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Thread: 'Quality' versus 'Strength'

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    Default 'Quality' versus 'Strength'

    Which is more important?

    On C1 I get S 74, Q 100 but on D3 I get S 82 Q 91.

    And what is the scale relative to, anyway?
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    Quote Originally Posted by bambbbam View Post
    Which is more important?
    Signal doesn't really mean anything, it's just the averaged voltage level received at that frequency regardless if it's a sat or the sun.
    The quality is the ratio of decoded bits received without relying on the redundant error correction bits which is far more useful as it indicates that your box is actually decoding something useful.

    On C1 I get S 74, Q 100 but on D3 I get S 82 Q 91.
    Possibly indicates you may not on D3 have the centre frequency selected or the skew might not be ideal.
    A quality of less than 100 indicates that your receiver is relying on a portion of the error correction bits to recover from the errors.
    With most transponders using 3/4 FEC a quarter of the transmitted bits are redundant to recover from errors. On the DVB-S2 transponders the FEC is 3/5 so 40% of the bits in the stream are for error correction.
    So if your quality level dropped down close to 75% you would have some serious picture break up and most likely couldn't even decode at all as the ECM's couldn't be correctly decoded.

    And what is the scale relative to, anyway?
    Percentage of bits succesfully decoded prior to relying on error correction FEC bits.

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    Quote Originally Posted by bambbbam View Post
    Which is more important?

    On C1 I get S 74, Q 100 but on D3 I get S 82 Q 91.

    And what is the scale relative to, anyway?
    The signal strength is the power of the signal received. The Quality of the the signal is relative to the MER ( Modulation Error Rate ) ,pre-Bit error post-Bit error and Noise margin.

    Now with to respect to C1 & D3, i found on my spectrum analyzer that D3 gives better numbers. will post comparative tomorrow.

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    Quote Originally Posted by davmel View Post

    So if your quality level dropped down close to 75% you would have some serious picture break up and most likely couldn't even decode at all as the ECM's couldn't be correctly decoded.
    I still get pictures on my receiver till about 45% quality......? (perfect picture quality) This is a lot less than 75%.
    Last edited by networkD; 16-11-09 at 09:31 AM.
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    If your reception is reliable (not pixellating or being lost altogether) then it doesn't really matter what the 'numbers' are, as there is obviously sufficient signal quality for your decoder to work ok.

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    Quote Originally Posted by networkD View Post
    I still get pictures on my receiver till about 45% quality......? (perfect picture quality) This is a lot less than 75%.
    I don't think some STB manufacturer's or the PC card software developers understand how to calculate the figure. Your box value of 45% is a perfect example. Maybe they have taken a logarithmic BER value and subtracted it from 100, but that's clearly not a percentage so just chalk it up as a bogus value with incorrect units.

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    Default The Numbers Game

    Numbers mean EVERYTHING.

    I have NOT seen an Professional installer trying to install a satellite dish with the results they get on a satellite decoder.

    That's the reason we pay a shit load of money for a half decent spectrum analyzer.

    Installers for carriers have a Minimum requirement for "Numbers" (mer,ber N/M,S/n) that they have to achieve to produce a reliable signal.these measurements ideally would be logged.

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