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The loudness measurement window has a default value of 120
seconds. This may be user-adjusted under
Setup / Radio / Loud-
ness Window: down to 30 seconds, as may be dictated by the sta-
tion’s programming format.
This metering method reflects the broadcast implementation of
the BS.1770 Standard, and is explained in further detail in EBU
Loudness Standard R-128.
SCA Subcarrier
Measurements
The % scale shows the injection level of the SCA subcarrier in
percent of total FM carrier modulation. The traditional figure
of 10% indicates ±7.5kHz deviation of the carrier. The
dB
scale
displays the audio level of the recovered SCA program. 0dB
equates to the deviation set by the Now Playing / Tuner / SCA /
Deviation (kHz):
slider (Page 19.) With the slider at its default of
5.0 , ±5kHz SCA deviation by a steady-state tone would drive dB
to 0 .
Synchronous
and AM Noise
Sync
(synchronous) FM noise refers to amplitude modulation of
the FM carrier by the FM baseband signal, predominantly by
program audio. If the passband of the transmitter is not fre-
quency-flat, then as the carrier deviates toward the channel fre-
quency extremes the carrier level might undergo amplitude
rolloff at the band edges, which would amplitude-modulate the
FM carrier.
AM
noise is considered asynchronous, or FM-carrier amplitude
modulation from any source other than baseband modulation,
such as mains ripple in the DC supply to the final RF amplifier
stage. This
AM
noise measurement is valid only when modula-
tion is not applied.
Both these noise measurements are expressed in dB, 0dB equal
to 100% amplitude modulation of the FM carrier.