Dante Inovonics 541, Installation & User Manual, Page: 23 / 56

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Under
RF Input:
select
Antenna
or
High Level
. This selection does
become a part of the saved
Preset Stations
data and would allow
automatic ‘pushbutton’ high-level input selection for your own
station and off-air reception for others.
Mono/Stereo
The setting here is
Stereo
by default, but may be changed to
Force Mono if, for instance, the lower noise during mono recep-
tion is considered essential to some measurement. This option
is also saved as a
Preset Stations
condition.
IF Filter
The advent, acceptance and implementation of the iBiquity Dig-
ital HD Radio™ digital broadcasting system makes measure-
ment of analog-FM signal parameters a challenge. The proximi-
ty of the HD Radio digital carrier groups to the analog-FM side-
bands requires stringent filtering in the RF domain to render
measurements of analog values accurate.
The four IF Filter: selections correspond to four distinct modes
of HD Radio “hybrid” (simultaneous analog and digital) trans-
mission. It is outside the scope of this manual to detail the
particulars of these transmission modes, but the avid reader
can find them explained in the iBiquity Digital Corp. document,
HD Radio™ Air Interface Design Description Layer 1 FM.
The 541 includes a utility that automatically applies the correct
filtering. Simply select
IF Filter: Auto
. The applied filter will be
highlighted in yellow.
SCA Subcarrier
Tuning and
Measurement
Audio SCA “narrowcasts” are received, and their parameters
measured, by a utility built into the 541. An SCA subcarrier
rides above the L–R (S') DSB subcarrier, typically at either
67kHz or 92kHz. SCA subcarriers have historically carried
background music for stores, readings for the blind and for-
eign-language programing. Noise performance of this auxiliary
channel has deteriorated over the years, first from overcrowd-
ing of the FM band, next by the advent of stereo-FM and by very
aggressive audio processing. SCAs have subsequently fallen
into disuse, replaced, ironically, by the additional subchannels
afforded by SCA’s most recent technical nemesis: HD Radio!
SCA Settings
Frequency: selects the SCA subcarrier frequency. A None selec-
tion turns the SCA decoder off.
De-Emphasis:
selects that pa-
rameter from among the values shown, with 150µs the histori-
cal default.
Audio fidelity of the recovered SCA program is somewhat lim-
ited and, as already mentioned, this service is plagued by inter-
ference from both the main channel, auxiliary and off-channel
sources. We’ve included two variable filters to help with this
situation: BPF Bandwidth (kHz): limits the reception bandwidth
around the subcarrier center frequency, and
Audio Bandwidth
(kHz): is a low-pass function following the SCA demodulator.
Use these controls to clean up the audio as best you can.
Deviation (kHz): defines the 100%-modulation point of the SCA
subcarrier. The default value of ±5kHz is the de-facto specifi-