minimum RX station

  • Thinking about a minimalistic QO-100 station, RX testing proved to be successful!


    Golden Media GM-201 LNB unmodified, DVB-T stick and USB powered LNB injector. Easy copy of CW signal and probably also PSK beacon once the LNB has reached thermal equilibrium. Thing is, that the operator is also nearing rapidly thermal equilibrium.. :D

  • Hi Achim,


    this is what I like most. A minimalistic approach. Could you please give me an info oon how you powered the Golden Media GM-201 LNB? Did you use a power upconverter? If yes which one did you use.


    Thanks a lot from sTef (Stefan) DM5TU ..... as you a paragliding ham.... happy landings es 73/72

    72 de sTef

    … -.-

    DM5TU / VY1QRP - DL-QRP-AG *GM* - GQRP #8769 - CalQRP #034 - NAP #1607

  • Hallo,
    i wil pick up the challenge to assemble a minimalistic system. The Octagons have a 6V internal regulator. We need 7,5 Supply for the LNB. The "USB powered injector" is a little step up ? More supply to the LNB means more dissipation and is unnecessary.
    73s
    Andreas

  • Thinking about a minimalistic QO-100 station, RX testing proved to be successful!


    Golden Media GM-201 LNB unmodified, DVB-T stick and USB powered LNB injector. Easy copy of CW signal and probably also PSK beacon once the LNB has reached thermal equilibrium. Thing is, that the operator is also nearing rapidly thermal equilibrium.. :D

    Hallo Achim


    I see on the screen that the frequency of the GM-201 does not drift, but how about wobbling ?


    73

  • step-up converter to make 12V from 5V (homebrew)

    And yes, it does drift but SDR-Console can handle it, doing a fantastic job locking on the PSK beacon even at these low signal levels. The GM-201 however is a bit wobbly, sounds a bit like aurora. So personally nothing I can wholeheartedly recommend.

  • The GM-201 however is a bit wobbly, sounds a bit like aurora. So personally nothing I can wholeheartedly recommend.

    Hmm that is odd.

    I have tried out at least five of these and never had anything else than clean signals. I have run both with 25MHz injection and unmodified and they look and sounds clean to me?? Listen to the MP3 I just recorded with an unmodified unit. It obviously drift but sounds clean to me. Is this how yours sound or is your worse 08-May-2019 18h59m34s - 10489.331 MHz, USB.mp3.zip?


    73

    //Harry

  • Thinking about a minimalistic QO-100 station, RX testing proved to be successful!


    Golden Media GM-201 LNB unmodified, DVB-T stick and USB powered LNB injector. Easy copy of CW signal and probably also PSK beacon once the LNB has reached thermal equilibrium. Thing is, that the operator is also nearing rapidly thermal equilibrium.. :D

    I have successfully uplinked with an 11dBi (13cm square) Wifi panel. I wonder what weak signal modes could work under those constraints (I'm thinking EM-comms usage here) . I suspect you'd still need to GPSDO the downlink, but then again, the uBlox modules can be reconfigured to output more than 1 PPS...Not sure if they can get to 25MHz tbh


    Finally.,C2H5OH (or related to it) can help "operator thermal equilibrium" :)

  • 5 mW in a 90cm wide offset dish still gives FT8 decodes which are 'way too loud' ; -)


    Concerning Ublox modules (NEO-6M, 7M) <-- have been several discussions on this forum here (and loads of discussions elsewhere) --> forget it ... doesn't work. If you don't believe, try it (and burn your time ; -)


    What works like charm is a cheap Ublox module, OCXO and a TIC (but that may be another thread . . . )

  • I can strongly support PA3FYM comments about the GPSDO. The GPS modules alone are pretty much worthless without a dedicated flywheel (OCXO) oscillator. That said, the few system which have this work very nicely.

  • Yes, I agree on that as well. I have some experience with both OCXOs and GPS modules.
    I run my downconverter from a 10MHz OCXO that I convert up to 25MHz and send up to the LNB and that seems to me is the way of doing it. A TCXO can also be used and is probably good enough especially if it sits in the rack and feeds the 25MHz remotely.


    In my view a OCXO don't really need constant GPS adjustments like in a GPSDO to keep it on frequency.
    It is nice to have but the drift is so low it is probably OK to just adjust it once a year just for crystal aging.
    If you do have the means to build or construct an GPSDO with a OCXO then by all means go ahead and do it but it might be overkill in my humble opinion.
    The OCXO I use is a rather affordable module and when I look at it's drift using either a Rubidium standard or a warmed up HP Z3805 the drift is so low, we are talking fractions of PPB for the most time that I don't have the skills to build anything to try to correct that without actually worsening the drift and jitter.
    Of course it can be done as evidenced by the HP Z3805 but for myself an OCXO that I re-calibrate once a year if needed is good enough and much smaller and easier to deal with (my HP Z3805 needs 48 hours of warm up to be really useful).
    But each to his own and other people will of course have other needs and opinions.


    73

    //Harry

  • The Challenge
    Here is my minimalistic system. It is an Octagon Single combined with 12cm Horn. The LNB is not modified. For the first quick test, the supply is a battery still. StepUp follows. The audio is clear with good short term stability. Of course there is a thermal drift.


    With 500Hz bandwith the CW-Beacon is up to 20 dB above noise. There is much qsb. Before further tests, it is not clear if the fresnel lense gives more gain.



    73s
    Andreas

  • Hallo,

    sorry, I have no idea where the horn comes from. It is just out of the junkbox, like the tripod also. I am not sure if the quarterwave structure of the grooves in the horn matches to x-band. But the radiation pattern seems to be ok.
    Finally it is nothing else but a little joke....and even the challenge.... ;)

    73s
    Andreas

  • Hi. My name is Michael. I'm a really newbie in SAT -operations. I have a RSP2Pro,software SDRUNO, a 80cm Dish, a HD-Line LNB ( not modified) , Fernspeiseweiche FSW40 F and my second PC runs with WIN 7 . This is my RX setup. The TX equipment is in order . I am not able to receive any signals. I dont know what is wrong with my system. Maybe the settings in the software ?
    Tnx for your paticene. Michael, -DL2LW-

  • Hi.

    I beg your pardon! I try to figure out to keep my Downlink runnig. But it would not work! I am trying different PLL LNBs ( e.g. Octagon) , checked several times the direction ( el and az) of my antenna, checked the cable and connetors. Installed the SDRConsole Software V3.07 + 3.09. But no sucsess!

    In the appendix you will find a pic from my software.

    Any idea for me to keep my system running ?

    Tnx for watching.

    73 de DL2LW-Micha-