Radio equipment is used to coordinate the activities of magnetic systems is also included. Electrical, visual, the many fleet units by linking them with each other and sound telecommunications are all used by the and with shore stations. In this volume we will discuss electrical types of telecommunications.
Usually, the term is used in referring to the transmission of intelligence A communications system consists of two or more code and sound signals, although television and radar units, each having its own separate identity, arranged also depend on electromagnetic waves. Navy communications systems vary from sim- possibly teletype communications.
Each system requires the integrated use electronics. You, the technician, need to become fa- of various types of equipment, so flexibility is of the ut- miliar with the diverse systems in use today. This flexibility is provided through a The primary means of communicating between complex arrangement of interconnections that allow ships and between ships and stations is known as tele- the physically separated sets, groups, and units to be communications. Telecommunications refers to com- selectively switched patched into the different circuit munications over a distance and includes any configurations.
A particular piece of elec- transmitted signal. You need to the original intelligence. Terminal equipment is used understand all the associated equipment in a system to primarily to convert the audio signals of encoded or data identify problems correctly and to make repairs transmission into the original intelligence. Thorough knowledge of system operations A basic radio communications system may consist will enable you to say with complete confidence, this of only a transmitter and a receiver, connected by the communications suite is operational. The transmitting equipment creates a radio-frequency rf carrier and modulates it Hazards encountered in servicing electronic with audio intelligence to produce an rf signal.
This rf equipment and the precautions to be taken against signal is amplified and fed to the transmitting antenna, them are covered thoroughly in Electronics Techni- which converts it to electromagnetic energy for propa- cian Volume 1, Safety, NAVEDTRA , and the gation. Observance of nating rf currents. The receiver then converts these safety precautions will keep your equipment operat- ing, help your career in the Navy, and possibly deter- currents into the intelligence that was contained in the mine whether or not you survive.
Always follow the transmission. Terminal equipment is used primarily where coded transmissions are employed, to convert the modulated signal into the original intelligence. Pay particular attention to the part used for communications. Rapid growth in the Radio equipment can be divided into three quantity and complexity of communications equip- broad categories: transmitting equipment, receiving ment and increased worldwide international require- equipment, and terminal equipment. Transmitting ments for radio frequencies have placed large demands upon the rf spectrum.
These demands include military and civilian applications, such as communications, lo- cation and ranging, identification, standard time, in- dustrial, medical, and other scientific uses. The military has modified the frequency spectrum for its use as shown in table A few general charac- teristics are described in the following paragraphs. The extremely-low-frequency elf , very-low- frequency vlf , and low-frequency lf bands require high power and long antennas for efficient transmis- sion antenna length varies inversely with the fre- quency.
Transmission of these frequencies is normally limited to shore stations. The commercial broadcast band extends from Figure This limits naval use to the. On board sively by the Navy for LOS and satellite communica- your command, you may find satellite communica- tions has pushed hf into aback-up role.
Mobile communications, radar over MHz , and special operations are some other uses. A significant portion of the very-high-frequency vhf band is assigned to the commercial television in- The super-high-frequency shf band is the work- dustry. Some naval uses of the vhf band are mobile horse of microwave communications. LOS communi-. Experimental use of the extremely-high- frequency ehf band is ending. The FEP is currently provid- ing ehf communications capability to Army, Navy, and Air Force ground, airborne, and oceangoing terminals.
We will discuss the FEP and its purpose in chapter 3. Infrared devices and lasers use even higher fre- quency ranges. Information on equipment using these frequencies can be found in Electro-Optics, volume 9, of this training series. The emission class of an rf transmitter is deter- mined by the type of modulation used. The interna- tional designation system for AM and FM emissions is shown in table It designates the rf emission by type, mode, and supplemental characteristics.
Generating the signal is the job of the transmitter. The following paragraphs will very briefly discuss basic transmitters and transmitter fundamen- tals. Equipment used for generating, amplifying, and transmitting an rf carrier is collectively called a radio transmitter. Transmitters may be simple, low-power units, for sending voice messages a short distance or highly sophisticated, using thousands of watts of power for sending many channels of data voice, tele- type, telemetry, t.
We will first describe the types of Modulation is the process of varying some charac- modulation. We will then describe briefly the basic teristic of a periodic wave with an external signal.
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The transmitters themselves. In na- the mark frequency. The unkeyed state is called a val communications the terms voice communications space. The audio signal is impressed upon the rf Phase-Shift Keying PSK carrier because it is impractical to transmit frequen- cies in the audio range due to their excessive wave- Phase-shift keying is similar to FSK except that the length.
The primary ad- vantage of PSK is that it can be accomplished in an am- Three characteristics of the carrier wave may be plifier stage. The following paragraphs Pulse Modulation discuss each type of modulation. Pulse modulation is accomplished by varying the Amplitude Modulation AM characteristics of a series of pulses. This can be done by varying the amplitude, duration, frequency, or posi- Amplitude modulations the process of combining tion of the pulses.
It can also be done through coding. Frequency modulation is a process in which the Remember, transmitters are generally divided ac- frequency of the carrier wave is made to vary. An FM cording to their type of modulation. In the discussion signal should remain constant in amplitude and change below, we describe very briefly how each type oper- only in frequency. Frequency-shift keying is considered a form of A basic CW transmitter is shown in figure CW FM.
It is a digital mode of transmission commonly is one of the oldest and least complicated forms of used in radioteletype applications. In FSK the carrier is communications. Two advantages of CW are a narrow present all the time. In a keyed condition, the carrier bandwidth, which requires less power out, and clarity, frequency changes by a predetermined amount called even under high noise conditions.
The major disadvan-. The signal is then dots and dashes. This method is very slow by modern amplified in the power amplifier and coupled to the an- day standards. A better method of transmitting is AM. Two important things to remember are 1 the AM Transmitter amount of variation from the carrier frequency de- Figure , a block diagram of an AM transmitter, pends on the magnitude of the modulating signal and shows you what a simple AM transmitter looks like.
The driver and modulator amplify The FM transmitter is better than an AM transmit- the audio signal to the level required to modulate the ter for communications purposes because FM is less carrier fully. The signal is then applied to the power affected by static and other types of interference.
An amplifier pa. The pa combines the rf carrier and the even better transmitter is the single-sideband transmit- modulating signal to produce the AM signal for trans- ter, or ssb. A block diagram of an FM transmitter is shown in In ssb communications, the carrier is suppressed figure The transmitter oscillator is maintained at a eliminated and the sideband frequencies produced by constant frequency by a quartz crystal.
This steady sig- the carrier are reduced to a minimum. This means no nal is passed through an amplifier, which increases the carrier is present in the transmitted signal. It is re- amplitude of the rf subcarrier. The audio signal is ap- moved after the signal is modulated and reinserted at plied to this carrier phase-shift network. Here, the fre- the receiver during demodulation. Since there is no quency of the carrier shifts according to audio signal carrier, all the energy is concentrated in the side- variations. The FM output of the phase-shift network is band s.
We can make ssb even more efficient by removing processes modulated signals and delivers, as an output, one of the sidebands.
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By filtering out one of the side- a reproduction of the original intelligence. The signal bands before it reaches the power amplifier, all the can then be applied to a reproducing device, such as a transmitter energy is concentrated into one side- loudspeaker or a teletypewriter. Other advantages are a narrower re- ceiver bandpass and the ability to place more signals in To be useful, a receiver must perform certain basic a small portion of the frequency spectrum. Figure functions. These functions are reception, selection, de- is a block diagram of a ssb transmitter. All that is needed netic wave passes through the receiver antenna and in- to complete the system is a radio receiver.
A receiver duces a voltage in the antenna. Circuits that perform this function are 10 decibels, or 3. Different forms of modulation require different detector circuits. All receivers generate noise. Noise is the limiting factor on the minimum usable signal that the receiver Reproduction can process and still produce a usable output. Ex- pressed in decibels, it is an indication of the degree to which a circuit deviates from the ideal; a noise figure of Reproduction is the action of converting the elec- 0 decibels is ideal.
Important receiver characteristics are The degree of selectivity is determined by the sharp- sensitivity, noise, selectivity, and fidelity. As the frequency to which the receiver is tuned is ap- The superheterodyne receiver was developed to proached, the input level required to maintain a given overcome the disadvantages of earlier receivers. A output will fall. As the tuned frequency is passed, the block diagram of a representative superheterodyne re- input level will rise.
Input levels are then plotted ceiver is shown in figure Superheterodyne receiv- against frequency. The steepness of the curve at the ers may have more than one frequency-converting tuned frequency indicates the selectivity of the re- stage and as many amplifiers as needed to attain the de- ceiver. However, there are important differences in put signal accurately. Generally, the broader the component construction and circuit design because of bandpass, the greater the fidelity. Measurement is differences in the modulating techniques.
Comparison taken by modulating an input frequency with a series of block diagrams figures and shows that of audio frequencies and then plotting the output electrically there are two sections of the FM receiver measurements at each step against the audio input. Good selectivity requires a narrow bandpass.
Good FM receivers have some advantages over AM re- fidelity requires a wider bandpass to amplify the outer- ceivers. During normal reception, FM signals are static- most frequencies of the sidebands. Knowing this, you free, while AM is subject to cracking noise and whistles. The number of decibels change between two power values can be com- Figure is a block diagram of a basic ssb re- puted by the formula: ceiver.
Though the ssb receiver is not significantly dif- ferent from a conventional AM superheterodyne receiver, it must use a special type of detector and a car- rier reinsertion oscillator. In some cases, a table You can see instantly the reason behind us- frequency stability of plus or minus 2 hertz is required. It is much easier to say the sig- You can see that frequency stability is the most impor- nal level has increased 40 dB than to say it has tant factor of ssb equipment.
Ssb receivers may use additional circuits that en- hance frequency stability, improve image rejection, or Examining table again, you can see that an in- provide automatic gain control age. However, the crease of 3 dB indicates a doubling of power. The re- circuits shown in figure will be found in all single- verse is also true.
If a signal decreases by 3 dB, half the sideband receivers. This is usually called the gain of the receiver. Table shows the common logarithms used to calcu- Gain is a term used to describe an increase in current, late dB. Normally the input signal is used as a refer- voltage, or power. For example, if the detector, which ence. However, sometimes a standard reference signal removes the desired intelligence, requires 1 volt to op- is used.
The most widely used reference level is a 1 erate and if the input to the receiver is 1 microvolt, a to- milliwatt signal. Decibels measured in reference to 1 tal amplification of 1 million is required before milliwatt are abbreviated dBm. A signal level of 3 detection. If the loudspeaker requires 10 volts, another dBm is 3 dB above 1 milliwatt and a level of-3dBm is voltage amplification of 10 is necessary between the 3 dB below 1 milliwatt. The formula for dBm is a varia- detector and the loudspeaker. The gain of an amplifier is expressed in decibels dB. The decibel is a means of measuring relative lev- els of current, voltage, or power.
Most often it is used to As a Navy technician, you will use the dBm system show the ratio between input power and output power. For example, a receiver rated at dBm will nus — sign placed before dB indicates a loss and a plus detect a signal dB below 1 milliwatt. Suppose the. In a transceiver, many of the components can be shared during both transmit and receive operations. A transceiver is a unit, usually enclosed in a single case, that combines a transmitter and receiver using a A disadvantage of using a transceiver is that common frequency control.
Transceivers are used ex- while duplex operation is not possible with most trans- tensively in two-way radio communications at all fre- ceivers, communication must sometimes be carried quencies, and in all modes. Although this is a. It also converts electrical energy into acoustical en- ergy for the reproduction of the received signal. To key a transmitter, the push-to-talk button is de- pressed, closing the dc keying circuit, which places the transmitter on the air. The handset is normally con- nected to a radio set control but can be used locally at the transmitter.
The radio set control provides the capability to control certain transmitter functions and the receiver output from a remote location. Some control units con- tain circuits for turning the transmitter on and off, voice modulating the transmission, keying when using CW, controlling receiver output, and muting the re- ceiver when transmitting. A representative radio set control unit is shown in figure This setup is often found aboard ship when a transmitter or receiver is controlled from various locations like the bridge or combat information center.
Figure The transmitter transfer switchboard allows the re- to a remote control station and has 8 operating posi- mote control station functions and signals to be trans- tions. Positions 1 through 6 correspond to attached ferred selectively to the transmitters. Figure transmitters. The seventh position X allows for shows a transfer switchboard that allows the functions and controls of anyone, or all, of 10 remote control sta- switching of the transmitters to another switchboard.
Each knob corresponds the system. The receiver switchboard allows the audio outputs from the receivers to be transferred to remote control station audio circuits. A representative receiver trans- fer switchboard is shown in figure This switch- board contains 10 seven-position switches. Each switch corresponds to a remote control station and each switch position 1 through 5 represents a re- ceiver. Position X allows the circuits attached to the switch to be transferred to another switchboard.
An antenna can be simply apiece of wire; but in practice, other considerations make the de- sign of an antenna system complex. The height above ground, conductivity of the earth, antenna shape and dimensions, nearby objects, and operating frequency are just a few of the factors affecting the radiation field pattern. But, if the load is a position of a shaft must be transmitted from one loca- heavy load and more torque is required, torque power tion to another without an actual mechanical linkage. You have seen examples of this in mast-mounted rotat- amplification is required. A control system capable of ing directional antennas and the automatic tuning func- delivering larger amounts of power or torque is known tion of receivers and transmitters from remote as a servo mechanism, or servo.
A widely used method employs ac machines that operate as single-phase transformers. These ma- You will encounter many systems that use sychros chines are called synchros. In chapter 1, we discussed basic system requirements. In this chapter, we will look at each equipment configuration. We will then link them together, forming a block diagram of the systems covered. We will discuss naval equipment from extremely-low-frequency through super-high-frequency. We also will look at microwave communications, the Single Audio System, teletype equipment, portable and pack radio equipment, and the Communications Link Interface Planning System.
At various points in the chapter, we review basic principles associated with the larger topic. The purpose of those reviews is to refresh your memory, in case you have not worked in the area for sometime. Identify system equipment configurations and how they link together Recognize various extremely-low-frequency through super-high-frequency naval equipment.
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The lowest level designator, part, describes one piece, like a resistor. The following paragraphs Shipboard communications are now highly describe the various levels in greater detail. Nearly all the communications requirements for a ship can be met with fewer, more versatile, pieces of equipment. Recall from chapter 1 that a communications As communications equipment became more system is a collection of equipment used together to capable and complex, the need for an orderly process satisfy a specific communications requirement.
Further, of identifying equipment by designation became as the following paragraphs explain, a system is a apparent. The process that was developed identified combination of sets, units, assemblies, subassemblies, equipment from the system level down to the part and parts. The requirement placed on the system could level. The highest level designator, system, describes be to send or receive voice, cw, or teletype information.
An typical system to meet these communication example of a unit is the power supply. Two examples are radio subassemblies joined to perform a specific function. A receiving sets and radio transmitting sets. An assembly maybe operational function. A good example is an antenna considered a subassembly when it is part of a larger or coupler group. A computer keyboard is a UNIT good example. By itself, it is an assembly. However, it is also a subassembly in a total computer system. A UNIT is a combination of parts, subassemblies, Another example you are very familiar with is a circuit and assemblies mounted together that can normally card.
A PART is one component or a combination of two The principal use of the very-low-frequency vlf or more components. A part cannot normally be communications system is to provide fleet broadcasts disassembled without being destroyed. Resistors, to the submarine fleet and associated ships and capacitors, and transistors are examples of parts.
Additional uses are in long-range navigation and time and frequency broadcasts. This section separates that equipment into types of systems and Vlf transmission is normally considered a identifies typical equipment associated with each type broadcast; that is, a one--way transmission, with no of system. A typical vlf radio transmitting station is shown operating at normal mission speeds and depths.
Elf can in figure This allows submarines to operate below the surface, improving their survivability by The vlf receive system receives fsk and icw radio making detection more difficult. Most communications to the fleet requires operation on all surface ships no longer receive vlf broadcasts. The low-frequency band is used for However, you will probably find one of these receivers long-range direction finding, encrypted medium- and mounted somewhere in your message center or radio long-range communications, and aeronautical radio room.
However, the Multichannel Broadcast System, operating at high. It provides eight channels then be patched to a teletype printer for plain text of frequency-division multiplex rtty traffic on each printing, or to a reperforator, where a paper tape will be transmission. Low-frequency The high-frequency hf band is shared by many transmitters are normally used only on shore stations. Portions scattered throughout the band are assigned to the military. A typical lf receive system is shown in congestion and, for some types of service, has replaced figure The antennas receive the lf signal and send hf for long-distance communications, pushing hf into a it to the multicoupler and patch panel.
The back-up role. We will cover satellite communications antennas and connect them to various receivers. In the in chapter 3. These Naval communications within the hf band are receivers operate in the frequency ranges of 30 to grouped into four general types: point-to-point, ship- kHz and 14 kHz to 30 MHz, respectively. All but the fleet broadcast are normally operated two-way. As we explained earlier, Point-to-Point this allows the received audio to be connected to numerous pieces of equipment. A trunk is normally a message circuit signal to dc for use by the teletype tty equipment.
The signal can then be sent to system connecting two locations. The two locations any crypto equipment attached to the patch panel. The signal can chance of interference, and boost the sensitivity of the. With the path length and direction powered transmitters, lower noise receivers, and more fixed, propagation factors are simplified.
This efficient antennas. Fleet Broadcast Ship-to-Shore As the name implies, this service involves High-frequency atmospheric communications broadcast area coverage from shorebased transmitters between shore stations are relatively easy because to ships at sea. To overcome propagation problems, shore stations have sufficient space for efficient messages are sent on several frequencies at the same omnidirectional antennas or arrays that provide hf time frequency-diversity. Space-diversity with coverage of large areas. Ship-to-shore hf communica- physically separated receive antennas also helps tions are more difficult because the ship is moving and overcome propagation problems.
Shipboard HF Transmit To overcome these problems, ship-to-shore systems have two major differences from point-to- The high-frequency transmit signal can contain point systems. First, shipboard antennas are omni- either voice or teletype information. Figure shows directional. Second, several frequencies are usually a typical shipboard high-frequency transmit system. This signal is fed communications. A aircraft moves much more rapidly than a ship. Examples of improvements that SRT switchboard. The voice communications are can only be made to the ground station are higher developed at a handset connected to the C radio.
The output of the radio set control is then fed to the switchboard. The transmitter transfer switchboard allows operators to select the proper transmitter for the selected frequency. The antenna coupler matches the output impedance of the transmitter to the input impedance of the antenna.
Antenna couplers also allow more than one transmitter to be connected to the same antenna as long as certain conditions are met. When the signal reaches the antenna, it is radiated into the atmosphere. Shipboard Hf Receive fed to a handset. The voice signal also can be sent from A typical shipboard hf receive system is shown in the switchboard to an AM remote speaker figure A transmitted signal similar to the one amplifier and then to a speaker.
This allows the user to previously discussed is received by the antenna and listen to the signal without having to hold the handset. The teletype signal from the switchboard Vhf Transmit follows the same path used by the low-frequency signal we discussed earlier. Identical pieces of A typical vhf transmit and receive system is shown equipment are used.
The voice signal from the receiver in figure On the transmit side, the operator, at a switchboard is sent to the C radio set control and remote location, talks into the handset. The handset is. The switchboard performs communications.
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The output of the switchboard is connected to the The uhf system uses a transceiver. The transceiver converts separately. Although this description pertains to voice the input signal to an rf signal for transmission and the communications, uhf equipment can process tty data in rf is radiated into the atmosphere by the antenna. Vhf Receive Uhf Transmit Again, look at figure The incoming signal is picked up by the antenna. This signal is fed to the A basic block diagram of a uhf transmit system receive side of the transceiver.
The transceiver output is shown in figure On the transmit side of the is fed to the receiver transfer switchboard. The nonsecure voice system, the operator at a remote switchboard output is connected to either radio set location talks into the handset. The handset is control or to a speaker amplifier, AM, or both, connected to a C radio set control.
The RPU is connected to the secure voice matrix, which is the tie point for the connection of The ultrahigh-frequency uhf band is used for multiple remote phone units. The matrix output is fed line-of-sight short range command and control to the secure voice equipment that encrypts the communications. As we stated earlier, line-of-sight information. The transmitter switchboard performs the same This band is also used for satellite com- function we described for previous systems. The munications.
The voice equipment and decrypted. This output is fed to coupler output is then fed to an antenna. The secure voice matrix output is fed to the RPU, where the signal is converted Uhf Receive back to its original form. We will, therefore, identify by specific designator only the As we discussed in the previous chapter, two components that are unique to the receive function.
The receiver output is connected munications will be covered in the next chapter. It is following paragraphs, we will discuss line-of-sight then connected to either the nonsecure or secure voice and tropospheric scatter microwave communications. A simplex relay system pro- If a secure voice transmission is received, the vides one-way communications and consists of a output of the switchboard is connected to the secure transmitting terminal, a certain number of repeaters,.
Figure A shows you such take a look at a typical microwave transmitter and a system. A duplex relay system figure B receiver. This is A typical microwave transmitters shown in figure done by using different transmitting and receiving In operation, the output of a telephone multiplex frequencies and by using a duplexer in the terminal, which consists of a frequency multiplexed transmission line. AM carrier signal, is applied to the terminal transmitter.
This input signal baseband signal also The rf equipment in terminal and repeater stations could be a television signal or any other form of signal are basically the same. Terminal equipment can be to be transmitted. A pre-emphasis network accentuates converted to repeater equipment and vise versa. The insertion amplifier accepts portion of the output power back to the klystron to the signal, amplifies it, and then applies the signal to the compensate for its nonlinearity.
This technique allows klystron oscillator. With this method, the input signal for optimum performance with modulation densities as directly modulates the carrier frequency, resulting in a high as channels. You should be aware that solid- frequency-modulated wave. Propagation takes place in the lower A typical microwave receiver is shown in figure Though not shown, sensing and alarm functions atmosphere and is affected by meteorological factors.
The A line-of sight microwave system consists of one signal then enters a waveguide filter tuned to its fre- or more point-to-point hops. Each hop is designed to be quency, which rejects all other unwanted frequencies. Next, the signal passes through an isolator that minim- Los system characteristics are as follows: izes intermodulation noise and holds the VSWR below 1. The signal is then mixed with the local oscillator Propagation—Free space as affected by the tro- LO output to produce the standard MHz inter- posphere. The signal is also applied to an IF discrimina- Range—Usually 50 to km 31 to 95 statute tor, a de-emphasis circuit, and a squelch circuit that miles.
This depends upon antenna height, earth curva- disconnects the baseband amplifier and demultiplex- ture, and intervening terrain. After the squelch circuit, the signal passes through a RF Power—Usually less than 10 watts. Antennas—Both transmitting and receiving antennas are horn-driven paraboloids, providing high Microwave communications systems operating gain and narrow beam widths.
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In some applications, in the shf portion of the frequency spectrum use the plane reflectors are used with the paraboloids. Countermeasures—Because of antenna directiv- Application—Meets the communications re- ity, the system is difficult to jam. Additionally, the sys- quirements between HF sites within its minimum tem should not be susceptible to nuclear disturbances of skywave one-hop distance of about miles and line- the ionosphere. It is especially useful where conditions prevent the use of line-of-sight communica- Application—Because of the bandwidth capa- tions or if adverse propagation conditions interfere with bility and minimum site requirements, los is well other transmission methods.
Multiplexing refers to the simultaneous transmission At microwave frequencies, the atmosphere has a of two or more messages over the same medium or scattering effect on electromagnetic fields that allows channel at the same time. Multiplexing may be for over-the-horizon communications. This type of achieved in various ways, but the most common meth- communications is called tropospheric scatter, or ods are time-division multiplexing tdm and fre- troposcatter for short.
Troposcatter takes place mostly quency-division multiplexing fdm. Although several at low altitudes, but some effect takes place at altitudes types of multiplexing equipment are available in the of up to 10 miles. Each Time-Division Multiplexing Tdm is a method of hop is designed so it can be integrated into the combining analog signals for serial transfer. The signals worldwide communications network of the Defense are sampled at intervals and interwoven for transmis- Communications System DCS.
Troposcatter links sion. The speed of this multiplexed signal is faster than have the following characteristics: the original individual channel speed by a multiple equal to the number of combined signals. For example, if 5 signals are multiplexed, the data speed of each sig- Propagation—Free space as affected by the tro- nal must be multiplied by 5 to keep the signals in syn- posphere. Time-division multiplexing also can be used with Range—Up to km statute miles.
RF Power—High; up to 75 kilowatts depending upon bandwidth, quality, and range. Coverage—Point-to-point only. Unlike tdm, which samples a portion of the sine wave, frequency-division multiplexing fdm Antennas—Both transmitting and receiving transmits and receives for the full degrees of the antennas are horn-driven paraboloids providing high sine wave. A channel is subdivided into smaller gain and narrow beam widths.
Each subchannel carries a separate signal. You can find more gation. An secure shipboard voice communications system. It SAS installation provides the unique capability to consists of telephone sets, voice-signal switching de- communicate in a secure or nonsecure mode, at the vices, various control devices, and field changes to discretion of the operator, from a single telephone or existing equipment, in conjunction with other ele- NTDS device. This single audio interface with various ments of the overall shipboard radio communications crypto or plain subsystems is the essence of the SAS.
Figure shows the major equipment The system can notify the user of the transmit groups, subsystems, and their interrelationship. The The system can notify the user by visual indica- voice switching equipment and means provided for tion if the voice station equipment is not con- user control over circuit selection are the two primary nected to a crypto or plain subsystem.
There can be different types secure voice configuration. Equipment types and The user can select a voice channel and have it quantities are dictated by the communications indicated visually. These equipment are part of the overall exterior communications switching system and are located in An audio indication to the user when the voice the main communications spaces, generally in the switch built-in-test BIT detects a trunk line vicinity of the technical control working area.
The short. This review consists of reading all of the supplemental questions and ensuring that the materials presented meet minimum qualifications. Step 3: Eligible list is created. All candidates will be notified via email regarding status of their application. Only candidates who meet the minimum qualifications will be placed on the equally ranked eligible list.
You have 14 days from the notice of the examination results to let us know if you disagree with your results. Please read the City of Portland Administrative Rule 3. Step 4: Hiring manager and subject matter experts review applications materials of those on the eligible list. Timeline: approximately weeks Step 5: Interviews and Offer: Once the hiring manager has reviewed the applications they will reach out to schedule interviews and finally make an offer.
ALL candidates will be notified throughout the process via email. If you have any questions regarding the status of your application you are welcome to contact the recruiter on this recruitment. Veteran's Preference: Ifyou are requesting Veteran's Preference, as identified below, please describein your answers any transferrable skills obtained during your militaryservice and how they relate to each of the required minimum qualificationsunder the "To Qualify" section above.
Additional Information Additional Information Work Status: Non-citizen applicants must be authorized to work in the United States at the time of application. You must request Veterans' Preference AND include a copy of your documentation for each recruitment to which you apply. Veterans' Preference documentation must be submitted no later than PM on the closing date of this recruitment.
ADA Accommodations: If you identify as a person with a disability and would like to request a reasonable accommodation when applying for this job, please contact the Recruiter below for assistance. Equal Employment Opportunity: It is the policy of the City of Portland that no person shall be discriminated against based on race, religion, color, sex, marital status, family status, national origin, age, mental or physical disability, protected veteran status, sexual orientation, gender identity or source of income. The City values diversity and encourages everyone who is interested in employment with the City to apply.
Did you know? Follow the link for the most recent list of scheduled dates: www. Sep 09, By leveraging technology, Maricopa County will continue to improve internal operations and enhance services to its constituents.
Nevedtra 14088, Electronics Technician Volume 03- Communications Systems; Chapter 3
OET team members enjoy a dynamic, can-do spirit within the organization and an opportunity to make a lasting impact on the future of Maricopa County. As a key member of the Maricopa County family, this position provides a critical communications element necessary to keep the public safe. Position Qualifications We recognize your time is valuable, so please apply if you meet the following required qualifications : Education: High School diploma or GED. Experience: Three 3 years of experience in electronics which includes diagnosis, repair or hands-on experience installing mobile radios or other electronic systems in vehicles.
OR C ombined education and experience qualifications: An equivalent combination of post-secondary IT education may substitute for the required experience on a year-for-year basis. Other Requirements: Possession of a valid Arizona driver's license, or the ability to obtain one by time of hire, is required. Our Preferred Candidate has: Associate's degree in Telecommunications Technology or closely related field. Transmitter power and receiver sensitivity 3. Both 1 and 2 4. None of the above. Provides extension to terrestrial teletypewriter network 2.
Provides a communications link between submarines and shore terminals 3. Provides a communications network for transmitting general-service message traffic between ships and shore installations. One 2. Two 3. Three 4. Subsystems consist of two parts. What are they? Baseband equipment; rf terminal 2.
Multiplexing equipment; satellite 3. Satellite; rf terminal 4. Transmitters; receivers. In modes 1 through 6, what are the uplink and downlink frequency bands used in Fleet Satellite Broadcast? Hf; shf 2. Uhf; hf 3. Uhf; shf 4. Shf; uhf. What system do subscribers use to receive Fleet Satellite Broadcast? Group broadcasts 2.
Interval broadcasts 3. Network broadcasts 4. Timed broadcasts. Secure voice uses digitized voice with a 3-kHz voice channel. What type of voice modulation does this describe? Multiband 2. Narrowband 3. Singleband 4. When using Secure Voice, a ship must contact what authority before initiating communications with a shore command? Fleet controller 2. Group controller 3. Net controller 4.
Voice controller. Which of the following is a subsystem specifically designed for special intelligence communications? Receive only 2. Transmit only 3. Transmit and receive. SSIXS 3. Because the reception of TADIXS information by a ship does not require an acknowledgement, the ship can l operate in what type of environment and still receive message traffic? Emission control 2.
Emission quiet 3. Transmit control 4.