHz. The Q of that antenna would be 7100 divided by 200 or a Q of 35.5

If you had an antenna that had a bandwidth of 5 kHz at 7.1 MHz, it would have a Q of 1420.

And just to wrap that up. This is helpful because just comparing bandwidth on different antennas doesn't tell you enough. Is an antenna that has 400 kHz bandwidth on 20m more or less selective than an antenna with 200 kHz bandwidth on 40m, what about 100 kHz on 80m?

Back to the small transmitting loop antenna or mag-loop. If you're using such an antenna on an amateur band like say the 40m band, you'll likely have to re-tune your antenna every time you even think about changing frequency. I've had the frustration of using a manual version of such an antenna and it can wear thin very quickly.

I'm bringing this up because it can also be a benefit.

Imagine that you need to make a contact on a busy band during a contest. Often you'll find yourself setting up the filters on your radio, trying hard to remove all the extraneous noise that comes from strong signals nearby.

What if your antenna could help with that?

What if you thought of your antenna as a pre-filter, something that makes the job of extracting just that signal from the bit of spectrum you're interested in?

My point is this.

We're talking about an antenna that from one perspective can be a pain to use, requiring constant retuning, constant adjustment, just to get on the air and make noise.

From another perspective, that very same antenna is a way to filter out the things you don't want to hear and extract the signal you care about.

How you approach this depends on your perspective and just considering your antenna as a filter might help you see another side of your antenna system that you hadn't considered before.

How you use this is entirely up to you. For my money, I'll be doing more experiments.

I'm Onno VK6FLAB

If you WSPR and nobody hears you ...

Sat, 06/20/2020 - 12:00
Foundations of Amateur Radio

The day came to pass when all my set-up and configuration was going to culminate in the moment of truth when I enabled TX on my WSPR mode station. Before I tell you of my experience, I should give you a little bit of background.

A few weeks ago I managed to erect a HF vertical at my home or QTH. That in and of itself was news worthy, well at least to me it was, since it was the first time since I became licensed in 2010 that I had actual real all-band HF capability at home. Last weekend I ran some RG6, yes, 72 Ohm Quad Shield, low-loss coaxial cable, from my antenna, through the roof, into my shack.

I was thrilled.

Immediately set about getting my HF station up and running. This involved installing WSJT-X, a tool that allows you to do weak signal work, perfect for when you're a low power or QRP station like me. I've previously reported using WSPR, Weak Signal Propagation Reporter on a Raspberry Pi and a dongle, but this time I was using my Yaesu FT-857d.

Reports were coming in thick and fast. Managed to hear stations on all the bands I'm allowed on, 80m, 40m, 15m, 10m, 2m and 70cm. Managed to make it report online and update the various maps around the place.


Now I wanted to do the next thing. Transmit and see who could hear me and how far my beautiful callsign might travel on 5 Watts.

So, after some abortive attempts, I configured the levels correctly, made sure that my antenna coupler, an SG-237, was tuned and hit "Enable TX" on the screen of my computer.

Dutifully my computer did what was expected, turned on the transmitter and happily made the fan run on my radio for two minutes at a time. I tried 80m, 40m and 15m. All worked swimmingly.

Then I looked on the map to see who had heard me.

Nobody. Nothing. Nada. Niets en niemand.

I could hear N8VIM using 5 Watts, 18649 km away, but nobody could hear me, not even the station VK6CQ who is 9 km from me.

So, what's going on?

Turns out that I'm not using a "standard" callsign. That's right, my VK6FLAB, authorised by the World Radiocommunication Conference 2003, implemented by the Australian regulator, the ACMA in 2005 and issued to me in 2010 isn't a standard callsign.

Seems that the deal-breaker is the four letter suffix, FLAB, that's killing my attempts at making contact.

Now I know that there are moves under way, not quite sure what stage they're at, to allow Australian amateurs to apply for any three-letter suffix and keep that regardless of their license level, but that to me doesn't really solve the underlying issue, where a perfectly legal callsign isn't allowed to be used by one of the most popular modes today.

I've lodged a bug report on the WSJT-X mailing list, but to accommodate this callsign will probably require a fundamental change in the way the WSPR mode and likely several other JT modes will work, not to mention the databases, the maps, API calls and other fun things like logging.

Technically I could have figured this out back in September 2019 when I was first allowed to use digital modes with my license, but I didn't have an antenna then.

In case you're wondering. I also investigated using a so-called extended, or type-2 message, but that allows for an add-on prefix that can be up to three alphanumeric characters or an add-on suffix that can be a single letter or one or two digits.

I could use something like VK6FLA/B, but I'm sure that the owner of VK6FLA would be upset and using VK6/F0LAB might have a French amateur yell Merde! at me when they spot their callsign being transmitted from VK6.

One suggestion was to upgrade my license.

What's the fun in that?

I'm Onno VK6FLAB

Using something for an unexpected purpose can give you many great rewards.

Sat, 06/13/2020 - 12:00
Foundations of Amateur Radio

The other day I was getting ready to go out when rain started pelting down. Not unexpected in this part of the world at this time of year but inconvenient for my plans.

I didn't particularly want to carry an umbrella and the thought of wearing a rain hood brought back memories of water trickling down my back.

For reasons I'm not quite sure of, my eye fell on my hat on its hook at the door. The hat I wear in the heat of summer to keep my brain from frying, the hat I use whilst camping with my amateur radio friends, the hat I've worn whilst loading massive hay bales with a tractor and the hat I've worn swimming in the Ord River - well, a descendent, third generation if I remember correctly. I shook my head in disbelief, after donning my raincoat, put my trusty Akubra Territory on my head and stepped out into the rain. Perfect. Kept me dry, kept my glasses clear and no drips down my back.

You may well wonder what this has to do with radio and that's a fair question. I will preface this with a disclaimer that you might not have this set-up in your shack just now, but perhaps it will inspire you to get started.

I've been talking a lot about Software Defined Radio, and I do believe that it represents the future for our hobby, but that doesn't mean that my traditional radio, in my case a Yaesu FT-857d, is headed for the scrap heap just yet.

As you might know, with some preparation you can connect your radio to a computer and control it. You can also connect both the send and receive audio to a computer using a variety of techniques which I probably should get into at some point.

Assuming that you have, and I realise you might not yet have done this, but assuming for a moment that you have made this all work, you can use this to do things like JT65, FT8, PSK31, SSTV and hundreds of other modes.

One thing I did during the week was use this set-up to listen to noise. Seriously, that's what I did. I picked a spot on the band with nothing but noise. No discernible signal and fired up the application WSJT-X, it's the tool you use for many weak signal modes. As an aside, as a tool, it is also helpful in getting your digital mode levels set correctly.

One of the windows in WSJT-X is the waterfall and spectrum display. On it you can see the signal as it is right now and how it's been in the past.

If you turn on one of the filters on your radio, you can see the display change. You can literally see what gets filtered out. On my radio I've got the standard filter, as well as a 2 kHz and a 300 Hz Collins filter. Using this technique, you can specifically see what each filter does. If I turn on the built-in Digital Signal Processor, the DSP, I can see what the adjustments do, as well as the impact of the mode on the filter. And how the various settings interact.

For example, until I saw this display, I didn't know what the "DSP HPF CUTOFF" and "DSP LPF CUTOFF" specifically did and how they interacted with the other filters. Similarly what "DSP BPF WIDTH" did and how.

I also didn't know that even if you set both the high and low pass filter frequencies to the same value, you still have a usable filter, even if you might think that nothing could get through.

Now I do realise that your radio may not have those specific settings, but I am confident that if you pick a spot on the band, set up a frequency display and waterfall, you'll discover things about your radio that you hadn't before. I also realise that you can hear some of this by just playing with filters, but seeing it on the scope adds a whole other dimension to the experience. Just one example is to see how a narrow filter interacts with the in-built DSP, something that's difficult to hear, but easy to see.

If you have a Morse beacon to hand, you can also see how various frequency shifts work and the impact of selecting filters in relation to that signal. No need to just listen to the beacon with just CW mode either. Have a look at it using SSB.

Using something for an unexpected purpose can give you many great rewards. As for the hat, really, I hadn't used my hat to ward off the rain until then; you live and learn.

What have you discovered recently?

I'm Onno VK6FLAB

How to pick a field operating position?

Sat, 06/06/2020 - 12:00
Foundations of Amateur Radio

Much of the operation that I've done as a radio amateur is conducted in the field. That is, I tend to either drive my car to a location, or go out with friends and set-up camp to play. After you do this for a while you start to notice the things that you look for in an operating position.

The very first one is accessibility. That is, how easy is it to get there? It's fine coming up with the ultimate location, but if it's an hour's drive away and you've only got an hour to play, you'll spend all your time getting there and you'll be home late.

By contrast, for field days lasting several nights, I've regularly driven more than a hundred kilometres to find the spot, sometime much more than that. The point is that the accessibility changes depending on your available time. The journey to the location can be just as much fun as the destination itself.

How long you plan to be there will determine what antennas you might want to set-up. If you're there for an hour, you'll likely use a vertical on your car. If you're there for the weekend, your antenna farm will be determined by how much wire you brought and what you can hang it off.

Hanging antennas is the next thing. You can bring your own poles, but for height, nothing beats a solid tree. The taller the better. More taller, more better. If you have several to choose from, you get to play with all manner of fun stuff. For one antenna contraption we had three trees that we ran a wire between. They were roughly spaced in a triangle about 200 meters apart from each other. As I recall, the antenna we built, a massive V-beam managed to talk to Europe for most of the weekend.

For another adventure a simple G5RV dipole was hoisted high into the trees. Another was accomplished by strapping a pole to a fence and setting up an inverted-V antenna. Recently we set-up an antenna that was nothing more than a wire running over the ground.

So, generally speaking height is good. You can cheat by having a low tree and a hill. Or a fence and a pole, or a gazebo and tent-pegs. What ever you can do to attach an antenna to will work to some degree. Which reminds me, if your hill is tall enough, it's likely to have a communications tower on it for someone, if not everyone. They're not the end of the world, but they can cause havoc with noise. Depends entirely on what the communication structure is used for. Bear in mind, some of these sites have noisy solar panel inverters or generators, so that too needs to be taken into consideration.

Another factor in picking a location involves water. Setting up a vertical on a jetty is gold. I've made many long-distance contacts using a vertical with a ground wire running into the ocean. Note that you don't have to actually get wet. Being near the ocean is often enough. I've had plenty of success from a beach car-park from a vertical on my car.

In general, man-made objects such as houses, factories, other cars, power lines, generators, boats, camping grounds with solar panels and plenty more are often bad news for HF communications. The biggest disappointment happens when you take the time to go to a site, set up camp, build your antennas, turn on the radio and all you hear is the noise from a nearby source of interference.

That said, you don't need to travel to the ends of the earth either. 15 minutes from my house is a lake with a park. There's a car park which on occasion attracts a motor home with a solar panel, but by enlarge it's a local park with people going for a walk. From a radio perspective, despite homes, businesses, schools and cars nearby, the place is heaven. It's quiet, it has shade, running water, fence posts and I regularly make contacts from there, right in the middle of the city.

That brings me to another aspect. Creature comforts.

Setting up near a busy road isn't fun. Neither is sitting in your car without shade. Having amenities within reasonable distance helps. For example, recently for a field day we set-up within 10 minutes drive from a regional centre. Didn't even notice it was there, happily dropped in for shopping and a meal. Some beers might have been consumed.

That same site also had high voltage power lines near our location. The only difference was that our site was above the power lines at the top of a hill, so we never even noticed them.

Finally, some of this is all about picking a camp-site that's suitable for radio, rather than a radio site that will handle camping. You get better at it the more you do it. If you check back after the adventure, you'll learn some stuff as well, so don't be shy to discuss your experience with your friends.

What ever you do, practice makes perfect.

I'm Onno VK6FLAB