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33 Cards in this Set
- Front
- Back
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Name 5 forms of wired communications |
Single wire Twisted pair Coaxial cable Hollow waveguide Fibre optical cable |
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Name 5 forms of wireless communication |
Uhf Vhf Lightwave (laser) Microwave Satellite |
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Electromagnetic frequency spectrum |
30 Ghz - 300Ghz: EHF 3 Ghz - 30 Ghz: SHF 300 Mhz - 3Ghz: UHF 30Mhz - 300Mhz: VHF 3Mhz - 30Mhz: HF 300Khz - 3Mhz: MF 30Khz - 300Khz: LF 3Khz - 30Khz: VLF |
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Draw a time domain diagram of 60Hz |
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What's the equation to calculate wave length? |
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Draw and fully label a frequency domain diamgram for radio stations in auckland |
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What are the three types of comms systems? Explain them and give and example. |
Simplex: information only one way e.g. Television Half-duplex: information two ways but only one at a time e.g. Walkie-talkies Duplex: information two ways simultaneously e.g. cellphone calls |
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What four requirements satisfy the aim of naval comms |
Security Speed World wide coverage Continuous availability 24 hrs a day |
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What factors affect radio comms |
Reliability Propagation effects Security Vulnerable |
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What do all radio transmitters consist of? |
Transducer Modulator RF oscillator Power amplifiers |
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Define an am wave |
The amplitude of the signal is changed in line with the instantaneous intensity of the sound |
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Draw a time domain diagram of the AM modulated waveform for a 50% and 100% modulated waveform. |
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Draw the block diagram of a basic transmitter |
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Given the power of an AM signal is 50 watts, Draw and fully label a frequency domain diagram for the DSB AM signal. Use 40% modulation. |
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Draw and label a frequency domain diagram for a 7MHz signal modulated by 2Hz to 20Hz |
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Draw and label the filter method for an SSB transmitter |
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Draw and label a block diagram for a SSB transmitter phase shift method |
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Define frequency deviation (Δf) |
The amount of frequency change of the the carrier from the carriers resting frequency. This change or deviation is determined by amplitude of modulating signal |
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Define modulating Frequency (fM) |
Determines the rate at which the FM swings above and below the carrier frequency |
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Define modulating index (mf) |
The ratio of the frequency deviation of the carrier, to the modulating signal frequency determines the transmitted power of the carrier power to power of the side frequencies or bandwidth |
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Equation to calculate modulating index |
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Use a diagram to explain frequency modulation |
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Draw a diagram showing the FM frequency spectrum for various levels of modulation while keeping the modulation frequency constant (ie sine wave). Use mf of 0.5, 1.0, 2.5 and 4.0 |
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Draw a diagram of an FM broadcast carrier with guard |
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Draw the block diagram of a low-level transmitter |
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Draw a block diagram of a high level transmitter |
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Using a diagram, explain pre-emphasis |
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What is the equation for percentage modulation |
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Draw a simple receiver |
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Draw a block diagram for a TRF receiver |
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Draw the block diagram for the AM superheterodyne |
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Name & describe the purpose of the AM superheterodyne parts (need to zoom to see all answers) |
Antenna: pick up RF and pass it on to the RF amplifier RF stage: tunes and amplifies received signal (fc) Mixer: has two inputs (fc & flo). Output is flo-fc and is called the intermediate frequency (455 kHz) Local Oscillator: oscillate at a determined frequency and pass on that frequency (flo) to the mixer. I.F. Amplifier: amplifies the intermediate frequency (flo-fc) Detector: remove intelligence from the international frequency. Automatic Gain Control (AGC): Automatically adjusts the gain of the RF stage and IF stage due to input variations. Audio and Power amplifiers: Amplify the remaining intelligence with sufficient power to drive a speaker. Speaker: reproduce the amplified signal. |
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Draw an FM superheterodyne |
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