Side Band-less Modulation?

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BR-549

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Hello, I read an article a while back where someone had come up with a film or a paint coating, that can prevent the passage of an electric field and a magnetic field....stop all EM fields. It was quite impressive. It can shield circuits from external interference or induction. And later, they found that if they added graphene tubes in a rarefied mat within the film.......they could modulate the passage of EM thru the film.....with a small current.

In conventional AM, one ac signal is electrically beat with another to form sidebands. And the need for channels comes to be. A bandpass.

What if we painted an antenna with this film. And then modulated the antenna with film current. Would sidebands be created, or would we have a true amplitude modulation of the carrier, and no sideband generation? And truly AM one skinny frequency. A bandpass of one.

Do you think it's possible? Shield modulation.
 
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I find the claim extremely dubious. Can you provide a link to such an article. Creating an equipotential surface with a metal barrier is conceivable, but the magnetic shielding is something else again. Most ferro-magnetic materials e.g. iron, nickel, and cobalt can reduce or redirect magnetic field strength but lack to ability to eliminate it entirely.
 
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That's what I thought too. But in the last 2 years or so, I have come across several articles about this, and the various methods, and the effects of such. And the different frequency characteristics.

I read so many different sites, I don't save a history. But I just did a quick search for EMF films and got many results. I did not go down thru those results.

Some of these new films can do some amazing functions. One of these films can be sprayed on a structure, when cured and small current applied, can map the stress on the structure continuously. This is a marvelous tool. They say the components are common and the application cheap. From bridges to submarines. The film can be applied between coatings.

But the film I want to see applied was the passive cooling films. Which absorb light and heat, and then re-emit at the 8-10 um IR slot out into space. No power required except the shine from the sun. Didn't mean to get off track.

If that film can truly block EM, it would be worth playing with. And one would think we would see it in circuit design shortly. A dream come true for many.....I would think.
 
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Your inability to provide even a single link related to such things greatly damages your credibility.
 
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If any modulation is involved, there are side bands.

No sidebands, no modulation.

If you filter the sidebands from an AM signal what have you got left?
Just the carrier, a single frequency of constant amplitude.

JimB
 
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BR-549 said:
would we have a true amplitude modulation of the carrier, and no sideband generation?
Click to expand...

That's a contradiction in terms.
"True" amplitude modulation has sidebands, which is generated by multiplying the modulation frequency and carrier frequency together.
It's the sidebands that carry the information so, as stated, no sidebands, no modulation, and no information transmitted.
You can suppress the AM carrier and transmit only one of the sidebands as in SSB, but you always have the sidebands.
 
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Well pardon me Papa. I thought maybe people here might know more about what I had read.

Let's install a film cylinder around a vertical AM antenna. Energize constant carrier. The emission has already been made without modulation. A clean single F. Now we vary the amplitude of an already emitted propagation..........without any physical or common electrical connection. Or interaction.

We modulate the path of signal, not the signal itself. Do you think that we would still get sidebands with that setup? What if we put the shield half way between TX and RX. Would the RX see sidebands? From a blinking shield?
 
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BR-549 said:
Would the RX see sidebands? From a blinking shield?
Click to expand...
Yes.

If the amplitude of the sine wave varies - it is no longer a "perfect" sine wave, it has been distorted. You cannot vary the amplitude without distorting the sine wave while the variation is happening.

That variation is additional frequencies, proportional to the rate of change, if you analyse the signal spectrum; sidebands.
 
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This is interesting and confusing. I was taught that all amplitudes of all emissions was continuously decreasing with propagation. Even found a universal rate. So just propagation itself causes distortion.....a distance distortion. Or a propagation distortion. I never thought of it that way.

I was thinking once the propagation was done, sidebands could not be attached to it. Or made from it. If two radio waves meet and superposition, they do not beat or make sidebands......from what I have read. But they can vary amplitude with phase. And then go on about their way, as if nothing happened.

I was hoping for skinny channels and slot receivers. A quiet place.

Edit: What would one call a singular signal that only the amplitude varied? AM would be perfect, but it's already taken.
 
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BR-549 said:
Well pardon me Papa. I thought maybe people here might know more about what I had read.

...
Click to expand...
I don't spend a great deal of time reading about the crap every Tom, Dick, & Harry manage to dream up. We are constantly bombarded with extraordinary claims and fantastical theories. Such claims require extraordinary evidence to gain any credibility. You have provided exactly NONE of that. Your lack of fanboys seems to bolster my position.
 
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BR-549 said:
What would one call a singular signal that only the amplitude varied? AM would be perfect, but it's already taken.
Click to expand...
But that is exactly what it is and what it's called.
You are trying to differentiate between AM modulation and varying the carrier amplitude but there is no difference.

Sidebands aren't "attached", they are an inherent property of varying the amplitude of a sinewave.
The sidebands appear in the frequency spectrum alongside the carrier frequency.
They can only be seen in the frequency domain (e.g. a spectrum analyzer), not the time domain (e.g. an oscilloscope).
You literally cannot vary the amplitude of a sinewave without generating sidebands.
You can attenuate the signal without generating sidebands, but that is not the same as varying the amplitude with some modulating signal.
 
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MXene rf shielding film. Here are a few links.


Containing our 'electromagnetic pollution': MXene can protect mobile devices from electromagnetic interference

If you've ever heard your engine rev through your radio while listening to an AM station in your car, or had your television make a buzzing sound when your cell phone is near it, then you've experienced electromagnetic interference. This phenomenon, caused by radio waves, can originate from...
phys.org

Blocking radio waves and electromagnetic interference with the flip of a switch

Researchers have developed a thin film device, fabricated by spray coating, that can block electromagnetic radiation with the flip of a switch. The breakthrough, enabled by versatile two-dimensional materials called MXenes, could adjust the performance of electronic devices, strengthen wireless...
www.sciencedaily.com

There are dozens of different types with various characteristics.

Search for MXene rf shielding film, for many results for the last couple of years.

Sorry for the 1st recommended search suggestion.

Enjoy.
 
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BR-549 said:
that can prevent the passage of an electric field and a magnetic field....stop all EM fields.
Click to expand...
BR-549 said:
There are dozens of different types with various characteristics.
Click to expand...

Nowhere does it make any claim that it can stop magnetic fields.


They are EM - Electromagnetic - shielding materials, which the article itself compares to such as copper shielding, just much thinner and lighter.

It is NOT "Magnetic" shielding, that would be a totally different thing.

EM shielding blocks photons and electrostatic fields, not electrical current (the material conducts) or magnetic fields.

Other than the "switchable" ability, if that works as implied, it does just the same as a coating or layer / sheet of metal shielding would do.
 
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BR-549 said:
I was taught that all amplitudes of all emissions was continuously decreasing with propagation. Even found a universal rate. So just propagation itself causes distortion.....a distance distortion.
Click to expand...

The relative amplitudes of each part of the waveform are not being changed in that case; there is no "modulation" or distortion effect, just due to a different overall signal level.

You are not changing the waveform "shape", to put it another way.
 
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