Re: [Discuss-gnuradio] Improve FSK4 decodes in OP25

[Andy Walls]

On Sun, Jan 22, 2017 at 7:19 PM, Luke Berndt <address@hidden> wrote:

> Well, there was definitely a lot of noise! and I am pretty sure the source
> was my computer. I got a couple of USB extension cables so I could get away
> from the computer and the USB hub and that helped a lot. I was able to noise
> floor by about 20db.
>
> Almost every transmission is coming in clear now.

Yay!


> Oddly enough though when I
> do a debug recording, it still doesn’t give me the 4 distinct levels. Any
> thoughts on what could be up?

You might be looking at a section of the IQ where there is no
transmission ongoing?

Or you've tweaked something (e.g. baseband level with a multiply
const) such that the
joint tracking loop in the 4FSK demod block loses track of the symbol clock?

IDK.

> Here is an example of the new and improved reception:
> https://www.dropbox.com/s/7is60h94ctf6d0t/34800-1485122982_4.90888e%2B08.raw

With this file, and the flowgraph I provided to you, I get the four
levels  (see one of the
two attached pictures).  The levels are a little noisy, but the symbol
slicer should sort
them out with only a few errors, and error correcting code should fix
the stray symbol errors.

There are parts in the IQ data where no transmission is being sent,
which will look like a
mess.  See the second attached picture.



>  - Luke

Regards,
Andy

Screenshot from 2017-01-22 19-49-58.png
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Screenshot from 2017-01-22 19-51-57.png
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