Transmit digital television signals over Qatar Oscar 100 satellite

Installation du firmware F5OEO PlutoDVB

The Adalm-Pluto also called PlutoSDR is an SDR transceiver offered by Analog Device at a relatively low price. It is presented as a platform for learning for students in the fields of science, technology or engineering.

Various software such as MATLAB or Simulink are graphical user interfaces (GUI) for applied developments.But in order to transmit in DATV we are not going to start on the road to development ourselves, since others are doing it for us.

Based on the AD9363, it is capable of generating or receiving analog RF signals from 325 to 3800 MHz, and up to 61.44 mega samples per second (MSPS) with a bandwidth of 20 MHz.


Acquiring Adalm Pluto

Obviously, the first thing is to acquire the equipment. Several suppliers make the box available, at different prices. I let you check the delivery conditions and customs taxes applicable by these intermediaries.

Improving the functioning and stability of Adalm Pluto

I am using an Adalm Pluto with hardware Revision B (See its label: PCB Rev.). You can observe – in any case in SSB transmission with SDR Console – from time to time crashes of the USB link. These easily disappear by applying a minor modification to the board. Either you change the resistance value of R88 from 1k to 10k, as indicated on the wiki website of Analog Device™ (and planned on the next revision C), or you make the simple modification (which I chose to implement) of connecting PGND and GND grounds together, for example as proposed by Lucien F1TE, by placing a conductor between D3 (GND) and R58 (PGND).

 

Improving stability

Replace crystal TCXO

I warn you right away that this change is not necessary, if you only intend to transmit amateur TV pictures to QO100. But as you often use your PlutoSDR transmitter for SSB as well, you might as well consider how to make this oscillator replacement. When it comes out of the box, the Adalm Pluto is rather unstable when transmitting on 2400 MHz. It is originally equipped with a reference quartz crystal, a 40MHz TCXO RAKON RXO3225M with a stability of +/- 25 ppm on its operating frequency range from -40 to 85°C. This means that at the frequency of rise to QO100, 2400 MHz, the signal will drift rapidly, depending on the temperature, by a few tens of Hertz. To use the Adalm Pluto SSB and the narrow band transponder of QO100, you will have to replace this unstable quartz by a TCXO with better stability.

Smaller than the original RAKON (3.2 x 2.5), the TCXO ABRACON ASTX-13-C-40.000MHz-I05-T is supplied with 1.8V like the original, its dimensions are 2.0 x 1.6 mm. It has an announced stability of +/- 0.5ppm. Some people advise to take advantage of this by placing the TCXO in a location that is less subject to temperature rises. I invite you to read Lucien F1TE’s (french) article on this subject.

TCXO ABRACON replacing the RAKON one

You can find this TCXO ABRACON at the major distributors of electronic components but also some other resellers:

Murata TCXO 0.2ppm 3.0V

Another alternative is to use the TCXO MURATA XNCLH40M000THJA1P0 which is given at +/- 0.2ppm, but with a dimension of 5.0 x 3.2 mm and is powered by 3.0V. DM4DS to propose a small adapter board (a divider bridge to pass the 3.3V power supply point (recovered on C165) as well as a video explaining the power supply points and connections.

Injecting an external reference signal

DL4TMA : Adding an external SMA connector

To improve the stability of the PlutoSDR, we can also bring instead of the TCXO, a very stable external signal which can be that of a GPS-controlled oscillator, or even a rubidium oscillator, like those embedded in satellites, why not. You don’t have to bring 40 MHz, but the Adalm Pluto can receive a signal in the range of 10 to 80 MHz. Of course, the PlutoSDR will have to be set up with the new reference frequency.

The existing TCXO has to be unsoldered and the external signal has to be brought in Pin 3, which has to be 1.8V peak-to-peak maximum. On the PlutoSDR board, C123/C124 as an AC divider to get things down to 1.3V p-p. The internal capacitance of the pin means we don’t actually need to stuff C124 to achieve this.

 


Another suggestion from F4DAV is to use pin 1 E/D (Enable/Disable) of the TCXO RAKON to enable or disable operation of the original TCXO. By setting Pin 1 to ground (GND), the TCXO RAKON is disabled.

Implementation by F4DAV

Original TCXO disable command for PlutoSDR

 

Program the new reference frequency and reboot your PlutoSDR

If your external reference or TCXO is not at 40MHz, but for example at 25MHz, you will need to indicate this change to the AD9363. To do so, connect to the Pluto (as described later in the paragraph Connection to the Pluto SDR by terminal in this article).

fw_setenv ad936x_ext_refclk "<25000000>"
fw_setenv xo_correction 25000000
pluto_reboot reset

To check if the changes have been taken into account, reconnect and launch the command

cat /proc/device-tree/clocks/clock@0/clock-frequency | xxd

That should bring you the line

# 00000000: 017d 7840 .}x@

The result is in hexadecimal. The hex value 017d7840 is indeed 25000000 decimal (check for example with this online converter), so our frequency has been applied.


Here are some references of GPSDO generators that can be used. However, I remind you that you must hold a maximum of 1.8Vp-p before C123. LeoBodnard’s programmable model, set to 36mA should give you 1.6Vdc on 50 ohms, so it is well adapted for that.

EA3HMJ proposes to add a switch on the TCXO power supply to allow the choice of the internal (TCXO) or external (GPSDO) source. It is then necessary to unsolder the C122 bracket and to connect it to the switch. Pin 4 of the TCXO is then isolated and can be connected to the switch.

TCXO/GPSDO selector switch

Implementation of EA3HMJ

14 thoughts on “Transmit digital television signals over Qatar Oscar 100 satellite

  1. Christian,

    Congratulations, this is one of the Blog articles I’ve read about how to setup a DATV station for QO-100.

    Thanks for sharing with the community.

    73’s
    Alex EA4BFK

    (Traduction)
    Christian,

    Félicitations, c’est l’un des articles de blog que j’ai lu sur la façon d’installer une station DATV pour le QO-100.
    Merci pour avoir partagé avec la communauté.

    73’s
    Alex EA4BFK

    1. Merci Christian Superbe tuto !! A bientôt sur QO-100
      73 de ON1RC
      Chris

      (Translation)
      Thank you Christian Superb tuto ! See you soon on QO-100
      73 from ON1RC
      Chris

      1. Bonjour Christian
        Mais quel superbe outil de travail, moi qui suis totalement néophyte dans le mode DATVet dans l’utilisation du logiciel OBS.
        Me voici équipé pour comprendre le fonctionnement et pouvoir parfaire mon installation.
        Félicitations pour la qualité de tes tutos qui sans nul doute vont être un fabuleux tremplin à beaucoup pour créer sa station.

        73 cordialement salutations et au plaisir de te retrouver sur le satellite Q0-100. F3CJ

        (Translation)
        Hello Christian
        But what a great tool, I’m a total neophyte in the DATVet mode in the use of OBS software.
        Here I am equipped to understand how it works and to be able to perfect my installation.
        Congratulations for the quality of your tutorials which will undoubtedly be a fabulous springboard for many to create their station.

        73 cordially greetings and I look forward to seeing you on the Q0-100 satellite. F3CJ

  2. Merci beaucoup Christian.
    Des informations très précises et détaillées.
    Superbe.
    73 de Aitor F4VTB EB2AT

    (Translation)
    Thank you very much, Christian.
    Very precise and detailed information.
    Superb.
    73 of Aitor F4VTB EB2AT

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  4. Thanks for the wonderful guide. Very comprehensive. Thanks again for sharing your experiences. With gratitude 73 de Ros i4wrm

    (Traduction)
    Merci pour le merveilleux guide. Très complet. Merci encore de partager vos expériences. Avec reconnaissance 73 de Ros i4wrm

  5. Bonsoir Christian F5UII,

    Merci pour votre tuto, très instructif. J’ai échangé avec Pascal F4BRF et Nicolas FR4LI au sujet de la modification à base de 2 x 4N35 (montage vu sur le net pour l’ADALM PLUTO).L’idée, une commutation TX/RX pour la partie amplificateur SG-LAB depuis le PLUTO.
    J’aimerai avoir votre avis avisé sur le sujet svp. En vous remerciant par avance.
    Au plaisir de vous lire Christian F5UII.
    73 de Axel FR5GS

    (Translation)
    Good evening Christian F5UII,

    Thank you for your tutorial, very informative. I discussed with Pascal F4BRF and Nicolas FR4LI about the modification based on 2 x 4N35 (assembly seen on the net for the ADALM PLUTO) The idea, a TX/RX switching for the SG-LAB amplifier part from the PLUTO.
    I would like to have your opinion on the subject please. Thank you in advance.
    Looking forward to reading you Christian F5UII.
    73 from Axel FR5GS

    1. Oui, le logiciel SDR Console et également le firmware PlutoDVB d’Evariste F5OEO pilotent les sorties GPO0 et GPO1 lorsque l’on passe en émission. On utilise les 2 sorties car toutes les deux passent en émission à la mise sous tension du Pluto pendant environ 5 secondes.
      Commutation émission PTT sur Adalm Pluto SDR
      On trouve deux schémas permettant la commutation PTT, l’un à base d’optocoupleurs, l’autre à base de transistor et relais reed. J’ai choisi de mettre en œuvre la seconde technique, avec double circuit de commutation, permettant d’alimenter distinctement 2 sorties indépendantes. Une commande groupée sera certainement prochainement proposée. Tous les détails sur cette page.
      Il existe une autre solution, mais que je ne conseille pas au vu du risque engagé sur le Pluto. Il s’agit de celle qui consiste à détecter l’activité du bit0 du bus 12 bits du convertisseur numérique /analogique. Pour la curiosité, je vous laisse découvrir cette mise en œuvre de DH1NFJ sur ce site internet (langue allemande).

      (Translation)
      Yes, the SDR Console software and also the PlutoDVB firmware of Evariste F5OEO drive the GPO0 and GPO1 outputs when you switch to transmission. Both outputs are used because they both switch to transmission when the Pluto is switched on for about 5 seconds.
      Amplifier PTT control - Adalm pluto SDR
      We find two schematics for PTT switching, one based on optocouplers, the other based on transistor and reed relay. I chose to implement the second technique, with a double switching circuit, allowing to supply separately independent 2 outputs. A grouped order will certainly be proposed soon. All details on this page.
      There is another solution, but which I do not advise in view of the risk involved on the Pluto. It is the one which consists in detecting the activity of bit0 of the 12 bits bus of the digital/analog converter. For curiosity, I let you discover this implementation of DH1NFJ on this website (German language).

      1. Bonsoir Christian,
        Merci pour toutes ces informations. Inscription faite de mon côté pour la prochaine commande groupée (PTT Pluto). 73 de Axel FR5GS

        (Translation)
        Good evening, Christian,
        Thank you for all this information. Registration made on my side for the next group order (PTT Pluto). 73 from Axel FR5GS

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  7. Christian,

    Congratulations, for great work.

    Thanks for sharing with the community.

    Jose EA3HMJ

    (Translation)
    Christian,

    Félicitations, pour votre excellent travail.
    Merci d’avoir partagé avec la communauté.

    Jose EA3HMJ

  8. Bonjour Christian,
    Merci pour vos articles qui nous permettre d’avancer sur la construction de notre deuxième station DATV à l’Ile de la Réunion. Nous sommes actuellement actif sur QO100 en bande étroite.
    La station DATV est en cours de construction en suivant à la lettre votre tuto.

    Nous recherchons un système à base d’Arduino capable de mettre off le PA du SG Lab lors d’un SWR élevé et qui serait capable de faire les mesures de puissance OUT/IN. Ceci en utilisant les points de mesures en tension prévu à cet effet. Avez vous une idée si un Om c’est déjà penché sur la question.
    Par avance merci,
    Nicolas Dhiver
    FR4LI

    (Translation)
    Hello, Christian,
    Thank you for your articles which will allow us to progress on the construction of our second DATV station in Reunion Island. We are currently active on QO100 in narrowband.
    The DATV station is under construction following your tuto to the letter.

    We are looking for an Arduino based system able to turn off the SG Lab PA at high SWR and which would be able to make OUT/IN power measurements. This by using the voltage measurement points provided for this purpose. Do you have an idea if an Om has already looked into the matter.
    Thank you in advance,
    Nicolas Dhiver
    FR4LI

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  10. This is a great guide, helped me a lot. Merci!
    Ed PY2RN

    (Traduction)
    C’est un excellent guide, qui m’a beaucoup aidé. Merci !
    Ed PY2RN

    1. Bonjour Rudy,
      La carte exploite le changement d’état de la voie GP0, et GP1 qui, lui, bloque le passage à l’émission lorsque le Pluto démarre (GP1 actif en même temps que GP0 au démarrage). Elle est compatible avec les logiciels qui font commande le GP0 au passage en émission du pluto. C’est le cas en effet PlutoDVB d’Evarise F5OEO et SDRConsole de Simon G4ELI. Peut être d’autres le propose… ou le proposeront.
      D’après ce qui est indiqué sur le wiki de l’Analog Device, on doit pouvoir ajouter cette instruction (entre autres lignes) pour ajouter la commande automatique de la voie GP0.
      iio_attr -a -D ad9361-phy adi,gpo0-slave-tx-enable 1

      Bons essais. N’hésitez pas à partager vos conclusions ici.
      73 Christian

      (Translation)
      Hello, Rudy,
      The board exploits the state change of channel GP0, and GP1 which locks the switch to transmit when the Pluto starts (GP1 active at the same time as GP0 at start up). It is compatible with the software that controls GP0 when the Pluto is transmitting. This is indeed the case of PlutoDVB from Evarise F5OEO and SDRConsole from Simon G4ELI. Maybe others propose it… or will propose it.
      According to the wiki of the Analog Device, it should be possible to add this instruction (among other lines) to add automatic GP0 channel control.
      iio_attr -a -D ad9361-phy adi,gpo0-slave-tx-enable 1

      Good try. Feel free to share your findings here.
      73 Christian

  11. Wonderfull site and good OM thanks for all your time

    GRTZ the Alain ON7ATV

    (Traduction)
    Site merveilleux et bon OM merci pour tout le temps passé

    GRTZ le Alain ON7ATV

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