How quickly can I retune?

I’m using the TVRX, and my goal is to be able to take enough samples to
listen to two arbitrary frequencies (more than 6MHz apart). Given that
the
bandwidth of the TVRX is 6MHz, I think that means I need
12Msamples/second
(I can do up to 32?). So for 2, that would mean 24Msamples per
second…would it be possible to retune the device in between each
sample?
Or would this be impossible?

Thanks
-Jonathan

On Wed, Aug 05, 2009 at 04:03:28PM -0400, Jonathan C. wrote:

I’m using the TVRX, and my goal is to be able to take enough samples to
listen to two arbitrary frequencies (more than 6MHz apart). Given that the
bandwidth of the TVRX is 6MHz, I think that means I need 12Msamples/second
(I can do up to 32?). So for 2, that would mean 24Msamples per
second…would it be possible to retune the device in between each sample?
Or would this be impossible?

Thanks
-Jonathan

The TVRX takes on the order of 100ms to tune. If you want two
arbitrary frequencies (more than 6 MHz apart), you’ll need two TVRX’s.

Eric

If, however, you want to retune without stopping and restarting
sampling or having underruns, I know how to do it and can explain /
send patches (for C++ – I never bothered implementing the Python
part).

In my experience, it takes a second or two before the local oscillator
on the TVRX really settles down.

Eric et al: I have some patches to the FPGA code that allow pausing
sampling for a predetermined number of samples (so you can retune
without losing track of time) and to improve the DDC startup behavior
a little (some state was leaking across runs, but I haven’t gotten it
fully fixed). Want them?

–Andy

On Wed, Aug 05, 2009 at 04:40:41PM -0400, Andrew L. wrote:

without losing track of time) and to improve the DDC startup behavior
a little (some state was leaking across runs, but I haven’t gotten it
fully fixed). Want them?

Sure!

Eric

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