From: John Woodgate
Subject: Re: How does a mixer work?
Date: Tue, 22 Oct 2002 17:42:55 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Tue, 22 Oct 2002 19:15:45 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Kevin Aylward
wrote (in <7Tbt9.2176$R24.email@example.com
r.ntli.net>) about 'How does a mixer work?', on Tue, 22 Oct 2002:
>With all due respect here, I see the issue here is that many are looking
>at this from a rather elementary view. Information theory is one of
>those high brow disciplines that you can not really understand by
>multiplying steady state sinewaves as you do in EE 101. Its all about
>random signals and the probability of detecting them. One really needs
>to look at this from more advanced standpoint.
I disagree. The subject is simple. Throwing advanced stuff at it just
confuses. In one representation there is a signal of varying amplitude,
in another there are three signals, one of which has constant amplitude.
These representations are exactly equivalent, and one is not more
equivalent than the other.
If this is not understood by students, they become hopelessly lost when
considering the infinite spectra of FM signals. They have a constant
amplitude in the time domain (oscilloscope display), but the spectrum
shows the carrier frequency amplitude varying, and even going to zero
under some conditions.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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