Re: [amsat-bb] technical question

["Assi Friedman" <4x1kx@xxxxxxxx>]

FM in the time domain is:

FM=A*COS(2*Pi*(Fc+b*X(t))*t)

Terms used in as simple terms as I can use:
FM= modulated FM signal
A = Amplitude of the FM signal - will determine output power
COS() = Cosine function and units used to calculate value are in radians
b = beta, also known as modulation index. This sets the maximum deviation
a modulating signal cause
Fc = FM carrier frequency in Hz
X(t) = time domain function of the modulating signal
t = time
Pi = 3.14159265 (can't remember more)

If you want to transmit a 1KHz tone: X(t)= COS(2*3.14159265*1000*t)
If you want to do FSK logic '1' = +1, logic '0' = -1.
If you want to do GMSK, you take the FSK signal and filter it using a
gaussian filter.

Here is a nice link of from a cool RF guy:
http://www.rfcafe.com/references/electrical/frequency_modulation.htm

Modulation theory is a whole world of wonderful knowledge - I really find
it the most fun aspect of electrical engineering! But it also gets very
very complex. You can never stop learning!

If you want to really learn this, there are a lot of good texts or find
your local university and sit in on a "introduction to communications"
class. Most profs don't mind a sit in - as a matter of fact they like the
idea that someone actually WANTS to listen to them!

Assi
4x1kx/kk7kx


> Hi All,
>    I need help, I found the following below as the description of FM
> modulation...
>
> Thanks
> 73
> Kevin
> WA6FWF
> #19623
> ----
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