DreamGEAR MSK 33 QPSK no, Measurement of signal noise ratio SNR, Carrier offset, Frontend locked

Const Menu

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

QPSK >

no

If the receiving unit of BACK 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.

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