Re: [Discuss-gnuradio] bell 202 modulation

[Eric Blossom]

On Wed, Mar 29, 2006 at 10:08:50PM -0600, Rick Parrish wrote:
> John Ackermann N8UR wrote:
> 
> >the use of AFSK with 1200 and 2200Hz tones is simply an artifact of that.
> 
> Instead of toggling back-and-forth between two independent tone sources, 
> how hard would it be to create samples for a 1200 hz tone spanning one 
> symbol period where the initial phase was arbitrary eg. if you used a 
> sin(theta) function, it wouldn't always start at theta = 0. Same for the 
> function to generate samples spanning one symbol period for the 2200 hz 
> tone.
> 
> The idea I'm getting at is you could have your signal transition 
> smoothly (as possible) between the two tones which would result in a 
> cleaner, more efficient signal.
> 
> A sample rate that is an integer multiple of the symbol rate is a nice 
> thing but isn't required.
> 
> -rick

gr.frequency_modulator_fc will give you continuous phase.

Eric