Definition?: Quality %

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crawfrdb

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SatelliteGuys Family
Jun 5, 2006
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Would any engineering types out there happen to know if the Quality % indication of a DVB FTA receiver used to peak DVB signals for FTA reception might be formally defined somewhere?

For example, if a Quality indication of a DVB reception on a satellite receiver indicates 30% and an increase to 60% is observed, would this correspond to a 3dB increase in digital power or is there some sort of non-linear relationship between % and power?

Thanks in advance for any replies.

-B
 

Larry1

SatelliteGuys Pro
Aug 24, 2005
1,594
138
Port Hope, ON Canada
The quality number of different receivers are not the same. It is just a guidline to represent the amount of data that is being received that is good. With a digital signal the error correction can rebuild the data stream from just a portion of the data.
 

dish_in_the_sky

SatelliteGuys Family
May 18, 2006
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Meaning of Quality

Quality reflects the BER (Bit Error Rate) of the incominfg signal

The receiver has FEC (Forward Error Correction) data supplied to it along with the desired data stream.

There are two ways the receiver could measure Quality:
1. Raw BER
2. Amount of FEC data applied to rebuild the desired data stream.

BER is probably some sort of logarithmic scale, and FEC is probably linear.

However, scaling and offset factors, logarithm bases, etc may vary from receiver to receiver, being dependent on hardware and software characteristics.

Therefore you cannot correlate these to hard numbers for BER or signal power. The same is true for the signal strength meter.

Maximuize quality and you'll get the best reception possible, especially in rainy weather.

Note that even with a monster dish perfectly aimed with a super quiet LNBF, you may not get even close to 100% quality.

One situation where that may happen is if the satellite signal is close to the system noise floor (including sky noise and terrestrial noise) even with a big dish. This can easily happen if you are trying to get a satellite clos to the horizon.

Another case may be where there is interference from other satellites or an improperly encoded signal.
 
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