SdrDx 2.10 -- Release -- Black UI Option
SdrDx 2.10 adds a choice between the grey UI introduced in the V2 series, and a shiny new black UI as shown here. Most of the UI changes are implemented via stylesheets. Another GUI addition is the ability to fill underneath the RF waveform display, as shown in the image notes, above.
I've also added sound-card based SDRs to the supported set. The approach is that SdrDx takes care of catching the received band segment through the audio coming in from the sound card you select; it also broadcasts the desired frequency (as you change it in the interface) via its TCP IPC mechanism, which would be caught by external controller programs which address the specific sound-card based SDR.
In this way, SdrDx can offer support for just about any sound-card based SDR without further modification; it moves the support load from me, to the manufacturer of the SDR.
SDR 101: "Software Defined Radio"
An SDR works with a simple, but sophisticated, chunk of hardware that is completely unlike a traditional radio.
Instead of using analog circuitry to select a single signal from those impinging upon an antenna, an SDR uses a fast, high resolution analog-to-digital conversion system to measure many of the received signals at once by acquiring an unbroken record of the exact voltage that comprises the received signal.
This can be literally everything at the antenna below the limit of f/2, where f is the sample rate, or it can be a sample taken of a portion of the signal which has been limited to contain only a certain range of frequencies, then "down converted" so the required sample rate is lower.
This measurement, taken at (at least) twice the highest (remaining) frequency of interest, is then used to mathematically extract any information required about the signal, other signals occurring at the same time, and so on.
As seen in the above image, this results in the ability to not only listen to, and extensively process, the specific signal of interest, but also to see everything happening nearby.
Some of the features I provide in SdrDx include recording wide portions of the RF spectrum for replay and re-acquisition later; extensive audio processing and filtering; visual measurement of both audio and RF signals; removal of noise and man-made interference; signal identification using an integrated database; signal peak tracking; distinct resolution of carriers that overlap by only a few Hz; and external control via TCP messages, MIDI control centers, and USB controllers.
I provide the software for free. SDRs vary from $20 for a simple one such as the FUNcube, which receives signals from 50 MHz to about 2 GHz, to premium units such as the RFSPACE SDR-IQ, which are hundreds of dollars. There are kits like the SoftRock, which are inexpensive, but require some soldering skills (and good vision.. the parts are small!) and there are pre-built units.
If you're a ham radio operator or a shortwave or utility listener, you owe it to yourself to experience SDR operation. You'll never look at an analog radio the same way again.
The software documentation may be found here.