Belar FMHD-1, Руководство оператора

Страница: 23 / 58

FMHD-1 Operator’s Manual
BELAR ELECTRONICS LABORATORY, INC. Page 15
“RF Level” bargraph just below the tuning frequency numerals indicates the RF input level of the signal
at the indicated station frequency. This bargraph indicates whether sufficient signal is present to properly
monitor the station. Status indicators and numerical readouts positioned around the screen display the
operational status of the digital FM transmission system and allow verification of operation.
Only two monitor parameters may be set in this screen: the station tuning frequency and the source
program stream for Digital Decoder #1. The tuning frequency is adjusted by manipulating the encoder
knob to highlight the frequency numerals in green, then dialing in the station frequency. (See Section 4.2,
“Front-Panel Operation” on page 11
. ) Adequate signal level can then be confirmed by observing the “RF
Level” bargraph. For a high-level RF feed from one or two transmission lines, the RF level should be
within a few percent of “
100%
”. For an RF signal from a receiving antenna, the RF Level indication
should fall in the green region of the RF level bargraph. (See either Section 0 on page 7 or Section 3.4 on
page 8, whichever is relevant.)
To the right of the tuning frequency readout are status indicators for the eight possible IBOC digital
program streams, “
HD
1” through “
HD
8”. If the status box adjacent to a channel designator is lit
yellow, the corresponding program stream is available from this station. An empty box to the left of the
channel designator indicates that no corresponding program stream is available in the received broadcast.
The program stream selected for processing by Decoder #1 is marked by a green box adjacent to that
channel’s designation. A red box indicates that a channel that is not available has been selected for
Decoder #1.
For operational convenience, this set of eight program status indicators can also be used to select which
program stream is sent to Digital Decoder #1. With the FMHD-1 output settings appropriately set,
selecting a digital program stream for Decoder #1 allows one to easily direct its decoded output to the
front-panel headphone jack, or any of the eight appropriately configured rear-panel monitoring outputs.
To select the data stream applied to Decoder #1, using the encoder, the cursor is first positioned to the
desired program stream indicator, one of the boxes “
HD 1
” through “
HD 8
”. Then the encoder knob is
depressed momentarily to highlight the marked indicator green. Of course, only channels marked yellow
are available for selection. This program stream selection may also be performed using the Program
Selection Screen. (See page 21.)
The upper-left corner of the Main Tuning Screen has three status indicators important for monitoring FM
IBOC digital broadcasts. The topmost “
HD Station ” indicator turns green when the FMHD-1 has
locked onto the IBOC digital carriers. Second from the top, the “
Digital Audio
” indicator lights
green when the selected digital audio stream is recovered. The “
SIS CRC
” indicator, third of the three,
remains green as long as cyclic redundancy checks for the Station Information Service data frames
continue to be valid. Note that the
Digital Audio
indication is typically the last of the three
indicators to light, due to the 6–8-second combined time alignment and diversity delays present in the
IBOC system.
The lower half of the Main Tuning Screen presents transmission performance information about the
digital component of the IBOC HD signal. These metrics are listed below, in top-to-bottom order in the
first column, then in the second.