Belar FMHD-1, Operator'S Manual

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FMHD-1 Operator’s Manual
BELAR ELECTRONICS LABORATORY, INC. Page 31
Infinite
- The spectral amplitude is replaced by any higher spectral amplitude that occurs in that spectral
bin. That higher value is held until a larger amplitude occurs in that bin or until the mode is exited and
restarted, whichever occurs first.
Hold Count:
The number of FFT’s used to calculate the “
Peak Hold
” spectrum.
Avg Count (for “Average Count”):
This is the number of FFT’s used to calculate the averaged spectrum.
0 dB Ref Lev (for "0 dB Reference Level"):
This is used to normalize a user-defined dB value to the “0–dB” reference point on the spectrum display.
It provides a way of setting an appropriate amplitude reference to which readings may easily be
compared. It ranges from 0.0 dB to –100.0 dB in –0.1-dB steps.
This parameter adjusts the position of the displayed spectrum relative to the display’s vertical scale. The
adjustment permits precise direct-reading level comparisons between on-screen amplitudes. By adjusting
the “0-dB Ref Lev” parameter so the reference signal falls on the C1 cursor, which is set at “0dB”, the
relative amplitude of any other signal on the screen can then be read directly by moving the C1 cursor to
the maximum amplitude of the other signal. Alternatively, by placing the C2 frequency cursor on the
signal in question, the relative numerical amplitude may be read directly at the right edge of the display.
If it is desired to compare the level of a low-level signal to that of a larger signal, possibly using the C1
cursor, one first determines the amplitude of the larger signal using the C1 cursor. By setting the "0-dB
Ref Lev" to this amplitude using the encoder, the signal spectrum will shift up so the "0 dB" label on the
vertical axis will be directly across from the vertical position of the desired reference signal. Readings on
the vertical axis for other signals will then directly indicate the amplitude relative to the desired reference
signal.
Curve Fill:
When Curve Fill is "
ON
,” that portion of the vertical display between the bottom of the spectrum graph
and the measured amplitude for each bin is lit in green. This makes the amplitude indication more
obvious. When Curve Fill is "
OFF
”, the amplitude indications consist of a single lighted pixel in each
frequency bin.
Colors:
When "
OFF
”, the entire RF spectrum is indicated in green. When “
ON
”, specific portions of the RF
spectral display are color-coded. When
Colors
is “
ON
”, the central analog region of the spectrum is
green, the main IBOC sidebands are yellow, and the regions mainly dedicated to the extended IBOC
sidebands are red. [The green highlighting extends to ±100 kHz. The red highlighting starts at ±100 kHz
and extends to ±122 kHz each side of the analog carrier. The yellow highlighting starts at ±122 kHz and
extends to ±200 kHz.]
Mask:
Setting
Mask
to "
ON
" superimposes an adjustable red-line overlay on the FMHD-1 RF spectrum display
to assist in determining compliance with NRSC and FCC emission standards. The mask is centered at the
analog FM carrier frequency, as set in the Main Tuning Screen. The central amplitude is set at “
0dB
” to
facilitate level measurements relative to the analog carrier, or in units of dBc. The relative amplitudes of
the two steps extending from ±100 kHz to ±200 kHz each side of the carrier are independently adjustable.