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[Discuss-gnuradio] uhd_fft differences with different wire-format
From: |
Anderson, Douglas J. |
Subject: |
[Discuss-gnuradio] uhd_fft differences with different wire-format |
Date: |
Mon, 5 Jan 2015 19:04:35 +0000 |
Hi all,
I'm trying to understand the impact that changing the wire-format of a USRP has
on the uhd_fft script provided by GNURadio.
Using UHD_003.008.001-42-g8c87a524 and GNURadio built by pybomb a few weeks ago
(3427a667c).
On a USRP N210 with 50 Ohm load, I ran
uhd_fft --wire-format=sc8 -s 25M -f 700M
uhd_fft --wire-format=sc16 -s 25M -f 700M
With sc16, I get a mostly flat FFT with slight roll-off toward the ends, as I'd
expect.
With sc8, I get a dip at the center frequency that increased by about 10dB on
either side as it moves out from the center freq.
The way I understood it is that wire-format is just the format used over the
ethernet cable, but that in both cases the internet representation in GNURadio
is unchanged (I used fc32).
Could someone help me understand why the wire format affects the FFT shape in
such a strange way?
I can attach screenshots if my description was unclear.
Thanks!
-Doug
- [Discuss-gnuradio] uhd_fft differences with different wire-format,
Anderson, Douglas J. <=