Sunday, August 23, 2015

WELCOME. This is the VERY basic tutorial to WebSDR.

Q: First, what is SDR?

A: Software Defined Radio. You are basically using the site to tune in radio stations as if it were your car radio. Most SDR sites are limited to a specific number of users. (More on that in a bit.) Depending on where their antenna is located, it will effect the quality of what you are listening to.

Q: What can you listen to with SDR?

A: A lot of stuff. News broadcast from across the globe, music in India, secret coded messages to spies, coded military messages, "mystery" broadcasts, HAM Radio operators, and much more. The frequency range for most SDRs is 170 kHz to 30,000 kHz.

Q: What are CW, USB, LSB, AM, and FM?

A: Basically, this is how the signal is transmitted and how you should set the SDR to receive depending on what you're listening for.
  • CW stands for Continuous Wave. A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off. Rarely used for anything other than Morse Code. 
  • USB stands for Upper Side Band, and LSB stands for Lower Side Band. In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. The sidebands consist of all the Fourier components of the modulated signal except the carrier. All forms of modulation produce sidebands. This is commonly used in modern radio broadcasts.
  • AM stands for Amplitude Modulation and is still the most common form of broadcast. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public. AM broadcasting is authorized in the medium wave band worldwide, and also in parts of the longwave and shortwave bands.
  • FM stands for Frequency Modulation. FM provide high-fidelity sound over broadcast radio.

Q: Got it, so how do I listen?

A: The easiest way to listen -and most popular- it by using University of Twente's webSDR. This is a popular SDR from the Netherlands whose antenna has excellent reception and very easy to use.

The SDR Page.

One disadvantage to this site is that it is limited to 420 users at a time. Normally, there is not that many users, but in the event of tensions between The United States and another country, users from Reddit and 4chan come en masse to monitor "SKYKING" (this tutorial was made to assist them to do such during "The Happenings") and the site might be overloaded. If this is your case as you read this, be patient and try again in a few minutes.

Additionally, I will be discussing "Sigmira" in a later post. It is a free to download and use software that allows you to connect to many different SDR antennas through the world (so you can listen even if the above WebSDR is at capacity).

For a quick guide to listen for SKYKING, follow these easy steps:
The rough and easy way to get started.

For Skyking you can also try their other primary frequencies: 24 hours - 11175 USB (usually a weaker signal than 8992 USB). Daytime (in the US) frequencies of 13200 USB & 15016 USB. Nighttime (in the US) frequencies of 4724 USB 6739 USB.
For those who want to explore more, keep on reading.

The basics.

  1. The Waterfall. This shows what frequencies are active. White denotes stronger signals and dark blue means there's no propagation on that frequency beyond static. You can place your mouse arrow on the waterfall and use your wheel to zoom in and out in order to find a signal's exact  frequency. 
  2. The Dial. It shows you what station you're on as well as what bandwidth you are using (more on that in a bit). 
  3. Tuner. You can type the frequency you wish to listen to or you can use the buttons to tune up and down the dial. 
  4. Band selector. This is where you select USB, LSB, CW, AM, or FM. 
  5. Volume and recording. You can record and download things you hear! You can also Squelch the signal from here, to avoid listening to static while you wait for the signal you want (such as HAM radio operators talking to each other). 

Let's Get Started!

Type "9730.00" into the tuner and hit enter. You should be hearing an English-language broadcast of Radio Romania International, or possibly a Chinese broadcast depending on the time of day. Now this is an AM broadcast, so press AM on your Band Selector. It should sound pretty good.

Zoom in on the signal in your waterfall. It will show your dial is in the center of the signal with its "arms" spreading in both directions.

Typical AM signal
You've just mastered the basics of SDR Radio. Zoom back out and look for strong signals (white on the waterfall) and zoom in on any one of them. click below its number and your dial will move over to it. Additionally, as you can see in the above pic, many stations are labeled. Just click on it and it will be selected for you.

So, what if your signal is not AM? Garbled, flooded with bleed over from other frequencies or just sound like noise? Well, we may need to select USB, LSB, or FM. Let's tune to 9745.00 kHz (Radio Bahrain). Notice it sounds odd?

Zoom in closely on it on the waterfall.

The signal has a strong line and the rest "bleeds" to the right. This is an Upper Side Band broadcast. Press USB on your band selector. Sounds a lot better, right? Notice your dial has one arm extending to the right instead of just centered like AM.

Now, if you come across a signal with a solid line and it "bleeds" to the left, that is a Lower Side Band broadcast.

As for FM, if you find a signal that propagates like AM but is nearly twice as wide, that's an FM signal. FM is not very common on the frequencies an SDR picks up, but you might find it.

You are now ready to explore the world of radio via your computer.

The next article will specifically deal with SKYKING and its unusual purposes.

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