Inputted is a sine sweep. Output at some sweep point starts to have another frequency, which is -fnyquist+fsignal (for fsignal smaller than 2*fnyquist), mixed in. This IS aliasing.
They all do. Amplitude or frequency of carrier carries amplitude of desired signal, say is a sample of desired signal. One cannot transmit fsignal on fcarrier smaller than 2*fsignal.
No. My words are the proper common meanings.
You still don't get it, do you? Aliasing can occur where sampling occurs. The presence of heterodyne tones does not guarantee that they are aliases, and so does not guarantee that sampling has taken place. No sampling means no aliasing, but intermodulation can create components at the same frequency as the first set of aliases would be if sampling had taken place.Grasso789 said:
Not true. Clearly you don't understand sampling, and perhaps do not understand AM radio. AM involves multiplication, not sampling. You can transmit fsignal on fcarrier smaller than 2*fsignal, but then you need to know the carrier frequency and phase to disentangle things at the receiver. You can use fcarrier=zero frequency! That is how SDR works.
You have fixated on the false idea that tape recording with AC bias involves sampling, therefore you assume that any heterodyne components are the result of aliasing and thus you deduce that the presence of aliases proves that sampling has taken place. This is a circular argument.
SDR often uses zero-IF techniques. You need to do more reading about radio. You could start by understanding AM. If you think AM involves sampling then you don't understand AM, so continue reading some more.
SDR often uses zero-IF techniques. You need to do more reading about radio. You could start by understanding AM. If you think AM involves sampling then you don't understand AM, so continue reading some more.
A sample is time-digital and space-analogue. Electrical sampling has been started with radio in the second half of the nineteenth century, an audible frequency modulating a HF carrier, used for morsing.
There are fully analogue computers, which calculate with reality. There also are semi-analogue ones, which calculate with samples, as for instance some CMOS bucket chain reverb machines. A/D converters sample and then rasterise, so the full-digital computer calculates with values.
In importance-diminishing order: Reality, samples, values.
There are fully analogue computers, which calculate with reality. There also are semi-analogue ones, which calculate with samples, as for instance some CMOS bucket chain reverb machines. A/D converters sample and then rasterise, so the full-digital computer calculates with values.
In importance-diminishing order: Reality, samples, values.
Every neuron in your brain is purely digital, either fully on, or fully off.
That means that everything you are able to perceive, every thought that you have, every emotion you experience - all are the result of 100% digital computations in your brain!
In short, every "reality" that you can perceive is the output of a digital signal processor that lives between your ears!
The idea that nature is entirely analog is appealing, but doesn't hold up when you look at it closely. Atoms are digital...sunlight (photons) act digital half the time...the smooth analog signal in a vinyl record groove is actually composed of rough clumps of tiny plastic grains, themselves composed of discrete vinyl molecules, in turn composed of discrete atoms.
-Gnobuddy
That means that everything you are able to perceive, every thought that you have, every emotion you experience - all are the result of 100% digital computations in your brain!
In short, every "reality" that you can perceive is the output of a digital signal processor that lives between your ears!
The idea that nature is entirely analog is appealing, but doesn't hold up when you look at it closely. Atoms are digital...sunlight (photons) act digital half the time...the smooth analog signal in a vinyl record groove is actually composed of rough clumps of tiny plastic grains, themselves composed of discrete vinyl molecules, in turn composed of discrete atoms.
-Gnobuddy
In principle, the width of the pulses in PWM is a (more or less) infinitely variable analog quantity, not quantized to discrete values.
In practice, "analog" electrical signals are made up of discrete packets of electric charge (electrons!), so if you look deeply enough, they are all quantized - a characteristic of a digital system. We're all familiar with this quantization in terms of the shot and thermal noise that it creates in our amplifiers.
I am not an expert on animal nervous systems, but everything that I have ever read about neurons says that they either fire, or they don't; yes, there is a transition in ion concentration over a short period of time, but the (analog) transition doesn't play a role in the end result - the neuron either fires, or it doesn't.
Also, from everything I've read, intensity is signaled by the number of neurons that fire simultaneously, not by modulating the strength of the signal from one neuron.
Not to lose the forest for staring at the trees: my point is that people often get into rigid mental positions about analog vs digital, but nature itself is pretty complex, and frequently displays both digital and analog characteristics.
I think this thread is perilously on the brink of disintegrating entirely into argument for arguments sake, which was perhaps unavoidable, given the topic. Perhaps it's time to let it fade away?
-Gnobuddy
Yes, safe bet -- I simply found your original description a little too simplistic and lost much of the subtlety. I think you covered it on round two well enough. 
(There's a lot that also goes into the sensitivity of propagation of synapses, inhibition and excitation that tend to be much more analog in nature)
(There's a lot that also goes into the sensitivity of propagation of synapses, inhibition and excitation that tend to be much more analog in nature)
Thou may read this anyway. Ordinary AM radio modulates amplitude of a carrier with a signal. If carrier and signal were the same, then modulation result were the square hence contain the doubled frequency. But radio uses a resonating sender and receiver, sending and receiving on a narrow frequency band, so this squaring would not work. Hence signal frequency must be much smaller than carrier frequency. Cut short, average carrier amplitude equals say is a sample of momentary signal amplitude.
Yet so many recordings are digital these days so I don't understand what the problem is, somewhere there are comments regarding someone playing digital tracks with a record cue at the beginning that totally fooled people. I suspect that unsighted these problems would go away...
Or maybe some aught to listen to the music more and their system less!
Or maybe some aught to listen to the music more and their system less!
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