Listening to amateur radio. Amateur radio WEB SDR receivers. So what is SDR

This video discusses such radio reception technology as WebSDR. This video is primarily intended for beginners who have just become interested in WebSDR radio reception and decided to try themselves as a listener to radio broadcasts on the Internet online. The video will be divided into 2 parts. The first, which is lower in the article, briefly talks about radio reception using SDR receivers. Listening to several amateur radio stations is demonstrated. The second part is a story about the digital side of radio reception, in which we will look at how to receive and listen to various digital signals, such as sstv images or having a meteofax.

You can listen online to SDR receivers located in Russia using the following links:

So what is SDR?

To answer this question, you must first understand what SDR receivers are in general. SDR stands for Software Defined System. The essence of this technology is that all signal processing occurs digitally in software.

Let's imagine that we have an antenna, an analog-to-digital converter, say, with a digitization frequency of 100 megahertz. Let's connect all these elements and assume that the antenna is matched to the amplifier. No loss or reflection. Now, according to Kotelnikov’s theorem, we know that a signal digitized with frequency f can be restored to frequency f in half. that is, our ADC can receive a signal with a frequency of up to 50 megahertz. So we get a simple SDR receiver. The signal from the antenna is amplified and digitized, and all other actions such as decoding, demodulation, decoding - all this happens programmatically in the computer to which the ADC is connected.

What frequencies can we catch and listen to on SDR? If we assume that the antenna perfectly receives all frequencies, then from 0 to 50 megahertz. But in practice frequency range will depend on the antenna used and the frequency band of the amplifier.

Now let's add a signal mixer and oscillator to the receiver circuit. If anyone remembers the school mathematics course, it says that the product of two cosines is equal to the cosine of the sum plus the cosine of the difference. Multiplying, say, a frequency of 70 megahertz with a frequency of 50 megahertz, we get 2 output frequencies of 120 and 20 megahertz. Now we just add a filter that will not pass the frequency of 120 megahertz. Thus, we can lower the frequency so that the ADC can digitize it. Roughly speaking, most SDR receivers are built on this principle.

What is WebSDR?

In 2008, a group of enthusiasts created software, which allows you to broadcast data from your SDR receiver to the network. That is, WebSDR is a regular SDR receiver, only via the Internet and you can listen to the signal transmission online. You can go to the website of any receiver and work on the radio in almost the same way as with a regular radio.

Let's go to WebSDR.org and open a receiver. Let's discover the most popular Dutch. The website of this receiver opens, we see various descriptions, even photographs of the device that works for our benefit. We scroll down, noise is heard in the background and we see data from the receiver, presented in the form of a so-called waterfall. That is, frequency is plotted along the horizontal axis, and time runs along the vertical axis. The amplitude is highlighted in color.

Let's go over the receiver controls. First, let's look at the waterfall itself, we see all 30 megahertz, a little less, with such a scale that absolutely nothing is clear. To change the scale, hover your mouse over the waterfall and turn the wheel.

Let's zoom out. To move the visible window, move the mouse over the waterfall, hold down left button mouse and drag to the side. It can be seen that around the frequency of 14.2 megahertz there are some signals that can be listened to. These are the radio amateurs we can catch on WebSDR. Let's tune in to some of them and listen online. To do this, we take a yellow carriage on the frequency axis; it indicates what frequency we are tuned to. We can move it. Left-click and drag.

In general, the interface is simple, after a few minutes of work you will understand it intuitively.

Continuation on the video from the Soldering Iron TV channel from 5 minutes.

The second part, which tells how to catch radio via the Internet

In the event of a war, with a very high degree of probability, the Internet will be turned off. There will also be power outages, so radio amateurs will remain the only source of unofficial information. Ordinary people who, using their radio stations, will be able to broadcast the situation in their place of residence. Therefore, remember the frequencies on which they communicate.

1. Frequency 3 MHz, and a little around it. This is the range in which radio hooligans communicate, that is, radio amateurs who go on the air without a call sign, illegally. You can listen to them with the simplest household radio that has a Short Wave (SW) range.

2. Frequency 3.5 - 3.8 MHz, this is the amateur radio range, which is called 80m. This is a purely night range. The communication range on it at night is up to 1500 km, with good progress- up to 4000 km. During the day it is almost closed, the communication range is a hundred kilometers.

3. Frequency 7.0 - 7.2 MHz, and especially frequency 7.175 MHz, this is the amateur radio band, which is called 40m. This is mainly a daytime range for local connections. Confident range during the day - up to 2000 km. At night, the range is not stable, there may be no connection at all, or it may be very distant, even with the other side of the planet.

4. Frequency 14.0 - 14.35 MHz, this range is called 20m. At night it is completely closed, and during the day there is reliable communication over thousands and tens of thousands of kilometers. That is, it is used purely for very long-distance connections, for example the Moscow-Sakhalin highway. The downside of this range is the presence of a dead zone of 400-1000 km.

As already written, any household radio will do for listening to radio hooligans. But to listen to radio amateurs, you need a receiver that can receive SSB signals, because these are the signals that radio amateurs use. There are not very many models: Tecsun PL-600, PL-660, Degen DE1103 and a number of other, more expensive ones.

Tips: - the receivers have telescopic antennas, but their length is not enough to receive distant or weak radio amateurs, so do simple antenna: - a piece of any copper wire 10-15m long, thrown onto a pole, fence, tree, as high as possible. Also, do not forget about solar activity, it greatly affects the communication range. If today you heard a radio amateur at a range of 4000 km, then tomorrow you may not hear him even at a distance of 500 km. Don't forget about this.

In any case, remember a very important rule!
In the event of war, among radio amateurs, unfortunately, there will definitely be both traitors and outright information saboteurs. We won’t point fingers, but you understand what kind of radio amateurs we are talking about, who know the Russian language very well and hate the “damned Muscovites”. They will definitely air misinformation to confuse people. Therefore, be VERY careful and balanced with any information you receive on the air from radio amateurs!

Now you can listen to radio amateurs through online receivers:
1. the highest quality, for the 80m and 20m range (in the Baltics): https://vk.cc/4QWo44
2. list of all online receivers on the planet (at the bottom of the site - map): http://www.websdr.org
Receiver setup - move the yellow diagram on the scale.

One of the interesting areas of developing SDR technology is the ability to control a remote transceiver, which is connected to the Internet, using a home computer with operating system Windows.

This solution allows you not only to listen amateur bands online, but also work on transmission, i.e. conduct full radio communications. To listen to online radio, you need to find links to SDR receivers on the Internet different countries and continents, and activate them. A large number of links are given in the table on the website: http://www.websdr.org/ . There are also programs with which you can connect to any of the remote receivers selected from the list, and some of them, for example: http://www.hamsphere.com/, allow you to communicate through a transceiver connected to the Internet, but for this You need to register on the website, install the program and transfer the required amount to the program developer.

For listening to radio stations and full control of the SDR receiver. You need to install the JAWA application on your computer. You can download it here: http://www.java.com/ru/ Using a remote receiver, you can check the quality of your signal, evaluate the operation of an antenna or power amplifier, determine the presence of transmission, and simply listen to the air in a particular country.

No less interesting, in my opinion, is the possibility of listening to amateur radio broadcasts using such mobile devices, How tablet computers and smartphones based on Android OS and iPhone with iOS. A lot has been written for these mobile OSs different programs, including amateur radio. In my cell phone(smartphone HTC Desire S), almost all programs are installed social networks, as well as the Echolink program, which allows you to communicate via the Internet with a microphone (IP telephony) with radio amateurs on all continents. At the beginning of March 2013 I came across a YouTube video in which Romanian radio amateur YO3GGX demonstrates the Pocket RXTX program for connecting to a remote SDR receiver.

The program runs on Android OS, has a nice interface and allows you to listen to the bands 80,40,30 and 20 meters.

The application is in preview status, but the author promises to finalize the program and turn the receiver into a transceiver if radio amateurs show interest in it. The program is free and can be downloaded using a smartphone connected to the Internet.
To do this you need to go to Play Market and enter the name of the program in the search bar. After downloading it

For those who are interested or who are interested or do not have the opportunity to purchase a real transceiver station, but are eager to find out what the fuss is about - there are utilities and several online services (the most stable) to turn the virtual tuning knob and listen to the broadcast:

1- FRN Client of the free radio network www.freeradionetwork.nl
...the principle of operation is similar to the HamSphere DX-ZONE transceiver. Allows you to provide links to all available countries (cities) servers.

2- HamSphere DX-ZONE online transceiver
...for those who wanted not only to listen, but also to control frequency ranges with the ability to broadcast by voice... there is such a virtual free transceiver (SDR transceiver with a VoIP channel), you can launch it without antennas, without equipment in the house, make QSO without QRM and QSB. Essentially, you work through a VoIP gateway with an SDR transceiver.

3- CB Radio Chat for Android
Walkie-talkie is a gadget (for Android, WM) that allows you to turn your smartphone into a kind of walkie-talkie. Communication via the Internet (traffic consumption is minimal). There is filtering by language of communication (channels) and region of coverage (simulation of communication range

). Lately there has been an increase in the number of our crazy comrades, but we are still far from the English and Polish daily hustle and bustle on the canals.