Foundations of Amateur Radio

By: Onno (VK6FLAB)
  • Summary

  • 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?".
    ℗ & © 2015 - 2025 Onno Benschop
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Episodes
  • Finding your path in this hobby
    Feb 1 2025
    Foundations of Amateur Radio

    As you might recall, recently I stumbled on an excellent list of 52 weekly challenges put together by Fabian, DJ5CW and friends. You can find it at hamchallenge.org. As I've previously mentioned, it contains activities right across the amateur spectrum, from designing a QSL card to making a contact on 80m or 160m, with everything in between. It's an excellent tool to set a weekly goal to achieve and I recommend that you have a go.

    It's not the only interesting tool around.

    Amal VU3FTH and Steph Piper, whom you might know as MakerQueen AU, have put together an "Amateur Radio Skill Tree". It's a collection of hexagonal tiles, each with a skill, displayed together in an attempt to track what you know and could know about amateur radio. The idea is that you print it out and colour in each tile as you complete it. You'll find things like "Explore D-Star", "Build a cw key", "Teach a friend about Amateur Radio", and plenty more. Can you get four activities in a row and which skills could do with more effort? There are 68 tiles ready for your colouring pencil .. Bingo!

    The Radio Amateur Training Planning and Activities Committee, better known as the RATPAC, put together an "Amateur Radio Challenges Checklist for 2025" and published it on mastodon.radio. It's a list of bands, modes, activities, builds and clubs that help you track what you've been up to throughout the year. While we're here, I should mention that the RATPAC in their words "comprises Amateur Radio Operators of a wide variety of backgrounds and experiences", and hosts two weekly Zoom meetings so anyone can participate in the talks published on the ratpac.us website. If you're unable to attend, you'll find the presentation on YouTube.

    Over the years I've been part of this amazing hobby, I've been telling anyone who will listen that there is plenty to do and see in our community, a thousand hobbies in one. The tools I've mentioned represent around one hundred and fifty activities and pursuits, but hidden behind each one is plenty to explore. For example, hamchallenge asks you to spend week 21 creating a GNU Radio flowgraph. That topic alone could fill a decade worth of exploration if you were so inclined. Similarly, one of the Skill Tree tiles is "Study RF propagation", something which you might realise is easier said than done. The RATPAC checklist has a tick box for "Work 100 countries", not something you're likely to achieve in an afternoon.

    My point is, you can do as much or as little of this as you like, to what ever degree floats your boat. As you might know, I'm deep in the weeds with GNU Radio and I expect to stay there for plenty of time to come, but you are under no obligation to follow me down the rabbit hole. In other words, it interests me, but it might not do the same for you.

    One final comment. None of these activities require you to upgrade your license, well, other than the Skill Tree tile "Upgrade your radio license". You can do most if not all of the activities I've shared with any amateur license and plenty of it can be done without a license at all.

    So, what are you waiting for?

    I'm Onno VK6FLAB

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    4 mins
  • Bald Yak, scene 7, building a circuit without burnt chicken smell
    Jan 25 2025
    Foundations of Amateur Radio The other day I was sitting on the couch lounging about when I came up with an idea and there and then I picked up a circuit board, soldered down a hundred or so components and built a noise cancelling gadget, all within about an hour .. right there, on my couch. Yeah, that didn't happen, least of all, my soldering skills are not up to scratch, never mind the couch. I did however build a noise cancelling circuit, on my couch, in about an hour, but no soldering iron was hurt and the room didn't smell of chicken afterwards. Instead I used GNU Radio to put together a series of blocks that allow me to apply noise cancelling to a signal. How does this work? Well, imagine a signal mixed together with the negative version of that signal, think of it as swapping positive and negative if you like. If you mix two identical signals together, one of them inverted, you end up with nothing, because they cancel each other out, where one is high, the other is opposite and low and vice versa. Mix a high signal with a low signal, you end up half-way. If they're the same but opposite, half-way is zero. Hearing nothing is not helpful, but what if the two signals were slightly different, let's say, one is connected to a proper 10m antenna and the other is connected to an antenna that picks up local noise. We'll call the antenna on 10m the "signal" and the local noise antenna the "noise". If you mix these together, you end up with a signal and noise combined, but if you invert the noise signal, you can, at least theoretically, filter out the noise that's common to both antennas. Now I did say "theoretically" and that's because while it sounds simple, it's far from it. Unless you have a special radio, the two signals are not coming from the same device and won't really be identical where it matters. For example, let's call it the volume or gain of one might be higher than the other. One might arrive slightly later than the other if the coax isn't the same length or the electronics in both radios are different. There are other things too, but let's just stay with this for a moment. You could amplify or attenuate one or both signals to make them the same or similar levels. You could change the phase, think of it as the time when a signal starts, and synchronise the two signals in time manually. Of course whilst you're doing this, inside GNU Radio, the computer is doing some serious math, which takes time to make these changes, which introduces further delays you'll also need to account for. Building it was simple. Testing it much less so. After coming to grips with the USB port on my computer, which for reasons best known to the manufacturer, cough, Apple, switches off ports that are in use, I managed to get two RTL-SDR dongles connected and working. This involved removing GNU Radio, which was installed using a tool called "homebrew", then installing it instead using "radioconda", twice, since the first time the installer failed with an error, actually three times, because the failed installation left all manner of rubbish behind, so that needed to be removed; then I had to disconnect my keyboard and track pad, because for reasons only known to the manufacturer, yeah, the same one, they won't play nice if there's an RTL-SDR dongle plugged into the USB-C hub, I finally got this running, which in turn involved figuring out what the GNU Radio "Device Arguments" look like for a locally connected dongle, in case you're wondering, it's "rtl=0" for the first one and "rtl=1" for the second. Clearly this project is living up to its name, Bald Yak. Now I can invert a signal, I can amplify and attenuate it, change the phase, shift the frequency, swap the I and Q, do a complex conjugate, and have a user interface that can change these settings as required. I'm going to ignore the hour of my life I'm not getting back to understand how variables, parameters and user interface items hang together and how they interact. It's logical, but it takes a bit to wrap your head around it and I'm a software developer, so I don't envy you if you're not. Anyway, I tuned to a local FM broadcast radio station and couldn't make any noise go away. I then discovered that my noise antenna was picking up the station just fine, so that didn't help. Then I swapped radios, actually, I just swapped the zero and the one in the "Device Argument" fields and tried again. In the process I discovered how you can create a so-called "Hierarchical Block" in GNU Radio and to my delight also discovered that there is one that can have a user interface, so I can make a stand-alone block, that has a user interface, that I can use in another project, which is how I intend Bald Yak to function. So, changing stations, I could finally hear noise, but still no reduction. Then I realised that I was using FM, not single side band, so I started hunting for an SSB decoder but had to abandon ship to go and do life. Overnight I realised that ...
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    6 mins
  • WSPR beacon QSY to 15m
    Jan 18 2025
    Foundations of Amateur Radio

    For quite some time I have operated a WSPR or Weak Signal Propagation Reporter beacon on the 10m band. If you're not familiar with it, I've dialled the power right down to 10 dBm, or 10 milliwatts. You'd think that this would be a fool's errand, but it was heard 13,945 kilometres away. Of late the reports have been far and few between, despite the 10m band being quite active.

    Encouraged by a friend playing on 15m, I made the decision to change bands. At the moment this is not a trivial process, though at some point in the not too distant future, hopefully before I need a Zimmer Frame, I intend to erect a multi-band Hustler 6-BTV antenna that has been in storage for several years. Before that occurs, since it involves all kinds of shenanigans, I went for a simpler option, replace the 40m helical whip antenna with a 15m helical whip, something I can do without climbing on the roof.

    In case you're wondering, using an SG-237 antenna coupler, the 40m antenna tunes fine on 10m, but not so much on 15m.

    After pulling the replacement antenna from its hidey-hole I discovered that it was missing a tip. I don't recall if it ever had one, it came from the estate of a fellow amateur, Walter VK6BCP (SK). I took it on faith that it worked on the band that it was labelled with and went looking for a way to close off the tip. In the end I used heat shrink with a glue lining and sealed it off, folded over the tip and used more heat shrink to keep it folded over. We'll see how well that works.

    I then unscrewed the 40m antenna from its mount and was frustrated that it would only come with the spring attached. Using a crescent and a pipe wrench I was able to unscrew the spring but discovered that the threaded stud that connects the two didn't stay in the antenna, instead it stayed in the spring, which meant that I couldn't attach my 15m antenna without breaking something.

    I remembered that I had another spring lying around, so I dug that out of storage, I really need to set-up a "part-db" to keep track of where everything is, and attached the 15m antenna to the spring and screwed it back into the antenna mount and I'm back in business.

    In putting away the 40m antenna I lifted it up after removing the spring and promptly got wet. Litres of brown water came pouring out of the antenna. It turns out that the adjustable tip isn't sealed and sitting on my roof for several years managed to fill it full of water, that's through a tiny opening at the tip, in a country known for hot and dry, it's expected to be 40 degrees Celsius here today. It made me wonder if that water was why the beacon wasn't heard recently.

    The next step involved changing the beacon frequency. The hardware is a ZachTek 80To10 desktop transmitter, built by Harry, SM7PNV. The software to change settings runs on Windows and since my system crash in June last year I've not had any Windows machines lying around. I went to the ZachTek website and discovered in the downloads section that there is a link to a web page configuration tool written by Phil VK7JJ, of wspr.rocks fame, that allows you to open a website, plug in your beacon, and configure it from any Chrome web browser. I was both astonished and delighted that this exists.

    I changed the beacon band from 10m to 15m and powered it up.

    One final step. As I said, for the last little while my beacon has only sporadically been heard, so I set up a local monitoring system. It consists of a little computer connected to an RTL-SDR v3 dongle and the included telescopic dipole. Using a Docker container written by Guenael VA2GKA, I monitor my own beacon. After updating the band from 10m to 15m, reports started flowing in.

    As an aside, the last time I did this I built a custom Raspberry Pi image and had to change several things to start monitoring after a reboot. This time I used an inbuilt Docker mechanism, "restart unless stopped", to launch the container. This means I don't need to alter the system and I can add and remove containers as I need to.

    This is important because it's likely how some of the "Bald Yak" project will also gain functionality.

    I'm feeling rather chuffed that on my first day back as a human after recovering from my first bout of COVID, I managed to move my beacon to 15m, get it on-air, configured and transmitting with confirmation in the log.

    The only thing missing now is your signal report.

    I'm Onno VK6FLAB

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    5 mins

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