AM electromagnetic waves: 20 KHz modulation frequency on anastronomically-low carrier frequency
"Don Bowey" wrote in message
...
On 7/4/07 7:52 AM, in article ,
"Ron
Baker, Pluralitas!" wrote:
snip
cos(a) * cos(b) = 0.5 * (cos[a+b] + cos[a-b])
Basically: multiplying two sine waves is
the same as adding the (half amplitude)
sum and difference frequencies.
No, they aren't the same at all, they only appear to be the same before
they are examined. The two sidebands will not have the correct phase
relationship.
What do you mean? What is the "correct"
relationship?
One could, temporarily, mistake the added combination for a full carrier
with independent sidebands, however.
(For sines it is
sin(a) * sin(b) = 0.5 * (cos[a-b]-cos[a+b])
= 0.5 * (sin[a-b+90degrees] - sin[a+b+90degrees])
= 0.5 * (sin[a-b+90degrees] + sin[a+b-90degrees])
)
--
rb
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