[mythtv-users] Which Signal Strength/Quality Alternative is best?

[Gary Buhrmaster]

A couple of quick thoughts:

First, be aware that no consumer device is calibrated,
so the readings are perhaps "in the ballpark", but not
accurate.  If you want accurate readings, you need to
use a (calibrated) meter.

As I recall, the specifications require the devices to
support roughly -12 to +15 dBmV ("ideal" is 0dBmV),
and to decode 256QAM at a CNR of at least 33
(there is no limit, but in practice you do not see
numbers more than around low 40's except in
very tight plants).

It is *strongly* recommended in practice to avoid
being near the edge ranges of any of those numbers
because real world plants have some variance
(a few dBmV changes across the year is not unheard
of).  And since you are using consumer equipment to
measure, it is even more important to stay well
within the middle of the ranges.

A high quality amp, and/or a high quality splitter
(with appropriate cabling and connectors) should
really not be introducing ~2dB SNR noise. And a
high quality splitter is usually closer to -3.5dB
than a 4.7dB loss.  Whether is is an artifact of the
measurement or the splitter/amp/cables is unknown.
Something feels wrong there.