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why dont we transmit digital signal in the air?
Because any transmitted signal needs a carrier which does as its name implies. You just can't start transmitting 1s and 0s.
Ron
But all these schemes still modulate a carrier with the 1s and 0s.Well, actually we do all the time. It's called "spread spectrum communications". Cell Phones, WiFi,Wireless home telephones, and the GPS satellite system all use it, for example...
Well, actually we do all the time. It's called "spread spectrum communications". Cell Phones, WiFi,Wireless home telephones, and the GPS satellite system all use it, for example...
communication
why dont we transmit digital signal in the air?
But all these schemes still modulate a carrier with the 1s and 0s.
Perhaps we talking semantics here, but if the signal is not at baseband (the original signal frequency components), then it's a signal modulated unto a higher frequency carrier. You may not be find anything that looks like a "carrier" signal in the spectrum since modern digital modulation methods use a suppressed carrier (to conserve power), but that doesn't mean there is not a carrier. With a suppressed carrier, the signal will appear as some band of modulation frequencies centered at, or on one side of the carrier (SSB-SC for example). If you don't think there's a carrier, try demodulating these signals without some method of regenerating the carrier signal in the receiver.Look at the GPS signal, for example, with a spectrum analyzer. I challenge you to find anything that looks like a "carrier". Ditto WiFI.
True.Look at the GPS signal, for example, with a spectrum analyzer. I challenge you to find anything that looks like a "carrier". Ditto WiFI.
Turning the carrier on and off with a digital signal is a form of modulation. If you look at the RF spectrum you will see the carrier plus harmonics of the on/off frequency.Let's get simple and think on-off keying. Carrier present =1, no carrier = 0 and through a chain of of ons and offs with some delineation we can pass information. I really do not understand this question. RF communication can be a form of serial data communication much like RS-232. So I don't get the question I guess, but I am in agreement with Mike at this point. Not the me Mike, the other Mike![]()
Because any transmitted signal needs a carrier which does as its name implies. You just can't start transmitting 1s and 0s.
Ron
That's not the only disadvantage. The other disadvantage is that you would be interfering with other legitimate signals in the spectrum and would soon draw the close attention of the FCC. The purpose of modulating a signal is to keep it in an assigned frequency spectrum and bandwidth as designated by the FCC. Operating outside these limits is illegal.so, that means we can transmit Digital signal means 1s and 0s in the air...! according to the ans of ajitkumar...!
if it require more bandwidth, this is the only disadvantage in digital communication.... isnt it....!