Re: [Discuss-gnuradio] Capturing channel power at desired rate

In experimenting, I discovered that I needed to add a log10 block at the
output of the complex-to-mag^2 block. With that put in, I'm getting
what seem to be quite solid results, and avoiding some of the issues
that the max-from-fft approach might suffer.

John
----
On 12/01/2017 03:55 PM, John Ackermann N8UR wrote:
> My current project is analyzing the strength of signals in each channel
> of the AM broadcast band from a recording made during the recent solar
> eclipse.  The goal is to see if the eclipse caused propagation changes
> leading to additional stations "popping up" out of the noise.  Thanks to
> help from Marcus and others, I have the PFB channelizer and main program
> flow working nicely, and now I'm trying to optimize the amplitude
> measurement.
>
> My prior attempts involved using a Power FFT block and taking the
> maximum value of the vector.  This always made me a little nervous,
> looking for just one point that represents the carrier.
>
> After Googling around I decided to switch tactics and instead of looking
> for a single peak, measure the total noise power in a very narrow
> channel around the carrier location (for now, 50 Hz).  The power will be
> almost entirely contained in the carrier, but using total power in that
> narrow width seems more straightforward than the FFT approach, as I'm
> not too worried about interference signals in this experiment.
>
> I've put together a hier block that uses a complex-to-mag^2 block
> followed by a moving average and a keep-1-in-N.  My goal is to generate
> output records at a set rate, almost always slower than once per second.
>
> Attached are a screenshot and .grc of the block I came up with, and I'd
> appreciate any thoughts about whether this is the best way to do it.
> Three notes:
>
>
> 1.  I know that this is not a calibrated system, and that the dB values
> I'm outputting are relative; that's fine for this experiment.
>
> 2.  I really wish I could figure out how to output the amplitude data as
> a string in a text file, rather than as floats in binary; all my
> subsequent analysis tools take one-value-per-line string input and it
> seems suboptimal at best to do an intermediate float-to-string
> conversion before I can use the output data.
>
> 3.  I want the option to record the raw samples as well as the channel
> power, and the selector block is meant to toggle that capability.  If
> the "save_samples" parameter is set to 0, I don't want that file to be
> created at all; if it's 1, then the file should be created and data
> dumped to it.  If this isn't the right way to accomplish that, I'd
> appreciate suggestions.  (This will be set at the beginning of the run,
> and won't change during runtime.)
>
> Thanks,
> John
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>

_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio