frequency responds of FM modulated signal

[Kristoff Bonne]

Hi,



I don't want to sound to much like a "lazy person", but can somebody 
help out with something I like to do with scilab?



In a couple of weeks, I will be giving a talk in our local radio-club 
here in Ostend on GMSK and D-STAR (ham digital voice).
As most of our members are not that technical, most of the talk will be 
about what GMSK looks like, how it is received by a FM tranceiver and 
how a D-STAR stream is structured.


I am just starting to learn DSP myself (and how to use scilab for that), 
so I know I am supposted to learn this myself, but I am a bit short on 
time here.


I like to do a simulation of a 2400 bps bittrain (0-1-0-1-...), FSK 
modulate it and get a frequency analysis of the result.
In addition to that, I like to do the same thing, but first apply a 
gaussian filter to the signal.


The goal is to show why a gaussian filter is applied in GMSK, i.e. to 
show that a GMSK signal is smaller then a plain FSK signal.

(I know, I can explain this in theory: the rizing and falling edge of a 
signal include high frequency, etc. etc. ... but it would be nice to 
have a visual way of showing this).

Is there a way scilab can be used for this?




Many Thanks in advance,

Kr. Bonne (ON1ARF)