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From: email@example.com (Gibbo)
Date: 22 Oct 2002 11:46:16 GMT
Organization: AOL, http://www.aol.co.uk
Subject: Re: How does a mixer work?
"Kevin Aylward" firstname.lastname@example.org wrote:
>"Fred Bloggs" wrote in message
>> Chuck Simmons wrote:
>> > At this point I take a stand against the hidebound conventionalism
>> > is the application of mathematics to engineering. I am very
>> > this because I have no engineering education whatever and ALL
>> > mathematical statements engineers make can be considered suspect
>> > of the hidebound conventionalism.
>> > Consider the equation:
>> > (1+sin(w1*t))*sin(w2*t)=sin(w2*t)+(sin((w2-w1)*t)+sin((w2+w1)*t))/2.
>> > This is really an identity. The left hand side says that the carrier
>> > varies in amplitude according the the operations on the field of
>> > numbers. The second says that, fully equivalently, there are three
>> > constant frequencies and amplitudes.
>> > It is pure hidebound conventionalism that says that though the two
>> > of the equation are correct, the right hand side is more correct.
>> > mathematical hogwash. There can be no justification for that sort of
>> > narrow thinking.
>> If the early developers adopted your perspective, there would be no
>> sideband communication.
>I do actually remember some stories like this, vaguely. Apparently,
>people were sceptical that sidebands were real, and that if you had a
>really sharp filter you could still recover the modulation. This was, I
>understand even experimentally "proven". In reality, they just did not
>use a sharp enough filter.
Just to throw a spanner in the works......
One side says "the carrier alone carries no information".
That's not strictly true. If you didn't know you needed to re-insert the
carrier at the receiving end you'd never be able to receive the transmitted
information. Now some people will say "but we already do know that we need to
re-insert the carrier". Well... that's like saying "we already know what's in
the sidebands, so we know what information is in them, so we don't need them,
so they don't carry any information either"
The carrier does carry some information. It carries the information of "this is
the carrier that you need to insert in order to demodulate the sidebands"
If you insist in filtering the carrier with an almost infinitely narrow filter
to prove that it is useless then try the same thing with one of the sidebands
and see how much information you can get out of it.
No flames please :)
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