Motivated, as noob, by following which no longer looks active (so posting here):
Questions:
How many such DVB-S2 digital channels can be transmitted here?
A transponder /TS stream generally is the 6-8 MHz analog BW equivalent, and can contain 6-8 SD TV channels.
Can we also do for DVB- T2 and DVB-C as well?
Re: transmitting old analog composite PAL video, can SDR Lime ( or generic SDR HW + gnu radio) take input TS streams, and output a unified analog video RF that can be put on a coax RG11 trunk ( so output can be received direct on the RF port of TV set)?
How many analog TV channels would a single Lime SDR transmit?
Note here that the TS stream(s) will be encoded and then go through DACs and RF modulators to generate above kind of output.
To me the answer here will serve to benchmark SDRs progress in comparison with “traditional” tuners, cvbs decoders and RF modulators available !
It depends on the settings, like RF bandwidth, modulation rate, FEC, and such. If we take maximum bandwidth 60 MHz and 32 APSK, you can get more than 100 Mbit / second data rate
The software I used for the demo is called gr-dtv and is part of the GNU Radio package. I have only tried DVB-S2, but it also seems to support ATSC, CATV, DVB-T and DVB-T2.
Not sure what you mean. It will output analog RF, not analog video. And you need a TS stream with constant bitrate.
Install GNU Radio 3.7.11 on a linux computer and experiment
Thanks. Since I am new it will be a while going thru some docs to understand what gnu can do …
Re: your last answer, what is the difference between analog RF vs analog video? I understand analog video might just mean composite video “baseband.”
What I meant was RF transmission of analog video broadcast channels, the kind sent out by cable TV headends over coax to homes with “regular” TV sets with an RF port on back. This is still the majority situation globally.
My understanding is (please correct with your expertise; I am learning):
The original satellite transponder signal is received by “professional” IRDs which are basically overpriced DVB-S2 satellite receivers ($10 each in quantity online with single DVB-S2 tuners and CVBS/HDMI outputs plus USB port(s) and power adapters, remote control, cables etc.)
From Alibaba, if you add up the costs for transmitting 96 analog RF channels, with TS stream inputs ( derived from commodity satellite receiver STB motherboards after the LNB tuner-demodulator stages), and add up costs for multiple 16-24 channel decoders ( converting TS input to individual CVBS channels after D/A stage) and 16-24 channel matching RF modulators ( converting CVBS channels input to single stream RF output via combiner ports), they come to about $40/TV channel.
Of course in the above traditional setup there is a lot of redundant conversion with unnecessary physical ports that drive up the price.
From the 60Mhz/ 100 Mbps estimate, it looks one might cover about 60 TV channels with a single LimeSDR unit. (6-8 Mhz “analog” bandwidth satellite transponder mux carrying 6-8 digital TV channels, each of which is then converted to an analog equivalent channel.) Satellite transponder bandwidth is single carrier 27-72 MHz, with “average” 27-32 Mhz.
In principle then each satellite DVB-S2 STB receiver gets this 27-32 MHz bandwidth as a TS stream post tuner-demodulator stages, but only decodes a single digital TV channel as analog CVBS or digital HDMI output. So each STB tunes-demods about 30 digital channels at once.
Analog video to me is when the video (as in motion picture) only exists as analog voltage on a cable.
I am only concerned with digital video, i.e. motion picture that exists as RGB values in a bit stream. This is first encoded and compressed using a video codec like H.264, then multiplexed into a MPEG-TS transport stream. This transport stream is modulated by the DVB-S2 modulator, which is the GNU Radio flowgraph, then converted to radio frequency using the LimeSDR.
