Posts by DL3DCW

    vu3jnm In your default.conf i see a wrong rx frequency (39675000 instead of 739675000). Please check your GQRX settings.


    If you set LNB LO frequency in GQRX to 9750000000 your rx frequency has to be set to 10489675000.

    For fast PTT detection the signal TX GND from ACC socket can be connected to CTS input of the USB/serial adapter (because via serial CAT command there will be some delay):



    If the SCU-17 sound card interface is used for CAT then there is a small modification of the CT-62 (RS232/CAT) cable required. For this cut the track on PCB between RTS and CTS pins and solder the emitter of a PNP transistor to the RTS pin and the collector to the CTS pin. Connect the base via a 4k7 resistor to TX GND signal of ACC socket:



    Remark: The original cable can not be used for this because there is no wire connected to TX GND. It has to be replaced.

    Next complete image will be running also on new Raspberry Pi 4.

    Beta version of new image for Raspberry Pi 4B now is running for first tests on my mini satellite station (described here).


    Many small improvements were made and on Raspberry Pi 4B all filters (like CW narrow etc.) from GQRX works well and without audio drops.

    My mini station based on Raspberry Pi for CW, SSB and digimodes:



    In the shack:


    - Yaesu FT-817ND transmitter with internal TCXO-9

    - Yaesu SCU-17 soundcard interface for digimodes

    - Yaesu CT-62 RS232/CAT cable (Mod for fast PTT detect)

    - Kuhne MKU UP 2424 A up converter with internal TCXO

    - Logilink AU0048 USB/RS232 cable (Mod for fast PTT switch)

    - Raspberry Pi 4B with SAT Controller SDR Nano beta software

    - NooElec NESDR Nano3 receiver with 0.5ppm TCXO (2x)

    - Official 7" touch display from Raspberry Pi foundation

    - Microsoft Bluetooth Mobile Mouse 3600

    - CTFWIKE-3 Wireless Bluetooth Keyboard


    On the roof:


    - Kathrein KEA850 with Octagon OSLO (unmodified) for RX

    - Kathrein KEA850 with Winkler helix (2.4GHz, 5-turn) for TX

    Yes, if LNB LO follows drift the beacon should be ok. Exception: The determined drift is wrong (e.g. unsuitable master signal, drifting sdr sticks, ...). At the moment i have no more idea ...

    Thats very mystic. If LNB LO is corrected the demodulated audio should be follow. At the moment i have no idea why not.


    If i correct my LNB LO frequency by 100Hz the demodulated audio changes excactly 100Hz too. For a simple test you can do this manually (GQRX/View/Input controls) with only GQRX is running.


    Important: After changing LNB LO frequency you have to retune to 10.489.548.500 Hz.

    Some questions:


    1. Do you use a non wobbling PLL LNB (like Octagon)?

    2. Do your SDR sticks both have 0.5ppm TCXO or better?

    3. Do you have run GQRX and SatControl 10-15min for warming up?

    4. Is "Drift correction" button switched on?

    5. Do you see a low drifting value in field "RX ERR"?


    Then all should be ok. The displayed RX frequency will be fixed on 10.489.548.500 but there should be no significant drift in demodulated audio. So the signal in audio waterfall (GQRX/View/Audio) should be stable on 1.5k.


    If not, maybe there is a problem with unstable/drifting SDR sticks. In my system i use two NooElec NeSDR Nano3. They works fine.

    You don't have to adjust a signal all the time manually.


    The LNB LO frequency of GQRX will be corrected automatically by the drift correction function of "SAT Controller SDR Nano" software. And thats all we need. Then the system is stable and there is no more (significant) drift in the demodulated audio.


    The displayed RX frequency will not change. But the "real" RX frequency (IF of SDR stick) changes automatically depending on changing LNB LO frequency.


    Only during warm up time of the SDR sticks there will be a little drift. But after that time (5-10min) your RX signal will be stable.