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

[Stefano M. <ste...@gm...>]

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: image.png]

For example, if you set it to
[image: 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...> 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 and the monitored transmission is available here: 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
> _______________________________________________
> Drm-devel mailing list
> Drm...@li...
> https://lists.sourceforge.net/lists/listinfo/drm-devel
>


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