Natpos: New Linux SDR Software for the RTL-SDR
Natpos is a new Linux based SDR program similar in operation and features to other programs like GQRX, HDSDR and SDR#. At the moment Natpos only works with RTL-SDR receivers as it runs via the rtl_tcp interface. The software demodulates the standard AM/FM/SSB signals and has a frequency scanner that automatically tunes to the strongest signal. There is a discussion over on Reddit regarding the software, and there the author writes about his favorite features as follows:
The thing I like most is that I can replay past transmissions by clicking in the waterfall history. Using other SDR software, when a new transmission pops up, I feel like I’m in a race to tune to it before it ends so that I can at least hear some of it, but in my software, I don’t even have to pay attention to what’s happening now, and so I seldom do. Usually I don’t notice transmissions on new frequencies until they’ve ended, but I still get to listen to them.
I also put some effort into trying to make sure AM and FM transmissions were equal in volume, as well as at the correct volume according to how well they were modulated, in that I aimed for 100% modulation leading to audio output that’s 6 dB below the ceiling. It seemed as if it was quite random in other software, as switching from AM to FM might cause a huge jump or drop in audio volume. I don’t like to play with my volume controls, so I did my best to make it so that I don’t have to.
I’m also not at all fond of the “click the numbers” method of changing the center frequency which seems to be so common. So in mine, I just type in the MHz on the number keypad and press enter.
I’m also much more fond of my waterfall coloring scheme than any other I’ve seen. It seems much smoother and more informative, at least to me anyway. I suppose that’s rather subjective.
…but it’s rather hard to compare it to other software given that I only got to use other software for two or three days. I rather soon knew I wanted to write my own, and I wanted to use the V4L2 API (that dvb_usb_rtl28xxu module you have to blacklist to use rtl-sdr is an SDR driver, not a video driver), but I had to upgrade to Linux Mint 18 to get access to it since it’s a new API, and after doing so, I haven’t been able to get any of the existing SDR software to both compile and work after it’s compiled. So I just focused on writing my own, since I was wanting to do so anyway. (No support for that V4L2 API though, as it turns out its buggy and offers no way to control the dongle’s gain, so it’s basically unusable.)
Always glad to see new Linux based software for ham radio and SDR. The more, the merrier.