discuss-gnuradio
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Discuss-gnuradio] fm, vector_source


From: Chuck Swiger
Subject: Re: [Discuss-gnuradio] fm, vector_source
Date: Sat, 25 Sep 2004 09:50:59 -0400

At 11:20 PM 9/24/2004 -0700, you wrote:
On Fri, Sep 24, 2004 at 05:28:25PM -0400, cswiger wrote:
> Hello -
>
> Q: How is gr.frequency_modulator_fc() used? I see it takes
> a 'sensitivity' arg, a float signal in and produces a complex out.
> What is being frequency modulated how?
>

If you look in CVS, gnuradio-examples/python/usrp1/fm_tx4.py
implements a four channel FM transmitter.  [Each instance of the
pipeline ought to have a "pre-emphasis filter", but that's just an
IIR.  The output is perfectly intelligible without it.]

Eric


Ok, I see - the modulator prepares a signal from the audio that is *later* mixed
with your local osc to create the FM signal. I was confused by something
called a 'modulator' with only one signal input ;)    The examples help a lot.
I made a quicky demo here: http://webpages.charter.net/cswiger/fm_modulation.html
which will get a lot more detail such as how to calculate k for deviation etc.
This would be a good point to learn how the interperlating filters work too.

--Chuck







reply via email to

[Prev in Thread] Current Thread [Next in Thread]