10
Spectrum Operation (Satellite)
The Spectrum Mode is displayed when the instrument is turned on in Satellite mode.
With a dish and LNB connected, it will show a display similar to that above. The
spectrum is displayed with the Start frequency at the top of the screen and the Stop
frequency at the bottom. The Span is the total frequency coverage or the difference
between Stop frequency and Start frequency. The current signal level (14.3 dBmV in this
example) is displayed for the frequency at the Marker. The knob is used to change this to
the frequency of interest.
When Spectrum Mode is entered, the peaks are checked to see if the demodulator can
lock. If a lock occurs, the NIT data for the transponder is displayed for automatic
satellite identification. NIT data on a transponder is repeated at least every 10 seconds
and on most satellite more often than this.
The span of the Spectrum can be changed in two ways. Pressing the keypad ‘3 Span’ will
change the spectrum to the minimum span of 250MHz. For this span, each division is
1MHz. An alternate method is to use the adjustable span. Pressing the knob allows the
span to be adjusted from a minimum of 250MHz to the maximum of 1231MHz. At this
maximum span, the entire IF band from 920MHz to 2150MHz is displayed.
When span is adjusted by pressing the knob, a second press of the knob allows the “DC
Offset” of the spectrum to be adjusted for best display. A further press of the knob
restores the operation to frequency adjustment. The span setting from the knob remains
as the current setting. The “DC Offset” is restored to 0.
The current band being displayed can be changed with the 22kHz signal using the
keypad ‘# 22kHz’. For Universal LNBs, when the 22kHz is off, the band is Lo Band
(920MHz to 11900MHz) and when the 22kHz is on, the band is Hi band (11520MHz to
2150MHz) There is a small overlap from 11520MHz to 11900MHz, so a Universal LNB
can tune this range with 22kHz either on or off.