Noise Is 3 Orders of Magnitude Greater Than A Wave Form

Feel free to take your meds.

If the medium has different attenuation at different frequencies, emphatically no. The measured attenuation will be the attenuation at the modulating carrier frequency (complicated by sidebands) and not the attenuation of the baseline signal. Your proposed modulation (multiplying by a sin^2 waveform) is even more complex than regular AM, because it includes a baseband component too. Radio stations filter that bit out.

(Actually, to get the full solution, you'd have to compute the entire spectrum of the complex modulated signal, and run each spectral line through the transfer function of the process, then recombine. Could get messy.)

If the attenuation is flat over frequency, why bother to modulate? Just measure at a high frequency, above the range of the bandlimited noise.

You can't fool Mother Nature with simple tricks.

John

How would that change the overall strategy? Even the original low frequency signal without noise is attenuated somewhat by the medium.

The real problem is getting a really precise 4 - 5 sig fig reading from the receiver to be able to have something meaningful left over after the noise is subtracted out.

. . .

In this case it isn't flat. High frequency waves are attenuated more than low frequency.

. . .

At least two famous physicists including Hawkings say that it's impossible to destroy even the smallest part of a signal no matter how hard you try.

I could be walking down the street minding my own business and get _ambushed_ by this 2 nano volt signal.

Bret Cahill

Just admit to yourself what is obvious to everyone else. You never had any interest in this subject in the first place.

The dunces are like a bunch of chickens or school of mackerel. They are attracted to anything shiny.

Then they reveal that they are dunces.

Bret Cahill

"When a true genius appears in the world, you may know him by this sign, that the dunces are all in confederacy against him."

-- Jonathan Swift

Yet more babble.

"When a true genius appears in the world, you may know him by this sign, that the dunces are all in confederacy against him."

-- Jonathan Swift

But the modulated signal doesn't have the same spectral components of the original (baseband) signal. If the attenuation is different at higher frequencies, the modulated signal isn't a surrogate for the low frequency attenuation. If the attenuation measurement at high frequencies is still useful, just use a high frequency signal, bandpass filter, and dump the modulation concept.

Then the modulated signal is not representative of the low frequency attenuation.

I'm working on a wideband preamp (audio to 20 MHz) looking for a roughly 1 nv signal. About the best wideband amps you can build have a nv of noise per root Hertz of measurement bandwidth, if, IF you do everything right.

You're bumping up against fundamental sampling and information theory limits. It's like conservation of energy: all sorts of tricks look feasible, but every one is blocked by nature, in simple or sometimes very sneaky ways.

John

It doesn't need to be identical in every respect.

That would depend on how much it is attenuated.

Even if it wasn't it could still yield a useful number.

There no mystery to this. A simple error analysis will show a

If they ever quantified the measurements/determinations made at the Wimbledon men's finals, i.e. the d theta/dt of the racket, the sig figs might be higher than the $ figs.

Bret Cahill

But the fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown.

Carl Sagan

It's an unconventional way of implementing a filter, but it's still a filter, and the end result will be equivalent to using some conventional filter to separate the carrier from the noise.

I'm not saying your technique won't work. Quite likely it could be made to work. But it won't work any *better* than using conventional AM modulation and filtering. It can't, for fundamental mathematical reasons.

It would be interesting if it's unconventional.

I came up with it a few minutes after the OP killing time because of a delay.

The system will not respond in the same way as to a conventional AM wave form.

For one thing, higher frequencies are attenuated more than lower frequencies.

The higher frequency here only changes sign as often as the signal wave so the media doesn't "see" a +/- high frequency AM wave but something much like the original low frequency signal.

Bret Cahill

"When a true genius appears in the world, you may know him by this sign, that the dunces are all in confederacy against him."

-- Jonathan Swift

But the fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown. Carl Sagan

Carl Sagan was the Bozo the Clown of science...

"So what if I'm a clown?"

-- Nietzsche

A good clown is much more likely to be a genius that the average person.

Bret Cahill

Carl Sagan was the Bozo the Clown of science... ==================================== Took over from Einstein, did he?

Sagan was a Nobel laureate?

Bret Cahill

Sagan, supposedly a popularizer of astronomy, was not really all that competent at public relations or politics either.

I once mentioned the nuclear winter theory -- it may be perfectly valid science -- that the well intentioned Sagan thought would disuade the monied interest classes from supporting Reagan's defense buildup. The democratizing effects of global nuclear war would be a political monkey wrench.

Would that tactic work?

My father went nuclear on that one:

BRET, THAT'S THE MOST STUPID IDEA I'VE EVER HEARD OF IN MY ENTIRE LIFE! THAT WILL N E V E R WORK. THEY'LL BE GRABBING AFTER THE MONEY RIGHT ON UP UNTIL THE SECOND THE BOMBS GO OFF . . .

I fled the house at that point.

Bret Cahill