Re: [Discuss-gnuradio] Swept FFT needs more tweeking

[Josh Blum]

I think that you are being bitten by the gnuradio scheduler. Gnuradio 
likes to pass around data in big chunks, so you are probably getting a 
bunch of tune frequencies at once, then a big wait, then another bunch.

It sounded good in principal, but trying to generate a nicely 
incrementing frequency based on sampling the output of a sawtooth is 
turning out to be very challenging with the current blocks.

It would be best to make a custom block in grc that spawns a thread that 
calls set on the variable, increments the freq, sleeps, repeats. You 
would need to write a little python.

Take a look at the writing custom blocks on the grc wiki page.
It would probably look like this:

        <make>None
def do():
    while True:
        self.set_tune_freq(self.tune_freq+incr)
        time.sleep(yawn)
threading.Thread(target=do).start()</make>

-Josh

On 05/10/2010 06:41 PM, William Pretty Security Inc wrote:
> Well, it looks like my swept FFT program still needs some tweaking. As
> helpful as Marcus was .
>
> I need someone else with a WBX board to test this flow graph.
>
>
>
> 1)            If you set the frequency span to 2300MHz (reasonable for the
> WBX) the center frequency jumps to 1.27866GHz immediately after you start
> the sweep.
>
>                  The next center frequency is 1.31699GHz. This is a
> difference of 38.33MHz. With this decimation the span is only 8MHz, so we
> have a problem L
>
>
>
> 2)            If you stop the sweep manually, the coarse slider takes on a
> life of its own and zooms off to the end of the control.
>
>
>
> Note: The controls on the Setup tab don't do anything yet.
>
>
>
> Any help would be appreciated .
>
>
>
> Bill
>
>
>
>
>
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