One electric circuit produces the audio signal - Sound waves are converted into electrical signals Another circuit creates a carrier signal (function of a carrier wave; to carry info from one place to another as an EM wave) A third circuit creates a modulated signal i.e. the two – previous signals are together “added” The carries speech and music and has a low, varying audio signal frequency. The is an electrical signal with a high, constant carrier signal frequency. and signal both have a high frequency. Carrier modulated OUTCOME 3 3.4 Plan, choose equipment or Background information: resources for, and perform a AM radio waves investigation to compare the Have relatively LOW frequency but LONG wavelengths quality of reception of AM and FM Long wavelengths allows for AM to diffract (bend radio waves around objects) with little loss of energy Useful when broadcast radio waves are needed Travel in straight lines Reflect off a layer of the atmosphere called ionosphere: allows for OUT-OF-SIGHT transmission useful in long distance communication Useful to carry only voice transmissions (quality of sound broadcast is relatively poor) Susceptible to interference e.g. storms can severely affect the quality Advantage AM circuitry is not overly complicated, cheap and – readily available / Disadvantage crowded with users – FM radio waves Have relatively LOW frequency SHORTER wavelengths than AM waves therefore they do not diffract as well objects reduce signal strength Travel in straight lines but spread out from a point source Must be LINE-OF-SIGHT as they do NOT reflect off Carry more information than AM waves higher frequency than AM waves Generally higher quality than AM EXPERIMENT COMPARING FM AND AM Independent variable type of signal –
One electric circuit produces the audio signal - Sound waves are converted into electrical signals Another circuit creates a carrier signal (function of a carrier wave; to carry info from one place to another as an EM wave) A third circuit creates a modulated signal – i.e. the two previous signals are “added” together The audio signal carries speech and music and has a low, varying frequency. The carrier signal is an electrical signal with a high, constant frequency. Carrier and modulated signal both have a high frequency. OUTCOME 3 3.4 Plan, choose equipment or resources for, and perform a investigation to compare the quality of reception of AM and FM radio waves Background information: AM radio waves Have relatively LOW frequency but LONG wavelengths Long wavelengths allows for AM to diffract (bend around objects) with little loss of energy Useful when broadcast radio waves are needed Travel in straight lines Reflect off a layer of the atmosphere called ionosphere: allows for OUT-OF-SIGHT transmission useful in long distance communication Useful to carry only voice transmissions (quality of sound broadcast is relatively poor) Susceptible to interference e.g. storms can severely affect the quality Advantage – AM circuitry is not overly complicated, cheap and readily available / Disadvantage – crowded with users FM radio waves Have relatively LOW frequency SHORTER wavelengths than AM waves therefore they do not diffract as well objects reduce signal strength Travel in straight lines but spread out from a point source Must be LINE-OF-SIGHT as they do NOT reflect off Carry more information than AM waves higher frequency than AM waves Generally higher quality than AM EXPERIMENT COMPARING FM AND AM Independent variable – type of signal
Senior_Science_Notes_-_Information_Systems_2.docx