Crystal Radio
Explore the process of uploading crystal radio spreadsheets in Lab 7. This tutorial covers the detailed steps for uploading, including important tips and considerations. Don't miss out on this opportunity to enhance your radio project skills. Follow along with clear instructions and make the most of this exclusive upload session happening today only!
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Presentation Transcript
Lab 7: Crystal Radio Spreadsheet Upload Only Today
Signal Flow Through the Radio Due to bandwidth limitations of the earpiece, it averages over the fast oscillation and gets zero without the diode. The amplitude modulating frequency is slow . The carrier frequency is fast compared to the response of the earpiece.
Fourier Series Fourier Series can be used to represent any periodic function with period T f(t)= a0+ cos(nwt)+bnsin(nwt) an n=1 T/2 T/2 T/2 a0=1 an=1 bn=1 f(t)cos(nwt)dt f(t)sin(nwt)dt f(t)dt T T T -T/2 -T/2 -T/2 w =2p = 2p f T
Fourier Synthesis Example: Square Wave In the time domain time t - - - - - 0 p 2t 3p 2t 5p 2t 2+2k -1 +1 +... f(t)=k T = 4 cos 3cos 5cos = 2 /4 = /2 p In the frequency domain In general, coefficienents can be complex numbers, so usually plot |c|^2 Frequency
Fourier Transform Fourier Transform is the Fourier Series in the limit as period T goes to infinity ?(?)?????? ? ? = ? ? = ?(?)? ????? Variables related this way very important in quantum mechanics
The Need for Windowing in FFT Windowed Incomplete periodic signal Complete periodic signal Incomplete periodic signal
Effect of scope limited time range/Window options see http://www.physik.uni-wuerzburg.de/~praktiku/Anleitung/Fremde/ANO14.pdf
Tips Power up the amplifier using the shielded probes Avoid a short circuit! 30 kHz 30 kHz Lights ON The electronic ballast in the fluorescent lights creates a strong 30 kHz signal, and many harmonics, when the lights are ON Lights OFF
