Fist things first..... A dongle is nothing more than a pigtail. Rather than plugging something directly into a computer, you use a short cable. Now, as to which SDR to buy. If you want to get your feet wet without breaking the bank, I suggest the $20 SDR. The $12 one ain't much of an SDR. Obviously, the $79 one is the best but I personally wouldn't spend that much. Something else to think about is how good do you want the received signal to sound? If you use a pair of cheap computer speakers, it's only going to sound as good as they do. I don't suggest you do what I did but if you have an old stereo around the house and a pair of decent speakers, you can shape the received sound to your taste. On my Ham rig, I pick up the audio from the headphone jack and input it into a 100 watt audio amp and then out to a really good speaker. I have total control over volume, bass, and treble. You can do the same thing by picking up the audio output from a computer and sending it through an old stereo system. For my music recording studio, I pick up the computer audio and run it through a JVC 80 watt stereo amp and then to 6 speaker cabinets housing 12" and 15" speakers and high frequency horns. One thing to keep in mind is the SDR software. There are numerous programs available. Some are better than others and some are free. The program that you choose is going to dictate how many features you have and how much control you have over those features. Finally, I like the SDRs that have two antenna connections. One for HF and one for VHF/UHF. Most of them are SMA connectors, so be prepared to buy some adapters for your antenna cables. Always use outdoor antennas and don't skrimp on how much wire you have to use in order to get a decent input signal. Those little indoor SDR antennas are so bad, you'll think SDR is a joke. With a proper antenna and good software, you'll be hearing things that guys with expensive Ham rigs can't hear.
