Orban OPTIMOD-FM 8500S, Руководство по эксплуатации

Страница: 230 / 335

3-66
OPERATION ORBAN MODEL 8500S
If the HD output is driving a channel without pre-emphasis but using a lossy codec,
you may want to allow headroom to compensate for data reduction-induced peak
overshoots at the receiver, which might otherwise cause clipping. In our experience,
2 dB is typically adequate.
Delay Difference between HD and FM Outputs
In order to make the receiver analog/digital crossfade free from comb filtering, the
time delays in the HD Radio’s FM and HD channels must have a fixed and predictable
offset, correctly implementing the HD Radio receiver’s “time diversity” processing. If
the 8500S’s built-in diversity delay is defeated, the 8500S’s HD output’s delay is auto-
matically adjusted so that it always exactly 10.500ms longer than the FM output’s
delay, regardless of the FM output’s delay (which can vary depending on processing
settings). Therefore, the HD Radio exciter should be preset to compensate for this
10.5 ms offset between the FM output and HD output. Once you have done this, the
time diversity delay will always be correct even if you choose a 8500S preset that in-
vokes a different processing structure.
You can apply the 8500S’s built-in diversity delay independently to any output emit-
ting the FM-processed signal. This eliminates the need to use the delay in the iBiq-
uity exciter, which allows you to apply the 8500S’s composite output directly to the
transmitter’s analog composite input. In turn, this allows you to use the 8500S’s com-
posite limiter, increasing the loudness of the analog channel. When the diversity de-
lay is active, the 8500S always maintains precisely the same delay offset between the
analog and digital channels regardless of the preset in use.
Section Label Control Name Values
Input/Output:Output1 Phone Src HD / Monitor / FM
Out Source (analog L/R) HD / Monitor / FM / FM+Delay
Input/Output:Output2 Out Source (AES 1) HD / Monitor / FM / FM+Delay
Out Source (AES 2) HD / Monitor / FM / FM+Delay
Input/Output:
Out Level 0… –20 dBFS; 0.1 dB steps
AES Output 1 and Samp Rate 32, 44.1, 48, 88.2, 96 kHz
AES Output 2 HD Bandwidth 15, 16, 17, 18, 19, 20 kHz
Word Leng 14 / 16 / 18 / 20 / 24 bits
Dither In / Out
Sync Internal / Sync In
Format AES3 / SPDIF
Out Level 0… –20 dBFS; 0.1 dB steps
Input/Output:
HD Digital Radio
Meter Select FMOutLevel / HD GR
HD HF Shelf EQ Pre / Post
Stereo/ Mono Stereo / MonoL / MonoR / MonoSum
Diversity Delay Trim 0.265 to 16.384 seconds
(HD) Polarity Positive / Negative
BS.1770
Safety Limiter
BS.1770 Loudness Control
Threshold
–31 to –11 LKFS/LUFS
BS.1770 Safety Limiter On / Off
Table 3-11: HD I/O Setup Controls