Foundations of Amateur Radio

Foundations of Amateur Radio The other day I saw a post by fellow amateur Gary N8DMT who mentioned an "RF circulator" and a PlutoSDR in the same sentence. Amplified by a response from a fellow Aussie Electronics Engineer, "ozeng", who helpfully added a link to a Wikipedia article about circulators, it finally twigged that I had such a gadget in my possession and for the first time I realised how I might use it. Now, before I continue, I'll preface this with a disclaimer, this is a hand-wavy description of what this very interesting device does. "ozeng" calls it "Absolute witchcraft." and that's an apt description if ever I've heard one. Imagine for a moment a radio with separate transmitter and receiver connectors, attached to the same antenna using a T-piece, as-in, there's a run of coax coming from each connector, joined together with a T-piece, which in turn is connected to an antenna. The aim of this, don't do this at home contraption, is to avoid the need for two antennas, but, and it's a big one, doing this will very likely destroy your receiver the moment you transmit for the first time, because likely half the transmission will go to the antenna, while the other half makes its way to the receiver, which is not going to be something you want to happen, unless you like the smell of magic smoke. You might think that adding an attenuator, something that reduces the power on the receive port would help. Well, yes, it would, but as a side-effect, it would also reduce the signal coming from the antenna. At that point you'll decide you need a switch. Initially you might switch this manually, but that's a pain if you're wanting to transmit and receive continuously and need to remember in which position the switch is in. The next step is to use an electronic switch, like a relay. It can trigger based on some signal from the radio when it's transmitting and turn off the receive path during a transmission. This raises an issue with delay. Do you trigger just before you hit the PTT, as-in, time-travel, or do you delay the transmitter until after the relay has switched, which will cut off the beginning of your transmission? You'll likely have heard this kind of issue when listening to a station using an external amplifier. Their signal either jumps from low power to high power after they key up, or you miss the beginning of their callsign. Not to mention that if you get the delay wrong, you blow up the receiver, fun for people watching, not so much for the equipment owner. Even if you get the timing right, you cannot transmit and receive at the same time. Of course an obvious solution is to have two antennas, but soon you'll discover that when you're transmitting and receiving on the same frequency, even using two antennas, you'll have the exact same issues. It's why the local 10m repeater here in Perth, VK6RHF, has the transmitter in one location and a receiver 12 km away, connected to each other via a 70cm radio link. Other solutions in this space are cavity filters, duplexers and diplexers. These all require that the transmit and receive frequencies are different and the equipment is generally tuned to a specific pair of frequencies. Physically cavity filters can be massive, not to mention fragile. So, solving the issue of having a transmitter and receiver together on the same frequency is one that is challenging to say the least. It's a common issue, think about mobile phones, satellites, broadcast transmitters, and even your own amateur radio station. An RF circulator is a device that solves this in an extremely elegant way. For starters, it's a passive device, which means that you don't need to power it, there's no moving parts, no switches, no delays, no external controls, it's a box, generally with three sockets or ports, though versions exist with more. At a basic level, it works like this. A signal inserted into port one, will only come out of port two. Similarly, a signal into port two, will only come out of port three and finally, a signal into port three, will only come out of port one. Think of it as a one way roundabout. How is this useful you might ask. I'll illustrate by plugging in three things, connect port one to an antenna, port two to a receiver and port three, a transmitter. When you transmit into port three, the signal only goes to the antenna, leaving the receiver safe and happy. Similarly, any antenna signal will only go to the receiver. So, how does this work? Remember, hand-wavy. Essentially, it's based on the idea that radio waves travelling in one direction combine and waves travelling in the opposite direction cancel. Different types of circulators achieve this in different ways and come in different sizes as a result. The RF circulator I have is roughly 60 mm square, 30 mm thick, weighing in at most of half a kilogram and as far as I know, intended for operation around 850 MHz. If I recall correctly, it came out of a CDMA mobile phone tower. The parameters that describe an RF circulator are the frequency range, the insertion loss, or how much signal gets lost getting from port one to port two, the isolation, or how much signal leaks between port one and port three and a couple of others. Hopefully I'll be able to use a NanoVNA, or PlutoSDR to get a sense of what these values are and confirm the frequency range. Now, if that doesn't blow your mind, wait until I tell you about the two hundred year history that accompanies it. I'm Onno VK6FLAB

Foundations of Amateur Radio The other day I received an email from Frank K4FMH asking me about an idea I'd worked on some time ago, namely the notion that I might monitor solar flux at home using a software defined radio. At the time I was attempting to get some software running on my PlutoSDR and got nowhere fast. Before I continue, a PlutoSDR, or more formally an ADALM Pluto Active Learning Module by Analog Devices, is both a computer and a software defined radio receiver and transmitter in a cute little blue box. I've talked about this device before. It's an open design, which means that both the software and hardware are documented and available straight from the manufacturer. Out of the box it covers 325 MHz to 3.8 GHz. You can connect to a PlutoSDR using USB or via the network, wireless or Ethernet, though I will mention that neither of those last two is currently working for me, but more on that later. Encouraged by Frank's email, I set out to explore further and came across a 2019 European GNU Radio days workshop, which discussed some of the tools that are available for the PlutoSDR, accompanied by two PDF documents walking you through the experience. One comment around why the PlutoSDR uses networking as one of the connectivity options spoke to me. From a usability perspective, networking makes it easier to access the PlutoSDR from a virtual machine, since most of the time that already has network connectivity, whereas USB often requires drivers. As you might recall, network connectivity is one of the many things that I'm trying to achieve with a project that I'm calling Bald Yak, since by the time we're done, there's not going to be much hair left from all the Yak Shaving. The Bald Yak project aims to create a modular, bidirectional and distributed signal processing and control system that leverages GNU Radio. As a result, I set about trying to actually walk myself through those PDF tutorials .. and got stuck on the first sentence on the first page, which helpfully states: "The necessary prerequisites have been installed on the local lab machine." It went on to supply a link to a page with instructions on how to acquire those very same prerequisites. Two days later, after much trial and error, I can now report that I too have these installed and because I cannot help myself, I made it into a Docker container and published this on my VK6FLAB GitHub page. To put it mildly, there's a few moving parts and plenty of gotchas. As an aside, if you think that installing Docker is harder than installing these tools, I have some news for you .. trust me .. by a long shot .. it's not. Right now I'm working on writing the documentation that accompanies this project such that you can actually use it without needing to bang your head against the desk in frustration. Mind you, the documentation part of this is non-trivial. For reasons I don't yet understand, my Pluto does not want to talk to the network directly over either WiFi or Ethernet, and connecting over USB through a virtual machine inside a Docker container is giving me headaches, so right now I'm connected across the network to a Raspberry Pi that's physically connected to the Pluto. As a result, I can now use the tools inside my Docker container, connected to the Pluto through the Pi and if you're curious, 'iiod' is the tool to make that happen .. more documentation. At this point you might well ask, why bother? This is a fair question. Let me see if I can give you an answer that will satisfy. Monitoring solar flux typically occurs at 2.8 GHz, which is outside the range of RTL-SDR dongles which top out at about 1.7 GHz. For the PlutoSDR however, it's almost perfectly within the standard frequency range. One of the tools that is introduced by the talk is an application called 'iio-scope', which as the name suggests, is an oscilloscope for 'iio' or Industrial I/O devices, of which the PlutoSDR is one. As an aside, the accelerometer in your laptop, the battery voltage, the CPU temperatures, fans, and plenty of others, are all 'iio' devices that you can look at with various tools. So, once I've finished the tutorials, I suspect that I will understand a little better how some of the various parts of the PlutoSDR hang together, and I can set it up to monitor 2.8 GHz. Of course, that's only step one, the next step is to make a Raspberry Pi record the power levels over time, better still, record it on the PlutoSDR itself, and see if we can actually notice any change .. without requiring anything fancy like a special antenna, some massive filters, a special mount and all the other fun and games that no doubt will reveal themselves in good time. It also means that, if I got this right, I have the beginnings of the bits needed to get the PlutoSDR to talk to GNU Radio. Why? Because I can, and because Frank asked, also Yak Shaving. I'm Onno VK6FLAB

Foundations of Amateur Radio The other day I went on my first POTA or Parks On The Air adventure, this time I was on my own. If you recall, my power company announced yet another planned network outage and I felt that I could use this time without electricity to my benefit, for a change. As is traditional, I did all the prior planning to prevent pretty poor performance. I made a list, checked that all the items on the list were in my kit, packed the kit days before, put it all ready to go in the hallway the night before, packed the car on the day and set out on my adventure. I will confess that I was slightly more sweaty than anticipated when I set off because the umbrella in the boot of my car has a nasty and recurring habit of getting in the way, specifically it stops things from getting pushed right to the full depth of the boot. Mind you, it wasn't until I started getting agitated that I realised that it wasn't the umbrella's fault entirely this time, since as it turns out, the folding chair that I was attempting to jam in place doesn't actually fit longways into the boot. Anyhoo, I set off and visited the local petrol station. I was not prepared for a customer to spend 15 minutes dribbling the last bit of diesel into their pretend Sports Utility Vehicle, but he looked like he was up for a fight, so I smiled sweetly and waited for him to pay and move his box on wheels. After paying for my own fuel and driving off, the pressure in my bladder had gotten beyond the "cross your legs and hope for the best" stages and I swiftly made my way to the nearest shopping complex where a local pharmacist helpfully told me that there were no toilets in the building and that the local hotel or fast food joint were the place to relieve the pressure. One problem .. they were both closed. At this point I was in pain, and discovered that I couldn't read the screen on my mobile phone in the lovely sunlight, because it was set to battery saving mode, since my charger was at home where the power was out. After disabling the battery saving mode I opened the local public toilet map shortcut on my phone, and discovered that fortunately the shortcut still worked, opening up my default browser, which suddenly didn't want to display a map. Copied the URL to another browser, still in pain, finally a map. Click on the nearest icon and it navigates me there from Darwin, or over 4,000 km from where I actually am. Luckily it has the GPS location which I copy and then paste into my mapping app, and I can finally navigate to the nearest toilet. Several comment worthy navigation moves later, I drive into the car park, lock the car, painfully shuffle to the building, do my business in the very clean facilities and then decide that I should just stop, sit, and take a breath. So, I get in the car and discover that my partner was right when they heaped scorn on our newly acquired thermos cup. It really does hurt your nose when you try to drink from it and the sharp edges in your mouth do nothing to make the experience joyful. Meanwhile there's some trucks moving around in the car park and a guy walks up to the car to ask me if I can move because they want to move a third, or was it forth, truck into the space. I swallow my sip of restorative coffee, wipe the now wet bridge of my nose, and move the car, only to be blocked from leaving the exit thanks to the slowest reversing truck I've ever encountered, one who then proceeds to sit at the next intersection for five minutes without indicating where it was going. Are we having fun yet? I finally made my way to the main road where I attempt to calm my nerves with the help of a Morse code edition of my podcast. It's been the only exposure I've had to Morse for way too long. This accompanies me to my first destination, breakfast. I'm going to skip past the drivers in the centre lane driving at 10 km per hour below the posted speed limit, or the ones who think that jumping out of a side street in front of you is normal and safe driving practice. At every traffic light I celebrate the pause with a sip from my coffee and a furtive wipe of my nose which is being assaulted by the lid of the cup. I arrive at my breakfast destination and fear the worst. Their car park is almost empty. I've never seen it this quiet and I didn't check to confirm that they were open, or not. I look at my map application and remember to turn my phone back to battery saving mode. According to the Internet, my cafe is open, so I cross my fingers and get out of the car. To my delight, they are absolutely open, make me a lovely breakfast and provide the needful for lunch too .. I have a big day planned after all. After enjoying breakfast and hot chocolate, with two marshmallows, I get back in the car and navigate to my planned set-up location. As I drive into the park I notice something that I hadn't the last time I was here. I'm descending, as-in, the deeper into the park I go, the more I go downhill. That in and of itself isn't a cause for concern, were it not for the fact that the local repeaters are on the hilltops that overlook the city and I'm several hills inland and travelling into a valley. I'm keeping my eyes open for side roads and alternatives, but gamely proceed to the formal entrance of the park, where I pay my $17 to have a car with a maximum of 12 passengers enter the National Park. I drive to the location I have planned and discover that there's a car park quite close to the gazebo I've earmarked, so I park there. I figure that before I get all set-up in the gazebo for a day of radio, I should first check what I can learn from where I'm parked, especially since I'll need to pull the gear out of the car either way. Before I get out of the car, I attempt to mark my actual location on the map, only to discover that there's no mobile phone coverage, so much for using Echolink as a fallback. I pull out the folding table which neatly fits next to the car, dig out the coax from the boot and lead it out the passenger door. The other end is connected to the boot-lip mount that has been there for years. In case of failure I did bring a magnetic base, but I'm optimistic. I remove the HF and VHF multi-band antennas from their storage spot, taped to the driver side rear passenger roof grab handle and pull out the previously errant folding chair. All is going well. I pull out the spare coax and my anxiety spikes a little, this is what I think might be what causes me to come unstuck. It's a 10 meter or so length of coax, it's untested, terminated with BNC and I'm concerned that I didn't bring enough adaptors beyond the BNC to PL259 and the SO239 barrel I packed hastily the night before. I push away my fear, since I'm not needing this right now and continue to unpack the radio, noticing that to my immense relief, the knobs are still attached, set it all up, pull the power cable from the 12 Volt, 80 Amp hour AGM Deep Cycle battery, "ideal for 4WD, caravan and camping trailers", which I bought four years ago to power my dash cams and radio. It's automatically charged by a 360 Watt DC to DC converter that's connected to the alternator in the car - because I don't want my dash cams, or radio for that matter, to stop me from starting the car. Ask me how I know. The power leads are long enough to make it out of the boot and I connect the inline volt meter to the battery, 12.6 Volt, the same as what I saw when I checked it a week earlier. I mount the VHF multi-band antenna, connect it to the radio after pulling out the N-Type to PL259 adaptor which is on the list and part of the standard kit. I take a breath and turn on my radio. Tune to the local repeater frequency and hit the PTT. The radio is set to 5 Watts and I'm hoping to hear the repeater tone. Nothing. I check all the repeaters in my radio, about seven of them, none of them do anything. Then .. I hear a click. I've been "on-air" for all of three minutes. I notice the radio is turned off. I've seen this before, sometimes stray RF gets into something and causes the radio to stop. I turn it back on and notice the voltage on the display of the radio, 9.65 Volts. That .. is .. not .. good. I check the inline volt meter, it doesn't even display anything. I turn off the radio to save what little power I have. I take a moment to consider and attach the HF antenna, hoping that I can run the radio for a few seconds to check the local 10m repeater. All is good to go, turn on the radio and it won't even turn on, just flickering on and off. I feel like I want to cry, but there doesn't seem to be any point. I pack everything back up, the water, my hat, the radio, the coax, the antennas, the table, the chair, put it all back in where it came from, even the sandwich I was going to have for lunch. After slowly reversing out of the car bay, looking carefully at the ground to make sure I didn't leave anything behind, I make my way out of the park. I've been there for a grand total of 29 minutes. I briefly entertain the idea of going to the nearest electronics store and spending $50 on a small battery, but I don't actually have a working charger, and spending several hundred dollars on a charger and battery is not really in my budget at the moment. Whilst I was driving home I got a notification that the power was out at my QTH. I got home 52 minutes after the power went out. It stayed off for the next six hours. So much for being productive. My friend Charles NK8O, tells me that his first few activations were a bust. He's a Sapphire POTA activator with 609 activations across 372 parks, so, there's hope for me yet. In looking back at this adventure, I was planning for failure. I'd thought through all the different permutations of what might happen. Not for one moment did I consider that my battery might be a single point of failure. That said, there were hints that not all was well. The 12.6 Volts was one hint, the fact that my dash cams have been acting up was another. I had been on the hunt for a battery monitor for the past two years to discover precisely what was going on, but I haven't found one that doesn't require a specific app that needs to know where you are or what's in your diary, so I put it out of my mind. As it happens, that was where I made my rookie mistake. Mind you, part of me knows that I don't have another battery anyway, so it really didn't matter if the battery was faulty or not. Either way, I wasn't going to connect my radio to my car battery, I learned that lesson well over a decade ago. I'm back to the drawing board. It's unlikely we'll use that location to activate for the 750th edition of F-troop, but when I get my power situation sorted out, it's still a lovely place to get on-air and make some noise. I'm Onno VK6FLAB

Foundations of Amateur Radio Recently my local power company notified me of a planned network outage, that's code for, we're turning off the power and your choice is to deal with it. If you've been paying attention, you'll note that this is not the first time this has happened in recent times. On this occasion I want to make a difference and actually use the day wisely. Coincidentally, the 750th instalment of F-troop is coming up and traditionally we try to find an excuse to get outside and set-up a station in a local park somewhere. If you recall, I recently went outside and came across a new park, one with picnic tables, gazebos, toilets and all the mod cons required for a party. Combine these unrelated events and you end up with testing the idea of running F-troop, a weekly net for new and returning amateurs, from this park, which also neatly turns that into a POTA or Parks On The Air activity, which raises several logistical questions. The first one being, what is the radio noise like in this park, followed shortly by the question, can I hit my local 2m repeater, any 2m repeater, or the local 10m repeater? If the answer to those questions is unsatisfactory, I might be required to rethink my plans. Combining those questions with a power outage at home seems like the perfect excuse to go out into the bright day to get on air and make some noise. One challenge. Having removed my radio from my car several years ago to accommodate the replacement of the transmission, I never did replace it and never used my radio in the car again, which truth be told is not a situation I ever imagined when I first installed it many years ago. This leads me to creating a list, which should come as no surprise, a list with what I need to bring as a minimum requirement to test the questions I need answers to. I will confess that the "making a radio packing list" skill-set has atrophied in recent times, so I started small. I'll need a radio, and a suitable antenna, in my case, at least two, one for 2m and one for 10m. Then there's the question of power, at which point I discovered that my trusty portable sealed lead acid batteries have finally died, not bad after 15 years, well, 12 years of regular use. Likely they would have continued to be of service if I'd used them in the past three years, mainly hampered by the death of my 12 volt battery charger. If you feel like I'm going off track, you'd be right. That was the exact experience I had when I started building my list. I added a digital multimeter, an antenna analyser, an antenna tuner and coax, then realised that I needed to check if the coax adaptors were the right ones and so it continued. The upshot is a preliminary list with 15 items on it, in various stages of fully populated, for example, I know I have a 2m and 70cm antenna in the garage, but I haven't touched it in years, so I need to go find it, and the battery in my digital multimeter needs checking, you get the idea. It's a good thing I started this caper well over a week before the planned outage, so at least I have half a fighting chance to get it to the point of usefulness before my screen turns black due to the threatened lack of electricity. It occurred to me whilst I was in the middle of this extended list creation process, that I was essentially replicating what I might have experienced the very first time I went outside with my station in 2011. In coming to that realisation, the stress levels that were building steadily at that point, pretty much dissipated with the understanding that I'd already done this and survived the experience. In other words, there was nothing worth stressing about. So, this leaves me with a question for you. What does this process look like for you, how do you prepare to get on-air and make noise, what steps do you take and what do you avoid, are there things you might share with a new amateur and if so, how will you do that? I contemplated sharing the list in a public place, but realised that the power of the list isn't the items on it, but in the process of making it, so, no list, but the notion that you too can do this, and if it transpires that you forgot something, there's always the next adventure. I'm Onno VK6FLAB

Foundations of Amateur Radio The pursuit of amateur radio is a glorious thing. On the face of it you're forgiven if you think of it as a purely technical endeavour. Far be it for me to dissuade you from that notion, but permit me to expand into other areas that rarely get a mention when we discuss this amazing hobby. It's the place where you go to communicate with other people, who live a different life, doing the things that they enjoy. It's also the place for finding an excuse to go outside and set-up your station on the side of a mountain, or a park, a museum or a lighthouse. Then there's the joy of finding new friends who introduce you to other aspects of life, super computing, the medical field, tow truck driving, radio astronomy and electronics, to name a few. While I was the first person in my school to save up their summer job earnings to buy their own computer, a Commodore VIC-20, I never did come across this. "It is pitch black. You are likely to be eaten by a grue." is a phrase that might mean something to you, or not. To set the stage, it's the 1960's, you're a science fiction author and you need a ravenous predator. With origins in Danish and Norwegian, "grue", from gruesome, seemed to fit the bill for Jack Vance while was writing his Dying Earth series, mind you, Robert Louis Stevenson used it in 1916 in a short story called "The Waif Woman", writing "and a grue took hold upon her flesh", which is more gruesome than predator. Flash forward to 1977, you're writing an adventure game for a PDP-10 mainframe computer whilst, let's call it studying, at MIT, and you need a way to stop people wandering off the map, and so the text adventure game "Zork" got its famous phrase. I'm mentioning this because I wondered if anyone had used their love for Zork as an excuse to set-up a server on HF radio that you could play with. I'll confess that I spent way too many hours looking at this and it appears that you can use the software "direwolf" as a way to get packet radio to work across amateur radio without needing anything more than a radio and a computer with a sound-card. There's even an article by Rick Osgood titled: "How to Setup a Raspberry Pi Packet Radio Node with Zork", though I will mention that it relies on hardware to connect to a radio, rather than use "direwolf". There's a few moving parts, but it looks like this is totally doable, there's already Docker containers for both Zork and direwolf, even a container called "packet-zork", and a multi-user version called "MultiZork", so how hard can it be? I jest. As an aside, because I'm a geek and I can, there's a common misconception that a Docker container is equivalent to a virtual machine. For lots of reasons, that's not true. A better way is to think of it as a security wrapper around an untrusted application. Speaking of untrusted, while we're all essentially bipedal lifeforms with a similar set of attributes, on a daily basis we seem to discover more and more reasons to find fault or demonise differences. Contrast this within the global community of radio amateurs, where we have this "weird" activity that we all seem to share. I think that the most under-reported, perhaps even undervalued aspect of our hobby is that it's an excuse to talk to someone else. It's like a force of attraction, the glue, the one starting point that you know another amateur has in common with you. So, next time you venture outside, either in real life, or virtually, consider, at least for a moment, that there are other radio amateurs among us, also having fun. I'm Onno VK6FLAB

Foundations of Amateur Radio The other day I came across an article written by programmer, artist, and game designer "blinry" with the intriguing title: "Fifty Things you can do with a Software Defined Radio". Documenting a weeks' worth of joyous wandering through the radio spectrum it explains in readily accessible terms how they used an RTL-SDR dongle to explore the myriad radio transmissions that surround us all day and every day. As you might know, I've been a radio amateur since 2010 and I must confess, even with all the things I've done and documented here, there's plenty in this adventure guide that I've yet to attempt. For example, when was the last time you decoded the various sub-carriers in an FM broadcast signal, including the pilot tone, the stereo signal, station meta and road traffic information? Have you ever decoded the 433 MHz sensor signals that your neighbours might have installed, weather, security and other gadgets? Or decoded shipping data, transmitted using AIS, or Automatic Identification System, and for context, we're only up to item 12 on the list. One of the biggest takeaways for me was that this is something that is accessible to anyone, and is a family friendly introduction to the world of radio that amateurs already know and love. The article touches on various applications that you might use to explore the highways and byways of the radio spectrum, including SDR++, SDRangel, WSJT-X, QSSTV, and even mentions GNU Radio. With enough detail to whet the appetite, I learned that SDRangel, developed by Edouard F4EXB and 70 other contributors, has all manner of interesting decoders built-in, like ADS-B, Stereo FM, RDS, DAB, AIS, weather balloon telemetry, APRS, even VOR. As it happens, you don't even need to install SDRangel to get going. Head on over to sdrangel.org and click on "websdr" and it'll launch right in your browser. Once you're up and running, you can use your RTL-SDR dongle to start your own small step into the wide world of radio, amateur or not. Sadly the PlutoSDR does not work on the experimental web version, so I had to install SDRangel locally. That said, I did get it to run and connect to my PlutoSDR which worked out of the box. The user tutorial is online and the Quick-Start walks you through the process of getting the software installed and running. One thing that eluded me for way too long is the notion of channel decoders. Essentially you configure the receiver, in my case a PlutoSDR, and start it running. You'll be able to change frequency and see the waterfall display, but nothing else happens, and there's no obvious AM, FM or other mode buttons you'd find on a traditional radio. Instead, you'll need to add a channel decoder, cunningly disguised as a triangle with circles at the corners with a little plus symbol at the top. You'll find it immediately to the left of your device name. When you click it, you're presented with a list of channel decoders, which you can add to the work space. This will do the work of actually decoding the signal that's coming into the software. SDRangel also supports M17, FreeDV, RTTY, FT8 and plenty of other amateur modes, and includes the ability to transmit. Oh, did I mention, it can also connect to remote kiwisdr receivers? I have to say, it's a joy to see software that I've previously looked at and admittedly shied away from, actually doing something with the radio spectrum around me. I will confess that SDRangel has a lot of moving parts and it's like sendmail, user friendly, just picky whom it makes friends with. So, time to dig in, play around and bring it to the next amateur radio field day "Show and Tell" and share with the general public just how interesting the radio spectrum around us can be. I'm going to work my way through the 50 items, just for giggles. What are you waiting for? I'm Onno VK6FLAB

Foundations of Amateur Radio The other day I went for a walk, I know, shock-horror, outside, daylight, nature, the whole thing, in a local national park, for the first time in too many years. Almost immediately I noticed that this would be an excellent location for an activation. If you're not familiar, it's an amateur radio excuse to set-up a portable station in a new location, in this case, potentially something called POTA, or Parks On The Air, but you don't need to find a formal activity with rules to get on air and make noise. I commented on how easily accessible it was, that it had picnic tables, gazebos for shelter, nearby toilets, free BBQs, ample parking, lots of open space, and no overhead power lines. I saw one solar panel on a pole and no evidence of any other electrical noise sources. It wasn't until later that I realised the act of noticing this, in that way, with those details, is not something I would have done before becoming a radio amateur. I'd have looked at the same location, considered its beauty and serenity and perhaps in passing considered that we could have a family gathering, or a place to come back to when I wanted some peace and quiet, or a place where I might have a BBQ with friends. Not that those things went away, just that I noticed other things, now that I'm an amateur. It made me consider just how much this hobby has irrevocably changed me. I know I've mentioned this before, since becoming an amateur I cannot walk down the street without noticing TV antennas pointing in the wrong direction, but this change in me is not limited to that. Now I cannot help discussing the best place to put a Wi-Fi base station in a building, or thinking about and checking on solar activity, wondering about battery capacity, RF interference, trees to potentially use as sky-hooks for wire antennas, power company substations, pole-top transformers, random weird and wonderful antennas and probably more. The point being that this hobby opens the door to a whole new way of looking at the world and I don't think I've overstated, if I say that amateur radio has literally changed my world view. In considering this, I suspect that it's related to a cognitive bias known as the Frequency Illusion, where you notice a specific concept, word or product more often after becoming aware of it. You might for example have experienced this with the brand or model of radio you use and suddenly discovered that there's lots of other amateurs talking about that particular piece of equipment. I've seen this with recurring topics during the past fourteen years of the weekly F-troop net. For example, every couple of years someone discovers magnetic loop antennas and starts talking about how they've built or bought one. The conversation inevitably goes past variable capacitors, through air variable capacitors, on to vacuum variable capacitors and then the conversation generally stops. While it's happening, multiple people come on the same journey, only to follow the exact same path. Several years later, the cycle repeats. Don't misunderstand, I welcome the discussion, point people at relevant resources and help them on this journey. I'm commenting on the recurrence of the journey, not the nature of it because it's easy to take this example and hold it up as "there's nothing new in this hobby", but nothing could be further from the truth. In my opinion, the level of complexity associated with radio communications is infinite and anyone, including you and I, can contribute to the discovery associated with it. So .. what things have you noticed that were caused by this somewhat eccentric hobby and perhaps the phenomenon of Frequency Illusion? I'm Onno VK6FLAB

Foundations of Amateur Radio I've owned a Yaesu FT-857d radio since becoming an amateur and at the time I was absolutely blown away by how much radio fits inside the box. It's smaller than most of the commercial radios I'd seen when I bought it. I came across a video by Michael KB9VBR, the other day showcasing a wooden cigar box with a complete, well, almost complete POTA, or Parks On The Air, activation kit. I say almost, since Dave KZ9V, the owner of the kit, points out that the box doesn't contain an antenna. It made me wonder how small is small? According to RigPix, the lightest transmitter on an amateur band, in this case, the 5 GHz or 5cm band, is an Amateur TV transmitter. Weighing in at 3.9 grams. The Eachine TX-06 is capable of FM with about 18 MHz of bandwidth with an audio sub-carrier. Of course, that's not a transceiver, but I thought it worth mentioning in case you needed an excuse for something tiny in your shack, besides, as far as I can tell, there's never too much Amateur TV in the world. I've built a crystal radio on a breadboard which is tiny, but it doesn't transmit, so to set the stage, I think we need to limit ourselves to transceivers, that is, a device capable of both transmitting and receiving, on amateur bands. Before continuing I'd like to express my thanks to Janne SM0OFV, for the rigpix.com database that he's been maintaining, in notepad, since 2000. Without the invaluable information documented for the currently 7,512 radios, I'd be spending an awful lot of time hunting for information. Moving on, the FaradayRF board is a transceiver, capable of using 900 MHz or the 33cm band. It comes in at 30 grams, but without a computer it's a circuit board with potential. The PicoAPRS by Taner DB1NTO, is a 2m transceiver specifically for APRS, weighs in at 52 grams and similar in look and a third of the weight of an Ericsson T18 mobile phone. Speaking of mobile phones, the PicoAPRS does WiFi and Bluetooth, can pair with your phone and act as an AX.25 modem. I'll confess, I'm drooling. Moving right along, for 70cm there's a Rubicson Walk 'n' talk, weighs in at 65 grams. Mind you, the RigPix database puts this under the "License-free / PMR446" section which comes with a sage warning, check your local laws before transmitting. There's a few Alinco DJ-C models for different markets that operate on 2m or 70cm, weighing in at 75 grams. The ADALM Pluto weighs 114 grams, but you'll need a USB power supply of some sort to make it do anything. It can operate between 70 MHz and 6 GHz, but the user interface is limited to a single button and LED, so if you want to interact with it, you'll need some external technology. Moving on to HF transceivers, weighing in at 199 grams, without the bag, but all the options, is the Elecraft KH1. Transmits on 40m, 30m, 20m, 17m and 15m and receives between 6 and 22 MHz. It's CW only, but you can receive SSB. If CW isn't your thing, RTTY and PSK can be used on the 40m band with a Silent System Handy PSK 40. Presumably the Handy PSK 20 runs on 20m. Both weigh in at 250 grams. The Zettl P-20xx SSB does SSB, AM, FM and CW, transmits on 10m, 11m, 12m and 15m as well as the MARS frequencies and receives between 14 and 30 MHz, weighs 300 grams. Even comes with CTCSS. Another Elecraft model, the KX2 weighs in at 370 grams, does 80m to 10m and the WARC bands, does SSB, CW and data. Mind you, you'll also need to add the weight for the microphone and paddles, and factor in a computer if you want to do more than PSK and RTTY. The Expert Electronics SunSDR2 QRP does 160m to 10m, the WARC bands and 6m. Weighs in at 500 grams, has a network port and two independent receivers. Operates at 5 Watts. There's no user interface, unless you count the reset and power buttons, so I'm not sure if it can operate on any mode with just a microphone, but given the "Depending on software" disclaimers throughout, I'm going to guess you'll need to bring a computer to make it sing. The Risen RS-918SSB does all HF amateur bands between 160m and 10m, has a user interface and display, even a big tuning knob, has built-in FreeDV and does FM, SSB and CW. I'd hazard a guess that this is the lightest self-contained transceiver that you can take out on a POTA mission to a park. Weighs 623 grams and comes with an internal battery. The Elecraft KX3 also does 160m to 10m, and 6m, with a 2m option. Weighs in at 680 grams, but that doesn't include any options. And finally, we pass 1 kilogram and hit 1,100 grams and discover a radio that does all bands and modes, the Icom IC-705 with a battery, but no antenna. The Yaesu FT-817, FT-817dn and FT-818 weigh 70 grams more, but that weight includes both a battery and antenna. Of course there are other options. For example, there's the (tr)uSDX by Manuel DL2MAN, and Guido PE1NNZ, does 80m, 60m, 40m, 30m and 20m, CW, SSB, AM and FM. Comes in a kit, weighs 140 grams. It's not on RigPix, so I only know about it because it was mentioned by Dave KZ9V. Similarly, I bumped into, wait for it, a single transistor transceiver called the Pititico, in case you're wondering, Pitico means very small in Portuguese and Pititico means very very small. Designed by Miguel PY2OHH, it comes in various revisions, including one by Ciprian YO6DXE, also known as DX Explorer on YouTube, complete with a circuit board design, and with some modifications can do AM in addition to CW. It's also not in the RigPix database and I have no idea what it weighs. The point being that this rundown is intended as a starting point to explore how small you can really get and still activate the Park or Peak you intend to. While you're contemplating weight, remember to account for power, control, and most importantly an antenna or six. Again, big thank you to Janne SM0OFV, for the rigpix.com website. Also, thank you for the memories of the Spectravideo SV-318 and SV-328, the last time I bumped into one of those was in 1980-mumble when I was working in a computer shop on the Haarlemmerstraat in Leiden, Mr. Micro Zap, if you're curios. What lightweight adventures are you looking for next? I'm Onno VK6FLAB

Foundations of Amateur Radio Over the past nine months or so I've been working on a project that I've called Bald Yak. If you're unfamiliar, the Bald Yak project aims to create a modular, bidirectional and distributed signal processing and control system that leverages GNU Radio. One of the, admittedly many, challenges I've set myself is getting data from a radio receiver into GNU Radio across the network, preferably the Internet. Today I can report a small step in the right direction and frankly I can't contain my excitement. Now, I need to acknowledge that I'm geeking out here. It's hard to contain excitement when you find something that seems to speak your language. It also means that I realise that I run the very real risk that I'm going to lose you before you get to why this is a milestone, so let's put that up front before I explain why. To whet your appetite, yes, you can access a KiwiSDR across the Internet and record raw data from it and control the process externally. This is a very big chunk of the problem I've been working on and turns out to actually be live and ready to play with. Fair warning this is technical, there are moving parts. I'll do my best to explain, but if I miss any, feel free to get in touch, you have my address, [email protected]. In passing, recently I made mention of the KiwiSDR community and tools that could potentially allow access to a remote receiver, although at the time I pointed out that I wasn't sure if the tools I found could access remote receivers, or if they were intended to access hardware locally. KiwiSDR is one of a group of so-called Web SDR tools. Essentially a website where you can access a remote receiver and tune to the radio signals it can hear. SDR, or software defined radio, is a way to convert incoming antenna signals into the digital realm where computers, and in this case, the Internet, live. Turns out that a tool called "KiwiClient" takes a hostname and a port as a parameter, so much so that the in-built help shows this as the first example. What this means is that you can essentially run a copy of KiwiClient on your own computer and use it to access a KiwiSDR across the Internet. The first commit was on the 8th of May 2017 and thanks to the efforts of about 14 developers, KiwiClient is the software equivalent of a KiwiSDR multi-tool. This is exciting all by itself, but this gets better. You can specify more than one server. This means that you can record two, or more, signals from across the globe, and capture these simultaneously. You can set the decode mode, which I immediately used to tune to a local broadcast station and recorded it from two different receivers across the Internet, allowing me to not only compare the difference in delay between the signals, but also the reception differences. It's fascinating to hear the same station from two receivers, one in each ear, all manner of different propagation artefacts become apparent. Then I got a little more adventurous and discovered that one of the supported modes is I/Q, which means that I can, and did, download raw sample data across the network, which can then be used within GNU Radio. This is important because the aim for Bald Yak is to process the signals separately from the receiver. It gets better. There is a radio fax receiver that automatically saves pages as they are processed, something that you could use to access weather fax services. Then there's a tool you can link to "WSJT-X", which you might recall is an application that can decode weak signals. Not only that, the tool supports "fldigi", a digital radio mode application. Both those applications can control the radio using Hamlib rigctl, which means that KiwiClient supports changing frequencies of the receiver, across the Internet, though truth be told, I haven't yet tested that .. my available computing resources are still strictly limited. Oh, the software also has the ability to record waterfalls, do scanning, and provides tools to analyse waterfalls in jupyter notebooks. Getting this to work wasn't too hard. The instructions on the KiwiClient GitHub repository are pretty good. I've made an initial Dockerfile on my own GitHub repository to download and install the software. It's unimaginatively called "kiwiclient-on-docker". I've yet to discover a good way to add or update Dockerfile functionality to existing projects, feel free to make suggestions. Now I absolutely understand that this level of excitement might not universally translate and that's fine. It's yet another example of how rich and diverse our amateur radio community really is. What gets your excitement levels going? I'm Onno VK6FLAB

Foundations of Amateur Radio The other day I stumbled on a random post by Gary N8DMT which caused me to view the world in a different way. The post outlined combining a PlutoSDR and an application called SATSAGEN to measure the frequency characteristics of a coupler. Aside from a detailed description, the post includes a couple of excellent photos showing the PlutoSDR connected to the coupler and the output piped back into the Pluto. Before I continue, a PlutoSDR is a Software Defined Radio or SDR, officially it's called the ADALM Pluto Software Defined Radio Active Learning Module. It's essentially a full-duplex radio and computer in a box. It runs Linux and connects to the world via USB, and of course radio, unofficially between 70 MHz and 6 GHz. I've talked about this device before. When I say full-duplex, I mean that it can transmit and receive at the same time. Gary's post triggered something unexpected in me. The notion that you could use two patch leads, one connected to the transmitter, the other connected to the receiver, joined together by a device that you might want to test. It immediately reminded me of another device that was given to me, a NanoVNA, a device that's specifically designed to measure things like impedance, frequency response, generate Smith charts and all manner of other characteristics. Not only that, it also reminded me of another device, a TinySA, specifically designed to analyse spectrum and to generate signals. Both the NanoVNA and TinySA are lovely tools, but in looking at the post it suddenly occurred to me that their functionality, at least superficially, appears to mirror the PlutoSDR, in that you can create a signal and then measure that signal. Turns out that I'm not the first to make this observation. For example, the YouTube channel "From Concept To Circuit" goes through the process of describing precisely the concepts behind both a spectrum analyser and a network analyser while showing the programming code in Python. The channel also provides that code in a GitHub repository, which includes several other very interesting examples, like a beamforming transmitter as well as a beamforming receiver, also covered on YouTube. Another example is a tool I already mentioned, SATSAGEN, by Alberto IU1KVL, which implements a wideband spectrum analyser. Although it's Windows only, Alberto includes information on how to run it using Wine under Linux and MacOS. As a bonus, SATSAGEN in addition to the PlutoSDR, also supports RTL-SDR dongles, HackRF, USRP, RSP1, AirSpy, and many others. If text is more your thing, "retrogram-plutosdr", shows a spectrogram in your terminal window. Check out the "r4d10n" GitHub repository belonging to Rakesh VU3RGP, who says that the "retrogram" project is "hacked from" the "RX ASCII Art DFT" example, which you can find on the Ettus Research GitHub repository. One thing to consider is that the various GitHub repositories I've pointed at, will give you access to the moving parts of how all this works. I will mention that my favourite tool in this space continues to be GNU Radio, but I understand that you might not want to roll your own tool from parts. That said, rolling your own is in my experience a great way to discover precisely what you don't know and to come away learning more, but then, that's just me. Regardless of your chosen tool, I think the takeaway should be that when you try something new, even if it's only new to you, the idea of writing down what you discovered and sharing it, is a fantastic way to grow our community. Remember, just because something is old hat to you, doesn't mean that it is to the person you share it with. Besides, based on the current global birth rate, there's at least a thousand babies born during the past four minutes, some of whom will become radio amateurs, so, share. Said differently, if you come across a person who has never heard of the "Diet Coke and Mentos" thing, it's your job to immediately drag them to the nearest grocery store and introduce them. In case you're wondering, xkcd 1053. Now, I'm going to update the firmware on my PlutoSDR and have a play, I already know about the Mentos, but if you don't, you're in for a treat. What are you going to do next? I'm Onno VK6FLAB