Belar FMHD-1, Operator'S Manual

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FMHD-1 Operator’s Manual
BELAR ELECTRONICS LABORATORY, INC. Page 25
interval set by the “Time” parameter for the appropriate RF level threshold alarm for muting to occur.
“
OFF ” disables all muting.
6.2 Composite Popup Menu
This popup menu allows adjustment of two settings dealing with the demodulated analog FM composite
signal used exclusively to provide the modulation indications for the Analog FM Stereo Screen and the
rear-panel Composite outputs.
Filter BW:
Four filtering options for the demodulated composite FM signal are available to improve the
suppression of noise and interference from the IBOC-HD carriers. It is recommended that the composite
filter bandwidth be set as large as possible, and no smaller than required to pass all the services present in
the FM signal.
In order of descending bandwidth, the filters are:
92kHz
Passes the entire composite up to, and including a 92-kHz SCA sub-carrier.
67kHz
Passes the composite signal up to, and including a 67-kHz subcarrier.
RDS
Passes the stereo signal, including the RDS sub-carrier. The cutoff of this filter is just above the
RDS sub-carrier at 57 kHz.
Peak Mod:
This sets the threshold of peak modulation required to activate the “
Total Peak
” alarm. It
is set in “
%
”, where 100% corresponds to 75-kHz peak deviation of the analog FM carrier. This threshold
may also be set via the Alarms/Relay Screen, where its timeout and the alarm activations may be
controlled.
6.3 Settings Popup Menus
The following Popup Menus are brought onto the FMHD-1 display screen by using the encoder to select
the “Settings” popup menu from the Popup Menu directory. The settings menus are then selected by
rotating the encoder to highlight the desired sub-menu, and depressing the knob.
6.3.1 Unit Settings Popup Menu
This menu provides display control settings for both the peak readings and the modulation bargraphs of
the
FMHD-1 , and controls several miscellaneous functions of the unit. Details not explained for the
Popup Menu below appear in the section “ FMHD-1 Modulation Readings: General Description”.
Time Mode:
In “
Real
” time mode, any measured peak that exceeds the peak value presently on the
display, replaces the peak value on the display with the new, higher peak value instantaneously. That peak
value is then displayed for the duration of the
Hold Time
, unless a higher peak is detected first, in
which case the process repeats. Minimum and Average readings during that interval are computed and
displayed in the bargraphs. The collection-interval timer is then restarted.