Posts by SWL-jsilva

    The Daxis LNB has no wobble at all and after being plugged in for 8 hours there is only a drift of about 800 Hz so much less than after 2 hours.

    maybe because the sun is not shining on the LNB in the evening so a cooler temperature is not so drifty?

    Anyway if the Opticum is no better I may as well keep this Daxis.


    Image shows drift over 4 mins on a slow waterfall.

    It's not so much about the absolute temperature, but about the change in temperature. If there is hot sun shining in an LNB with a black case, and there are some gusts of wind, for example, it can drift quite a bit back and forth, as the sun heats it slightly, and then comes the wind and cools it down a little. If the temperature is stable, its absolute value does not matter that much. I also observed my unmodded LNBs tend to be more stable at night here at my location, but YMMV.

    They will drift even if they are of the PLL type. The crystal in there is quite sensitive to temperature. You will need to modify one to inject an external reference signal, from a GPSDO for instance, so that the PLL locks onto it and remains stable. Many also drift quite a bit while warming up, but if the temperature remains reasonably stable after warming up, it will work to an extent.


    I am pretty sure all of them will have screws, probably the screws are covered in silicon glue. Do you see some blobs of glue or just a small "line" around the perimeter of the lid? If you can see some blobs, try scraping away and check if there is a screw underneath.


    How did you conclude that the LNBs you opened are DRO? Did you see a cavity oscillator or another clue? Beware that some of the PLL LNBs have the crystal on the underside of the PCB, so it may be hidden.

    I have no hands-on experience with DRO LNBs, probably because they are very old.


    Something you can try with that particular HQDL LNB is to check the noise floor at 10489 MHz (739 MHz IF) while pointing it at the sky, and while pointing it at a warm surface (the ground for example). The noise floor should rise when aimed at a warm object. Check if the noise changes equally when tuned to 739 MHz and when tuned to a frequency that lies inside of the supported band (950-2150 MHz). If the noise changes are practically equal, it should be an indicator that your LNB will work at 10489. If they are very different, then maybe not. That's my guess.

    You should use the V Low for the Narrowband Transponder and H Low for the Wideband transponder, assuming you apply the correct skew for your location. If you mess the skew up by 90 degrees, you will need to swap the H/V connectors.


    We are kinda working out of spec since QO-100 downlinks outside the official supported range for common COTS LNBs. While most of them work on 10.489, one should not take for granted that every single LNB will work outside of the specified range.

    Thanks SWL-jsilva, appreciated.


    I have managed to find an Octagon quad outlet LNB that appears, as far as I can tell, to be the same as the one on a clear internet site. It shows how to modify it with photos. It's in Greece though and shipping is more than the cost of the LNB itself, but hey, you can't take it with you I guess [Blocked Image: https://forum.batc.org.uk/images/smilies/icon_e_smile.gif] I will open it with some trepidation when it eventually arrives, hoping in reality it IS the same. This is all probably easy to the more experienced here, but the first time is always the most worrisome :)


    Regards, Chris 2E0ILY

    No problem.

    When I did my first mod, it was on a single LNB, and I also screwed it up. Mainly because the metal case had little room for my big SMD components (0603), and when I closed it was shorting something out. It is okay tho, I always order more than one, preferably 3, as people say: one to replace the first one that I screw up, and other to spare. I can get them locally for about 3 euro (the single LNB version), so it was not a problem for me. Good luck !

    The proper way, IMHO, is to make a parallel resonance circuit on 25 MHz. That will keep the reference where it is supposed to be.
    Personally I use 150nH and 270pF. Note that with SMD these can be "stacked" making it easier to find space for them.

    Hm, yea, I get your idea, basically the same we are doing to prevent the 25 MHz from leaking into the IF path, but instead to keep it out of the DC path. Didn't think of that, I just figured a big inductor will work like in a bias T.
    Next time I mod an LNB I will try an LC tank instead of just an inductor and see if the results are better. Thanks.

    I think most LNBs that have a crystal should be lockable to an external ref. http://www.pabr.org/radio/lnblineup/lnblineup.en.html#
    As of now, I have successfully injected a 25M reference into the 3566 marked chip found in many chinese LNBs, and also the RT320M, which is a twin LNB chip. I am pretty sure it can be implemented in quad LNB chips aswell.

    It is just a matter of removing the crystal, and injecting your reference with a simple diplexer (LC series and LC parallel) into one of the crystal pads, just like this http://www.hybridpretender.nl/single.pdf


    Also, something that is not covered in that document, and I had problems with, is cutting the wiggly line going to the voltage regulators and adding an SMD inductor. That wiggle line is enough inductance to block the IF going into the regulators, but is not enough to block a 25M signal, and the decoupling caps at the input of the regulator were eating all of my 25M reference preventing the LNB from locking. Once I added an external inductor (820 nH IIRC) it locked just fine.


    Attached is a picture of a cheap 3566 single LNB where I did the mods. Sadly i did not take pictures of the RT320M LNB I modded.

    Thank you.
    I think the Pluto with stock firmware filters the traffic from different subnets, so you can't foward the pluto port (33431) directly to internet.


    You can see the solution here: https://wiki.analog.com/univer…luto/devs/port_forwarding


    What I want is to change this filter rules to accept other subnets traffic.

    If you have a machine that is in the same subnet as the pluto, and also connected to your VPN, you can do something like this:
    You should have an IP configuration similar to this (VPN IPs would be different):

    Pluto has IP 192.168.2.1
    PC1 in the same subnet has two IPs: a local one 192.168.2.2, and a VPN one 10.0.0.1
    PC2 anywhere in the world, but connected to the same VPN has IP 10.0.0.2

    If you have access to PC2, you can run this command:

    Code
    ssh -nNT -L 30431:192.168.2.1:30431 user@10.0.0.1

    The "user" above, should be a valid username present on PC1, not on the pluto.



    Then you can use "ip:127.0.0.1" as an IIO device in any software that connects to Pluto.

    Based on the AD9361 reference manual, I think 40 MHz is the magic number that allows the PFD to run at 80 MHz using the internal doubler.


    AD9361 Reference Manual


    They recommend running the PFD as close as possible to 80 MHz. 40 MHz is the lowest you can go while stil achieving 80 MHz.