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Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
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. 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? Cheers Mike |
Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
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. |
Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
On 9/12/06 3:57 PM, in article
, "Radium" wrote: 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. There is no such thing as a .00000000001 dB signal 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. In fringe areas, analog cell phones could be well understood despite the poor signal-to-noise ratio. Digital cell phones in a fringe area just quit working, or lose sync and you hear bits of other conversations. 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. |
Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
Don Bowey wrote: On 9/12/06 3:57 PM, in article , "Radium" wrote: 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. There is no such thing as a .00000000001 dB signal Whats stops a .00000000001 dB signal from existing? 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. In fringe areas, analog cell phones could be well understood despite the poor signal-to-noise ratio. Digital cell phones in a fringe area just quit working, or lose sync and you hear bits of other conversations. 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. |
Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
"Don Bowey" wrote in message
... There is no such thing as a .00000000001 dB signal Sure there is. It's very close in amplitude to a 0.0dB signal. ;-) Tim -- Deep Fryer: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms |
Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
On 9/12/06 10:04 PM, in article , "Tim Williams"
wrote: "Don Bowey" wrote in message ... There is no such thing as a .00000000001 dB signal Sure there is. It's very close in amplitude to a 0.0dB signal. ;-) Tim Yes Master.... I had a momentary lapse of acumen, but it is clear now. dBm to the people. :-) |
Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
"Michael A. Terrell" wrote in message
... dB without a reference is meaningless. How can you have a ratio without a reference? Easy. "dB" in general usually refers to acoustic power, where the reference is some ungodly small power level (10^-12W/m^2 IIRC?). I forget if there's a similar radio context used... Tim -- Deep Fryer: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms |
Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
The answer is this:
It would be far more suceptable to interference than the AM equivalent. The far higher bandwidth gives you a far higher noise bandwidth than the narrower AM equivalent. So because of the large bandwidth, AM would beat it hands-down. Sam |
Receiving Pulse-Code Modulation on AM radio at 3 Mhz?
"Radium" wrote in message oups.com... 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? I think you need to be a bit clearer in your thinking. I see several people have commented on your use of dB and it seems Mike dealing with the digital side so I'll not pick up on those. I'd like to comment on " the antennae and receivers are so sensitive that they can pick signals as low as........" and your other comment about wide bandwidth. Firstly, a "sensitive antenna" isn't a good concept, better to think in terms of gain. However, more importantly, sensitivity isn't just about how "small" a signal your receiver system can "pick up"- you can (in theory) just add more and more gain. The issue is the ratio of the signal to the noise- that is the noise your receiver introduces and that which is "picked up" by the antenna. Winding up the gain doesn't help much with the latter- the noise in the available bandwith is amplified as well. Often a good way to get a better signal to noise ratio is to reduce the bandwidth so, before you get too hung up on having a wide bandwidth, think about what you need to do the job. I also notice someone mentioned Galois- there was a thread some time back in uk.radio.amateur where I explained the maths behind these. I'd sure a search of Google Groups will turn it up. -- 73 Brian www.g8osn.org.uk |
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