November 1996 ECE Board Exam - Communications

(ECE Board Exam November 1996) Term/Answer

Definition/Question

Cladding Helical antenna 7½

Dielectric material of an optical fiber surrounding the core Antenna that is circularly polarized A word in telegraphy consists of ______ characters plus a word space Number of voiceband channels in a master group per CITT standard Power of standard test tone Navigational system used primarily for obtaining your fixed location over large distances Provides less amplification for low signals

300 1 mW LORAN Expander in a companding device -90 dBm Code 4/3 83 dB FSK RS 422

Aperi period odic ic anten tenna Diffraction Humidity, temp, and pressure Length Beat Beat frequ frequenc ency y oscill oscillato atorr Perigee 45 V rms

Capture area Modems Isotrop ropic antenna Communic Communication ations s satelli satellite te

Pulse duration modulation 2 rectifiers in parallel with opposite polarities 30 days B8E Space or direct

At what power level does a 1 kHz tone cause zero interference (144 weighted)? One character or a sequence of characters forming a part, or the whole of a message with a specific meaning K factor under normal atmospheric conditions in a microwave radio data profile calculation calculation IBM’s asynchronous data link protocol designation Modulation for telegraphy Standard that specifies a balanced interface cable that will operate bit rates up to 10 Mbps with span distances up to 1200 m Anten tenna which ich is not res resona onant at partic rticul ula ar fre freq quenci encies es and socan be used over a wide band of frequencies Occurs when the microwave beam is at a point of grazing over an obstacle Atmospheric condition is controlled by ________. The characteristic impedance of a transmission line does not depend on its _____. Gener Generate ates s a 1 kHz kHz note note for for Morse Morse code code Point on the satellite orbit closest to the earth The potential difference between any exposed structured to ground in any electrical installation should not exceed  _______. Is directly proportional to the gain of the antenna Are required to connect the computer to telephone lines because the telephone network will pass direct current. Standard reference antenna for the directive gain It is a spacecraf spacecraftt placed placed in orbit orbit around around the the earth earth carryin carrying g on board microwave receiving and transmitting equipment Uses pulse that appear as a group and which vary in number according to the loudness of the voice A device to be connected across the headset in telephone receivers to reduce the effects of acoustic shock Judgement on the case against an ECE shall become final and executory after Independent sideband emission When transmitting and receiving antennas which are in

Phase shift

 The clocking is derived from the data in synchronous transmission F1 25 pins SSB Indirect Communications code -90 dBm Hertz antenna Pulse width modulation Purpose of squelch circuit  TACAN Synchronous Infinite

 To provide an acceptable replica of the information at the destination Antenna gain Binary communications 2 Determined by the sender and receiver Broadside array

Data switching systems  Yagi-Uda Definite 256 to 2048 Hz Balun No Input

Detector stage

line of sight with each other, the mode of propagation is  ____ wave. Passive crossover components cause some frequencies to be delayed with respect to the other frequencies at the crossover point  The difference between asynchronous and synchronous transmission

Lowest layer of the ionosphere How many pins are there in a RS232C interface? ½ bandwidth for DSBFC transmission Method of generating FM used by broadcasting Agreed upon in advance between the sender and receiver Reference tone level for dBm Undergrounded antenna Pulse modulation that is analog To prevent amplified noise from reaching the loudspeaker during the absence of an incoming signal Navigational aid providing hearing and distance indication In ________ transmission, a unique SYN character is transmitted at the beginning of each message If the terminating impedance is exactly equal to the characteristic impedance of the transmission line, the return loss is _______   The main purpose of a communications system

The numeric ratio relating the radiated signal strength of   an antenna to that of another antenna _________ is better because the components are simpler, less costly, and more reliable In the phase shift method, how many circuits must be balanced?  The correctness and accuracy of the transmitted message content is _______. Consists of a number of dipoles of equal size, equally spaced along a straight line with all dipoles fed in the same phase from the same source Improve the efficiency of data transfer A type of array antenna which consists of one half-wave driven dipole, one reflector, and one director Power is a ________ amount of energy used in a specific period of time The midrange frequency range of sound is from _________   To connect a coaxial line to a parallel-wire _____ is best to use. In AM, the carrier carries _______ intelligence. Characteristic impedance of a transmission line is the impedance measured at the ______ when its length is infinite Cross modulation on a receiver is eliminated at the  _______ 

 The local loop of the telephone system  The equatorial region Quantizing Beamwidth

Undergrounding Noise weighting curve

Lies in the different definitions of the modulation index Unbalanced 6 dB over the gain of one antenna Residual noise level

Ultraviolet absorption Limiters 30 to 53 kHz  Termination Character oriented Ground 0.66 0 dB Log normal fading Local oscillator Modem No transmitter power is wasted in the carrier

 _____ is a two-wire or four-wire communication circuit between the customer’s premise and the central office In what region of the world is sporadic-E most prevalent? The process of assigning PCM codes to absolute magnitudes It is a measure of the microwave power radiated from an antenna as a function of angular direction from the antenna axis This is not one of the basic electrical protection measures in the Philippine electronics code ________ shows the interfering effect of other frequencies in a voice channel compared with a reference frequency of one kilohertz  The difference between phase and frequency modulation

When a transmission line uses ground return, it is called a/an ____ line What is the gain of four identically polarized antennas stacked one above the other and fed in phase? The ratio of the level of the modulated output of a transmitter under conditions of standard test modulation to the level of the demodulated output with no modulation applied both measured with the same bandwidth An absorption los caused by valence electrons in the silica material from which fibers are manufactured In an fm receiver, which circuit removes amplitude variations? The frequency spectrum of the stereophonic FM signal ____ means load connected to the output end of a transmission line Asynchronous protocol is __________  Transmission lines are either balanced or unbalanced with respect to the ___  The velocity factor for non-foam dielectric 50 or 75 ohm flexible coaxial cable such as RG 8, 11, 58, and 59 Gain of isotropic antenna Radio fading resulting from obstruction After the IF stages have been aligned, the next state to align in FM receiver Is a device in data transmission to interface a data terminal equipment to an analogue transmission line What is the primary advantage of DSBSC in AM?