Post by RYRYRY on Apr 17, 2014 2:32:53 GMT
Here we go. You can point SW noobs at this, hopefully.
General operational stuff
- What is this thing?
This is a WebSDR: a shortwave radio that you can control over the internet. It can pick up frequencies from ~0 kHz to ~29155 kHz, support AM, SSB, and FM modulation modes, and stream the audio to your computer.
- Where is the receiver located?
The receiver is located in the University of Twente, in the Netherlands.
- Are there servers like this in other locations?
Try websdr.org; there are other WebSDR servers elsewhere but they may have limited band ranges or other constraints.
- What should I use, Java or HTTP Audio?
If you're running on a computer with less than or equal to two cores, and less than or equal to 2 GB of RAM, use the Java applet. Otherwise, use HTTP. HTTP lets you make recordings of what you hear, but it requires the browser to save all the recorded data in memory until you stop and click download.
- What can I expect to hear on this?
Depending on the frequency band and propagation conditions, you can expect to hear mediumwave and shortwave broadcasts from Europe and Russia are audible, as well as from the east coast of the US.
- Okay, how do I listen to a given frequency?
Find the text field marked with "Frequency", and then input a frequency in kilohertz. You can also drag up and down the waterfall, or click the +/- buttons for fine-tuning. You can also use the scrollwheel. Make sure you pick the correct modulation mode.
- Well, what modulation mode should I be using?
It depends on who's transmitting. For regular broadcast stations (found in the broadcast bands marked with the pink lines on the waterfall), use AM. For voice broadcasts elsewhere (eg., amateur and others), use either USB or LSB. For morse broadcasts, you can either use one of the CW modes, or use USB or LSB.
- How do I tell whether to use USB or LSB?
Again, it depends on who's transmitting. For voice transmissions, it's easy to figure out. Look at the frequency pattern of the voice on the waterfall. Speech tends to have strong lower frequencies, and fade the higher the frequencies go. So if you see the pattern radiating to the right, use USB; if it's to the left, use LSB. For other modes, it's more difficult to say, and can depend on the mode.
- So how do I tell the mode then?
You can do this with your eyes on the waterfall, or by your ears. Audio is pretty easy. For upper sideband voice, it'll look like the spectrogram of voice: "wavy" shapes that are concentrated in energy at low frequences and fade out at higher ones; for lower sideband, it'll look like this but reversed in direction. For Morse transmissions, you'll see a single "dotted line", but the line will draw out the Morse code. For RTTY, you will see two pulsing lines on the waterfall, close together, but not any further than 1 kHz generally. For AM, you'll see a strong center line (the "carrier"), and two mirrored voice-like patterns on either side of the carrier.
www.rtl-sdr.com/signal-identification-guide/ has some good visual examples.
- What are these woodpeckery noises?
Most likely some sort of over-the-horizon radar system. These could be coastal RADAR systems (CODAR), or you may hear Russian OTHR systems on the UTwente WebSDR. Some of the harsh, wide-spectrum buzzing noises you might hear elsewhere on the spectrum may also be OTHR systems.
Numbers stations & other popular frequencies
- Where's The Buzzer/UVB-76
Enter in a frequency of 4625 kHz, and then use USB.
I can't hear the Buzzer? Is it happening? What's wrong?
There could be many reasons why the Buzzer isn't audible: you may have tuned wrong (using LSB instead of USB), the station is out of propagation -- the signal doesn't reach the Netherlands during the Russian daytime. If it's the Russian nighttime and you cannot hear the Buzzer, it may have been taken down temporarily for maintenance.- What is The Buzzer/UVB-76 anyway
Wikipedia has a good article: en.wikipedia.org/wiki/UVB-76
- I found something transmitting DESVO? What is it?
This is SVO, a marine ship-to-shore station in Greece. "DE" is Morse shorthand for "from".
- I found something transmitting Morse (on a frequency between 250 and 500 kHz)? What is it?
This is probably a NDB, or non-directional beacon, used by aircraft for radio navigation, and usually transmit a short Morse identifier. See en.wikipedia.org/wiki/Non-directional_beacon
- How can I tell what a signal is?
If it's well-known, tune in, then first zoom "max in". If you're lucky, you'll find a label on the frequency with a short description of what the station is. Otherwise, click on one of the buttons listed under "Station information", which will open a new tab or window and query that external site's logbook for what that frequency might be.
- I found something transmitting numbers/letters and numbers? What is it?
First look at what frequency they are broadcasting at. If they are within an amateur radio band (look to see if there is a green line below the waterfall where you are tuned to), then this is probably amateurs (hams, individuals licensed to transmit shortwave radio) talking to one another, and isn't terribly interesting.
In rare cases, though, you may have found a "numbers station"; take a look at some of the recordings here, compare, and see what you might have found.
I'll add more to this later. This'll do to start, I guess, and some pictures and sound files might be useful too.