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rate, which the MSK 33 can measure, is 1.0 e-8. If the rate is lower than these
values, the display of the BER jumps to zero „0“ (no longer bit error). The highest
BER, which can be displayed, is 1 e-2. Generally, it can be assumed, that picture
disturbance can occur by a BER of ca. 1 e-3.
Measurement of signal noise ratio (SNR)
The conception of the MSK 33 allows the S/N ratio of the I- and Q- data stream to
be displayed in addition to the C/N measurement on the digital carriers in the
Const-menu. The measurement is carried out after the QPSK demodulation and
can be called in as an indicator for the noise on the I/Q signals. Differences in the
result to the C/N measurement in the spectrum menu can be caused by the com-
plex interfering influences of the digital signal or by differences in the input level.
The SNR value is displayed on the upper edge of the TFT screen.
The best value, which the MSK 33 can measure, is 12 dB. If the value is better
than 12 dB, this is indicated with a arrow in front of the measured value.
Carrier offset
The carrier offset display represents the difference between the set receiving fre-
quency on the MSK 33 and the transmitting frequency of the digital signal in MHz.
The carrier offset is displayed on the upper edge of the TFT screen.
With the cursor buttons, ◄►, the receiving frequency of the MSK 33 can be
changed and the frequency offset can be set to zero. The carrier offset displays,
which frequency position the LO of the used LNB has.
Frontend locked
If the receiving unit of
the MSK 33 is locked on
the carrier frequency of
the received signal, the
display „frontend locked“ appears on the
screen. „Not locked“, appears in the
display, if a representation of the
constellation diagram is not possible. An
analysis of the constellation diagram or an
assessment of the measurement results
can first occur, as soon as the receiving
signal is locked. The symbol rate and the
code rate are to be set here to the
required values. The inversion of the
spectrum (inverse /no) is automatically
set.
The display shows the following values:
- BER = Bit error rate: 1.7 e-06
- SNR = Signal noise ratio: 9.5 dB
- Carrier-Offset: -0,3 MHz
- Frontend locked
- Carrier frequency: 11347.00 MHz
– Digital measurement (D)
– Carrier level: 49.0 dBµV
The last set menu is called up
.
QPSK >
no