New operational mode

    • Official Post


    I have a proposal for a "new" operational mode for NB.

    The traditional QSO using USB in all frequencies is half duplex. This is due to the fact that is impossible to Rx during Tx. Using USB is possible two stations or more to talk at the same time without interfering each other.

    The proposal is that two or more stations talk together like a telephone conversation. Of course callsigns must told every few minutes according to ham radio laws.

    This will provide a more "natural" mode of communication that is impossible to implement with out QO100.

    Hi George,

    Sorry - I don't get it.. I'm confused..

    Isn't this what is already mandatory according our NB Transponder Bandplan and Guidelines which state:

    --> Full-Duplex operation is mandatory

    Thus, your equipment shall be designed for Full-Duplex, i.e. RX and TX capable at the same time,.

    Some operators do already practice that, even in larger rounds. When two people start to talk together at the same time, the other will stop or the 3rd. person will listen to both of them at the same time..

    For that reason since the launch of QO-100 we have always advocating to build or buy full-duplex equipment. Unfortunately some vendors constantly ignore this request,

    However - sometimes you also hear people talking many minutes over each other. They may not have that capability our just turned their audio down while talking, not to get confused because of the delay..

    But anyway, good that you bring up this discussion again.

    73s Peter

  • Hi Peter,

    My consept is to use FDX as a future not as a bug. The QO100 users can see this way as a new ham radio way of communication, similar to a telephone one, without more resources. It is our responsibility all the time to respect the other ones. QO100 is a great opportunity to discover new ways of communications. My goal is to use the FDX capability of QO100 as a way to have a more user friendly ham radio communication, comparing to the others. There is a negative approach of using QO100, saying that it is nothing more than a repeater in the sky. My view is that is a great area of new expirements.

    • Official Post

    Once again George, what you mean is real full duplex operation. With a noise cancelling microphone or DSP programmed you can push the PTT all the time down in SSB (!) and "telephone" during the QSO. I hope I've understood you correct now. It is a good idea to bring "satellite full duplex operation" near to our shortwave friends.

  • Hi,

    a couple of minutes ago, I did a test with a friend. We used the two sidebands. Receiving and transmitting at the same time in different sidebands is very easy with the Console. Switch off the receiver muting also. The result is a crosstalk like a phone call. The delay caused by the satellites distance is no problem, because you do not hear your own voice while speaking. It was interesting to see there was no interference between the closed sidebands.
    Again, use headphones without an acoustic feedback to the microphone. Probably switch the receiver AGC to a fix value.
    Have fun.

  • Hi George,

    I understand your plan. But I think it will be hard to surpress your own speach. You get confused because of the delay. This is not the case, using two different sidebands. As long as there is enough space, the occupied bandwith doens't matter.
    In a real duplex qso it happens that both stations talk at the same time to interrupt each other. On the same frequency there will be an interference with no copy.
    At least, it was an limited experiment. It was very easy to do. It was fun and showed how linear our amplifiers are. And the Pluto with Console is good for full duplex.

  • Hi,
    as Peter wrote above. Start a discussion. Collect ideas, do experiments. Test your equipment. Have fun. That's it. Of course there are more than one way to operate duplex. Switching to another sideband is one mouseclick.

  • Hi,

    A progress report for the echo cancellation project on QO100.

    The frequency offset was coarse founded using 750 BPSK beacon. Also the delay was manually coarse founded. After that the delay can be fine tuned. The frequency can then fine measured within about 0.2 Hz.

    Also knowing the delay the frequency offset can be coarse founded.

    The goal now is to coarse find both frequency offset and delay without knowing one of them.

    The results when signals are within 1Hz is that the audio practically desapears in the nulls of 1sec period. The suppression is not below 10 dB as the audio SNR in not above 10 dB without cancellation.

    It is important to mention that normal voice is used to determine frequency and time offset. Tests are on 950 by default.

    The 'bird' is a nice place for expirements and not just a repeater in the sky.

  • --> Full-Duplex operation is mandatory

    Sorry to sidetrack this interesting thread a bit. I don't, yet, operate TX on QO100 but I can't find the reasoning behind the "why" for full duplex. Is it simply to monitor for LELA? (Or why max 2.7KHz either when there seems to be a lot of unused space on the satellite - of course I understand if it's busy and operating close to others). Interested from an experimentation point of view.

    Back to the thread. In broadcasting there is a technique called "mix minus". I have an audio mixer has a telco channel so that a person who telephones into the station cannot hear their own voice back - they only hear the presenter (live or talkback for cueing) and, optionally, the station output. So If I understand correctly this is the same technique but using DSP cancellation and delay compensation that is being tried out here - interesting.

    Many thanks, David.

    • Official Post

    Hello David

    The "why" behind full-duplex operation is an often asked question, also from our short wave friends QRV now on QO-100 (I'm more than 30 years QRV on OSCAR's). I found a good article about this theme:…key-to-satellite-success/

    I wish you success and 73

  • Thanks very much for the link. Interesting reading, but doesn't really answer the question IMHO. I understand full duplex is needed to listen for relay confirmation in an orbiting sat and to correct for doppler. But with QO100 being a stable platform as such I'm still curious about this from a geostationary point of view. If I'm being asked to follow rules, I'm always curious to know why the rules are there :)

    It seems, to me, that the requirement for mandatory full duplex is more than just monitoring your own transmission - which is a good practice of course - which does not seem to work anyway as there are some poor quality signals on the satellite!

    I do intend to be full duplex anyway once I get TX working, and my interest is in measuring the full path audio response from transmitter to receiver. I've also got a little project underway to build a 2.4GHz CW/FSK (AM) transmitter from a DDS/PLL. I put AM in brackets as it would be easy to modulate the PA to allow for some voice - I know, I know... I think that is the subject for another post :)

    Thanks 73.