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Thread: Signal Quality Values

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    Signal Quality Values

    It will probably not be obvious to most people that as of OpenVix 5.2.22, the problem of 100% signal quality reports present on most if not all tuner types should have been fixed. In particular using Signal Finder on the "Tuner config" menu page, and NOT forcing legacy stats on the "Tuner setup" pages :

    * The dB figure should not be much below ~20 dB when lock is achieved, nor much above ~50 dB (precise figures will depend on whether satellite, cable, or terrestrial).

    *The % figure should only be 100% for dB figures >= 42/62/50 dB for satellite/cable/terrestrial i.e. close to a main transmitter in the case of terrestrial.

    * Results from different tuner models should agree within a few dB.

    If these criteria are not met there would appear to be a remaining problem, probably specific to that tuner type. I am aware of a problem with one SundTek model, but are there others?

    Please note that the ABM DVB-T Frequency Finder and the Terrestrial Scan plug-in use the % figure to identify the best signal when receiving from more than one transmitter - if this is always the same value then the first found rather than necessarily the best will be chosen.
    Xtrend Xt10000 with 3 Freeview tuners

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    ccs (02-02-19)

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    This is what I see with a Sundtek MediaTV Digital Home USB Tuner Cable / Terrestrial HD (DVB-C/T/T2)

    The only value which changes is BER

    Code:
      <?xml version="1.0" encoding="UTF-8" ?> 
    - <e2frontendstatus>
      <e2snrdb>100 dB</e2snrdb> 
      <e2snr>100 %</e2snr> 
      <e2ber>0</e2ber> 
      <e2acg>100 %</e2acg> 
      </e2frontendstatus>
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    I am not getting the constant 100%. Am I doing something differently to what I should be?

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    Sicilian (03-02-19)

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    Quote Originally Posted by EMJB View Post

    * Results from different tuner models should agree within a few dB.
    Your right in theory they should, but in practice they don't. I seen variances of up to 30-40% signal from boxes connected to same dish or terrestrial feeds.

    My bet is if you test the same boxes on other 3rd party images you'll get the same results, therefore you are welcome to ask the manufacturers to fix their drivers for whatever box you have.
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    Also see attached
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    D I S C L A I M E R

    My right to post information is protected under the rights for freedom act. In all instances, information discussed here on my posts are either hypothetical in nature, out of general curiosity, common knowledge, public knowledge, or role-play. Any use of the collective descriptions and shared knowledge from any of my posts are at the sole discretion of the reader. I am not responsible for what you do with it!

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    Quote Originally Posted by abu baniaz View Post
    I am not getting the constant 100%. Am I doing something differently to what I should be?
    For me, Com6, C60- (785.8MHz) drops to zero signal quality when it rains, I'll check the sundtek tuner again when the signal starts to deteriorate.

    No other mux's are ever affected.

    Maybe I should have said in my previous post that there are no dB levels, just %'s, which is odd.
    Last edited by ccs; 03-02-19 at 11:10.

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    Quote Originally Posted by Sicilian View Post
    Your right in theory they should, but in practice they don't. I seen variances of up to 30-40% signal from boxes connected to same dish or terrestrial feeds.

    My bet is if you test the same boxes on other 3rd party images you'll get the same results, therefore you are welcome to ask the manufacturers to fix their drivers for whatever box you have.
    With the old API the term point at which SNR was measured was ill defined leading to discrepancies in what was being measured, but with the new API the definition looks fairly watertight. Another complication is that the frontend.c code for the old API has lots of correction factors for some tuners, and none for others which may reflect the fact that no-one has bothered to make the corrections rather than them not being needed. Were your 30-40% variations seen with tuners using the latest API?

    Incidentally, I assume your percentages apply to the dB values i.e. around 10-15 dB - a 40% variation in (linear) power is less than 2dB.


    EMJB
    Xtrend Xt10000 with 3 Freeview tuners

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    Quote Originally Posted by abu baniaz View Post
    I am not getting the constant 100%. Am I doing something differently to what I should be?
    Something looks very strange with the screenshots you have posted - the AGC and SNR % figures are always identical - it looks as if the wrong data is being displayed for one or other or both. The skin you are using does not display the SNR in dB terms, which is unfortunate as the percentage is derived from the dB figure by applying an estimated upper limit so the dB figure gives more information than the % figure. I find using the WebIf "/web/signal?AGC=" command on your browser to be accurate and reliable, though tuner selection is less convenient.

    Incidentally the reported type for your tuner is slightly different from that of ccs, which I believe is "Sundtek DVB-C (III) (1/0) (USB) (DVB-T2)", which might explain the differences in behaviour.


    EMJB
    Xtrend Xt10000 with 3 Freeview tuners

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    Quote Originally Posted by ccs View Post
    Maybe I should have said in my previous post that there are no dB levels, just %'s, which is odd.
    It is the skin you are using - compare the screenshots I sent you recently with Abu's above.
    Xtrend Xt10000 with 3 Freeview tuners

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    Quote Originally Posted by EMJB View Post
    It is the skin you are using - compare the screenshots I sent you recently with Abu's above.
    Could the lack of a db reading be.......

    Menu -> Setup ;> User Interface -> Swap SNR in % with SNR in dB = yes/no
    Xtrend ET10K, 2 x satellite tuners 28.2 (Sky FTA), 2 x hybrid (UK Freeview), Zgemma H9S (satellite)

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    Quote Originally Posted by adm View Post
    Could the lack of a db reading be.......

    Menu -> Setup ;> User Interface -> Swap SNR in % with SNR in dB = yes/no
    I've got it set to no.

    On my Si2169 tuners I see %'s on the top line, and dB below left, setting to yes swaps these round, but the Sundtek remains unchanged.

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    I think it depends on skin & whether your tuner is in lib/dvb/frontend.cpp and conversion factors are in place.
    Gigablue Quad 4K & UE 4K
    .........FBC Tuners:
    ------------------> DUR-Line DCR 5-1-8-L4 Multiswitch to 1.5M dish(28.2E)
    ------------------> Spaun SUS 5581/33 NFA Multiswitch to 80 cm dish(19.2E)
    .......................> FBC & DVB-S2X into 90cm dish (27.5W) Opticum robust Unicable LNB
    AX HD61, Edision Osmio 4K+, Zgemma H9Combo, Octagon SF8008 , gbtrio4k, h9se using Legacy ports on multiswitches
    Zgemma H9 C/S into Giga4K

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    Well it started to rain much sooner than expected, and I'm seeing reduced snr levels, as I'd expect (well, hoped that it would match the signal level indicator on the tv as soon as it dropped ever so slightly).

    No dB levels, I guess this is a SundTek issue - I can't see how a skin will help, I've tried Vix-night-hd and Simple_1080 - any others??

    Any ideas why just one mux would be so sensitive to local rain - new aerial, new cabling, new variable gain signal booster/splitter, tree branches reduced significantly.
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    Quote Originally Posted by ccs View Post

    Any ideas why just one mux would be so sensitive to local rain - new aerial, new cabling, new variable gain signal booster/splitter, tree branches reduced significantly.
    Roof or loft mounted aerial?
    Xtrend ET10K, 2 x satellite tuners 28.2 (Sky FTA), 2 x hybrid (UK Freeview), Zgemma H9S (satellite)

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    Quote Originally Posted by adm View Post
    Roof or loft mounted aerial?
    Roof - the rain only lasted for an hour, and soon after Com6, C60- (785.8MHz) was back to normal.

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