There are so many variables and approximations involved that it would seem
difficult to be very precise about 8.0 or 8.5 dB S/N ratio or some other
number. The decision probably involves the type of signal involved. 8.0 dB
in one application gives the minimum acceptible performance for one kind of
signal. A more critical system might want more than 8.0 dB to achieve a
better bit error rate, for example.

Bill W0IYH

"AndyS" wrote in message
oups.com...

William E. Sabin wrote:
Agilent App Note says:

Tangential sensitivity is the lowest input signal power level for which
the
detector will have an 8 dB signal-to-noise ratio at the output of a test
video amplifier.

http://www.home.agilent.com/upload/c...orOverview.pdf

Bill W0IYH


Andy writes:

I used 8.5 db, tho , as you know, it has a LOT to do with who is
making the measurement and positioning the pulse on the scope....
I'm not sure that I am proficient enough to position an 8db pedestal
to within a half db accuracy...... Agilent probly used a math
derivation.
I have seen it called out at several numbers, tho 8.5 is the one I
always used....

I will probly start using 8 db if the Agilent App note says so since
there is always somebody wanting to get a "reference", and it's
much easier to just give them the App Note source than try to
explain....
Once they actually see the scope presentation, they will understand
the problem...
Andy in Eureka