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9.10 Comparing CableRater Readings to Signal Level Meter Readings
The CableRater Receiver is not intended to accurately measure the signal level
of TV signals on a cable system. It is not as accurate as a Signal Level Meter
(SLM) intended for this purpose.
The CableRater does not have the selectivity to measure a single TV channel. It
measures TV Channel 3 and several adjacent TV channels. Because it measures
several channels at once, the measured level is higher than an SLM measure-
ment.
Also, because the CableRater uses a reference level of 10dBmV for its 0dB indi-
cation, it starts off reading 10dB lower than an SLM.
In general, because of the difference in selectivity and the reference level, the
CableRater usually reads about 6 to 8dB lower than the actual level of TV chan-
nel 3. For example, if the CableRater Receiver reads 0.0dB when connected to an
operating cable TV system, the level of Channel 3 is probably about +6 to +8dBmV.
There are many variables that can affect the reading, so it should be understood
that the reading is a ‘guestimate’.
It is not appropriate to compare the readings of an SLM and a CableRater. The
SLM will undoubtedly be more accurate for measuring the signal level on the
cable. However, if an SLM is not available, the CableRater can be used to make a
comparison measurement between a location known to have good signal level,
and a location in which the signal level is unknown. This will give the user a
rough idea of how the unknown signal level compares to a known good signal
level.
