Down Converter V3d defect?

  • Thank you for the instructions.
    I just tried to use the simplest possible set up for the Down Converter. Unmod. LNB -> Down Converter (no GPS, but either external clock reference of 10MHz from the osci or nothing at all) -> Pluto. I set the Jumper to 14V supply for the NB and 25 MHz, removed the connection between WB out and NB in and connected the LNB to the NB in as you suggested. I also configured the I/O device in Gqrx to 2 MHz bw.
    Then I swept through the spectrum in 100 KHz steps from 140 MHz to 150 MHz. But I coudn't see any of the beacons. somewhere around 146 MHz there was a very high peak. But It appeared out of the blue. It was suddelnly in the middle of the screen instead of shifting in with 100 KHz steps as i was sweeping. Do you ave any idea what might cause this or if its related to the problems I have?


    Alright, it seems you are not a ham-radio operator, otherwise you'd knew what a handheld or walkie talkie is.

    Yes, I am not ... yet. :D



    Ok, 40ish MHz an 25ish MHz is good! Means the TCXO in V3D is working and you have output, just not disciplined by GPS.

    Now, who modified the LNB? Was it someone who can check it ?

    Great that means there is hope.
    I have the modified LNB from the Shop here (https://shop.amsat-dl.org/produkt/qo-100-modifizierter-lnb/). So guess I could sent it back to be checked but I would like to be sure that it is really not working before I do so. And as things are going i Suspect there is something wrong with the V3D rather than the LNB. (I connected the bias tee to the Pluto and unmod. LNB again just to be sure the antenna and LNB are still correctly aligned and I was able nicely see the beacons and transmissions around 740 MHz)


    Do you have how i could further test whats wrong with the V3D?


    Cheers,

    Jonas

  • somewhere around 146 MHz there was a very high peak. But It appeared out of the blue. It was suddelnly in the middle of the screen instead of shifting in with 100 KHz steps as i was sweeping. Do you ave any idea what might cause this or if its related to the problems I have?

    Well, maybe it is generated somewhere in your Receiver chain, things like this happen.

    Your gqrx should look like this: lower beacon , psk-beacon, upper beacon. The rest are signals from stations talking. The beacons are always there, even when no one is using the satellite.



    Yes, I am not ... yet. :D

    Well, nobody is perfect...


    Umm.... The pluto can receive on 144MHz? Unless you modified it, it starts at about 340MHz? So set your V3D to 435,5 or 439,5Mhz output and try again...


    Could that be the problem?


    V3D Manual says:

    Für Stellung 8 und 9 (70cm) muss das standardmäßig eingebaute 2m Filter auf der Platine mit einem möglichst kurzen Draht überbrückt werden.

    You can modify the pluto firmware to make it receive down to 60MHz i think.

    Ohne Gewähr: https://docice.bohramt.de/2018/11/plutosdr-aufpimpen/

    This might be outdated.

  • I just talked to Sigi, DG9BFC. He said, the newer Plutos with newer firmware can no longer be modified that easy.

    So depending on your firmware it is possible easily or with tricks only.


    But the easiest way for now is: Use V3D as 25MHz reference for the modified lnb, feed the signal over a device like this:

    Make sure you get one that blocks DC to the outputs and ONLY LET DC GO ONE DIRECTION ---> IN. IN connects to your lnb NB socket feeding 14V. Connect the WB socket directly - bypassing the Splitter - to V3D 's WB & 25MHz socket to feed 18V and 25MHz.

    Now hook your pluto to out 1 of the splitter, your V3D's NB socket to out2, leave out 3 open or put a terminator resistor on it.

    Receive on 740MHz with your Pluto. Leave the bnc on V3d unconnected for now. You can hook up a 2m-radio later if you want.

    Jeeez, why did it take so long to come up with this...


    EDIT: You have a bias Tee, so: Pluto -> bias Tee-> NB of your lnb.

    V3D WB IN & 25MHz out -> WB out & 25MHz in of your lnb. Set Pluto to 740MHz. Should work.

  • I just talked to Sigi, DG9BFC. He said, the newer Plutos with newer firmware can no longer be modified that easy.

    So depending on your firmware it is possible easily or with tricks only.

    I am very sure I did "hack" the Pluto to widen the bandwidth. But I also just tested with a local radio station (106.9 MHz) and it worked perfectly. So I think the range of the Pluto is not an issue.


    EDIT: You have a bias Tee, so: Pluto -> bias Tee-> NB of your lnb.

    V3D WB IN & 25MHz out -> WB out & 25MHz in of your lnb. Set Pluto to 740MHz. Should work.

    That was a great idea! I am learning a lot these days, thank you!

    I did just that. But the result was still an empty spectrum. So I replaced the modified the modified LNB with the unmodified one and ignored the second line. And i got the signals and beacons again.
    I tried to look around a bit to find possible error sources. And even though I have measured it before I measured the WB+Ref again. Surprisingly this is what I got:

    That seems like the LNB doesn't get voltage supply. The question is why?

    And how can I fix it? Another bias tee?

  • Ok, check V3D with a Voltmeter if there is 14V on the NB input and 18V on the WB input. Check the jumpers for the supply voltage.

    [Blocked Image: https://amsat-dl.org/wp-conten…DownConverter-V3-JP14.jpg]

    My V3D had the problem that there was a short on one of the F-sockets (soldered in too hot) , this caused the power to fail. Once the short was removed, power was back. Unfortunately, the circuit diagram can no longer be magnified as it was some months ago, so i can't locate the circuit that converts 12V to 14 / 18V . Try to locate it. Measure before and after the circuit ( ithink there are fuses before the circuit, they may be open) . You should find 12V before and 14 / 18V after . If there is a short in one or both f-sockets, the fuses may protect the unit.


    Edit: The Converter is IC3 LNBH26PQR, you should find 12V input @ pin 17 or @ F1 - a fuse- , NB 14V out @ pin 20, WB 18V out @ pin 11 or at the corresponding pins @JP2.

    If there is no voltage, remove the jumpers 14A and 14B and check if there is voltage now. If so, the F-sockets have a short.

    There is a new scalable circuit here: https://amsat-dl.org/wp-conten…019/11/SingleDown_V3d.pdf

    Thanks DB2OS for providing it so fast.

  • I took my Multimeter today. And I once more confirmed that the biggest bug is sitting right in front of the computer.
    The reason why I go the strange osci reading was that the pin of the adapter I used to connect the WB+REF coax cable to the osci was broken. It took me quite a while to figure that out. I didn't expect to still get a partially correct reading when the hardware is broken like that. But in RF many things are possible I suppose :D
    Anyway another valuable experience. The readings my multimeter showed me were as you might expect. All the jumper pins gave the correct voltage all the coax sockets gave the voltage according to the jumper position. So I am back to the point that the LNB should work fine in theory but it doesn't.

    So I wanted to test both LNBs with the V3D again. But now I keep getting initClk on the display. It doesn't get past this state anymore. I cant remember seeing it before. I am not using any external reference only the built in clock. I have unplugged the power several times but it doesn't change anything.

  • Ok, here my last idea.

    Verify there is power for the GPS-Antenna wether gps antenna is attached or not, just to be sure power is always there.

    Fire up V3D , leave it for 20 minutes. Get a cup of coffee. If it still won't finish the setup routine, remove power, remove gps-module, fire up V3D.

    In either case, determine the frequency @ WB-IN as exact as you can. Now, 10489.750-(390*<your measured frequency>) = <something near or far off 739MHz> .

    Set Pluto to <something near or far off 739>. See Signals?


    73, Martin