From: internetado@bbs.alt119.net   
      
   Catching signals from others is how we have started communicating as   
   human beings. It all started, of course, with our vocal cords. Then we   
   moved toÿsmoke signals for long-distance communication. At some point,   
   we discovered radio waves and are still using them for contact. This   
   article will describe how you can tune in using Fedora Linux and an SDR   
   dongle.   
      
   My journey   
      
   I got interested in radio communication as a hobby when I was a kid,   
   while my local club, LZ2KRS, was still a thing. I was so excited to be   
   able to listen and communicate with people worldwide. It opened a whole   
   new world for me. I was living in a communist country back then and   
   this was a way to escape just for a bit. It also taught me about ethics   
   and technology.   
      
   Year after year my hobby grew and now, in the Internet era with all the   
   cool devices you can use, it';s getting even more exciting. So I want   
   to show you how to do it with Fedora Linux and a hardware dongle.   
      
   What is Ham Radio   
      
   Amateur Radio (ham radio) is a popular hobby and service that brings   
   people, electronics, and communication together. People use ham radio   
   to talk across town, worldwide, or even into space, without the   
   Internet or cell phones.   
      
   What's SWLing?   
      
   To broadcast with your ham radio or SDR system, you need to obtain a   
   license from a governmental body. But to intercept signals and listen   
   to the open communication between two amateur radio stations, you don't   
   need one.   
      
   The term SWLing comes from the abbreviation of Short Wave Listener,   
   where you listen to stations communicating in the shortwave bands   
   between 3 and 30 MHz. This can be used for long-distance communication   
   using the ionosphere, a layer of the Earth's atmosphere.   
      
   To get started, you don';t need a license. Still, I recommend getting   
   yourself an SWL sign to identify yourself in a listening contest. These   
   are competitions for categories like who will discover the most   
   connections in a month or who can listen to contacts from each country   
   in the world.ÿ   
      
   How to get an SWL Sign?   
      
   There are two options:   
      
   Contact your national radio club and ask them to issue one for you. I   
   got my Czech one, OK1-36568, after a few weeks.Join theÿShort Wave   
   Amateur Radio Listeningÿcommunity and request a sign there.   
      
   You will get more information and help from either of these locations   
   if you get stuck in some fashion!ÿ   
      
   QSL Cards   
      
   You can also use your sign to send QSL cards via post or   
   electronically. This is a great way to communicate with people   
   worldwide and make friends.   
      
   Per Wikipedia,ÿAÿQSL cardÿis a written confirmation of either a two-way   
   radio communication between two amateur radio or citizens band   
   stations; a one-way reception of a signal from an AM radio, FM radio,   
   television, or shortwave broadcasting station; or the reception of a   
   two-way radio communication by a third party listener (in our case).   
      
   A typical QSL card is the same size and made from the same material as   
   a regular postcard; most are sent through snail mail.   
      
   Replace the radio receiver with your Fedora Linux.   
      
   The focal point of the ham radio hobby is the radio   
   transmitter/receiver. Most of the time, enthusiasts build their radio   
   from scratch, but this differs from what I will write about here.   
      
   SDR   
      
   A software-defined radio (SDR) system is a radio communication system   
   that uses software for the modulation and demodulation of radio   
   signals. In other words, a piece of hardware and software takes the   
   place of a radio transmitter/receiver.  This helps you discover more in   
   a way that you are familiar with - a User Interface with built-in   
   functions instead of the limited interface of a radio receiver.   
      
   My explanation oversimplifies things, so if you want to go deep and   
   read more about SDR, here is an excellent start.   
      
   SDR Set Up under Fedora Linux   
      
   Choosing the proper hardware   
      
   If you search the Internet for an SDR dongle, you'll find tons of ideas   
   depending on your budget. In this tutorial, I'll work with the one I   
   have, which works well under Fedora 37 - it is available from Nooelec.   
      
   A note: The dongle covers frequencies from 25MHz to 1750MHz, which   
   doesn't cover the Short Wave bands. You would need an additional device   
   to listen to them. This is included in the package I linked above. Some   
   other hardware providers offer all-in-one products.   
      
   Check if the dongle is visible   
      
   Before installing anything,  detect whether Fedora Linux recognizes   
   your USB dongle. I hope you didn't buy a fake one :-). Use the   
   following command to list the USB devices on your system.   
      
   lsusb   
      
   One of the output lines (in the case of Nooelec) should be   
      
   Realtek Semiconductor Corp. RTL2838 DVB-T   
      
   Now proceed by installing the software you need   
      
   Fedora offers a set of tools and drivers packaged as a group. Even   
   though you would not use all the components in this package from the   
   beginning, I recommend installing it. You'll have more software to play   
   with.   
      
   sudo dnf group install 'Electronic Lab'   
      
   I advise you to explore what's in the group by running this command:   
      
   sudo dnf group info 'Electronic Lab'   
      
   Now check if you have everything set up correctly by running:   
      
   rtl_test   
      
   You should see something like this:   
      
   Do not forget to kill this process because the device will be busy and   
   cannot be used in the next step. A simple Ctrl + c  works.   
      
   Gqrx   
      
   You have the dongle already in your device's USB port and all the   
   software you need to get started.   
      
   ÿNow it's time to intercept your first signal. Start the program called   
   Gqrx. Don't be alarmed by the strange interface. You'll get used to it.   
      
   Configure the I/O Device Screen   
      
   From the "Device" Dropdown, select the 'RealtekRTL2838...'   
      
   Leave the rest untouched for the moment.   
      
   If you don't see your device there, click the "Device Scan" button at   
   the bottom of the screen.   
      
   When your device is selected, click "OK" and the dialogue will close.   
      
   Configure the frequency screen   
      
   Before you start intercepting signals,  ensure there is something out   
   there that proves that everything works correctly. Since the dongle   
   covers the FM radio band as well,  do this:   
      
   Locate your favorite radio station's frequency. Mine is 105MHZ   
      
   Set it in the Frequency field   
      
   Select WFM (stereo) in the "Mode" dropdown. If you don't do this, you   
   will not hear a sound.   
      
   Play   
      
   And now, you need to start the reception by clicking the "play button"   
   in your main menu. You will see the frequency visualized like this:   
      
   If you hear a sound, everything is ready to move to the next step.   
      
   If you don';t hear anything, check if everything is set up correctly.   
   You may ask a questions in the comments for this article; I can direct   
      
   [continued in next message]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)