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Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
Radium wrote: Mike Gathergood (G4KFK) wrote: Radium wrote: My question: Will the received PCM audio signal remain noticeably "clean" to the listener or will he/she notice the EMI, RFI, and heterodynes affecting the audio? I ask because I think -- but definitely don't know -- that because the received signal is digital, it is less likely that the EMI, RFI, and heterodynes would cause noticeable auditory disruptions when compared to analog. Do I guess correct? You guess correct, assuming that FEC is applied to the digital signal before it is used to modulate the transmitter. What if FEC is not used? With no FEC, your receiver would be more prone to those errors that you were worried about in the first place. But you wouldn't do it that way anyway. Raw PCM is too bandwidth inefficient. You'd use MPEG layer 2, or apt-X, or something like that to reduce the bandwidth without noticeably degrading the audio quality. You'd probably also multiplex several different channels (programmes) together onto one RF carrier as well, to make better statistical use of the RF bandwidth. Just to amplify on this, anything that you can do to reduce the bandwidth of the digital signal before it's used to modulate the transmitter will help. One very big advantage is that you can wind down the bandwidth of the receiver, thus reducing the level of background noise in the system. Why did you choose 3MHz? What's the application? Cheers Mike |
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