Posts by pe1chl

    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.

    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).

    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.

    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.