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Hands up everyone who knows how radio works...
If you were an avid electronics nerd like me, no doubt you built your own "crystal set" way back in the days when there were only one or two AM radio stations within normal reception distance of your house.
I recall endless hours spent fiddling with OA95 diodes, large coils of copper wire, long runs of antenna wire, poles on the roof, crystal earpieces and large variable capacitors -- all in the goal of catching broadcast signals from the ether and delivering them as audio into my ear.
The old crystal set was the ultimate in "green" radio -- no batteries, no electricity consumed and they ran forever -- or at least as long as the antenna was connected.
Of course these days, a crystal-set radio would likely be pretty impractical -- mainly because there are just so many AM broadcasters littering the countryside that such a device's limited selectivity would have all the signals being spat out at once. The resulting cacophony of noise would not be pleasant or sensible to listen to.
But now, budding tech-nerds have a new take on the crystal set. Something that will excite young and old alike. Something that is so elegantly simple as to be as astonishing as those self-powered radios of yester-year.
I'm talking about Software Defined Radios (SDRs).
Instead of relying on pure analog circuits to capture, resonate and demodulate the signals plucked from the ether, an SDR does a bit of amplification and then leaves the "hard work" up to software.
No germanium diodes, no variable capacitors, no multi-tap inductors -- just a small PCB and some ancillary components deliver gobsmacking functionality, thanks to the power of today's modern computers.
Whereas the old crystal set would work with only the strongest signals and only when those signals were AM-modulated and only when within a fixed band of frequencies, the SDR creates a huge virtual window into the world of RF communications.
Being able to span a range of frequencies from 100KHz up to 1.7GHz or more, these ultra-low-cost setups can also deal with a raft of different modulation types. AM, FM, CW, FSK, etc. It's just amazing what you'll find when you start scanning the RF spectrum with a device like this.
Back in the old days you'd need a healthy wad of cash if you wanted to listen-in on what was happening over a wide spread of the RF spectrum. Although many of the older radios had "short wave" bands, these were usually quite limited and restricted to AM modulation. What's more, those radios were not all that cheap and their performance was often marginal.
By comparison, a modern SDR is gobsmackingly good and very powerful.
I am still in awe of the fact that a modern $30 SDR has greater capabilities than some of the communications and test equipment I paid thousands of dollars for just a few short decades ago. In fact, without SDR technology, the very significant success I've had to date with my Sense And Avoid system would not have been possible.
If you're interested in taking a look at SDRs then you'll find oodles of information on the Net and YouTube also has some nice vids on the subject. The real masochists amongst us can even have a play with GNU Radio and really test your brainpower.
However, if you're the kind of person who was "Wowed" by listening to your first crystal set "way back when" then I really suggest you have a play with SDR. It's fun, it's cheap and it's really cool.
Who knows what you'll find out there on the radio-waves?
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