Simplex operation

  • What is the "official" position w.r.t. solutions that provide only simplex operation where the operator cannot listen to his own signal when transmitting?

    In my experience with older high-orbit satellites it is really required to be able to listen back while talking, even when it can cause annoying problems due to the path delay (stuttering or slow talking), so when doing anything but calling one would turn down the volume on the receive a bit while talking.

    However, with equipment that is inherently unable to receive while transmitting, it will be very difficult to judge if the signal is above the beacon, if the LEILA2 system is acting on it, and (when the station is not perfectly calibrated) if one is transmitting over someone else.

    I think it would be recommendable to always have the capability to receive while transmitting in the transverter design ("full duplex" operation), and maybe this should be stated in the operating recommendations?

    I understand the attraction of having a simplex transverter that could e.g. be used with a single FT-817 to form a portable station, but IMHO it will be very limiting to have no possibility to monitor one's own signal.

    • Official Post

    Hi Rob,

    fully agreed !!

    Full Duplex operation should be mandatory when working satellites...

    Otherwise you will never be able to adapt your uplink power accordingly and you would not hear LEILA... I would even not have thought that someone would really consider simplex operation..

    Thanks for pointing this out, I will add this to the guidelines..

    73s Peter

  • DK2ZF: seit OSCAR-6 im Oktober 1972 dabei.

    Das ist doch das Fazinierende: volles "durchhören". Ich weiss nicht, wer überhaupt auf die Idee kam nun Simplex machen zu wollen.

    Beim FT-847 kann man dann mit zwei ZF`s und den beiden

    "gekoppelten" VFOs ganz einfach Duplex machen und braucht sich nicht mehr umständlich "einpfeifen"...

  • As far as I understand the idea is that a simpler transverter and simpler overall station (using a single single-band trx) can be used when this simplex operation is used, and the opinion of the designer is that full duplex is unusable anyway due to the delay in hearing one's own transmission back.

    However, I agree with the others that full duplex really is required. Even when there is no doppler and everything is GPS-stabilized (so the tuning could be calibrated perfectly), the issue of power limitation and monitoring remains.

  • Just as aside, a LNB+RTL dongle+ Your chosen SDR software should suffice for the downlink, even providing a nice waterfall so you can _see_ as well as hear that you are no stronger than the beacon, and not transmitting over others.

    This would then let you use a single single-band trx just as an uplink.

    I certainly intend to have at least one dongle constantly monitoring at least one beacon just as an extra receiver

  • apart from the problem of excessive transmitting power, I think that the problem is also the aesthetics of the conversation. I remember beautiful technical conversations with three or four correspondents who intervened in real time to comment on an aspect of the topic under discussion. The discussion is more vivid if the correspondent can ask for a clarification in real time.

    If you have to pass only the locator and 5/9 then you can go in simplex.

    my two cents

  • Just as aside, a LNB+RTL dongle+ Your chosen SDR software should suffice for the downlink, even providing a nice waterfall so you can _see_ as well as hear that you are no stronger than the beacon, and not transmitting over others.

    This would then let you use a single single-band trx just as an uplink.

    That is the solution I plan to use. I have a receiver ready with an SDRPlay RSP1a (can easily be swapped for an RTL dongle) and I also have an old ICOM IC-R7100 that I could use. Then an FT-817 with uplink transverter can be used and I have full duplex capability (and waterfall monitoring).

  • Once the power of the ground station is adjusted
    properly (i.e. below level of the LEILA2-jammer)
    there is no need for monitoring your uplink signal constantly.

    That does not work, because the transponder has AGC (at least all earlier transponders did, I presume this one will have it as well) so the downlink signal for a given uplink output level will vary depending on the other activity on the transponder.

    When you have adjusted your power at a busy time, you will cause too strong downlink signal (and LEILA2 warnings) when it is quiet.

  • Rob, since 30 yrs we are not friends. Reading your (written)
    words, I think this forum is not the place to 'grab your point of view' and
    'bash' me. I have another perspective: agree to disagree
    (and hope you agree with that).

    Let's wait until the satellite is launched and the amateur payload is up
    and running . . .

  • In addition, there is another factor, who will be have an impact on the signal strength: Water.
    Please don't forget, that clouds, fog, raindrops, snowflakes are also responsible for the pathloss on the downlink (espescially), but also on the uplink. So the signal strenge will change every day.
    In fact: a serious Operator will do full duplex :)

  • Knowing (at least) two other (Dutch) initiatives for an

    Es'hail-2 SDR-Web-RX (commonly known as 'WebSDR'

    (c ) PA3FWM) -and being involved in one of them-

    I am not the person who speaks in terms of 'good'

    (and/or 'bad').

    Framing and bashing that 'simplex operation' is 'bad' is as evil

    as framing that 'duplex operation' is 'good '.

    I prefer to speak in terms of 'different perspectives (and/or

    opinions)' and explore these opinions with respect, instead

    of bashing/judging a priori.

  • Remco,

    Please stop taking this discussion into "personal" affairs and as "framing/bashing/judging".

    It does not surprise me that you do it, after all it was you that started that row long ago, but I will not discuss such matters here. Nor will I discuss other remarks you have made about your plans.

    My question to the builders is just about the preference and operating practices to be used on the satellite, no matter by whom, and the reply from Peter and many others has been clear. It is only to serve as a guideline for anyone who is designing a satellite station or copying another design, and has to make decisions about simplex or duplex operation, not as a personal attack to anyone.