Re: [Discuss-gnuradio] Units of data saved by filesink

On 07/29/2019 12:30 PM, Ellie White wrote:

Hi Marcus,

If you look at lines 34 and 39, I think you will see that I did consider the values for y. I've reattached the program here in case I originally attached an older / incorrect version. Let me know if you still see a problem. Thanks!

E.

It looks like you're plotting the squares of the means, instead of the mean of the squares.  Which will be very very different values.

Computing the arithmetic mean of a series of voltage samples doesn't really give you anything useful, since they'll be (to a first approximation)
  uniformly distributed around zero, with a slight DC offset in one direction or another.

On Mon, Jul 29, 2019 at 12:19 PM Marcus D. Leech <patchvonbraun@gmail.com> wrote:

On 07/29/2019 08:22 AM, Ellie White wrote:
> Hi Marcus,
>
> Thanks for the interesting tidbit -- and yes, I'll be following your
> advice on using the integrated block for sure. And by the way -- I've
> got one more question on a similar theme as the previous one. I
> modified my flowgraph again (attached), and am now saving two data
> streams -- real and imaginary -- to two separate data files and
> processing them using the attached python program. In the python
> program, I am performing the same conversion as the Complex to Mag^2
> Block, but yet again I am getting different answers from what I expect
> (on the order of 10^-5 instead of ~0.01). Do you have any suggestions
> as to what could be causing the difference I am seeing? I am wondering
> if it has something to do with Python's handling of the different IO
> types, but could definitely be wrong on that. Any advice is much
> appreciated!
>
> Thanks Marcus! Take care,
> Ellie
>
Looks like your python program isn't squaring the real and imaginary
components -- the values for "y" are never considered in your program :)