Sunday 3 November 2013

Listen to Amateur Radio Hams using the internet!

When I was sixteen (many years ago now - I would have to print the year in Roman numerals to tell you what year it was!), I took the UK Amateur Radio Exam (RAE) after joining the Harwell Amateur Radio Club for a year or so and taking part in a 24hr Ham Radio contest stuck on the top of the cold and windy Chiltern Hills all night trying to keep awake! Unfortunately, I failed the exam by just 1 grade (I was in the middle of revising for and taking 10 GCSE O-levels at the same time, so I sort of had an excuse... and the RAE wasn't multiple choice like it is today!). If I had passed the RAE, I believe I would have been the youngest person to have become a licensed Ham in the UK (at that time). Shortly after that, my family moved from the Berkshire countryside into the middle of Oxford City and so I waved goodbye to my hand-made 102' aerial on it's 30' mast strung up to my bedroom window and attached via coax to my Trio ham radio receiver and self-built valve notch pre-amplifier... and never went back to Ham Radio ever again (sigh...).

Have you ever wanted to listen to Amateur Radio (aka Ham Radio) but didn't want the expense and bother of buying the equipment and erecting an aerial, etc? Well why not listen to it over the web?

You may have heard of SDR (Software Defined Radio).
A basic SDR system may consist of a personal computer equipped with a sound card, or other analog-to-digital converter, preceded by some form of RF front end. Significant amounts of signal processing are handed over to the general-purpose processor, rather than being done in special-purpose hardware. Such a design produces a radio which can receive and transmit widely different radio protocols (sometimes referred to as waveforms) based solely on the software used.

Well, if you connect an SDR PC to t'internet, you get a highly tunable radio that can be controlled by anyone on the web. The University of Twente in the Netherlands have made just such a thing available for us all here.
Twente - Wide-band WebSDR

1. Click here to go to the website - if you get a Security Warning, don't worry, it needs to run an app. -  so enable it to run.

2. Next scroll down the page until you see the cyan box for HTML5 and click the 'Click for test of the HTML5 audio' button - if it works then enable HTML5 for both Waterfall and Sound. This gives a better and more controllable display.

2. Next, type in your name or nickname in the log-in cookie box (optional).

3. You should see a moving waterfall display. The frequencies are shown along the X-axis. There is an Amateur band shown in green at 20m, so click on the dark green 20m text. This should move the yellow pointer to that position.
4. Now we need to zoom in for better control, so click on the 'Waterfall view - zoom in' button just below the waterfall graph until you have the whole 20m band in view. If necessary, click and drag the waterfall display across, so that the 20m band is in the correct position. If you zoom in enough, you will see some known station id markers appear - see below:
5. Now find a station in the green 20m band - start with one of the strong white ones and either drag the cursor to that position or use the Frequency adjust buttons (---, --, -, +, ++, +++) to move the frequency cursor. Make sure the AM button is clicked to start with.

6. When you start to hear a channel that sounds like a voice (but it may sound like mickey-mouse or Johnny Cash if a side-band is being used), then use the same Frequency buttons to fine tune for the strongest signal by looking at the signal strength bar:

7. Now we need to find out what type of transmission it is. If the voice sounds like it has been pitch-shifted, try clicking one of the LSB (Lower Side Band), USB (Upper Side Band) or other similar buttons to get the most intelligible sound. If you can hear more than one voice or have other interference, try narrowing the bandwidth using the 'narrower' button. If the signal is weak, try the 'wider' button to try to get as much of the signal as possible (without picking up other broadcasts). Amateur transmissions are not normally FM (Frequency Modulated), so you shouldn't need this unless you are listening to BBC Radio 3!

8. You can now try the squelch and autonotch check-boxes to see if it improves things.

9. Once you have found something and it is nice and clear, use the store button to save that frequency and all other settings. You can also record it using the 'Recording - Start' button.

Have fun!

P.S. OK, so it is nothing to do with USB, but you can get USB SDR receivers and with special software, hack them to make your own SDR - search for SDR on YouTube if you are interested or click here for a Hak5 video by 'Snubs' using a $20 dongle.

If you know of any other web SDRs or have anything to add, please add a comment.

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