Support for SDR (Software Defined Radio) devices

Ideas for the future versions
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voy
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Joined: Sat Nov 13, 2021 10:30 am

Support for SDR (Software Defined Radio) devices

Post by voy »

Is it possible to add support for SDR (Software Defined Radio) devices to receive terrestrial broadcasts (DVB-T, DVB-T2 etc.)? :) These devices tend to be much more sensitive than regular DVB devices. I am a user of one of them and it is SDRplay RSPdx, to which the Sirio SD-1300N broadband antenna and the Qorvo-based preamplifier are connected. Some time ago, the Qt-DAB program was created, with which you can listen to DAB+ radio. SDRplay RSPdx uses the so-called AGC (Automatic Gain Control), which prevents signal distortion and possible receiver damage when the signal is too strong.

For SDRplay products full API is available: https://www.sdrplay.com/docs/SDRplay_AP ... _v3.08.pdf

When starting Alt-DVB, RSPdx is detected as Mirics BDA Filter. The device is based on the Mirics Flexi MSi001/MSi2500 hardware platform, it also has built-in hardware DAB, MW and FM filters.
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Mr. Orbita
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Re: Support for SDR (Software Defined Radio) devices

Post by Mr. Orbita »

The main issue for any SDR device is that it does not demodulate the signal.

All "classic" DVB cards are demodulating the signal, and providing packetized 188-bytes TS output, ready to be consumed with AltDVB or any other app. The basic idea is that AltDVB (or other DVB player) puts a tuning request to device, device locks signal internally (or not :mrgreen: ) and responds with stream.

SDR provides a raw bandwidth instead and demodulation has to be done on software level. This is a pretty big task to create a versatile DVB-S/S2/S2X, DVB-T/T2, DVB-C/C2 software level demodulator. It's not completely impossible, but GNU Radio shows how complicated it is, when anybody would try to demodulate eg. DVB-T.

I've never seen any stand-alone project with full automated DVB software demodulator for SDR. There are multiple smaller projects like DATV demodulator, which covers DVB-S/S2/S2X (S2 & S2X partially): https://github.com/f4exb/sdrangel/tree/ ... /demoddatv

An interesting thread about creating DVB-S/S2 software demodulator for SDR devices: https://forum.amsat-dl.org/index.php?th ... modulator/
Project is closed source and after 3 years it is still not fully completed, although author has got limited time to maintain it.

For SDRplay, as the maximal bandwidth is limited to 10 MHz, probably only DVB-T/T2 and C/C2 could be achievable (DVB-S/S2/S2X up to Symbol Rate ~7500 ksps, so SCPC only).

Because the way of dealing with received data is dodally different between "classic" DVB cards and SDR devices, I'm afraid that this won't be possible.

For ordinary RTL-SDR dongles it is possible to watch DVB-T/T2 channels, but only if drivers will be replaced back from Zadig ones to default, because in I/Q mode RTL SDR bandwidth is limited to ~2,4 MHz, which is not enough for DVB-T/T2.

Side Note: For quite some time I'm thinking about ordering LimeSDR, which might be currently suited the best for eventual usage on satellite (bandwidth exceeds 61 MHz, this means that still some very high SR broadcasts would be out of reach), but I'm not expecting to be able to use this device in any DVB player. SDR applications might be the only way.
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