I wanted to find a way to listen inexpensively, which is also great for someone testing out listening to Ham operators communicating. So I found out about SDR (Software Defined Radio). Without going into a lot of detail it's taking a radio receiver that can listen to a wide range of frequencies, then using a computer to do computations and separate out the frequencies across the screen. From there you can select which frequency you want to listen to. For the most part you can see what's going on within a wide range of frequencies at the same time.
You wonder what's the benefit of that? Well imagine trying to find a station by slowly turning a tuning knob until you hear something. But there is a couple of problems with that. One is that a station might not be used but a small percentage of the time. So you may tune through it and it just isn't being used at that particular moment. The other thing is you may be missing something being used quite frequently and you're so far away from it. But with a SDR type setup you can see a whole range of frequencies at one time. Some busy, some intermittent, and you can see patterns of use that might be of interest.
Below is one I picked up on E-Bay for around $8 US and that included shipping. It goes by various names but typically called a USB2.0 Digital DVB-T SDR+DAB+FM HDTV TV Tuner Receiver Stick HE RTL2832U+R820T .
What they found out is that instead of just receiving AM, FM, and TV it actually can pick up 25Mhz to about 1.7Ghz. I've even found a mod for the technically inclined to allow it go down to much lower frequencies. In any case that's an $8 radio which you can listen to a lot of activity.
So far I've just used it one day with the antenna provided. I got the software installed and learning the in and out of using it. I really need to spend another day trying to find some local hams on the air. I was able to pick up some FM stations and a few other transmissions that were continuous so not sure if they were harmonics or what. So definitely need some more time on the unit. Took me a while to find the RF gain so I could crank it up. So probably wasted a lot of time not hearing weak signals.
One thing to point out. This unit draws a lot of power and does get quite warm. Which is actually normal for it. However if you're planning on trying to run it on a laptop for very long might not be good. I don't if it was because my laptop had drained and I plugged it into the AC power and the SDR dongle at the same time but the laptop AC adapter got really hot. So my next run will be with the laptop fully charged so the AC adapter doesn't run as hot while I'm outside testing it.
So hoping for another day to break this out and find a Ham somewhere on the air before I call this one a total success. If you want to read more about this sort of thing check out:
