Inovonics 525N, Installation & User Manual

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RECEPTION SNR AND AUDIO RESPONSE GRAPHS
Figure 1 plots the program audio output noise floor against the RF level at
the antenna connector. Signal-to-noise performance of the 525N is a direct
function of the incoming RF level. The figures shown reference 100% mod-
ulation with 10kHz audio bandwidth and NRSC de-emphasis.
Figure 1 - Model 525N
SNR Performance
Figure 2 illustrates the effect of the menu-programmable audio-cut filter in
the program audio and headphone outputs of the Model 525N. This filter
does not affect modulation measurements, which always follow the FLAT
response noted, regardless of the audio cutoff selected.
Figure 2 - Model 525N Off-Air Measurement Response (FLAT)
and Program-Audio Cutoff Options
Figure 2, above, does not reflect the ‘truncated’ 75µs NRSC de-emphasis
characteristic graphed below in Figure 3. De-emphasis is a menu option
that is normally engaged to compensate for complementary transmission
pre-emphasis mandated by the 1985 NRSC Specification.
Figure 3 - NRSC De-Emphasis Curve for AM Broadcasting