ELECTRONICS SYSTEMS AND TECHNOLOGIES QUESTIONS AVERAGE QUESTION

1. In electroacoustics, what do you call the equation show to measure reverberation time?

RT60=0.049

−Sln(1−a)

ANSWER: Norris-Eyring Equation

2. What is the maximum core diameter in (um) for a fiber if it is to operate in single mode at a wavelength of 1550 nm if the half angle of acceptance cone is 6.89O?

ANSWER: 9.9 um

3. This is the highest-ranking office in the DDD network in telephony in terms of the size of the geographical area served and the trunking options available.

ANSWER: Regional Center

4. In E-GSM 900, the frequency of the Absolute Radio Frequency Channel Number (AFCN) refers to its center frequency and the allocated is 200 KHz, what is the downlink (BTS to mobile Station) frequency range?

ANSWER: 925 MHz-960 MHz

5. A telephone subscriber line must have an SNRdB above 40. What is the minimum number of bits?

ANSWER: 7

6. The ability of an antenna to send or receive signals over a narrow horizontal directional range is referred to as

ANSWER: directivity

7. A 400 km repeater system consists of m identical cable section with α = 0.4 dB/km and m identical amplifiers with

30 dB maximum gain. Find the required number of sections so that Pout = 50 mW when Pin = 2 W.

ANSWER: 5

8. In an optical fiber, those geometrical paths which pass through the axis of symmetry and obey the self-interference condition are known as _____.

ANSWER: Meridian ray

9. Calculate the total transmitted power of an am transmitter with a 10 kw carrier which transmits 11.2 kw when modulated at 50% with another sine wave.

ANSWER: 12.45 kW

10. How far from the transmitter could a signal be received if the transmitting and receiving antennas where 40 m and 20 m, respectively, above level terrain?

ANSWER: 44.5 km

11. An isolator has a forward loss of 0.7 dB and a return loss of 26 dB. A source provides 1 W to the isolator, and the load is resistive with an SWR of 3. How much power is dissipated in the load?

ANSWER: 638 mW

12. A signal propagated in a waveguide has a full wave of electric intensity change between two further walls, and no component of the electric field in the direction of propagation. The mode is

ANSWER: TE20

13. Find the velocity of a satellite in a circular orbit 500 km above the earth’s surface.

ANSWER: 7.6 km/s

14. What is a packet based data network, which is well suited for non-real time internet usage including the retrieval of emails, faxes, and asymmetric web browsing, where the user downloads much more data than it uploads on the internet? It can support many users but in a “bursty” manner.

ANSWER: GPRS

15. It is a more advanced upgrade to the GSM standard that requires additional hardware and software of existing base stations. It allows for nine different (autonomously and rapidly selectable) air interface formats. It is known as multiple modulation and coding scheme (MCS), with varying degrees of error control protection. What is this that was developed from the desire of GSM and IS-136 operators to have a common technology path to eventual 3G high speed data access?

ANSWER: EDGE

16. For a given length of RG 8A/U coaxial cable with a distributed capacitance C= 96.6 pF/m, a distributed inductance L= 241.56 nH/m, determine the velocity factor.

ANSWER: 0.69

17. Assume a receiver is located 10 km from a 50 watt transmitter. The carrier frequency is 900 MHz, free space propagation is assumed, Gt = 1, Gr = 2; find the power at the receiver in dBW.

ANSWER: -91.5 dBW