DMR back talk channel for QO-100 ATV

1st Official Post

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    Hello OMs,

    In addition to the already broadcastable stations on the Wide Band Transponder from QO-100 there are certainly 100 times to viewers. Also, I am one of them who can not yet produce the power to operate ATV broadcasting. Every night I watch but interested. Only you can never contact someone to possibly get rid of a question. Other QO-100 SWLs (of course licensed OMs) are the same.

    So the Genanke was close to wanting to have a return channel. Since the footprint is indeed considerable, FM and KW (depending on the day) are safe. An FM channel may not be operated in the narrow band of the satellite, according to Amsat.

    What remains is an FM channel in the WB of the Sats (is that allowed ??). Or a connection via the new digital relays, which are now installed everywhere. Since many OM already have radio for the digital modes, I once wrote to the DMR Brand Master Team (bm262.de) and asked for their own TG for the return channel for QO 100.

    The positive answer was that the TG 265100 is set up as a DMR response channel for QO 100.

    In Germany, at least the relays listed at BM can be reached. http://bm262.de/dl/

    This makes it possible to personally connect with the ATV-OM worldwide. It would be nice if sending stations were on 265100 QRV. The use is of course not a must ... but helps me and other OM questions to ask if (already) sendable OMs are received by us.

    Hamspirit just :)


    73 Ronny

    DH5UW

    dh5uw@online.de

    DMR-BM TG 262907 Home

    DMR-BM TG 265100 QO-100

    Hallo Ronny,


    ich hatte schon wenige Tage nach Betriebsaufnahme vom QO-100 einen Schmalband FM-Rückkanal auf dem Breitbandtransponder vorgeschlagen:

    DATV Talk-Back Channel (Narrow 12,5 kHz FM) in WB-Transponder ?


    Es gab etliche Befürworter, es wird an der Zeit dieses Thema wieder hervorzuholen. Der Breitbandtransponder hat kein Problem mit ein oder zwei Schmalbandsignalen (auch unterhalb der Bake) und die DATV-Betriebstechnik würde Mega Fortschritte machen. Ein WB-Webempfänger könnte das Audiosignal sogar ins WEB streamen......


    vy 73 de

    Henry

    Why not just set up a chat group in mumble if speech is what you wish for then participants do not need to have another uplink channel.


    But the WB text chat channel is good enough for many when listening to the transmit stations audio. If there are two many ways to chat, which one becomes the preferred and which ones get left behind, it can become a situation where some use one system and some another and it looses cohesion.

    Keep it simple and limited would be my thoughts, I have asked several questions on the WB Chat and always had a response, I am not yet able to transmit pictures, but can give reports on stations OK.

    GM Henry,

    deinen Eintrag hatte ich vorher nicht gelesen, aber er trifft genau auch mein Anliegen. Evt. könnte man den FM Kanal sogar mit der TG koppeln. Bei Vorführungen oder portablen Aktionen über QO 100 hätte man dann eine höhere Wahrscheinlichkeit mit dem im Bild zu sehenden OM auch Kontakt zu haben.

    Welche Frequenz wäre dafür geeignet? 10,491 ? Oder 10,491,500 so das der Kanal evt noch im Spechtrum zu sehen wäre.

    Für Tests wäre ich verfügbar.

    73 Ronny


    Hallo Ronny,


    find ich prima, dass Du das Thema "Rücksprechkanal" wieder ins Rollen gebracht hast...

    Der WB-transponder beginnt offiziell bei 10491 MHz , ich halte die 10491,025 MHZ für einem FM-Rücksprechkanal gut geeignet: Der Abstand zur Bake ist ausreichend, der Träger ist noch im WEB-RX-Spektrum zu sehen und weitab vom DATV-Geschehen . An meiner 40 Turn-Helix benötigte ich damals ca. 20 Watt für einen ausreichendes S/N mit 3KHz Hub.

    Der WB-Chat ist ja soweit OK, aber für einen flüssigen QSO-Ablauf ist ein Gegensprechen einfach unerlässlich. Bin gerade am Stationsumbau für DATV mit einer 1,2M-Schüssel und der Urlaub steht an, hoffe das ich dann im Herbst wieder sendeseitig QRV bin.


    Vy 73 de Henry

    DH5UW DK0IT  DL4SAC first of all.. this is a folder of the english forum, so please avoid to write here in german.

    Regarding talkback there are solutions already in use.

    1. The top one solution is when two stations are doing datv qsos on two channels full duplex. so both have their pictures and sounds available at the same time.

    2. There are OMs like myself, which post in the WB chat the talkback frequency so that the datv staion can listen the talkback on the NB transponder in SSB parallel to their datv transmision. That is the usual way talkback will be performed today.


    Therefore I see no need to integrate more.

    What should be the advantage to use DMR or FM on this satellite. There should be only modes derivated from ssb modulation or dvb-S2 what can also be used for very efficiant datatransfer. We should focus to implement datatransfer. then there is whith QO-100 a good possibility to offer HAMNET to the african continent, where usually no internet is available. :)

    • Official Post

    First of all, we appreciate any open diicussion.


    I also don't understand why the talk back channel needs to be in DMR? I guess the next one wants DSTAR? Why not SSB?


    We should keep in mind that we are talking about a satellite transponder and not terrestrial use.


    The transponder does have some limitations, for example power and lifetime of the TWT...

    The satellite operator is very carefully looking at the performance conditions to achieve maximum life-time of our TWT, because it may be needed in case other TWT's decrease prematurely before EOL of the satellite..


    For that reason we are always promoting power and spectrum efficient modulation on amateur radio satellites.


    Maybe some people believe we are doing wideband DATV and therefor we don't need to care about spectrum efficiency?

    But the opposite is true: DVB-S2X is implementing the most efficient modulation and coding techniques, very close to the Shannon limit.