Posts by PY2SDR

  • AMSAT-BR QO-100 FT8 QRPp Experiment

    The experiment is a reverse beacon (receive only).


    73, Edson PY2SDR

  • SDR under Linux or Windows?

    Hello John,


    This looks VERY VERY nice!


    73, Edson PY2SDR

  • Pollin LNB GM201

    Quote from DB8TF

    OK here it is the TFF1017 PLL in the LNB.

    If the weather is good enough tomorrow i will try an unmodified GM201 and report the differences to the octagon OTSLO


    VY73 DB8TF

    The PLL loop-filter components are external to the T105/1017 chip. May be the loop-filter could be improved. But changing components will be a major challenge due to the small sizes.



    73, Edson PY2SDR

  • Pollin LNB GM201

    Quote from DB8TF

    I took some Pictures


    vy73 DB8TF

    I have a LNBF with the T1015 (NXP TFF1015) and it wobbles. The wobbling doesn't seem to be related to temperature. It may be something intrinsic to the PLL.


    73, Edson PY2SDR

  • Pollin LNB GM201

    Do you know what mixer/pll chip the GM201 uses?


    73, Edson PY2SDR

  • Maintenance on the NB Transponder!

    Quote from DB2OS

    Hi Edson, the reduced noise level shalll not have an effect on the actual S/N of individual users. Some brief measurements seems to indicate that the beacon level actually did not change. Keep in mind also, that the beacons are currently send from AMSAT-DL HQ in Bochum and we have a lot of wind and rain at the moment ;)

    On the other side we have observed that the CW, SSB and PSK signals now sound much clearer which indicates that the transponder might have been in the non-linear regio before. Lets wait for exact measurements and more observations in the next days... Unfortunately the "tombstone" signal disappeared, which might have also been a good indicator.. hihihi 73s Peter


    Hi Peter!


    Thanks for the comments. My concern is that the new levels could impact stations with 90cm dishes at the edge of the footprint. But this concern needs to be substantiated with actual observations and measurements. I will request some amateurs here to observe.


    I will also redo the tests with my antenna at different times.


    73, Edson PY2SDR

  • Maintenance on the NB Transponder!

    Hello Peter,


    Transponder noise floor now just about 2.5 dB above LNB noise floor here (GG56tv - southern Brazil). The SNR for the BPSK400 beacon has also decreased about 2 dB.


    My setup is a 120 cm offset dish and Octagon OSLO LNBF.



    It would be nice if the transponder noise floor could be a little bit higher. This would give those of us at the edge of the footprint a little more margin.


    73, Edson PY2SDR

  • Pollin LNB GM201

    Quote from HB9SKA

    Hello

    Which LNB is better now if I don't want to modify it. Just for plug'n'play.

    An Octagon Optima model https://www.octagon-germany.eu/produkte/lnb/optima-serie/ or the one from Pollin https://www.pollin.de/p/univer…edia-gm-201-0-1-db-571751 ? Both with PLL of course. Or can I take any one with PLL?


    Tnx Thomas

    Thomas,

    I have been testing some LNBF models with PLL and some are not good for our application. The best ones so far are the ones that use the RDA3565ES chip. The ones with RDA3560 chips are also ok. But watch out for the ones with chips labeled 3566 or 3568 (not sure these chips are RDA). The LNBFs with the 3566/3568 chips suffers from some rapid wobbling frequency changes. I have also tested a couple of LNBFs with the NXP TFF1015 chip and they also suffers from some wobbling.


    73, Edson PY2SDR

  • PSK125R

    I did some tests with PSK125R (125 bps BPSK + NASA r=1/2, k=7 convolutional FEC code) via the transponder and could copy my own signal very well. I am using FLdigi and 1.5W into an 1.2m offset dish. RX is an Octagon Optima OLSO without mods. The FLdigi AFC can track the LNBF LO drift quite well.


    I will be calling CQ around 10489.625 GHz tonight and for the next few days after 22:00 UTC. Replies will be much appreciated.


    73, Edson PY2SDR

    AMSAT-BR

  • NB Station Description and User Reports, Statistic

    Call: PY2SDR (Edson)

    QTH: GG56tv (São Paulo state, Brazil)

    RX antenna diameter: 1.2m offset

    NB noise floor increase: 10.5 dB

    TX antenna diameter: 1.2m offset (being prepared)

    SSB RF power: 1W (being prepared)

    RX Rig: Octagon OSLO (unmodified), SDRPlay RSP1A, SDRUno

    TX RIg: SDRAngel, PlutoSDR, WiFi driver amp, WiFi PA

  • ADALM-Pluto

    Quote from DD4YR

    Latency of Adalm-Pluto...


    I think a not negligible problem is the digital processing times plus the latency over the satellite. Since come equal 1500 mS together (RX 600mS - Sat Latency 250mS - TX 600mS). Maybe a problem for FT8?

    For FT8, a delay of 1500 msec is not an issue.

  • NB passband monitoring

    This could be a good project for cubesats (one or more, perhaps an international effort between AMSAT organizations). A receiver on 2.4 GHz with a linear demodulator, an ADC and some embedded FFT software that would store spectrum for later analysis. Triangulation could be done using similar algorithm as the one used by the Argos satellites. Since the life span of Es'Hail-2 is over a decade, there is enough time to implement such project.