Missing functions in gnuradio?

Hello,

I am relatively new to gnuradio and plan to write a weatherfax decoder
in gnuradio.

I want to try different schemes for decoding the signal (coherent /
noncoherent / short-time DFT)

As there is phasing in the signal I am most interested in the
non-coherent approach. But there I am really lacking a square-root block
in gnuradio. It should not be difficult for me to implement it - but I
wondered why such a block is not present in the library.

Should such a block (or a general “power of” block) included in the
library?

Best regards,

Horst

You may be able to find an existing weatherfax decoder that can be
ported
more easily. This worked for the multi-mon project. Somebody just took
the
dos code that had been around for a while and got it to use data from
the
gnu radio instead of a sound card like it did originally.

-Clark

I want to try different schemes for decoding the signal (coherent /
Best regards,

Horst


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On Sat, Apr 15, 2006 at 11:03:23AM +0200, Horst Eyermann wrote:

in gnuradio. It should not be difficult for me to implement it - but I
wondered why such a block is not present in the library.

Should such a block (or a general “power of” block) included in the
library?

Hi Horst,

We do have gr.rms_cf and gr.rms_ff which compute estimates of RMS
power for complex and float signals respectively.

There’s also gr.complex_to_mag for complex signals.

We generally avoid continuously computing the square root (it’s
expensive). In our examples so far we’ve generally wanted to compare
power to a threshold, and in that case it was easier to factor the
(absence of) square root into the threshold setting than to burn the
cycles computing sqrt on every sample.

Eric