Adding Software Defined Radios (SDRs) to my Radio Toolkit

After seeing some of my fellow radio hobbyists’ (particularly @MilcomMP and @lamdaprog on Twitter) reports about using Software Defined Radio (SDR), I decided to begin my own SDR adventure. A couple of weeks ago, based on what I’d seen and read, I bought an Airspy R2 because it seemed to be one of the best VHF and above SDRs for the money. I’ve had a lot of fun using the R2 with both my shack computer and my laptop, and even though I still have a lot to learn I’ve quickly come to realize that it’s a great tool for the radio hobby. After working with the R2 for a bit, I decided to buy a less expensive SDR to devote to trunked radio system analyzing with Unitrunker, so I purchased an Nooelec NESDR Smart v4 because it’s a narrower unit and plugs into my laptop without blocking the adjacent USB port.

Airspy R2
Nooelec NESDR Smart v4

The Airspy R2 has been a fun experience. At home, I use a BNC to SMA adapter to connect it to my home antenna system. When I’m using it with the laptop, I’ve got an SMA extendable whip antenna I attach to it and even in the Faraday Cage-like environment of my home away from home in Brunswick it receives well. The R2 gives me a receiver to go along with my scanners; by receiver I mean something with a few more tools to aid and enhance reception. I can play around with the gain and filtering through SDR# software to bring up weaker signals or filter out adjacent interference. While I primarily use it for tasks associated with scanning and monitoring, the R2 also has me listening to some FM broadcast stations again.

Airspy R2 with an extendable whip antenna connected to my laptop

I’ve found the Airspy R2 a most useful tool for searching and hunting for what frequencies are being used. It’s spectrum and waterfall displays are great for finding frequencies that are in use and pouncing on them to see what’s there. For instance, if I hear a flight of jets working one of the local ranges, but I’m not hearing anything on any of the known air-to-air frequencies, I can turn on the Airspy and use SDR# to look for activity in various chunks of spectrum; if I see a spike or line in the waterfall, I can click on the spike or line and hear what’s there. An example can be seen below; while the R2 is parked on 132.925, you can easily see on the scope and waterfall that there is activity on 132.425 as well; if I didn’t know that 132.425 was Jax Center Hunter Ultra High, I could easily click on the spike on the scope or the line on the waterfall and hear the traffic.

Airspy R2 monitoring 132.925 (center) with traffic on 132.425 clearly visible to the left

I bought the Nooelec NESDR Smart v4 for a specific use – Unitrunker. I’ve used Unitrunker in the past, but I’ve had to tie up a scanner to provide the signal, which isn’t exactly a cost effective use of the scanner. The SDR is considerably cheaper and better for monitoring a single frequency. I’ve combined the the NESDR with an SMA antenna from a Uniden Home Patrol scanner to provide the signal for Unitrunker to decode. Using Unitrunker, I can search for new talkgroups, identify radio IDs, and use various pieces of information to identify unknown talkgroups.

Nooelec NESDR Smart v4 (left) plugged into my laptop, feeding a signal into Unitrunker software
Unitrunker screen shot

Even though I’ve just dipped my toe into the Software Defined Radio pool, I’ve truly developed and interest in them and found them to be very useful. They’re relatively inexpensive when compared to scanners and receivers and can be an excellent addition to any radio hobbyist’s toolbox. After I get my head wrapped around the Airspy R2, I’m looking at investing in an Airspy HF+ Discovery and a loop antenna to get back into HF/Utility monitoring. I’ll try to keep the blog up to date with my experiences!

Categories: Amateur Radio, Computer Aided Scanning, Scanning, SDR

Tags: , , ,

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