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IT and Communications Engineer Examination Part 2

By: Firas Abbas

Please choose the most suitableanswersfrom the following multiple choices answers (Questions from 1to 16). Note that each question mayhave more thanone correct answer:

1) Satellite Dish was pointed toward vertically polarized incoming signal. The polarization anglewas +37 degree. If this dish should now receive a horizontally polarized signal, the new

polarization angle should be :

a) -37b) -127c) +127d) -532) A satellite dish is pointed toward W6 satellite. The LNB was horizontally polarized and the

BUC was vertically polarized. This means:

a) The satellite dish can received only horizontal signalsb) The satellite dish can receive only vertically polarized signalsc) The dish can transmit only vertically polarized signalsd) All The above3) What does the standard Ku PLL LNB needs to operate well :a) 10 GHz local oscillatorb) 10 MHz signalc) DC voltaged) All the above4) A 30 dBm RF power amplifier fed by -10 dBm IF signal, This means :a) Output power is 1 Wattb) Gain is 20 dBc) Gain is 40 dBd) All the above5) Non saturated Block up converter is fed by -19 dBm IF signal. It is needed to increase the

output power of this BUC by 2 dB, what is the IF input signal power :

a) -19 dBmb) -21 dBmc) 2 dBmd) -17 dBm6) Sat modem generates an LNB low current alarm, this means,a) LNB is short circuitb) Cable is short circuit.c) LNB Cable is shortd) LNB cable is Open7) Two signals ( used to modulate 1024 kbps data) was monitored by spectrum analyzer, the first

is about 50% less in bandwidth than the second one, this means that :

a)

The first signal is 8PSK and the second is QPSKb) The first is QPSK and the second is 8PSKc) The first is ASK and the second is QPSKd) All the above

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8) QPSK signals means that :a) There are 3 bits in each signal symbolb) There are 2 bits in each signal symbolc) The signal is Phase modulatedd) The signal is amplitude modulated9)

QPSK is preferred if compared to 8PSK if :

a) less satellite segment bandwidth is availableb) less end to end delay is requestedc) Less transmitted RF power is availabled) Less received EbNo is available10)Satellite modem is receiving 8.2 dB EbNo, this means that :a) The ISP is transmitting 8.2 dBmb) If the modulation is QPSK, then the site is better immune against the storms than 8PSK.c) If the modulation is 8PSK, then the site is better immune against the storms than QPSKd) The modem is working fine if the modulation is 8PSK for 1E-9 BER.11) If the received signal frequency is 11250.067 MHz, This means:

a) The RF input signal has carrier of 11250 MHz and offset 670 KHzb) The RF input signal has carrier of 11250 MHz and offset 670 MHzc) The RF input signal has carrier of 11250 MHz and offset 67 KHzd) The RF input signal has carrier of 11249 MHz and offset 1067 KHz12) If a PLL LNB has +/- 10 KHz frequency stability, this means that the modem sweep rangeshould be set to:

a) 1 MHzb) 20 KHzc) 30 KHzd) 60 KHz13) If the RAW BER of sat modem is 10 E-3, this means :a) The modem can receive 1Mb data with only 1000 Bits errorb) The modem can receive 10Mb data with only 1000 Bits errorc) The modem can receive 1Mb data with only 100 Bits errord) The modem can receive 1Mb data with only 10000 Bits error14) A QPSK signal with data rate of 96 kbps and FEC code rate, will have the following

symbol rate:

a) 48 kspsb) 84 kspsc) 64 kspsd) 36 ksps15) ISP told us that our RX frequency is 12625.1234 MHz. What is the RX IF frequency that will

be set to our sat modem?

a) 1325.1234 MHzb) 1725.1234 MHzc) 1225.1234 MHzd) 2625.1234 MHz

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16) ISP told us that our TX frequency is 14325.1234 MHz. What is the TX IF frequency that willbe set to our sat modem?

a) 1775.1234 MHzb) 1275.1234 MHzc) 1375.1234 MHzd)

2275.1234 MHz

17) ISP send to us the following information :ISP Uplink Frequency is 14103.5630 MHz, Transmit polarization is horizontal, data rate:640kb, Modulation: QPSK FEC . ISP Downlink Frequency is 12612.1630 MHz, Receivepolarization is Vertical, data rate: 640kb, Modulation: QPSK FEC . The used satellite has adown conversion frequency of 1500 MHz. The site should be used with Cross Pole OMTDish. Fill the following blanks with the wanted information:

a) The ISP Transmit IF Frequency ....MHzb) The Remote Receive RF frequency....MHz

c) The ISP IF Receive frequency ... MHzd) The Remote Transmit IF Frequency ..MHz

e) The Remote Transmit RF Frequency .MHzf) The ISP Transmit RF Frequency ...MHz

18) The following data was taken from a modem monitoring menu,Raw BER 1.5 E-4, Corrected BER 1.5 E-9, RSL = -49 dBm, EbNo = 10.3 dB, LNB Current =257 mA, ODU Current = 1924 mA, RX L-Band frequency: 1234.9876 MHz, and TX L-Band

Frequency: 1000.1234 MHz, Fill the following blanks (with True or False):

a) The modem is working fine. b) The BUC RF power is 2 Watt .c) The Transmit frequency is 13050.1234 MHz. ..

d) If the LNB LO =10 GHz, the receive frequency is 11234.9876 MHz. .e) BER is 1.5 E-4.

f) LNB Cable is not shorted. ..g) Modem Received signal is good. ..h) Modem sensitivity is higher than -49 dBm. ..