Mike Gathergood (G4KFK) wrote:
Radium wrote:
What would these errors sound like?
An error in a PCM system would manifest itself as a difference between
what you put in at the analogue input to the transmitter, and what you
got out of the analogue output of the receiver.
The magnitude and polarity of the difference would depend entirely on
whether the bit error was the MSB (polarity would be wrong), or one of
the LSBs (the amplitude would be wrong). It wouldn't "sound" like
anything in particular.
What about the heterodyne tones present on analog AM radio? Would they
be audible on a linear-PCM receiver that receives PCM signals on an AM
station?
Well, my application was more to do with reception than transmission.
I'd like to know what I would hear on a 3MHz AM carrier whose receiver
[both the AM and the linear PCM part] is at its maximum bandwidth. The
3 Mhz AM receiver is attached to a linear-PCM receiver [once again,
both receivers have the maximum bandwidth possible for them]. The
linear-PCM receiver is attached to a DAC which converts the linear-PCM
signal to analog. This analog signal [which was PCM] is then sent to a
loudspeaker. Just to make things more interesting, the antennae and
receivers are so sensitive that they can pick signals as low as
.00000001 dB. Most likely, what would I hear?
Have a look he http://www.imdb.com/title/tt0375210/ :-)
Seriously though, I have no idea. Why don't you try it and post the
results here?
Easy for you to ask. I doubt any store has the device. And the
equipment required to amplify .00000000001 dB to an audible level would
take up the entire room.
So the best I could do -- at least for the moment -- is guess.
I am aware though that just because the PCM-receiver is digital does
not mean its completely immune to heterodynes, EMI, or RFI. If the
heterodyne, EMI or RFI has a waveform that sufficiently resembles a PCM
signal, it may very well be picked up by the PCM-receiver that is
connected to the AM receiver.
Physically, the digital reciever is still an electronic device and
hence it has some reception of EMI, RFI, and heterodynes. Its just not
affected as much as an analog receiver would be.
Cheers
Mike
I've seen that "white noise" movie. But thats more like Sci-Fi. Yet it
is one thing that gave me the interest to hear whatever is buried DEEP
in background noise.