Re: [Drm-devel] MDI based transmissions, Experimental live broadcast in Budapest

[Rafael D. <ra...@ri...>]

The only comment is that you don't need to support everything, like
run-time changes or all the modulation types. One could just set in the
CS which will feed Dream MDI input what is supported by Dream currently.

I'm also interested in having Dream to support MDI input (as we already
have an open source CS in svn).

Best regards,
Rafael Diniz

On 6/12/19 4:44 PM, Ádám Kiss wrote:
> Hello!
> 
> DReaM doesn't generate baseband IQ signals since our soundcard cannot
> output low frequenty signals, and also the (presumably) different
> phase-shit difference would kill the signal quality after the generator.
> We are using a 12 kHz intermediate frequenty.
> The IF is 12 kHz, and we are putting positive IQ signals to the vector
> modulator. (The left is the I and the right is the Q channel) The SMIQ
> is just a temporary solution, we will change it to my homemade IQ
> modulator built from two SA612, and a passive, fix-freuqnty
> phase-shifter. This already works, but we are going to reduce its EVM
> under 5% before we install it permanatly.
> 
> We are using our homemade pre- and power amplifier. Nowdays I am not at
> the university, so I cannot take any photo.
> 
> We are using a monopole antenna tuned to the desired freq (26060 kHz)
> with a network analyzer.
> 
> 
> With further investigation in the code I found that implementing the MDI
> transmission would require some other changes. For eg. implementing
> hierarhical modulation with service priority and run-time change between
> modulation types. it's a bit different to implement them without
> previous experance with the project.
> 
> Bests, Adam
> 
> Stefano Mollo <ste...@gm... <mailto:ste...@gm...>>
> ezt írta (időpont: 2019. jún. 10., H, 17:36):
> 
>     Hi Adam, 
> 
>     excellent initiative and I can confirm that the MDI feature in TX
>     mode is not yet implemented; I wanted to do exactly the same you are
>     trying to do, and I learned it "the hard way", after few days of
>     banging my head against the .... PC monitor :-) !!
> 
>     However I am VERY much interested in some more detailed description
>     of your TX setup; such as:
> 
>     1) you write that DREAM generates the baseband IQ samples of the DRM
>     signal to be transmitted, then outputs these IQ signals through a
>     SoundBlaster Live! card, which you feed into a Rhode & Schwarz IQ
>     modulator (R&S SMIQ). 
>     *Question*: what settings - and why - exactly do you use in DREAM TX
>     in the "OUTPUT" dialog box? (The default is shown below)
>     image.png
> 
>     For example, if you set it to 
>     image.png
>     then how do you know which channel is*I *and which channel is *Q*?
>     I.e.,*I* will be on the Left or on the Right channel of the sound
>     card output port? 
> 
> 
>     2) you continue writing that the  Rhode & Schwarz IQ
>     modulator then drives the consecutive power amplifier chain and antenna;
>     *Questions*:
>     (a) what power amplifier are you using? Characteristics, brand,
>     model .... etcétera;
>     (b) are you using any filtering between the amp and the antenna?
>     (c) what kind of antenna are you using?
>     (d) are you using an antenna tuner? If so, could yo please describe
>     in details what are you using?
> 
>     ===
> 
>     See, I have been trying to do exactly what you are doing for about a
>     year now, but I am stuck at the DREAM output stage, and I never
>     managed to go on air. I did, however, managed to send the DREAM I/Q
>     stream over IP, and it worked VERY well, with SNR > than 60 dB at
>     the receiving end! REALLY really good stereo quality,using OPUS ;-)
> 
>     Finally, the R&S modulator is probably something a normal person can
>     afford; any idea for a simple I/Q modulator, say, re-purposing some
>     Electronics originally meant for other uses? For example, how about
>     using the PI as a modulator taking advantage of the RPI TX project?
> 
>     Cheers, and congratulations for the initiative; I firmly believe DRM
>     is THE way to the future for radio. 
> 
>     Stefano Mollo
>     Perth, Western Australia
>     VK6WFM
> 
>     On Sun, Jun 9, 2019 at 11:35 PM Ádám Kiss <kis...@si...
>     <mailto:kis...@si...>> wrote:
> 
>         Dear DReaM Developers,
> 
>         I am a student of the Budapest University of Technology and
>         Economics, taking part in our DRM transmitter project. Basically
>         we are on the air now, aiming to provide opportunity for signal
>         propagation experiments and receiver tests still in the
>         development phase.
> 
>         We currently play out a 25-hour prerecorded program via mplayer
>         to the onborad soundcard of a PC running Linux. Dream receives
>         the data of the monitor port of this card, encodes the sound
>         using FAAC, generates the baseband IQ samples of the DRM signal
>         to be transmitted, then outputs these IQ signals through a
>         SoundBlaster Live! card, which we feed into a Rohde & Schwarz IQ
>         modulator (R&S SMIQ). This later one drives the consecutive
>         power amplifier chain and antenna. (Further details can be found
>         on www.drm.org <http://www.drm.org> and the monitored
>         transmission is available here: nmhh.hu/drm <http://nmhh.hu/drm>).
> 
>         Since our goal is to provide opportunity for all receiver
>         manufacturers worldwide to test their products on a live system,
>         we intend to transmit a stream which contains Journaline data
>         and slide show as well in addition to the audio data. To this
>         end we would have to feed an MDI stream into the DREAM modulator
>         software. We tried to reconfigure DReaM to use this data stream,
>         then we saw that this feature is not implemented yet. I checked
>         the source code of DREAM and saw that MDI decoding is
>         implemented, although it is not integrated with the transmitter
>         module.
>         Do you have any plans for implementing this feature in the near
>         future? I would like to rely on free software as long as I can,
>         and DReaM fits well to this objective.
> 
>         Thank you for your consideration.
>         With best regards
>         Adam Kiss
>         Budapest University of Technology and Economics
>         Department of Broadband Infocommunications and Electromagnetic
>         Theory
>         HAM: HA8KDA
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> 
> 
>     -- 
>     *************************
>     Stefano Mollo
>     MARA <http://www.mara.gov.au/> Registered Migration Agent
>     MARN 1570954
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>     Level 2
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> 
> 
> -- 
> *Kiss Ádám*
> *HA5KFU
> *
> *Simonyi Károly Szakkollégium
> *
> <mailto:kis...@si...>kis...@si...
> <mailto:kis...@si...>
> 
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