Setup Modulations. On both instruments, for symbol rates below 7000 MSymbols/sec,
the signal identification may take several seconds.
A constellation pattern is shown which is formed from a small subset of the IQ decision
points received by the demodulator. Occasionally, during an attempt to lock, a
calibration pattern can be observed momentarily. This is not a real signal, but is an
artefact of the demodulator process.
The current state of the 22 kHz signal and the LNB voltage are displayed at the left.
These are mirrored by the blue L D displays.
Once a transponder signal is locked, the Network Information is displayed at the top of
the screen. This can take some time to appear once the transponder is locked. The first
information that will appear is ONID (Original Network ID) and TSID (Transport Stream
ID) data and then the NIT name and Orbital Position will follow. The ONID and TSID are
displayed in hexadecimal. The transponder is supposed to send this data at least every
10 seconds, but sometimes there will be a transponder not sending any NIT data. Also
you should be aware that sometimes a transponder will send incorrect satellite position
data, because they are being used to repeat a transport stream used on another satellite.
Visible Thermometer Bars
There are four thermometer bars displayed to indicate the state of the signal being
received. For all of these, the higher the thermometer bar, the better the signal quality.
ach of these thermometer bars has the recent maximum displayed as a single bar. This
maximum decays over time and so automatically allows for peaking adjustments. The
four thermometer bars are SIG, SNR, B R and M R.
SIG
SIGSIG
SIG
This is the power level of the signal
signalsignal
signal at the current frequency. It is always displayed
whether the signal is locked or unlocked. This is not the same as the display on the
Analog screen.
SNR
SNRSNR
SNR
This is the signal to noise ratio
signal to noise ratiosignal to noise ratio
signal to noise ratio of the locked signal. This is a measure of the meaningful
power in the signal to the background noise of the signal. It is shown in dB and is
calculated by the demodulator using
SNR = 10log
10
(P
signal
/P
noise
)
B R
B RB R
B R
This is the bit error ratio
bit error ratiobit error ratio
bit error ratio
of the signal. The lower this value is, the better the signal. It is
shown in reverse on the thermometer bar for convenience so that a maximum can be
easily found. For DVB-S QPSK signals, this is
B R = rror
preViterbi
/(Bit
Rate
Time
Lock
).
For DVB-S2 QPSK or 8PSK signals, the B R is estimated from the ratio of Un-correctable
blocks to Correctable blocks.
M R
M RM R
M R
This is the modulation error ratio
modulation error ratiomodulation error ratio
modulation error ratio in dB. It is calculated from the constellation pattern and
represents how close the I and Q decision points are to the ideal position. A typical M R
value is 16 dB. A higher value is better and represents a closer spread of IQ decision
points. A sample of 200 points is used for the calculation.
