76.605(a)(3)
Fact
The aural center frequency of the aural carrier must be 4.5
MHz +/- 5 kHz above the frequency of the visual carrier at
the output of the modulating or processing equipment of a
cable television system, and at the subscriber terminal.
Myth
"If it's good at the Headend, it's good at the Test Point"
While this "should be" true, there are certain types of intermittent failures in modulators
and processors that can cause drift, or complete loss of the Audio Carrier for one reason
or another. This problem can be hard to detect if you rely on your subscribers to do your
troubleshooting for you, as the forgiving nature of todays televisions can employ
countermeasures for these types of effects. The fact remains that you are required to
measure the audio frequency if not at, in at least some simulated form of the
subscriber's terminal.
Measurements
Even though there is no suggested method under 76.609 (Measurements), it is pretty
obvious that you are going to need some sort of counter or spectrum analyzer to
perform this test. A link to 76.609(a) is provided here however, for some suggestions on
how to perform other tests as well as 76.601(a)(1), which provides test point and data
collection information.
76.609(a)
76.601(a)(1)