On Tue, 2 May 2017 15:31:40 -0700 (PDT), "Ron D."
wrote:

Incidently,
The CECB reports signal strength in 0 to 100 arbitrary units.
The "Dumb" Samsung TV just reports s/n ratio
The $1000 tuner reports both s/n and signal strength in real units.

The 0 to 100 is not quite arbitrary. It starts out as an 8 bit number
(0 to 255) from the receiver demodulator. That gets fed to a
microprocessor, which converts it to 0 to 100. That's because most
users do not count in binary or hex, and must therefore be supplied
with their numbers in decimal format. Seems rational. In cellular
handsets, there is a conversion algorithm or lookup table that relates
actual signal strength at the receiver input to the 0 to 100 numbers.

There is also a conversion to the number of bars (usually 5 bars),
which are totally at the discretion of the handset manufacturer.
That's what got Apple in trouble when they initially provided a
linearized conversion from RSSI to bars and discovered that it made
the iPhone 4 looks bad when the user grabbed the antenna.

Ok, back to the TV. The SNR (signal to noise ratio) in not the usual
analog style:
(signal + noise + distortion) / (noise + distortion)
Instead it's based on the BER (bit error rate) or MER (modulation
error rate). Basically, it's a measure of how many errors the receive
has to deal with in order to display a decent picture. The more
errors that need correction, the lower the SNR. I believe that
there's yet another lookup table correlating the BER to what the SNR
would be if it were an analog receiver, but I'm not sure that this is
really true.
http://blog.solidsignal.com/content.php/2768-DTV-Antenna-Help-and-a-touch-of-SNR-BER-MER

What I wanna see is Eb/N0 (energy per bit to noise power spectral
density ratio):
https://en.wikipedia.org/wiki/Eb/N0
This for European DVB, but the theory is about the same for US DTV:
"Bit Error Ratio BER in DVB as a Function of S/N"
https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/7bm03/7BM03_4E.pdf




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