Mike Gathergood (G4KFK) wrote:
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.

What would these errors sound like?




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?

44,100 X 24 = 1,058,400

1,058,400 bps requires that the frequency of the carrier be at least
2,646,000 Hz. To make it safe, use 3 MHz.

What's the application?

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?


Cheers
Mike

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

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.

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.

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.

On 2006-09-13, Radium wrote:


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?

Nothing, it's just indistinguishable from a 0db signal.

In other words it's about half the amplitide of a 3db signal...

It's a logarythmic scale.

Bye.
Jasen

jasen wrote:

On 2006-09-13, Radium wrote:

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?

Nothing, it's just indistinguishable from a 0db signal.

In other words it's about half the amplitide of a 3db signal...

It's a logarythmic scale.

Bye.
Jasen


No, without a reference, its use is meaningless. He was trying to
use dB for an absolute signal level, not a ratio.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

"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

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. ;-)


dB without a reference is meaningless. How can you have a ratio
without a reference?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

"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