New QO-100 station - Nooelec v5 SDR stick gain settings / signal strength with properly aligned dish

    • New

    Greetings,


    first of all - since this is my first posting here - let me introduce myself: I'm Yannick, 39 years old and my QTH is Saarbrücken in southwest germany near the german-french border.

    I'm lincensed since august 2023 (class A since march 2024), but because i live in a flat and have no possiblities to put up large antennas for the short wave bands, QO-100 is a welcome opportunity to be QRV at home.


    Another OM from our local club gave me a 85cm TV dish with an Megasat Diavolo Twin LNB for free and i have a Nooelec v5 SDR stick at hand. Not the ideal setup to start, but a point from where to improve step by step. Despite of the fact the LNB drifts like hell, i want to first improve reception before modifying for frequency stability. Unfortunately i may not put the dish on the balcony railing, so it sits on a tripod, but i don't think this will worsen the downlink.


    The problem is: If i set the Nooelec stick to 0 dB gain, i get the middle beacon with not more than S4-S5 with SDR Console. Increasing gain seems not useful since the noise floor is also increased.


    Since i have no reference, what is a typical signal strength of the middle beacon, if the dish is aligned correctly?


    Many thanks in advance!


    73,

    Yannick - DK8YS

    • New

    Hallo,

    the Level-Information from the Console for any signal exceeds the real values. It depends from the the zoom of the spectrum and modulation. Both WebSDRs give realistic SNR of the Beacons. It is less then 20 dB.

    There is an AMSAT-Document with a graphic that shows possible SNR is going into a saturation of approx. 20 dB with increasing dish size. By the way any SNR-information has to be completed with the receiving bandwith. In a CW-Channel ist less noise so the SNR of a single carrier goes up with lower bandwith. Usual is SSB with 2,4 KHz.

    In this thread the improving of receiving is discussed.

    Post
    RE: Antenna size for edge of footprint reception (3.9 degrees)
    Hi Simon,
    the QO-100 with its narrow band transponder will show a characteristic picture, two beacons at the edges and one in the middle. My recommendation is to use a wide spectrum for searching with more than 500 KHz. Do not look at a specific signal but at the peaks of the beacons. Don't care about the exact frequency of signals but try to optimize the levels first.
    My "search equipment" is a bias tee, a little battery and a RTL-Stick, I prefer SDR#. It is completed with a small laptop. This…
    DL5CN

    73
    Andreas

    • New

    Hallo George,

    Probably this is not a good news but this S-Meter readings don't show the real situation. All user signals, the beacons also are referred to the transponders ground noise. How much noise you will see depends from the overall gain in your receiving chain. And all the user signals are not more than 20 dB above the basic nose. This is a graphic out of an official AMSAT-Information edited by DH2VA.



    Believe or not, the max. SNR reaches 20 dB even with big dishes . Don't worry about your S-Meter, you are not alone. Most of commercial radios have this problem. The worst is ICOM, in some ICOMs below S9 one S-Unit is 3 dB only. Don't know who did this but it is total unacceptable. From my point of view it is more than respectiveless against the radio amateurs. Who is ICOM that they define their own S-Units? Hope, I am not the only one who is going to critisize this.

    (I own a HERMES with PowerSDR-Software. I can show a straight line from -130dBm to -14 dBm (overdrive of the AD-Converter). And one S-Unit is 6 dB at all levels. And this is not a commercial radio. PowerSDR was done from a handful of highly qualified radio amateurs. Sorry, but I am excited about this always).

    SDR-Console is a wonderful program too. I and all my friends are very lucky about it. I did many recommendations to them.
    Simons work has to be highly appreciated, no question. The advantages while satellite operation is unreached from other solutions. But the level measurement is a bit to optimistic. We know this and all is fine.

    73
    Andreas