Wireless Oom » modulation http://wireless.pyncus.com Build and Share wireless technology Wed, 01 Feb 2012 15:38:03 +0000 http://wordpress.org/?v=2.8.4 en hourly 1 Why is bandpass modulation needed for radio transmission? http://wireless.pyncus.com/2009/06/24/why-is-bandpass-modulation-needed-for-radio-transmission/ http://wireless.pyncus.com/2009/06/24/why-is-bandpass-modulation-needed-for-radio-transmission/#comments Wed, 24 Jun 2009 23:58:35 +0000 wirelessoom http://wirelessoom.wordpress.com/?p=306 In other words, why is it necessary to carry a message waveform onto a carrier wave of much larger frequency than that of the message?
Is it possible to configure a radio with only a microphone, power amplifier and antenna?
wavelenth = light speed / frequency
Thus, for human voice (whose frequency is around 3000Hz),
wavelength = 3*10^8 / 3000Hz=100000m = 100km
The antenna size should be really large.
If carrier frequency is 3*10^9, then the wavelength is 0.1 meter which is a feasible and reasonable antenna size.
Furthermore, how you can differentiate your local voice and far away voice?
]]> http://wireless.pyncus.com/2009/06/24/why-is-bandpass-modulation-needed-for-radio-transmission/feed/ 0