• Foundations of Amateur Radio

  • 著者： Onno (VK6FLAB)
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Foundations of Amateur Radio

著者： Onno (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?".
    ℗ & © 2015 - 2024 Onno Benschop
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あらすじ・解説

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 - 2024 Onno Benschop
物理学
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  • Suddenly there were 700...

    Suddenly there were 700...
    2024/11/23
    Foundations of Amateur Radio Thirteen years ago I opened my mouth to express my thoughts on what to do with an amateur license after hearing an operator complain they needed more power to talk to a station across 600 kilometres, whilst I used the same 10 Watts to communicate with a station nearly 15,000 kilometres away. In all, I've shared my thoughts some 700 times, documenting my journey though this majestic hobby, describing what I've been up to, reporting my successes and failures, sharing my observations and making recommendations. I've built projects and attempted to start new processes, I've encouraged, cajoled, on occasion berated or applauded as I found it. Throughout the experience I've attempted to build this wonderful community, to inspire and to grow it. Sometimes I might even have succeeded. I could not have done this without you. So, thank you. If I haven't mentioned your name or responded to your email, it's not because I didn't see your contribution. You have delighted me and lifted me up and I thank you for sharing your thoughts. At this point you might wonder if I'm hanging up my microphone and to that I say: No, not even close. Instead I'm continuing with this experiment, rough and ready though it is. It occurs to me that over the years I've started a great many projects and documented them as they happened, either here, or on my vk6flab.com website, or on GitHub. These projects take time and effort that go beyond what you encounter here. Sometimes it's hours, sometimes it's weeks. Recently a lot of my musings have been about things I've wanted to do, rather than describing things that I've done. Mind you, not for lack of desire. I want to try something different. I'm going to, at least for the next little while, bring you along with a project as I'm building it. No doubt I'll get distracted by squirrels along the way, but I'm going to attempt to build something for us as a community, for amateur radio, because I want to actually do something, rather than talk about it and I need to manage my limited resources and this way I get to build something and you get to have me sharing my thoughts. From my perspective, win-win. So, let's dive in. Amateur radio is a hobby that takes all kinds. A lot of activity is curtailed by money, or rather, lack of money. That doesn't have to be the case and I think I can show you how. That's not to say that this is going to cost nothing, but you can likely start with what you already have and work your way up as your budget allows, rather than require a significant outlay just to get your toes wet. Over the past few weeks I've been talking about a toolkit called GNU Radio. It can be used to build systems that can process data, like say radio signals which come in all shapes and sizes. You can start by connecting an antenna to a sound card and use that as a radio tuner. You can also use a sound card as a way to listen to signals coming in via the Internet, or a radio you might already own. Sound cards exist in most computers but can be purchased for around $10. If you want to handle more data, you can spend $50 and use an RTL-SDR dongle. This incremental path continues. You can build a digital radio, or buy a learning kit, or something else, all the while still being part of the same ecosystem. I want to build a system where you can experiment with radio without needing to buy new hardware every time you want to try something new. I want it to work with a sound card as well as with the latest $7,000 radio you can get shipped to your door. I want to do this in such a way that we can start to embrace all that is possible within the realm of software. Ultimately I want to be able to use any signal source anywhere and GNU Radio seems ideally suited as the tool for the job. I envisage that we'll build a distributed system, where signal processing and the signal itself don't have to be in the same spot, which is useful for a whole host of reasons, even though it increases the level of complexity by at least an order of magnitude. This isn't going to be easy. It's not going to be working tomorrow, perhaps not even a year from now and as long as new radios are invented, it will never stop, but we'll see how it goes. For example, I spent a week attempting to install GNU Radio on my Macintosh, asked two expert groups and got nowhere. In stark contrast, I installed it on my Linux Debian workstation and the example I tried worked out of the box. In other words, plenty of obstacles to overcome. Before I go, I'll make this explicit. I want this to be open source, so anyone can play. I haven't yet decided on which specific license to use, but I'm cognisant that there are many large companies making obscene amounts of money from the volunteer efforts of the open source community and as one of the volunteers, I'd like to be able to pay for food and a roof over my head. I expect and appreciate your feedback, so don't be shy. I'm Onno VK6FLAB
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    5 分
  • Why does your Wi-Fi connection drop out when cooking lunch?

    Why does your Wi-Fi connection drop out when cooking lunch?
    2024/11/16
    Foundations of Amateur Radio Have you ever attempted to download an email attachment, or watch a streaming service whilst your microwave was cooking lunch or dinner and noticed that something odd was happening, or is my asking that question the first time that you joined the dots? This phenomenon is not by accident, though it isn't on purpose. In 1947 the International Telecommunications Union, the ITU, was meeting in Atlantic City where the "delegate of the United States, referring to his request that the frequency 2450 Mc/s be allocated for I.S.M., indicated that there was in existence in the United States, and working on this frequency a diathermy machine and an electronic cooker, and that the latter might eventually be installed in transatlantic ships and airplanes. There was therefore some point in attempting to reach world agreement on this subject." Several things to unpack there. It's 1947 and experimentation is happening at 2,450 Mega-Cycles per second, what we call megahertz today; you might recognise the frequency as 2.45 GHz. At that time, experiments using radio frequencies for medical purposes has been in full swing for decades. Nikola Tesla wrote a paper on the subject that was presented in absentia to the American Electro Therapeutics Association in 1898. In 1947, a diathermy machine exists; today its used to aid with blood flow, muscle and joint pain as well as inflammatory and degenerative bone disease. There is a working electronic cooker, a microwave oven to you and I, and whilst the one you could buy in 1947, a Raytheon "Radarange", if you forked over $5,000, or $70,000 in today's money, had space for a 2 meter tall, 340 kilogram, 3 kilowatt behemoth, you have to admire the imagination that one day this would fit on an aeroplane to travel the world, let alone be available for $100 at your local supermarket. One other thing, I.S.M. or Industrial, Scientific and Medical is a concept we still use today. The idea being that there are uses for radio waves that are nothing to do with communication, like microwave ovens, steel smelting through induction heating, surgical uses like cauterising wounds, some cancer treatments and plenty more. One of the ideas behind ISM is that equipment operating in those frequencies must tolerate any interference generated by ISM applications. The other part of the ISM idea is that it's unlicensed, which is very attractive to people who experiment and why it became popular for other uses beyond heating your lunch. Consider that baby monitors, garage door openers, car security systems, video senders, cordless phones, wireless speakers and microphones, cordless keyboards and mice, radio controlled models, and smart power meters all share the same radio frequencies. Then there's Wi-Fi, Bluetooth, and Zigbee, also using the same 2.4 GHz ISM band. Yeah, even the two most popular network technologies on your phone and computer, Wi-Fi and Bluetooth are competing with each other and the microwave oven in the kitchen. There are six global ISM bands and six additional ones with specific local requirements. Things like industrial microwave ovens, Near Field Communications or NFC and LoRaWan use frequencies like that. You'll also find satellite communications, radio location, CB radio, radio astronomers and radio amateurs on those bands. So, why are these technologies sharing the same frequencies? Essentially because they're unlicensed spectrum. Just so we're clear, this doesn't mean that it's unregulated spectrum. All it means is that unlike licensed spectrum, you don't need to buy access to the spectrum to use it, but you do need to have compliant equipment when you do. Compliance depends on local laws, location, band and power levels. So, next time you need to watch a movie whilst cooking lunch, eat an apple or go outside and get some daylight onto your skin instead. A quick word on power. Whilst all these uses share the same frequency band, their human impact varies considerably. A Wi-Fi network uses a tenth of a Watt. A diathermy machine uses 250 Watts and produces a "gentle heat" at the surface of the skin, suitable for treatment. Contained inside a metal box, a microwave oven uses 1,000 Watts or more. Even that doesn't cook food from the inside out, instead it vibrates water molecules in the food, which heat up, which in turn cooks the food. It doesn't penetrate very far and doesn't work on frozen water, which is why you need to defrost your food before you can cook it. It's also why when you stand between your Wi-Fi router and the computer things slow down, or why your hand position on your phone or tablet can make a difference, since your body, made from 60% water, is blocking the signal. Finally, here's something to consider. A licensed radio amateur has access to some ISM bands, but does it require an amateur license to actually use any of those bands? In other words, if my amateur license doesn't permit my access to 2.4 or 5.8 GHz bands, ...
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    7 分
  • A new radio every week ...

    A new radio every week ...
    2024/11/09
    Foundations of Amateur Radio The hobby of amateur radio is one of experimentation and change. For decades this came in the form of circuit diagrams, components and scrounged hardware from anything that wasn't bolted down. New functionality came with the aid of a soldering iron. More recently, functionality comes from participation in the global electronics market where you can buy any radio you like and have it shipped to your door within hours at an unbeatable price. Mind you, buying all those unbelievably cheap radios does start adding up and if you want to use more sophisticated hardware, that too is possible, at a price, somewhere between $50 and a new Porsche. Whilst that's an option for some, for the rest of us, there are better and cheaper ways. Of course it doesn't stop there. If you connect any radio to a computer, you can use whatever software you like to encode and decode any signal you can imagine. With a traditional radio connected to a computer you can make it participate in hundreds of different so-called digital modes. Before I continue, let's look at radio in a slightly different way. Consider an antenna as a continuous source of voltages that are amplified, filtered and demodulated in some way by a radio. You can think of the combination of antenna, radio and computer as a stream decoder. To decode a signal in a new way requires a new decoder, which you could build from components or as I've said, buy online. During the week I've continued experimenting with GNU Radio. If you're unfamiliar, it's a toolkit that allows you to build so-called flow graphs that can process a signal stream. Think of it as a box of Lego that you can put together to build any type of decoder. Let me say that again. Imagine that you want to decode or transmit a mode like FreeDV, M17, APRS, Olivia, Contestia, or Hellschreiber. With the GNU Radio toolkit, all of this is possible and you won't need to buy new hardware or bust out the soldering iron every time you want to experiment with a new mode. If you have been playing with digital modes already, you'll likely point out that you can already do this today by using software running on a computer, and that's true. What that doesn't tell you is that this comes with a very specific limitation, namely that all those modes require that they fit inside a single audio channel because all those digital modes you might be familiar with are essentially using an SSB or FM signal with the audio generated or decoded by a computer. Even if you have a modern radio like for example an ICOM IC-7300, you'll still be limited in what modes of transmission you can make. ICOM limits the transmit bandwidth to 2.9 kHz. Flex Radio appears to double that to 7.9 kHz, but numbers are sketchy. The point remains, most current amateur radio technology is based around the notion that a mode essentially fits within a single audio channel and a very narrow one at that. So, why does this matter? If you run out of FT8 space on a band, right now you need to change to an alternate frequency to play, but you'll only be able to see the stations that are using the same alternate frequency, as long as they fit within the bandwidth of an audio signal. If you wanted to check out the main frequency, you'd have to change frequencies and keep switching back and forth. Using this idea, monitoring all of FT4, FT8, WSPR and all CW beacons, all at the same time becomes unimaginable, not to mention costly if you needed a radio for each band and each mode. What if you wanted to use another mode that took more than about 4 kHz, like say a 5 MHz wide DVB-T signal which you could be experimenting with on 70cm? Or, what if you'd like to compare a repeater input with its output at the same time? Or compare two repeaters together? Or find the best band to operate on right now? The point being, that there are things that simply don't fit within a single audio channel that you won't be able to play with using a traditional radio. As it happens, that too is a solved problem. Remember that I mentioned that you can think of an antenna, radio, and computer combination as a stream decoder? What if I told you that an SDR, a Software Defined Radio, is essentially a device that translates antenna voltages into numbers which you can process with GNU Radio? Whilst that does imply replacing your radio, you don't have to jump in at the deep end to start playing and even if you do decide to buy new hardware, you can get your toes wet with all manner of self build or commercial kits. Even better, you can start with the gear you already have today and become familiar with GNU Radio and when you're ready to expand your station, you can add in an SDR and continue to use the same tools to experiment. Not only that, you can do interesting things by combining what you already have. Consider for example the idea of using an RTL-SDR as the receiver with a traditional radio as the transmitter. You could decode all of the ...
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    6 分

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