RFtoLitetoRF
join:2002-08-11
Mechanicsville, VA
| reply to BillRoland
Re: digital cable and splitting
Yes, 20-27dB CNR is too low. Consider this...FCC spec for analog carrier CNR is >43dB, so if digital carriers are set 8-10dB below the analog carriers at the headend, corresponding minimum digital CNR would be about 33dB. The margin of headroom here is about 5-8dB, so minimum digital CNR is about 25dB. Less than this and the BitErrorRate begins to climb. This then creates the "tiling" of the picture. If your at 25dB now, any fluctuations is signal strength or purity will surely affect your reception.
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