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Hello Leif….!!
In your opinion exists e way…to having bpp output on digital coaxial output on pc…..and a fm transmitter with digital coaxial input….that converts mpx-signal and transmits it…..!!!….always in digital domain…..Thank you..
Rocco…Absolutely. Any sound card with AES/EBU digital output coupled with an exciter with AES/EBU digital input will do exactly this. You’ll want to use a digital direct-to-channel exciter like the Nautel M50 for there to be any real advantage though, as otherwise there’d be a D/A conversion in the transmitter anyway.
Please note that while you may gain a theoretical advantage, you won’t gain an audible one. D/A’s today easily do 100 dB signal to noise ratio. FM does 70 dB on a *very* good day.
///Leif
Ok..Leif…..
But is there a way to take mpx out of bpp(+rds)…in digital mode(like coaxial or optical output 192khz) and trasmit it…by exiter with digital input???Can you make an example of configuration???
thank you….
and sorry for my english..
Rocco.You can get digital MPX output from BBP by using a sound card that supports 192k digital output, however:
There are, as far as I know, NO exciters with digital MPX input.
In the configuration I described before, the exciter would have to do the stereo gen and rds.
///Leif
Hello..Leif…..
Read this..🙁look at Digital-MPX)…:
http://www.nautel.com/Resources/Docs/Wh … h_DMPX.pdf
http://paginas.fe.up.pt/~hmiranda/paper … le2001.pdf
Thank you..
Rocco..Hi, Rocco!
Yes, Frank Foti tried to get his idea for digital MPX adopted by the industry in the 90s, but it never took off.
I believe if it will ever happen in the future, Ethernet will be the interface, because of it’s extreme ubiquity and extremely low cost. Either that or AES 192 i guess.
///Leif
Hello everybody!
This is my first post here and I would like to congratulate the creators of BBP and this community!About me and this topic:
Recently I designed and manufactured a digital FM modulator. It accepts 16…24bit digital L/R audio (AES/EBU coax or optical), and produces the FM stereo carrier.
There is no PLL/VCO, or any other ordinary analog modulation concept, like almost everybody is using for decades now (and I HATE IT!). The carrier is genarated by DDS (Direct Digital Synthesis) straight in 87.5-108 MHz band, without upconversions – thus no phase noise. A 32-bit mCPU running at 66MHz, accepts the digital audio and does all the math (MPX matrix, pilot, baseband, etc). It decides what frequency should produce at the output, 540.000 times per second.
So rocco123456, I can tell you it is possible to make a DDS modulator that accepts MPX. Actually, it is more simple than creating internally the stereo coder, RDS, etc. Unfortunately, there is an issue: There are no radio links capable to carry 192kHz digital audio. Even if they exist, they will require a lot of RF spectrum (thus more fees to Authorities). By implementing the stereo and RDS inside the DDS modulator, you need less STL bandwidth to do the same job.
On the other hand, you can put BBP at the transmitter site and use ordinary digital STL equipment. BUT, in case you are operating a network of transmitters, you need to put one BBP at each site…After all this, isn’t it better to let the exciter do the MPX work?… 🙂
(*) Gossip:
Yesterday, with some audio-expertised friends, we evaluated the performance of my DDS modulator, among RVR PTX-30UHT, and Rohde & Schwarz SU125. For the two analog FM exciters, we used the internal stereo encoder of BBP to create the MPX via 192kHz soundcard output (Julia). For the DDS, we used plain L/R via AES/EBU optical cable. Well, the DDS was the winner for it’s clarity and high frequency response. The SU125 came in second place, and PTX-30 in third place (which, by the way, had very bad sound compared to DDS…). The stereo separation ("BBP coder" versus "DDS coder") was the same, +/-2dB’s.So Sigmacom…
Is it possible to make unit which will use MPX digital input ? (generated digital 192kHz MPX output from Julia)Sigmacom.. If you can make an exciter which will take 192Khz digital mpx input (compatible with Breakaway) I will upgrade upwards of 20 client transmitters immediately!
Leif, if this exciter is possible, the need for your IP STL program will become IMMEDIATE!! and I’m sure you will have a huge incentive to develop it quickly so you can try it. Imagine…. Digital audio source, Breakaway processing, digital audio and mpx all the way through the chain, digital mpx into a DDS exciter!! Imagine the seperation, Imagine the SNR!! Viva La Revolution! FM finally joins the 21st century.
We could totally be amongst the first to implement this tech and have world beating audio!
Sigmacom, that looks AWESOME! Direct digital synthesis in a 66 MHz CPU, how the hell did you do it?? 🙂
///Leif
I was searchnig some new products of exciters .. and RVR have one.
http://www.rvr.it/en/fm-exciters-ptx-dds.phpHello again!
@Boki:
– Yes! and by software programming perspective, it is much easier than constructing the MPX inside the mCPU.
– About the RVR DDS, it creates the modulated carrier at 10 (or 12?) MHz. Then, using a PLL, upconverts it to 70 MHz. Then, with another PLL, upconverts it finally to FM band.
I strongly disagree using PLL oscillators, because they insert noise. If they were using XTAL oscillators, would be better.@yorkie98:
– If you are willing and can test it in actual environment, let me make one prototype and send it to you as sample.
I will inform you here in this topic for my progress.@Leif:
– Sorry, I didn’t describe the details… My omission! 😳
The 66MHz mCPU drives another chip that does the DDS, which runs @ 300 MHz.[quote author=”sigmacom”]Hello again!
@Boki:
– Yes! and by software programming perspective, it is much easier than constructing the MPX inside the mCPU.
I strongly disagree using PLL oscillators, because they insert noise. If they were using XTAL oscillators, would be better[/quote]
That is what i want to try 🙂 To see how generated Digital MPX works.I wrote link about new RVR unit, but MPX input on that same unit is again analog.
Sigmacom Great Job!
BestSigmacom, that’s still kickass. Must be a very optimized algorithm, considering you’d have to have a sampling rate of at least 250 MHz or so (right?), that’s only a single cpu cycle per sample! Very impressive.
Are you selling this solution? This is extremely interesting.
///Leif
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