what is that that ? Winamp ?
Hahaha. No.
The program itself is called SDRUno. It's a "software-defined radio" program. SDR is basically the idea that you replace much of your physical radio hardware with software that performs those functions.
In this case, I have a device called an SDRPlay; it's basically a small black box with a USB port on one end and an antenna port on the other. To break it down to simple terms...inside is a digital tuner and a *very* fast analog-to-digital converter that basically digitizes the RF output of the tuner, in this case my device supports up to 10msps (10 million samples a second) at a resolution of 12-bits per sample. In lay terms, this thing is capable of digitizing around 10 megahertz of RF spectrum.
This digitized RF spectrum, which is in an I/Q format; is then sent in to the SDRUno software. There you can tune the segment of RF you want and the software will do all the demodulation.
It's basically a digital tuner on steroids since you're not getting an analog signal until it comes out of your sound card. All the functions outside of capturing the RF from the antenna are done entirely in digital and mostly in software. If you're wondering how software can demodulate either an AM or FM signal...just remember that all modulation schemes can be expressed as math in some form...so it can be done in software. The advantages of this is upgradability. If some new modulation scheme comes out; I'll be able to support it with a software upgrade.
It also eliminates a lot of variables in the quality of your tuner output. While the sound quality of a physical tuner can depend on a million variables; software is just working on a mathmatical level. The audio it produces from demodulation can be considered "mathmatically perfect". The only real variable in quality is the digitization of the RF spectrum.
Further in to that; you can do some interesting things you can't do with a traditional tuner. I can adjust the width of my IF spectrum to just about anything I want...symmetrical or asymmetrical. In some cases when I DX broadcast FM, I can actually reduce the IF to "ignore" a local adjacent station. This produces very distorted audio due to having half the deviation cycle; but it's enough you might be able to catch a station ID. This program happens to feature "FM Stereo Noise Reduction", which applies some noise reduction to the MPX portion of the signal. Of course, it can also apply RF noise reduction to the entire spectrum as needed. In fact, this is really handy when you're trying to listen to AM...and of course...flexible IF in the software means I can listen to a *full* 20khz AM channel vs the 10khz you usually get out of a real radio.
So in the screenshot I posted, the big spectrum in the bottom right is the current incoming RF spectrum from the SDRPlay...I don't run it 10mhz wide because I don't have a PC that can keep up with it...so this is just a 1mhz slice of the FM band. You can see three stations in this screenshot, two have HDRadio carriers and the one I'm tuned to doesn't. The spectrum above it is the IF spectrum. Kinda useless on FM...but when you're dealing with AM it's very handy for helping set your IF width as well as notch filters. Yes, I can actually set notch filters to block out interference within the IF. The hardware itself is extremely frequency agile...supporting 100khz up to 1.2ghz continuously.
Of course, this isn't a high-end unit; it only cost around $120 so it's performance is far below an SDR that might cost a few thousand dollars. But the real jewel of this thing is just how flexible it is as a tuner...completely redefines what one think is possible. Here's an example:
This is a small slice of the AM Band. You can see on the big spectrum the local "powerhouse" on 1460khz at a full 20khz. You can also see another "local" station on 1420 that's putting out a full 20khz but looks narrower due to the signal level. I'm actually tuned to 1430 WNAV. On a normal radio, the sidebands from 1420 would swamp it; but as you can see, I'm mostly tuned to the upper sideband and a portion of the lower that's not getting swamped. Does it sound great? It's a noise bandwidth-limited AM signal, but it's clear enough I was easily able to identify it. I'm also doing "synchronous AM" detection, entirely in software. You can also see a very faint carrier at 1440 and one at 1450...and at 1410. Impossible to identify...but really neat to see something. I can tell from experience by looking at the "dashed" line at 1450 that it's actually TWO am carriers that are "zero beating" each other.
This is a pretty complex and expensive device if your goal is to just listen to local broadcasts. However, it works really well for those applications in addition to letting you tune in to the rest of the RF spectrum. Another interesting feature that appeals to the DXer in me is the ability to record entire swaths of RF spectrum to listen to later. So instead of recording a single station, I can record the *entire* AM band at once and then "tune" it as if it was coming in live. Record an entire hour of the AM broadcast band and all you have to do is then retune and listen for station ID's; you won't miss anything.