C/N is carrier-to-noise and is in dB. The higher the number the better the signal. I don't know if your receiver provides the option of showing signal quality or C/N or both. Also, type of modulation and FEC dictates the minimum C/N in order to lock the signal. There are charts that show the relationship. That's it in a nutshell.
Well after buying a Satlink meter It has a db and BER readout. The signal qualitt readout on it is pretty useless as it is always between 60 to 69 on all locked transponders. I never paid attention to db and ber but am learning by using this meter and have to say it is very helpful...
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my take away is that the Signal Quality in % is relevant only within your receiver. In other word, on a given signal, one receiver might say 70% and another receiver connected to the same dish might say 50%. I suspect it has to do with what the manufacturer decided 100% would be. If they decided 100% was a 20dB SNR, then you would rarely get above 80%, and anything above 50% would be good signal. But if they decided 10dB would make 100% quality, then a 90% signal might not work (depending on the modulation and FEC). I'm intentionally exaggerating a bit. The bottom line is that you should use the quality only to fine tune your dish to get the highest number, but you should not worry about comparing that number with others.
As mentioned above, the modulation and FEC dictate the minimum SNR required for locking a signal. 8psk requires more SNR than QPSK, and the closer then FEC is to 1, the less capable it is at correcting the errors, so it requires a cleaner signal. Note that usually, common wisdom is that DVB-S2 requires a higher quality than DVB-S, but that's not exactly true. DVB-S2 often uses more demanding modulation and FEC (8psk, 3/4 or 5/6), but a QPSK DVB-S2 signal can work with a lower SNR than a similar DVB-S signal. It's just that we don't see many QPSK, low FEC DVB-S2 signals out there.
A bit complex for those who just want to watch TV, in my opinion, unless they are willing to spend some time customizing it. But for the enthusiasts like most of us, who are probably as much- if not more- interested in "what can I receive with this thing?" as in regular TV Viewing, it is really great. The SNR in dB is nice, the transparency is probably the best aspect. It gives a lot of details that are important to us but boring to the average TV viewer - modulation, protocol, FEC, etc. My Amiko is also a great receiver but it does not give any of those, which is frustrating.
