Toe-dipping into Radio

As a perfectly contented computer geek, I have always been aware of the world of amateur radio but I had too much going on in the IT world to really pay it much notice. Of course the Internet is the place where worlds collide and at some point a couple of weeks ago I found myself reading about a project called RTL-SDR, which meant nothing to me so as always when that happens I did a little digging to understand more about it.

That was the subtle start of my fall into the rabbit hole of Amateur Radio and I’m not sure if I’ll be coming back…

RTL-SDR is a portmanteau of Realtek, a familiar brand of cheap network card processors I’ve used for many years and SDR which stands for “Software Defined Radio“. I had never heard of SDR before so I digged down a little and discovered that this was a new technology essentially leveraging the power of modern PC’s to emulate the functions of a radio that traditionally have been implemented in hardware. The RTL-SDR project is developing software that exploits a design quirk of a very cheap USB TV tuner chip made by Realtek to receive radio signals from an antenna and use SDR software to interpret them. I found a seller on eBay selling a package containing the TV Tuner, some additional antenna connectors and a custom-made CD containing all the SDR software you need for about £15, which seemed worth a punt just out of curiosity about what was going on in the airspace around me.


The software in the image above is SDR-Sharp, which is a Windows application for scanning the radio waves. The TV Tuner is sensitive from the HF band at 24MHz, way up to 1.8GHz which is above the TV signals (clearly, important for a TV Tuner!) but just below the frequency of a cordless phone. I attached the tuner to one of my house’s antennas which is otherwise unused, without a booster. Being designed for TV this antenna is most sensitive in the ranges used for broadcast radio and television. The frequency in the image is between the two in a band of frequencies allocated for amateur radio users in what they call the 70cm band, referring the the wavelength. I’m actually tuned in to what seems to be a very popular repeater in Duckinfield called GB3PZ* and from this I’ve found myself exposed to a world that has an order-of-magnitude more jargon than I’ve ever encountered in the world of IT!

I’ve found the whole experience fascinating and as such I’m struggling with one of the design quirks of my own brain in trying to stop myself compulsively learning as much as I possibly can, as fast as I can! I liken the experience to climbing a small uninteresting looking hill to find behind it a rich valley full of cities and farms and it’s own indigenous population you’ve never encountered before. Amateur radio is an intellectually driven hobby, it’s all about learning, applying, discussing ideas and exploring what is a very broad and progressing discipline with specialist areas such as long-distance communication across the world known as DX-ing, learning and using morse code, which I could’ve assumed was all but dead but apparently it’s alive and kicking here! Even space and satellite experiments, the ISS has an amateur radio on board and it’s possible to converse with the astronauts for a short time while they are overhead!

Like the title says, I’m dipping my toe into this world and unfortunately, or fortunately if you’re my partner, my very limited time will mean I cannot dive head first into getting the required license to transmit on amateur radio frequencies however I may look into buying a shortwave radio and listening to whats out there in the forgotten LW/MW/HF bands as signals bounce across the sky from distant places. I’m keen to try and find another numbers station because I once discovered one by accident using a guitar distortion pedal and a very loud amplifier, in hindsight this was probably very very fortuitous being that numbers stations broadcast on random frequencies for short periods of time and this accidental set-up just happened to pick up a Chinese broadcast that had the sound of children and a woman’s voice repeating a message with breaks of Chinese music, very eerie!

Perhaps next year I’ll go for my license and take this further but for now I’m signing off, or as they say “7 3”.

* If anyone reading this is familiar with GB3PZ they might notice the frequency is not correct which did throw me a little when I was trying to understand what I’m listening to because GB3PZ transmits on 430.9MHz, I put the discrepancy down to the fact I’m using a 15 quid TV tuner on a TV aerial using some hacked together software!

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