Computers, Digital Modes, Software Defined Radio

Now is the Time!

11/11/2017

Believe it or not, it was not all that long ago when computers were new and amateurs started to integrate computer technology into their shacks. Fast forward 30-40 years and most amateurs have a computer somewhere in their radio room. Or at least I am guessing this is the case. I am not so sure that I would bet the family farm on this statement. Perhaps better to say I presume such is the case. I bring this up because I see a great deal of hesitation for folks to try new things, particularly when it comes to computers, digital modes, and software-defined radios (SDRs).

My interest here is the latter case, trying out software-defined radios. Yes you need a computer for most SDRs, but one can even use a tablet or their smart phone as an interface for some of these radios. Perhaps just by the fact we refer to them as software-defined may throw some people off trying them. It sounds a bit mysterious, after all, and even for many conversant with their computers, software is rather ominous if one is not adventurous.

It looks complicated, but it’s really not. As you use features it quickly becomes familiar

The truth is, if you can run common programs such as word processors, web browsers, and similar software, an SDR should not be a problem at all. Any SDR manufacturer has a vested interest in getting you up an running, and the Internet is filled with resources to explain setup, troubleshooting, and operation of both the radios and the software used to make them work. The capabilities of these radios cannot be overstated. Creative people have found dozens and dozens of uses for them, with many of these uses having serious practical applications.

Just this last week in my local amateur radio club, one of the members showed how he had turned an Airspy SDR into a portable spectrum analyzer for under $200 using a simple inexpensive Windows tablet, antenna, and an external battery source to extend the life of the tablet. How cool is that!! His example inspired me to dig out an old Dell 8″ tablet I had in a drawer, download the software for the Airspy on it (free, BTW), and attach an antenna. Voila! A portable spectrum analyzer ready to go (minus his external battery, for now!).

This view combines a waterfall (bottom) with a Spectrum Analyzer view (top)

One of the more interesting uses for a software-defined radio to me is the ability to record large patches of radio spectrum at one time. As the capabilities of SDRs increase, so does the ability for one of these radios to “listen” to wider and wider segments of a shortwave, amateur, or broadcast band. I once recorded the entire AM broadcast band on a particularly static-free evening, just as a means of seeing how many different stations could be heard over the course of an hour or two. By playing the recording back through the radio software, I could point my mouse at a signal on the screen and listen to it at my convenience. Not to mention I had recorded a slice of history!

Wondering where the signals are popping up over the police and public service bands in your area? Look at the waterfall or spectrum display of an SDR and see the signals rise and fall as transmissions start and stop with regularity. With some additional software you can even decode P25 digital signals, DMR signals, and even DStar and other digital modes in common use. Some radios cover the VHF through 2-GHz range, while others will even go down into the LF range right through HF, giving you a full functioning receiver in a box the size of a pack of playing cards.

For some of you reading this blog you have already taken the plunge into SDR, but for others, you’ve waited, a bit unsure, perhaps overwhelmed by the variety of radios and the amount of information out there. Trust me, now is the time to take the plunge (or just get your toes wet!) with SDRs. Prices are extremely good, the hardware and  software are both mature enough now that they work well together, and there are literally dozens of uses you will find for them once you get comfortable controlling the radios with whatever software you choose. Find one that fits your budget and jump on in!! 73, Robert

 

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