SDR: Software Defined Radio – overview

SDR: Software Defined Radio – overview

I’m going to start this post by first telling you, that you need one of these gadgets.. Trust me.

Okay, so what is SDR?

Software Defined Radio, is typically a small device that connects to your Desktop, Laptop, Chromebook, Tablet, or Phone via USB connection. This connection is required so that your ‘Control Device’ can tell the SDR unit what to do, in our case, what radio frequency to tune to.

So a Software Defined Radio is really just a hardware device, that is controlled by software, maybe these should have been called SCRs?

Now that I’ve established the basics, you should be asking yourself, ‘Okay, so I can use my PC, Tablet, etc to listen to a radio signal, why not just use a radio?’ and if you are only interested in listening to normal broadcast AM, FM, AirBand, or even NOAA Weather forecasts, you would be right, an SDR is overkill for you.

But you can do so much more with an SDR.. You can listen to shortwave stations from around the world (taking into account proper antenna, and weather conditions), you can listen to HAM Radio Operators, you can capture and decode digital transmissions, you can configure your SDR to scan through your favorite frequencies, and you can go searching for transmissions that you may not have any idea exist in your area.

In short, you can spend quite a bit of time tinkering with your SDR.

Let me drill down into some of those things I just mentioned. Shortwave stations are located across the world, and typically broadcast with very high power, they operate on frequencies that provide the best chance to reach a large audience that might be thousands of miles away. As I explained in a previous post, radio waves can travel extreme distances by actually bouncing off the Ionosphere, lower frequencies have a much higher chance to do this than VHF, or UHF frequencies.

The same can be said for many Ham Radio communications, any High Frequency communications have a much greater chance to travel over extreme distances than your local VHF/UHF radio communications, that being said, those VHF/UHF communications can reliably be monitored and will not be at the mercy of all the variables that are needed for those long distance communications. You can program in a list of your local VHF/UHF repeaters, and if you have an active number of Amateur Radio Operators in your area (~50 miles) you will be able to listen in without any issues, and with very modest antenna requirements.

While I’m talking about UHF/VHF, you can also receive satellite transmissions that typically provide imagery for use in forecasting weather. Thats right, you can grab the same imagery the NOAA, and your local news channel uses to forecast the weather. Can you think of any other times it would be very useful to see what your part of the world looks like from a satellite’s view? I can.

I mentioned ‘digital transmissions’ a bit ago, your SDR can receive those transmissions, and to our ears, they sound a bit like a FAX signal, but processing that signal through software, we can see text being received. Think of this like a modern version of morse code. Why bother with digital transmissions when you can just listen to voice comms? Well, like the old time morse code, digital transmissions don’t require the same high-power output, and reliance on agreeable weather conditions to dependably send your message. I talked about stealth radio communications in an earlier post, and while digital transmissions aren’t at all ‘stealthy’, it’s obvious that these transmissions get monitored by far fewer people than voice communications. I can think of many useful examples of using digital transmissions to communicate with other interested parties, can you?

In the next post, I’m going to get into more detail on the SDR devices, available options, prices, and how I have my SDR setup for both home, and portable use.


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